marshall haze 40 combo - Page 2

BCnSTL · 10-22-2009, 03:54 PM

Quote:

Originally Posted by the_best_of_fools

How would you compare the Haze 15 to the 40?

I don't know honestly. In my experience there can be fairly big variations in how different power-tube configurations/types can sound so I'm hesitant to state anything about them categorically. The Haze 15 sounds, well, classically "Marshally" to me. Like I've said before - the "Marshall" sound covers a LOT of ground. Think classic/hard rock Marshall, not detuned heavy-metal Marshall. The Haze 15 is somewhere between a Plexi and a JCM800 - it has an overall 'softer' distortion like the plexi but with a tighter low-end. That's just my impression and I am NOT a credible Marshall afficiando.

Quote:

Originally Posted by the_best_of_fools

Also, the fact that there's no Master volume is kind of a turn off for me since I don't see the purpose of building a practice amp that can't be played at low volume and still offer all the signature sounds it was designed for.

Thanks,
tbof

There is a master volume on the dirty channel. The interaction between the gain and volume controls lets you get a nice overdrive happening at very reasonable volume levels. However, the amp comes alive when you push the output section a bit - say when the volume is on 3 or higher, and that's pretty loud but certainly significantly less so than a 50 or 100 watt amplifier.

Personally, I think all the angst and criticism about these amps amounts to fetishism. They are made with MDF not birch plywood enclosures, they are not hand-wired point-to-point. They ARE inexpensive and sound great and yet do not diminish the cachet and lust-factor associated with the higher-end Marshall amps.

spikei · 10-22-2009, 04:42 PM

I'm one of those older guys who doesn't want to brake my back carrying an amp around anymore, i want good on board fx and not have to fuss about tap dancing on stage, and i wanted the valve sound of my old jmp 50 combo, i got all in the haze 40 w combo. good clean, crunch and overdrive sound from a rasonable priced amp.for pubs and clubs its a winner. my only concern is reliability as i have already had to have the popping between channel sorted (they sent me a new amp in three days)
only time will tell if this is a big seller, but its got what i want from a small amp.

PS one other issue is you can connect up to a cab but you fave to disconnect the internal speaker, which to me is crazy.

srv · 10-23-2009, 07:45 AM

What did they do to fix the popping?
Mine is doing that and any information I could pass on to the tech might shorten my time with out the amp.

Thanks

srv · 10-23-2009, 07:51 AM

Quote:

Originally Posted by spikei

I'm one of those older guys who doesn't want to brake my back carrying an amp around anymore, i want good on board fx and not have to fuss about tap dancing on stage, and i wanted the valve sound of my old jmp 50 combo, i got all in the haze 40 w combo. good clean, crunch and overdrive sound from a rasonable priced amp.for pubs and clubs its a winner. my only concern is reliability as i have already had to have the popping between channel sorted (they sent me a new amp in three days)
only time will tell if this is a big seller, but its got what i want from a small amp.

PS one other issue is you can connect up to a cab but you fave to disconnect the internal speaker, which to me is crazy.

So the fix was to send you a new amp, to bad I was hoping it could be fixed.

MajorWatt · 10-23-2009, 09:02 AM

Quote:

Originally Posted by srv

So the fix was to send you a new amp, to bad I was hoping it could be fixed.

Having done factory warranty repairs in the past, I know sometimes it's cheaper and easier for them to just replace rather than repair. This tells you something about the quality of the design and components. At this stage anyway.

spikei · 10-23-2009, 04:08 PM

they sent a new amp because it was only a day after i bought it and i insisted it was sorted, i was not about to wait about for some one to get it fixed. SRV if yours in under warranty and you got it from a supplier dont leave it as it is get it sorted, marshalls have a three year warranty (with clause). this is a well known problem get them to sort it. even if its second hand i would have a go at them.
good luck
ps if it helps i think it was resisters

srv · 10-23-2009, 07:20 PM

Thanks, the guy I am taking it to is factory certified to repair every amp I have ever heard of and a few I haven't so, if it can be fixed he can do it!
Just a little disturbing as this is it's second trip in the 3 weeks I have owned it!!! first was for a bad 12AX7.

Glad to hear it was your choice to send it back not marshall's. Rather have an amp that has had this stuff fixed then take the chance on starting all over with a new one.

Thanks for replying. I will post whatever I learn.

srv

tarznamps · 10-24-2009, 12:33 AM

A few post seem to imply that Marshall's marketing dept. controls the designs of a new Marshall amp. That is rubish.

Just because you don't like the Haze series because it isn't a $5,000 handwired super Marshall doesn't mean that it isn't needed in the market place. Why would anyone imply that an amp should not exists because they don't like or need it?

