Funny sound as note decays? - Page 2

jcmjmp · 10-20-2009, 11:39 PM

Quote:

Originally Posted by Wilder Amplification

WTF!? Your screen resistors are missing.

Ummm.... yeah, what he said!

At first, I would have guessed x-over distortion but it looks like that was ruled out.

Wilder Amplification · 10-20-2009, 11:49 PM

That and that does not look to be the original power transformer...looks like it originally had a standup mains and someone replaced the PT with a laydown and modified the chassis to accomodate it. Not sure if this has anything to do with your problem but it would explain the low B+.

MajorNut1967 · 10-20-2009, 11:49 PM

Quote:

Originally Posted by Wilder Amplification

WTF!? Your screen resistors are missing.

This is an old one and a lot of the 50 watters didn't have them. I was just being a stock fanatic, plus the B+ was always so low.

MajorNut1967 · 10-20-2009, 11:54 PM

Quote:

Originally Posted by Wilder Amplification

That and that does not look to be the original power transformer...looks like it originally had a standup mains and someone replaced the PT with a laydown and modified the chassis to accomodate it. Not sure if this has anything to do with your problem but it would explain the low B+.

All the '68 models I've seen have had laydown PT.

MajorNut1967 · 10-21-2009, 12:01 AM

Quote:

Originally Posted by Wilder Amplification

Well, based on the incoming VAC RMS x 1.414 rule you're rectified/filtered "no load" voltage is within 2% of my calculation based on an RMS of 275VAC (I calculated 388.85VDC out filtered). Is that transformer original?

Also, what schematic are you going off of when you refer to the "standard Marshall test points"?

No it's not a stock PT. and the test points are from the jcm 800 tech manual so an early jcm 800 sch. wil have the same lay out.

MajorNut1967 · 10-21-2009, 12:06 AM

Quote:

Originally Posted by MartyStrat54

Wow! I'd hate to see that.

Sorry that it's still sucking. Those 6CA7's are nice tubes. Maybe you should take them out until you get this figured out. I'd hate to see you ruin those nice tubes.

Oh ya they went right back in the box after 90 seconds!

PaoloJM · 10-21-2009, 03:30 AM

I'm not familiar with the Marshall standard points you mention.
Can you give the voltages in the normal format, as in per pin of each valve?

My calcs concur with Jon on your PT so I don't believe we need to worry about that either.

Were the rectifier diodes always wired like that?

They seem to be practically hanging there, and are routed very close to the signal wire on the right hand side power valve, which also doesn't have any grid stops. I've never seen a diode rectifier take a ground directly from a mounting screw like that.
It seems bizarre that a noise making circuit, like the rectifier, would be mounted directly over a signal wire.

That would definitley be my first thing to check out!!

Wilder Amplification · 10-21-2009, 03:54 AM

Quote:

Originally Posted by PaoloJM

I'm not familiar with the Marshall standard points you mention.
Can you give the voltages in the normal format, as in per pin of each valve?

My calcs concur with Jon on your PT so I don't believe we need to worry about that either.

Were the rectifier diodes always wired like that?

They seem to be practically hanging there, and are routed very close to the signal wire on the right hand side power valve, which also doesn't have any grid stops. I've never seen a diode rectifier take a ground directly from a mounting screw like that.
It seems bizarre that a noise making circuit, like the rectifier, would be mounted directly over a signal wire.

That would definitley be my first thing to check out!!

Good call on the rectifier. Another and much neater way I've seen it done on these heads is to use a self contained bridge rectifier, but only the positive side gets hooked up, effectively making it into a positive full wave center tap rectifier.

MajorNut1967 · 10-21-2009, 12:03 PM

Quote:

Originally Posted by PaoloJM

I'm not familiar with the Marshall standard points you mention.
Can you give the voltages in the normal format, as in per pin of each valve?

My calcs concur with Jon on your PT so I don't believe we need to worry about that either.

Were the rectifier diodes always wired like that?

They seem to be practically hanging there, and are routed very close to the signal wire on the right hand side power valve, which also doesn't have any grid stops. I've never seen a diode rectifier take a ground directly from a mounting screw like that.
It seems bizarre that a noise making circuit, like the rectifier, would be mounted directly over a signal wire.