Marshall has a great line-up of amps for all styles and price points. Pick the one or two or three that you want and don't worry about the rest!

BCnSTL · 10-26-2009, 12:47 PM

I went with the Haze 15 because: a) I wanted the protability and versatility of a head/cab setup b) I didn't want 40 watts of power and c) In this case I prefer the smooth overdrive of the 6V6 vs EL power tubes - sacrilege I know.

Related aside: weren't the very first Marshall amps 6L6 based?

pacAir · 11-02-2009, 07:23 PM

Marshall MHZ40C Haze
Repair Narrative 11/2/09

Up front, let me state that I have played guitar for over 40 years and have repaired amps and worked in electronics design and manufacturing for over 35 years. I am not a vintage "snob" or a newbie. I am a technically informed user who was attracted to the Haze for its potential, small size and light weight. What follows is my story, findings and opinion.

I bought a Marshall Haze 40 combo "kit" from a major online retailer. It is a "kit" because it didn't survive its return shipping from the customer. It was returned then shipped out to me (apparently without any further handling or repackaging). This amp could have had 3 transcontinental UPS Ground rides!

Even though the original packaging material was all there, the amp was pretty much a basket-case when it arrived here. The results of my troubleshooting, repairs and rebuild should shed some light on a number of design and construction issues discussed in this forum, this thread and elsewhere.

Apparently, an existing electronic problem caused the first owner to return it and the subsequent physical shipping damage to the amp led it to find a home with me at a much reduced price. I'll cover the physical damage and construction of the amp first, then cover the electronic problem and design observations.

Cabinet

The main physical failure on this amp (and on at least a few others from what I have seen and read) is when it encounters a good drop or other mistreatment during shipping. While the cabinet itself may be made of MDF (I have not confirmed this but it appears to be so), the grill board is made of 9/16" particle board (or "chip board" as it may also be referred to).

My amp arrived with the loudspeaker completely detached from the grill board! Even though T-Nuts were used to mount the speaker, large chunks of particle board were still mounted to the speaker at the T-Nut locations! The remaining grill board was missing these chunks and has completely de-laminated in several places. It looked like a small bomb went off! The cabinet was filled with splinters, chunks and sawdust from this failure.

The 12AX7 phase-splitter tube (I assume, as a schematic does not seem to be available online) was completely naked (no glass) because the rogue speaker took it out. Also, the magnet of the speaker had some small chips missing off the edges due to the speaker's repeated collisions with the chassis AND the output transformer! The output transformer mounting bracket (very lightweight and cheap) was almost completely separated from the chassis and was dangling at a 45 degree angle. The chassis, while scratched and marked-up, was not otherwise damaged.

The cabinet was otherwise undamaged (except for a few small gouges and scratches along with some lifting and wrinkling of the Tolex on the top front lip which I will have to address). The grill board will have to be replaced and I will make a replacement out of the best plywood I can get in order to have a more bulletproof unit.

Amp Chassis

I repaired the output transformer mounting problem by crafting a couple of "bar washers" to fit the footprint of the transformer mounting brackets (after these were hammered back into shape, sort of). Once the output transformer mounting issue was repaired, the broken ECC83 (I assume) was replaced with a Tung-Sol 12AX7 I had handy. The amp chassis was now ready to be plugged in and tested.

The amp came alive on the bench and put out an honest 40 watts RMS. Both channels worked as advertised and channel switching from the front panel seemed to be fine. While the effects and its front-panel switching arrangement seemed to work at first, I noticed a strange problem.

Electronics Problem

Regardless of WHICH effect was invoked (delay, chorus, vibe), turning one or both of the adjustment controls past about 1 o'clock started causing the effects and the front-panel LED indicator to turn on and off in concert with the speed/modulation setting (more or less)! It was as if the modulation signal was turning the switching on and off! As the amp warmed, I started to get a bunch of clicking relays to go along with the flashing LED! Not good, an out-of-control mode of functionality!

I connected the external footswitch and found that while switching the effects button on and off turned the foot pedal's Effects LED on and off, there was NO switching occurring in the amp itself! The footswitch was NOT controlling the effects at all (although channel-switching was correct). I did some signal tracing to confirm that the footswitch itself was working fine and that the problem was electronic in nature.

I deduced that there might be a microcontroller somewhere doing all the relay switching (rather than a hard-wired state-machine) and I found it living on the main board, out of sight (UNDER the DSP Effects board). I traced the final destination of both footswitches to their respective controller pins (pin 2 for effects, pin 4 for channel-switching). I found the OFF state for the channel-switching function was 3.6Vdc, while the same condition in the effects-switching circuit only yielded a 2.9Vdc reading. THIS was ultimately the golden clue!

After measuring and comparing the surrounding components I found a voltage-dropping resistor in the channel-switching circuit that was 4.7k, while the same component in the effects-switching circuit was 27K! An incorrect resistor value had been installed at the factory! I changed R54 to the correct 4.7K value and the problems disappeared! All the amp switching circuits started to work as expected with no surprises. I also re-seated the microcontroller as it was not fully inserted into its socket.

It is my belief that this resistor may be the culprit involved in the footswitch "popping" so many owners have complained about. If you have a local tech, have him check the value of R54. It is located under the DSP Effects board (which must be removed) and is just forward of the microcontroller chip (socketed and with a handwritten firmware label on top of it).

As soon as I can get the cabinet and speaker issue resolved, I'll be able to give the amp a proper sonic evaluation.

MHZ40C Design, Quality and Conclusions

Let me start by stating that overall I was favorably impressed with the amp's design and most of the basic construction qualities. For a low-priced (for Marshall) amplifier, it uses a good quality double-sided PCB and a nice heavy-duty chassis in a reasonably strong cabinet (not including the grill board). The quality of the workmanship inside is BETTER than I expected... the wire dress, soldering and attention to most details is quite good.

The first place that showed "too many pennies pinched" is in the choice of grill board materials. DO NOT STRAY FROM quality PLYWOOD PLEASE! 13-ply Baltic Birch if you can get it! The ease with which this grill board was destroyed (without effecting anything else) surely paints this squarely in the "weak link" corner! Who knows, humid conditions in India may well give this problem a head start (this material tends to absorb moisture and turn to oatmeal given half a chance).

The packaging material was better than some but could still use improvement. The amps need to be cradled and shock-mounted, not merely "suspended" with destructable styrofoam. Also, the transformers are certainly inexpensive but appear to be adequate for this level of amp and output power.

The next area that could have been better was the front-panel pots, but the jury is still out on the longevity factor. At least these pots have sturdy mounts to protect and strengthen them.

The wrong resistor in the footswitch circuit is probably due to a human error or typography/transcription error in a BOM. This is a teething problem that will disappear once it get sorted out at the factory. It does not appear to be a design problem (although without a printed schematic I couldn't say that for sure). I hope not too many amps suffer from this particular problem. It isn't difficult to fix but the shipping, handling and assembly/disassembly are all out of proportion to the tenth-of-a-penny resistor at the heart of the problem.

The opinions offered above are done so without listening to the amp at all (only observing its performance visually on an oscilloscope and eyeballs on the product's manufacturing qualities). I would have personally preferred more of an open back on this amp but the semi-closed back may improve the tone. I won't know until I can get a complete cab to wrap around this chassis!

With the immediate problems fixed, the amp can then be judged by its sonic performance. Contray to some people's opinion, I see a lot more to be happy about here than to be afraid of. I think this may be a great lightweight alternative that many of us could make good use of as long as it has a base of reliability we can trust.

As I see it, there are two standout design features:

1. The "Effects per Channel" memory (the effects previously used on the Clean channel, Gain channel and "Boosted Gain" channel are remembered individually and recalled when that "channel" is selected). This feature is unique in its price range.

2. The fact that when the DSP Effects are shut off and the rear-panel effects loop is bypassed (by the switch next to the jacks), the Haze 40 combo presents an ALL TUBE signal path. This is NOT the case with the Fender Deluxe VM, a very good amp in the same category.

Coupled with the small size and light weight, I think this makes the amp's configuration flexible enough to meet the needs of a variety of players. I look forward to playing through it live as soon as I can get that new grill board created and installed.

Steve

hmstrat · 11-02-2009, 09:21 PM

As far as the MARSHALL HAZE head goes, India is hardly a mecca for "tube" amps. The "Haze" is simply Marshall's attempt to compete with those cheap Chinese-built Orange, Vox, Egnater, etc., and other competitor's foreign-built amps...

P.S. - No offense to anybody living there, but can anybody name even a moderately successful tube-amp indigenous to India???

JohnH · 11-03-2009, 12:10 AM

Hi PacAir - I just want to say welcome, and to thankyou for a very interesting and insightful post

John

pacAir · 11-03-2009, 03:27 PM

Quote:

Originally Posted by JohnH

Hi PacAir - I just want to say welcome, and to thankyou for a very interesting and insightful post

John

Thanks! I know my posts can be incomprehensible or of no interest to some but sharing information is how things get done and how we can all learn on the internet. You just drink as much as you need from the firehose!