That would definitley be my first thing to check out!!

Hi Paolo,

Yes this amp has always had low B+, but it always sounded amazing so I never worried about it. Plus I saw in my JCM 800 service book that the 2204 only has a B+ of 367vdc. ya I have seen other late 60's 50 watters like that, with the A10D10's laying out like that Diode x=scary huh.

And yes I will do a PIN diagram for you mate!

Wilder Amplification · 10-21-2009, 12:54 PM

Quote:

Originally Posted by MajorNut1967

Hi Paolo,

Yes this amp has always had low B+, but it always sounded amazing so I never worried about it. Plus I saw in my JCM 800 service book that the 2204 only has a B+ of 367vdc. ya I have seen other late 60's 50 watters like that, with the A10D10's laying out like that Diode x=scary huh.

And yes I will do a PIN diagram for you mate!

Yeah any amp with a 275-0-275 tranny will have a low B+ like that. Just not what we're used to seeing on a Marshall...that's why we questioned it.

MajorNut1967 · 10-21-2009, 02:37 PM

Here Paul

Then the Marshall standard test points as follows:
1. .966v pin 3 V1
2. 186.4v pin1 V1
3. 1.63v pin8 V1
4. 220.2v pin6 V1
5. 236.1v last half of the last 50x50uf cap
6. 263.5v first half of the last 50x50uf cap
7. 1.25v pin8 V2
8. 150.3v pin6 & pin2 V2
9. 143.2v pin3 V2
10. 295.6v previous to the 82k & 100K in the PI
11. 22.3v NFB feed
12. 184.7v pin1 PI
13. 175.9v pin6 PI
At the bias split: -30.78

PaoloJM · 10-21-2009, 02:55 PM

Can you verify that you do not have any DC on the first three stage grids?
You may have a leaky coupling cap that it throwing preamp biasing off.

MajorNut1967 · 10-21-2009, 06:28 PM

Quote:

Originally Posted by PaoloJM

Can you verify that you do not have any DC on the first three stage grids?
You may have a leaky coupling cap that it throwing preamp biasing off.

I changed all the coupling caps out and all brand new off the reel. Infact I changed the signal caps too!

jcmjmp · 10-21-2009, 06:34 PM

Can you tap the circuit before the PI, send that signal to a different power amp to see if the problem persists? If not, maybe the OT is shot?

MajorNut1967 · 10-21-2009, 11:45 PM

Ok, you blokes won’t believe what the problem was! It was the Choke! Under light load like when I was testing the Preamp and the Power section separately no issue. But under full load the Choke had a burnt winding and it would get hot you guys know what happened next. I had a choke for a twin reverb in a box I slapped it in as a last resolve and Bang ear melting pleasure for all! Only thing is this choke is only rated for 90mA.

Gentlemen thank you for all your input and expertise. Your knowledge is priceless and appreciated.

Cheers Mates!

Wilder Amplification · 10-22-2009, 12:12 AM

Quote:

Originally Posted by MajorNut1967

Ok, you blokes won’t believe what the problem was! It was the Choke! Under light load like when I was testing the Preamp and the Power section separately no issue. But under full load the Choke had a burnt winding and it would get hot you guys know what happened next. I had a choke for a twin reverb in a box I slapped it in as a last resolve and Bang ear melting pleasure for all! Only thing is this choke is only rated for 90mA.

Gentlemen thank you for all your input and expertise. Your knowledge is priceless and appreciated.

Cheers Mates!

Nice...I'd have thought that would've caused some "ghosting" while playing at normal volume rather than causing a funny sound to appear on note decay. Great work Major!

PaoloJM · 10-22-2009, 06:08 AM

Quote:

Originally Posted by MajorNut1967

Ok, you blokes won’t believe what the problem was! It was the Choke! Under light load like when I was testing the Preamp and the Power section separately no issue. But under full load the Choke had a burnt winding and it would get hot you guys know what happened next. I had a choke for a twin reverb in a box I slapped it in as a last resolve and Bang ear melting pleasure for all! Only thing is this choke is only rated for 90mA.