I'll check back and post some observations on the amps sonic performance when I get the grill board re-done. I got the wood cut last night and should have the amp back together in the next week.

I have enough Marshall experience as a player to have a reasonably valid opinion on how the Haze combo will sound. I used a full stack JCM800 50w (2204 single channel head) back in the early '80s and I still own and occasionally use a pair of early & mid-80's JCM800 50W 2x12 combos (4104 single channel), a Marshall 9000 series all-tube guitar preamp and a Marshall Guvnor pedal. I am also currently rebuilding a 1979 JMP 50 2x12 combo "basket case".

Marshalls are fun (some just weigh more than others!)!

Steve

pacAir · 11-05-2009, 08:48 PM

Since the previous poster's internal photos are no longer available, I'll post a few of mine (hosted on my own server so they won't disappear anytime soon).

Note: The only "surface mount" components are on the plug-in DSP Effects board. The "black boxes" seen on the main board are switching relays, NOT integrated circuits.

Enjoy!

Steve

spikei · 11-06-2009, 12:37 PM

great post Steve, your amp looks like it has been to hell and back in a mixer, and I'm not sure how many amps would survive that sort of treatment, but you still find very positive things to say about the amp, most of us may have given up and topped our selves when we opened up the box. look forward to seeing your results.
im very happy with mine atm.

pacAir · 11-06-2009, 05:14 PM

Well, I AM a glutton for punishment! I certainly wouldn't expect most people to go this route but it's "my thing". I'd rather get the basket case and rebuild it than get a perfect one at twice the price. It's a little like being a car enthusiast who rebuilds classic automobiles except these amps are not yet classics and they are much cheaper & smaller than a car!

I just finished creating a new grill board for mine (1/2" Baltic Birch plywood) with all the holes and T-nuts in the right places and painted black. Tonight, I will be carefully removing the grill cloth and logo from the broken grill board and transferring them to the new grill board. I also had to remove a length of the white piping and re-set some of the Tolex on the front top edge of the cabinet (it has bubbled and wrinkled for some reason). Now that the glue is set I'll have to get this put back together as well before the grill board, speaker and chassis can be re-installed.

If all goes well, I ought to have the amp biased and completely reassembled sometime this weekend. Only THEN will I get to play it for real! I think it always sounds better when you have some effort invested in the amp and you know everything is as it should be and every screw is tight because you have personally checked it!

Steve

pacAir · 11-09-2009, 03:03 PM

I got the whole Haze finished and reassembled this weekend. I found the clean channel to sound very good and much better than any of the previous Marshall amps I have owned (primarily JCM800 vintage).

The drive channel surprised me at being so low in gain that even with the gain turned up to 10, it was only hinting at what it might sound like with a pedal ahead of it. Is this lower-gain drive channel normal or do I have a bad 12AX7? I was expecting something a bit higher gain than this but I was wondering what the experience has been with other owners. I wakes up a bit with a Tube Screamer ahead of it but this particular amp is surprisingly docile on the gain channel without the pedal.

I'm beginning to think there is one more problem to locate! Perhaps the second tube got damaged by the same thing that annihilated the phase-splitter tube (the loose speaker).

The built-in effects are serviceable but not as easily configured as a 3-knob pedal is. This is one area where the Fender Deluxe VM is better. On the VM amps the effects are individually switchable on the included footswitch (4-button) and are adjusted in the traditional 3-knob fashion.

Steve

tibboh · 11-10-2009, 04:46 PM

Quote:

Originally Posted by srv

Thanks, the guy I am taking it to is factory certified to repair every amp I have ever heard of and a few I haven't so, if it can be fixed he can do it!
Just a little disturbing as this is it's second trip in the 3 weeks I have owned it!!! first was for a bad 12AX7.

Glad to hear it was your choice to send it back not marshall's. Rather have an amp that has had this stuff fixed then take the chance on starting all over with a new one.

Thanks for replying. I will post whatever I learn.

srv

Bought my Haze 40 last month - popping back (when switching channels) got quite bad once warmed up. Emailed Marshall and they recommended that I send it back via dealer. Had it back after 2 weeks and fault has been rectified. Excellent customer service in my view

Ernie · 11-11-2009, 01:38 PM

Hey, I noticed you've had to reply tubes...

My Haze 40, after less that 10 hours use, lost the boost channel. It pops a little, sizzles like bacon frying, and wehn turned all the way up, you can barely hear the guitar. Sounds like its far, far away.

I am new to this -- can you advise -- do the symptoms mentioned here sound like a blown tube? Are there differnent tubes for each channel, since the clean channel is working very well?

pacAir · 11-11-2009, 08:58 PM

Quote:

Originally Posted by Ernie

Hey, I noticed you've had to reply tubes...