Gentlemen thank you for all your input and expertise. Your knowledge is priceless and appreciated.

Cheers Mates!

Wow, great fault finding Major. I must admit that the choke would be one of last things on my list to check, it's pretty rare to have them fail.
Enjoy your warm, fuzzy and satisfied feeling at a job well done!!

MajorNut1967 · 10-22-2009, 03:25 PM

Quote:

Originally Posted by PaoloJM

Wow, great fault finding Major. I must admit that the choke would be one of last things on my list to check, it's pretty rare to have them fail.
Enjoy your warm, fuzzy and satisfied feeling at a job well done!!

Xactly, when have you ever had a Choke gone tits up on you? I been toying with amps for 25 year and never had a Choke go bad. Till now. I took it apart and it was full of rust!

Again "thank you" to Paolo, Wilder and Marty for the great info and guidance! It's good to know that there are a few that really know what they are doing and are willing to share their skill and knowledge just to be genuinely helpful.

MartyStrat54 · 10-22-2009, 04:54 PM

That's great. Wow...a choke? Who would have thought? I'm glad the issue has been resolved, because I think you would have replaced every part one at a time.

Hey Major. I got a bump here. In regard to the Ritchie Blackmore thread that is heating up, I just posted some info on it out of my original September 1978 Guitar Player magazine, featuring Ritchie. It says that he had Marshall install two more KT88's in his Majors. (Which is what they should have done from the start.)

My question to you? When you built your mini-Major, did you use the KT88's like in the original amp? In other words, are they pegged to make the 50 watts each? I've been wondering if you have them pegged, or if you detuned it to say an 80 watt, two tube power section. Let me know.

Wilder Amplification · 10-23-2009, 01:18 AM

Quote:

Originally Posted by MajorNut1967

Xactly, when have you ever had a Choke gone tits up on you? I been toying with amps for 25 year and never had a Choke go bad. Till now. I took it apart and it was full of rust!

Again "thank you" to Paolo, Wilder and Marty for the great info and guidance! It's good to know that there are a few that really know what they are doing and are willing to share their skill and knowledge just to be genuinely helpful.

Anytime Major! Enjoyed helping as it was a learning experience for me as well. As these guys mentioned, I never would've even thought of the choke due to there being no "ghosting", and again when do you ever hear of a choke going bad?

I know you're all about being "era correct" and all, but something tells me that not having the screen resistors installed may have taxed the choke by allowing the power supply to draw more current than normal through the choke and screens. And if you ever have a screen short, the choke is gonna feel the brunt of that. If it were my amp I'd get those installed. At least they'll act like a fuse and blow open in the event of a screen short.

MajorNut1967 · 10-23-2009, 02:32 AM

Quote:

Originally Posted by MartyStrat54

That's great. Wow...a choke? Who would have thought? I'm glad the issue has been resolved, because I think you would have replaced every part one at a time.

Hey Major. I got a bump here. In regard to the Ritchie Blackmore thread that is heating up, I just posted some info on it out of my original September 1978 Guitar Player magazine, featuring Ritchie. It says that he had Marshall install two more KT88's in his Majors. (Which is what they should have done from the start.)

My question to you? When you built your mini-Major, did you use the KT88's like in the original amp? In other words, are they pegged to make the 50 watts each? I've been wondering if you have them pegged, or if you detuned it to say an 80 watt, two tube power section. Let me know.

Thanks Marty, the ol' 50 watt is back up and running fine.

Ok Major part 1: I had heard the rumor that Ritchie had a six tube Major built by John Stillwell. Now I have seen the Chassis for the 6 tube (KT88) that Stillwell still has to this day! Now Ritchie has a real bad habit about making up stories about his equipment. Now with that all said, the GP 1978 article has some half truths in it. But here’s the real Beef about this: If RB had a six tube major built here are the serious problems that would be run into. First you would need a serious power transformer. Just adding two KT88’s would add 3.2 amps extra demand just on the heater supply, so in total with 6 KT88’s the total current draw with 3 12AX7’s would be 10.5 amps of heater current! Have you seen a PT with a 10.5 amp heater supply, I haven’t except in Military gear. Next you need tons of current in the HT output of the PT to keep the plate supply in check. So one hurdle. Now if Marshall had designed for 6 power tubes and reduced the plate voltage down from 620 down to 553 dc the Major would have faired better.

Hurdle No. 2: To find an Ultra-linear 300> watt OT would be next to impossible, with the correct primary impedance! It would have to be custom made. And on top of all a Marshall Major head weighs 90lbs already, adding the super transformers would have made it ridiculously heavy.
Now I know for a fact that Ritchie had Stillwell add an extra ECC83 to the majors, there is already a hole there; you know the one normally covered by that little round metal plate. Ritchie is actually quite knowledgeable about tube electronics, so he knows what he wants and even may know how to do it (one of Ritchie’s first jobs out side of music was working at the airport maintaining radio equipment)!

Ok I’m getting friggin windy here!

Ok now on my mini majors I reduce the plate voltage clear down to 453 @ plate to plate imp of 4300 ohms so I can use modern production KT88’s (I only get a realistic 70 watt of true power RMS @ 2% THD). Now if I was a rich guy and had an endless supply of NOS genalex KT88’s I would run at 553vdc @ 4500 ohms. Now I also increase the screen resistors from 250 ohm to 1250 ohms also so it is quite tame current draw wise. And I used a much better OT then Marshall did so it doesn’t sound exact! That all she wrote, for now. I hope my jaw’s flapping helped a bit?

solarburnDSL50 · 10-23-2009, 02:29 PM

This thread was an absolute treat to watch all of you exert your expertise in finding a solution. Amazing.

MartyStrat54 · 10-23-2009, 02:50 PM

Okay. That answered all but one question. I assume that you are using an ultra-linear OPT. I think it was smart to detune the mini, because you and I both know that a current production tube can go down the well without warning. 70 watts is still a lot of power.

The thing that blows my mind is when someone posts and asks about KT88's. There are some people who think that if they install KT88's in their old 800, it is going to put out more power.

I had to tell this guy with a 50 watt that the KT88's would put out around 50 watts in his 800. Some people don't understand that you have to have power to make power. Even two KT88's set up for a 35 watt draw per tube needs a solid power supply.

The biggest power tranny I personally saw was in a 1953 Zenith TV/Radio/Turntable. It had a separate power supply. The power tranny was huge. I mean way huge. It was almost as wide as the chassis. It was part of a dual rectifier power supply. It had a special wiring harness coming out of it. I sold it on EBAY for around $35. It cost about that much to ship it.

MajorNut1967 · 10-23-2009, 03:34 PM

Quote:

Originally Posted by MartyStrat54

Okay. That answered all but one question. I assume that you are using an ultra-linear OPT. I think it was smart to detune the mini, because you and I both know that a current production tube can go down the well without warning. 70 watts is still a lot of power.

The thing that blows my mind is when someone posts and asks about KT88's. There are some people who think that if they install KT88's in their old 800, it is going to put out more power.

I had to tell this guy with a 50 watt that the KT88's would put out around 50 watts in his 800. Some people don't understand that you have to have power to make power. Even two KT88's set up for a 35 watt draw per tube needs a solid power supply.

The biggest power tranny I personally saw was in a 1953 Zenith TV/Radio/Turntable. It had a separate power supply. The power tranny was huge. I mean way huge. It was almost as wide as the chassis. It was part of a dual rectifier power supply. It had a special wiring harness coming out of it. I sold it on EBAY for around $35. It cost about that much to ship it.

Ya I used a UL OPT it’s a Hammond 1650N rated at 60watts, impedance of 4300 and handles 318mA of current. It has a 4-8-16 output but not switchable.

Its funny that these guys think that the KT88 will make the amp put out more power. It's like they think its supposed to be like putting a 4 barrel in place of a 2 barrel carb on a V-8, insta power! Most of the time the benefit is the tonal change. Its the hardest thing to get these guys to learn is "power in equals power out" and that the stock PT on a 50 watt is way short to supply KT88's as whole.