My Haze 40, after less that 10 hours use, lost the boost channel. It pops a little, sizzles like bacon frying, and wehn turned all the way up, you can barely hear the guitar. Sounds like its far, far away.

I am new to this -- can you advise -- do the symptoms mentioned here sound like a blown tube? Are there differnent tubes for each channel, since the clean channel is working very well?

That sounds like and could be a tube failure. The preamp tube farthest away from the output tubes (far-right when looking at the back of the amp) should be input stage and clean channel. The second preamp tube should be the distortion channel and tone control stage and the third ECC83/12AX7 tube is most likely the phase-splitter that drives the push-pull output tubes. I say "should be" because this is a typical configuration and the Haze schematics do not yet seem to be available.

If you take the back off (unplugged of course) you can reach behind the chassis and find the tubes. The first tube (input) has a metal shield over it. The second tube from the right is probably the culprit if a tube is at fault. The factory ECC83 tubes in the Haze don't impress me as being of high quality manufacture (they don't look like a quality assembly inside when compared to the JJ or Electro-Harmonix/Sovtek tubes I had handy) and I have heard of a number of people who have had these tubes fail.

Steve

10-22-2009, 04:42 PM	#32 (permalink)
spikei Senior Member Join Date: May 2008 Posts: 124	Re: marshall haze 40 combo I'm one of those older guys who doesn't want to brake my back carrying an amp around anymore, i want good on board fx and not have to fuss about tap dancing on stage, and i wanted the valve sound of my old jmp 50 combo, i got all in the haze 40 w combo. good clean, crunch and overdrive sound from a rasonable priced amp.for pubs and clubs its a winner. my only concern is reliability as i have already had to have the popping between channel sorted (they sent me a new amp in three days) only time will tell if this is a big seller, but its got what i want from a small amp. PS one other issue is you can connect up to a cab but you fave to disconnect the internal speaker, which to me is crazy. __________________ V M 50 w Combo Haze 40 w Combo AVT 100 w Combo TSL 60 w Head 1936 Cab Gibson LP Fender Strat JV Squier Ibanez LP

10-23-2009, 07:45 AM	#33 (permalink)
srv Junior Member Join Date: Oct 2009 Location: Florida Posts: 7	Re: marshall haze 40 combo What did they do to fix the popping? Mine is doing that and any information I could pass on to the tech might shorten my time with out the amp. Thanks

10-23-2009, 04:08 PM	#36 (permalink)
spikei Senior Member Join Date: May 2008 Posts: 124	Re: marshall haze 40 combo they sent a new amp because it was only a day after i bought it and i insisted it was sorted, i was not about to wait about for some one to get it fixed. SRV if yours in under warranty and you got it from a supplier dont leave it as it is get it sorted, marshalls have a three year warranty (with clause). this is a well known problem get them to sort it. even if its second hand i would have a go at them. good luck ps if it helps i think it was resisters __________________ V M 50 w Combo Haze 40 w Combo AVT 100 w Combo TSL 60 w Head 1936 Cab Gibson LP Fender Strat JV Squier Ibanez LP

10-23-2009, 07:20 PM	#37 (permalink)
srv Junior Member Join Date: Oct 2009 Location: Florida Posts: 7	Re: marshall haze 40 combo Thanks, the guy I am taking it to is factory certified to repair every amp I have ever heard of and a few I haven't so, if it can be fixed he can do it! Just a little disturbing as this is it's second trip in the 3 weeks I have owned it!!! first was for a bad 12AX7. Glad to hear it was your choice to send it back not marshall's. Rather have an amp that has had this stuff fixed then take the chance on starting all over with a new one. Thanks for replying. I will post whatever I learn. srv

10-24-2009, 12:33 AM	#38 (permalink)
tarznamps Senior Member Join Date: Apr 2009 Location: Music City, USA Posts: 213	Re: marshall haze 40 combo A few post seem to imply that Marshall's marketing dept. controls the designs of a new Marshall amp. That is rubish. Just because you don't like the Haze series because it isn't a $5,000 handwired super Marshall doesn't mean that it isn't needed in the market place. Why would anyone imply that an amp should not exists because they don't like or need it? Marshall has a great line-up of amps for all styles and price points. Pick the one or two or three that you want and don't worry about the rest! __________________ Tarz-N-Amps Marshall Heads - JTM 45, Haze 15, JCM 2000 DSL 100, JCM 800 2205, JCM 900 4100, Vintage Modern 2466, 1987x Plexi Marshall Cabs - 1960BX, 1960A, 1960AV, 1965B, 425A, 1936, Haze A&B Marshall Combos - JMP 4140 Club & Country, DSL 401, JTM 615, JCM 900 4501

10-26-2009, 12:47 PM	#39 (permalink)
BCnSTL Junior Member Join Date: Jun 2009 Posts: 8	Re: marshall haze 40 combo I went with the Haze 15 because: a) I wanted the protability and versatility of a head/cab setup b) I didn't want 40 watts of power and c) In this case I prefer the smooth overdrive of the 6V6 vs EL power tubes - sacrilege I know. Related aside: weren't the very first Marshall amps 6L6 based?