The biggest PT I have seen was for a tube driven radar unit. The dc output was 20kvdc at 100amps and a heater supply of 12vac @ 200amps LOL

Wilder Amplification · 10-23-2009, 07:10 PM

Good points! Power comes from the "POWER SUPPLY". The power supply supplies current. The valves use the input signal to "open the valve", which controls how much of this current goes to the OT, and in turn to the speaker, much like a metering "valve" (hopefully some will start to see where they get that name

). The stronger the signal, the more the valve will open, and the more current the valve will allow the power supply to pull through the valve and the OT.

Eventually you will reach a point where there's no more current to be had, and the valve is open enough for more current to pass, but the current is simply not there to pass. This is where the valves "saturate", just like putting a large hose on the garden spigot. Once the water source is flowing all the water it can, increasing the hose size will flow the same amount of water, but the pressure will drop since there's now less resistance to water flow. The same thing happens on a power supply (not enough circuit resistance will flow max current while causing the supply voltage to drop).

KT88s ARE CAPABLE OF passing more current, but the current has to be available to pass in order for it to.

People also think that everything is about voltage, when it reality, yes voltage comes into play, but voltage without current is nothing. You have to have both to have power, just like horsepower in an engine is both torque and RPM.

It always amazed me when people with PA systems think that their power amps are PUSHING power, when in reality the speaker is PULLING current, and the amount of current it's allowed to pull is determined by the voltage out on the amp's outputs, which you set with the main mixer fader. It's nothing more than an adjustable power supply. Most guys will get power amps for their PA systems that are rated for EXACTLY the amount of power they need for the volume they want. Well that's like building an engine with JUST ENOUGH power to make the car travel at 40mph...you'd have to run the car at wide open throttle at all times. I'd much rather size the amps to be CAPABLE OF delivering more power than what's needed so that when I'm at the volume I want to be at, the amps are just cruising along. Much cleaner and fuller sound that way.

MartyStrat54 · 10-23-2009, 07:34 PM

Well hell Major...I didn't know we could include military components. Now I was around some massive power supplies, but the transformers were hardly conventional. I mean to handle that sort of load, they were oil filled with finned outer shells. Have you ever heard of the military "elephant cage?" There are only 7 of them in the world. I was around two of them. They had all sorts of transformers providing power for equipment that was hooked up to the cage.

The biggest conventional military transformers I worked around were in some specialized equipment. One ran 660VDC and the other was around 820VDC. Now I was a buck sergeant in Japan and my first-line supervisor went to pull a component card out of this particular gear. Oops! He forgot to power down the gear and take his wedding ring off. The HV blew his finger off. It was laying inside the equipment. As some other people attended to the sergeant, I powered the gear down and pulled his finger out. Bad news, it was overcooked like a Christmas goose. The doctors were not able to use it and they had to surgically cut the bad finger down to the knuckle.

Just think, and old Super Lead could do the same thing to you. Yet everyday, I know people are sticking their fingers into a "hot" amp. "Wow! I got zapped!!!" "How could it have happened?" "I pulled the plug." You know that sort of stuff.

Little side bar: I noticed that the Ultra-Linear transformer in your mini is rated below the 70 watt output you stated. Does this ever concern you, or can you get away with this?

MajorNut1967 · 10-24-2009, 12:27 AM

Quote:

Originally Posted by Wilder Amplification

Good points! Power comes from the "POWER SUPPLY". The power supply supplies current. The valves use the input signal to "open the valve", which controls how much of this current goes to the OT, and in turn to the speaker, much like a metering "valve" (hopefully some will start to see where they get that name

). The stronger the signal, the more the valve will open, and the more current the valve will allow the power supply to pull through the valve and the OT.

Eventually you will reach a point where there's no more current to be had, and the valve is open enough for more current to pass, but the current is simply not there to pass. This is where the valves "saturate", just like putting a large hose on the garden spigot. Once the water source is flowing all the water it can, increasing the hose size will flow the same amount of water, but the pressure will drop since there's now less resistance to water flow. The same thing happens on a power supply (not enough circuit resistance will flow max current while causing the supply voltage to drop).

KT88s ARE CAPABLE OF passing more current, but the current has to be available to pass in order for it to.