11-02-2009, 07:23 PM	#40 (permalink)
pacAir Junior Member Join Date: Nov 2009 Location: Portland, Oregon Posts: 15	Marshall Haze 40 Footswitch Problem & Tech Review Marshall MHZ40C Haze Repair Narrative 11/2/09 Up front, let me state that I have played guitar for over 40 years and have repaired amps and worked in electronics design and manufacturing for over 35 years. I am not a vintage "snob" or a newbie. I am a technically informed user who was attracted to the Haze for its potential, small size and light weight. What follows is my story, findings and opinion. I bought a Marshall Haze 40 combo "kit" from a major online retailer. It is a "kit" because it didn't survive its return shipping from the customer. It was returned then shipped out to me (apparently without any further handling or repackaging). This amp could have had 3 transcontinental UPS Ground rides! Even though the original packaging material was all there, the amp was pretty much a basket-case when it arrived here. The results of my troubleshooting, repairs and rebuild should shed some light on a number of design and construction issues discussed in this forum, this thread and elsewhere. Apparently, an existing electronic problem caused the first owner to return it and the subsequent physical shipping damage to the amp led it to find a home with me at a much reduced price. I'll cover the physical damage and construction of the amp first, then cover the electronic problem and design observations. *Cabinet* The main physical failure on this amp (and on at least a few others from what I have seen and read) is when it encounters a good drop or other mistreatment during shipping. While the cabinet itself may be made of MDF (I have not confirmed this but it appears to be so), the grill board is made of 9/16" particle board (or "chip board" as it may also be referred to). My amp arrived with the loudspeaker completely detached from the grill board! Even though T-Nuts were used to mount the speaker, large chunks of particle board were still mounted to the speaker at the T-Nut locations! The remaining grill board was missing these chunks and has completely de-laminated in several places. It looked like a small bomb went off! The cabinet was filled with splinters, chunks and sawdust from this failure. The 12AX7 phase-splitter tube (I assume, as a schematic does not seem to be available online) was completely naked (no glass) because the rogue speaker took it out. Also, the magnet of the speaker had some small chips missing off the edges due to the speaker's repeated collisions with the chassis AND the output transformer! The output transformer mounting bracket (very lightweight and cheap) was almost completely separated from the chassis and was dangling at a 45 degree angle. The chassis, while scratched and marked-up, was not otherwise damaged. The cabinet was otherwise undamaged (except for a few small gouges and scratches along with some lifting and wrinkling of the Tolex on the top front lip which I will have to address). The grill board will have to be replaced and I will make a replacement out of the best plywood I can get in order to have a more bulletproof unit. Amp Chassis I repaired the output transformer mounting problem by crafting a couple of "bar washers" to fit the footprint of the transformer mounting brackets (after these were hammered back into shape, sort of). Once the output transformer mounting issue was repaired, the broken ECC83 (I assume) was replaced with a Tung-Sol 12AX7 I had handy. The amp chassis was now ready to be plugged in and tested. The amp came alive on the bench and put out an honest 40 watts RMS. Both channels worked as advertised and channel switching from the front panel seemed to be fine. While the effects and its front-panel switching arrangement seemed to work at first, I noticed a strange problem. *Electronics Problem* Regardless of WHICH effect was invoked (delay, chorus, vibe), turning one or both of the adjustment controls past about 1 o'clock started causing the effects and the front-panel LED indicator to turn on and off in concert with the speed/modulation setting (more or less)! It was as if the modulation signal was turning the switching on and off! As the amp warmed, I started to get a bunch of clicking relays to go along with the flashing LED! Not good, an out-of-control mode of functionality! I connected the external footswitch and found that while switching the effects button on and off turned the foot pedal's Effects LED on and off, there was NO switching occurring in the amp itself! The footswitch was NOT controlling the effects at all (although channel-switching was correct). I did some signal tracing to confirm that the footswitch itself was working fine and that the problem was electronic in nature. I deduced that there might be a microcontroller somewhere doing all the relay switching (rather than a hard-wired state-machine) and I found it living on the