People also think that everything is about voltage, when it reality, yes voltage comes into play, but voltage without current is nothing. You have to have both to have power, just like horsepower in an engine is both torque and RPM.

It always amazed me when people with PA systems think that their power amps are PUSHING power, when in reality the speaker is PULLING current, and the amount of current it's allowed to pull is determined by the voltage out on the amp's outputs, which you set with the main mixer fader. It's nothing more than an adjustable power supply. Most guys will get power amps for their PA systems that are rated for EXACTLY the amount of power they need for the volume they want. Well that's like building an engine with JUST ENOUGH power to make the car travel at 40mph...you'd have to run the car at wide open throttle at all times. I'd much rather size the amps to be CAPABLE OF delivering more power than what's needed so that when I'm at the volume I want to be at, the amps are just cruising along. Much cleaner and fuller sound that way.

Great points!

MajorNut1967 · 10-24-2009, 12:43 AM

Quote:

Originally Posted by MartyStrat54

Well hell Major...I didn't know we could include military components. Now I was around some massive power supplies, but the transformers were hardly conventional. I mean to handle that sort of load, they were oil filled with finned outer shells. Have you ever heard of the military "elephant cage?" There are only 7 of them in the world. I was around two of them. They had all sorts of transformers providing power for equipment that was hooked up to the cage.

The biggest conventional military transformers I worked around were in some specialized equipment. One ran 660VDC and the other was around 820VDC. Now I was a buck sergeant in Japan and my first-line supervisor went to pull a component card out of this particular gear. Oops! He forgot to power down the gear and take his wedding ring off. The HV blew his finger off. It was laying inside the equipment. As some other people attended to the sergeant, I powered the gear down and pulled his finger out. Bad news, it was overcooked like a Christmas goose. The doctors were not able to use it and they had to surgically cut the bad finger down to the knuckle.

Just think, and old Super Lead could do the same thing to you. Yet everyday, I know people are sticking their fingers into a "hot" amp. "Wow! I got zapped!!!" "How could it have happened?" "I pulled the plug." You know that sort of stuff.

Little side bar: I noticed that the Ultra-Linear transformer in your mini is rated below the 70 watt output you stated. Does this ever concern you, or can you get away with this?

Ya I know I didn't play fair huh Marty? Military stuff counted. lol Lets see elephant cage wasn't that part of a High Frequency Direction Finding System? So did you work on the one at Clark AFB? Man that SGT got his arse tore up bad.

Ya mate I get concerned that one of the kids in here will get Zapped for real and get hurt for true!

Now on the the power rating of the OPT, Hammond transformers are very conservatively rated. So if it says 60 watt I real safe with pushing 75-80 rms through it. Plus my plate voltage is only 453 on the KT88's so we are not even close to swing voltage and the transformer arcing. And remember the Radio Spares Deluxe OPT was only rated at 30 watts in the JTM 45! And I've heard some quite loud JTM 45's and they never blew OPT's.

10-21-2009, 03:30 AM	#37 (permalink)
PaoloJM Senior Member Join Date: Jun 2008 Location: Cork, Ireland Posts: 534	Re: Funny sound as note decays? I'm not familiar with the Marshall standard points you mention. Can you give the voltages in the normal format, as in per pin of each valve? My calcs concur with Jon on your PT so I don't believe we need to worry about that either. Were the rectifier diodes always wired like that? They seem to be practically hanging there, and are routed very close to the signal wire on the right hand side power valve, which also doesn't have any grid stops. I've never seen a diode rectifier take a ground directly from a mounting screw like that. It seems bizarre that a noise making circuit, like the rectifier, would be mounted directly over a signal wire. That would definitley be my first thing to check out!! __________________ www.youtube.com/paolojm