main board, out of sight (UNDER the DSP Effects board). I traced the final destination of both footswitches to their respective controller pins (pin 2 for effects, pin 4 for channel-switching). I found the OFF state for the channel-switching function was 3.6Vdc, while the same condition in the effects-switching circuit only yielded a 2.9Vdc reading. THIS was ultimately the golden clue! After measuring and comparing the surrounding components I found a voltage-dropping resistor in the channel-switching circuit that was 4.7k, while the same component in the effects-switching circuit was 27K! An incorrect resistor value had been installed at the factory! I changed R54 to the correct 4.7K value and the problems disappeared! All the amp switching circuits started to work as expected with no surprises. I also re-seated the microcontroller as it was not fully inserted into its socket. It is my belief that this resistor may be the culprit involved in the footswitch "popping" so many owners have complained about. If you have a local tech, have him check the value of R54. It is located under the DSP Effects board (which must be removed) and is just forward of the microcontroller chip (socketed and with a handwritten firmware label on top of it). As soon as I can get the cabinet and speaker issue resolved, I'll be able to give the amp a proper sonic evaluation. *MHZ40C Design, Quality and Conclusions* Let me start by stating that overall I was favorably impressed with the amp's design and most of the basic construction qualities. For a low-priced (for Marshall) amplifier, it uses a good quality double-sided PCB and a nice heavy-duty chassis in a reasonably strong cabinet (not including the grill board). The quality of the workmanship inside is BETTER than I expected... the wire dress, soldering and attention to most details is quite good. The first place that showed "too many pennies pinched" is in the choice of grill board materials. DO NOT STRAY FROM quality PLYWOOD PLEASE! 13-ply Baltic Birch if you can get it! The ease with which this grill board was destroyed (without effecting anything else) surely paints this squarely in the "weak link" corner! Who knows, humid conditions in India may well give this problem a head start (this material tends to absorb moisture and turn to oatmeal given half a chance). The packaging material was better than some but could still use improvement. The amps need to be cradled and shock-mounted, not merely "suspended" with destructable styrofoam. Also, the transformers are certainly inexpensive but appear to be adequate for this level of amp and output power. The next area that could have been better was the front-panel pots, but the jury is still out on the longevity factor. At least these pots have sturdy mounts to protect and strengthen them. The wrong resistor in the footswitch circuit is probably due to a human error or typography/transcription error in a BOM. This is a teething problem that will disappear once it get sorted out at the factory. It does not appear to be a design problem (although without a printed schematic I couldn't say that for sure). I hope not too many amps suffer from this particular problem. It isn't difficult to fix but the shipping, handling and assembly/disassembly are all out of proportion to the tenth-of-a-penny resistor at the heart of the problem. The opinions offered above are done so without listening to the amp at all (only observing its performance visually on an oscilloscope and eyeballs on the product's manufacturing qualities). I would have personally preferred more of an open back on this amp but the semi-closed back may improve the tone. I won't know until I can get a complete cab to wrap around this chassis! With the immediate problems fixed, the amp can then be judged by its sonic performance. Contray to some people's opinion, I see a lot more to be happy about here than to be afraid of. I think this may be a great lightweight alternative that many of us could make good use of as long as it has a base of reliability we can trust. As I see it, there are two standout design features: 1. The "Effects per Channel" memory (the effects previously used on the Clean channel, Gain channel and "Boosted Gain" channel are remembered individually and recalled when that "channel" is selected). This feature is unique in its price range. 2. The fact that when the DSP Effects are shut off and the rear-panel effects loop is bypassed (by the switch next to the jacks), the Haze 40 combo presents an ALL TUBE signal path. This is NOT the case with the Fender Deluxe VM, a very good amp in the same category. Coupled with the small size and light weight, I think this makes the amp's configuration flexible enough to meet the needs of a variety of players. I look forward to playing through it live as soon as I can get that new grill board created and installed. Steve Last edited by pacAir; 11-03-2009 at 12:15 AM. Reason: New Photo

11-02-2009, 09:21 PM	#41 (permalink)
hmstrat Member Join Date: Dec 2007 Location: Texas Posts: 65	Re: marshall haze 40 combo As far as the MARSHALL HAZE head goes, India is hardly a mecca for "tube" amps. The "Haze" is simply Marshall's attempt to compete with those cheap Chinese-built Orange, Vox, Egnater, etc., and other competitor's foreign-built amps... P.S. - No offense to anybody living there, but can anybody name even a moderately successful tube-amp indigenous to India??? __________________ JCM 900 MKIII (2500) ... JTM 622 ... DSL 401 ... DSL 100 LP Standard, Strat, Tele, Tele, Erlewine Automatic, HM Strat

11-03-2009, 12:10 AM	#42 (permalink)
JohnH Senior Member Join Date: May 2008 Location: Wollongong NSW Posts: 640	Re: marshall haze 40 combo Hi PacAir - I just want to say welcome, and to thankyou for a very interesting and insightful post John __________________ DSL401 8412 cab Crate Powerblock 1 x 12 Vintage 30 cab '76 Shergold Masquerader '93 Les Paul Studio '83 Roadstar

11-05-2009, 08:48 PM	#44 (permalink)
pacAir Junior Member Join Date: Nov 2009 Location: Portland, Oregon Posts: 15	Marshall Haze 40 Internal "Gut" Shots Since the previous poster's internal photos are no longer available, I'll post a few of mine (hosted on my own server so they won't disappear anytime soon). Note: The only "surface mount" components are on the plug-in DSP Effects board. The "black boxes" seen on the main board are switching relays, NOT integrated circuits. Enjoy! Steve Last edited by pacAir; 11-06-2009 at 04:57 PM.

11-06-2009, 12:37 PM	#45 (permalink)
spikei Senior Member Join Date: May 2008 Posts: 124	Re: marshall haze 40 combo great post Steve, your amp looks like it has been to hell and back in a mixer, and I'm not sure how many amps would survive that sort of treatment, but you still find very positive things to say about the amp, most of us may have given up and topped our selves when we opened up the box. look forward to seeing your results. im very happy with mine atm. __________________ V M 50 w Combo Haze 40 w Combo AVT 100 w Combo TSL 60 w Head 1936 Cab Gibson LP Fender Strat JV Squier Ibanez LP

11-06-2009, 05:14 PM	#46 (permalink)
pacAir Junior Member Join Date: Nov 2009 Location: Portland, Oregon Posts: 15	Marshall Haze 40... Rebuild Almost Done! Well, I AM a glutton for punishment! I certainly wouldn't expect most people to go this route but it's "my thing". I'd rather get the basket case and rebuild it than get a perfect one at twice the price. It's a little like being a car enthusiast who rebuilds classic automobiles except these amps are not yet classics and they are much cheaper & smaller than a car! I just finished creating a new grill board for mine (1/2" Baltic Birch plywood) with all the holes and T-nuts in the right places and painted black. Tonight, I will be carefully removing the grill cloth and logo from the broken grill board and transferring them to the new grill board. I also had to remove a length of the white piping and re-set some of the Tolex on the front top edge of the cabinet (it has bubbled and wrinkled for some reason). Now that the glue is set I'll have to get this put back together as well before the grill board, speaker and chassis can be re-installed. If all goes well, I ought to have the amp biased and completely reassembled sometime this weekend. Only THEN will I get to play it for real! I think it always sounds better when you have some effort invested in the amp and you know everything is as it should be and every screw is tight because you have personally checked it! Steve

11-09-2009, 03:03 PM	#47 (permalink)
pacAir Junior Member Join Date: Nov 2009 Location: Portland, Oregon Posts: 15	It is Alive! I got the whole Haze finished and reassembled this weekend. I found the clean channel to sound very good and much better than any of the previous Marshall amps I have owned (primarily JCM800 vintage). The drive channel surprised me at being so low in gain that even with the gain turned up to 10, it was only hinting at what it might sound like with a pedal ahead of it. Is this lower-gain drive channel normal or do I have a bad 12AX7? I was expecting something a bit higher gain than this but I was wondering what the experience has been with other owners. I wakes up a bit with a Tube Screamer ahead of it but this particular amp is surprisingly docile on the gain channel without the pedal. I'm beginning to think there is one more problem to locate! Perhaps the second tube got damaged by the same thing that annihilated the phase-splitter tube (the loose speaker). The built-in effects are serviceable but not as easily configured as a 3-knob pedal is. This is one area where the Fender Deluxe VM is better. On the VM amps the effects are individually switchable on the included footswitch (4-button) and are adjusted in the traditional 3-knob fashion. Steve

11-11-2009, 01:38 PM	#49 (permalink)
Ernie Junior Member Join Date: Nov 2009 Posts: 5	Re: marshall haze 40 combo Hey, I noticed you've had to reply tubes... My Haze 40, after less that 10 hours use, lost the boost channel. It pops a little, sizzles like bacon frying, and wehn turned all the way up, you can barely hear the guitar. Sounds like its far, far away. I am new to this -- can you advise -- do the symptoms mentioned here sound like a blown tube? Are there differnent tubes for each channel, since the clean channel is working very well?

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