10-21-2009, 02:37 PM	#41 (permalink)
MajorNut1967 Senior Member Join Date: Jul 2009 Location: South Pacific Posts: 710	Re: Funny sound as note decays? Here Paul Then the Marshall standard test points as follows: 1. .966v pin 3 V1 2. 186.4v pin1 V1 3. 1.63v pin8 V1 4. 220.2v pin6 V1 5. 236.1v last half of the last 50x50uf cap 6. 263.5v first half of the last 50x50uf cap 7. 1.25v pin8 V2 8. 150.3v pin6 & pin2 V2 9. 143.2v pin3 V2 10. 295.6v previous to the 82k & 100K in the PI 11. 22.3v NFB feed 12. 184.7v pin1 PI 13. 175.9v pin6 PI At the bias split: -30.78 __________________ MJN1967 aka BA (Bad Attitude) 1968 model 1987 50watt. A Baby Major (Half-Power) I built from the ground up. JTM 45 Clone combo Ground up build. JCM 800 Clone Ground up build. Custom Built Warmoth Strat 75' Fender Tele-Deluxe '70 style strat custom build w/Custom Shop 69's PU's

10-21-2009, 02:55 PM	#42 (permalink)
PaoloJM Senior Member Join Date: Jun 2008 Location: Cork, Ireland Posts: 534	Re: Funny sound as note decays? Can you verify that you do not have any DC on the first three stage grids? You may have a leaky coupling cap that it throwing preamp biasing off. __________________ www.youtube.com/paolojm

10-21-2009, 06:34 PM	#44 (permalink)
jcmjmp Senior Member Join Date: Nov 2008 Posts: 1,341	Re: Funny sound as note decays? Can you tap the circuit before the PI, send that signal to a different power amp to see if the problem persists? If not, maybe the OT is shot?

10-21-2009, 11:45 PM	#45 (permalink)
MajorNut1967 Senior Member Join Date: Jul 2009 Location: South Pacific Posts: 710	Re: Funny sound as note decays? Ok, you blokes won’t believe what the problem was! It was the Choke! Under light load like when I was testing the Preamp and the Power section separately no issue. But under full load the Choke had a burnt winding and it would get hot you guys know what happened next. I had a choke for a twin reverb in a box I slapped it in as a last resolve and Bang ear melting pleasure for all! Only thing is this choke is only rated for 90mA. Gentlemen thank you for all your input and expertise. Your knowledge is priceless and appreciated. Cheers Mates! __________________ MJN1967 aka BA (Bad Attitude) 1968 model 1987 50watt. A Baby Major (Half-Power) I built from the ground up. JTM 45 Clone combo Ground up build. JCM 800 Clone Ground up build. Custom Built Warmoth Strat 75' Fender Tele-Deluxe '70 style strat custom build w/Custom Shop 69's PU's

10-22-2009, 04:54 PM	#49 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,583	Re: Funny sound as note decays? That's great. Wow...a choke? Who would have thought? I'm glad the issue has been resolved, because I think you would have replaced every part one at a time. Hey Major. I got a bump here. In regard to the Ritchie Blackmore thread that is heating up, I just posted some info on it out of my original September 1978 Guitar Player magazine, featuring Ritchie. It says that he had Marshall install two more KT88's in his Majors. (Which is what they should have done from the start.) My question to you? When you built your mini-Major, did you use the KT88's like in the original amp? In other words, are they pegged to make the 50 watts each? I've been wondering if you have them pegged, or if you detuned it to say an 80 watt, two tube power section. Let me know. __________________ MARTY 2009 Gibson Explorer-Hell Raising Machine 1989 Fender Strat Plus USA 2008 Fender Tele USA 2004 Schecter Elite w/DiMarzio's TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers. TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends." DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker. Tubes: Let's just say they are NOS that kick ass.

10-23-2009, 02:50 PM	#53 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,583	Re: Funny sound as note decays? Okay. That answered all but one question. I assume that you are using an ultra-linear OPT. I think it was smart to detune the mini, because you and I both know that a current production tube can go down the well without warning. 70 watts is still a lot of power. The thing that blows my mind is when someone posts and asks about KT88's. There are some people who think that if they install KT88's in their old 800, it is going to put out more power. I had to tell this guy with a 50 watt that the KT88's would put out around 50 watts in his 800. Some people don't understand that you have to have power to make power. Even two KT88's set up for a 35 watt draw per tube needs a solid power supply. The biggest power tranny I personally saw was in a 1953 Zenith TV/Radio/Turntable. It had a separate power supply. The power tranny was huge. I mean way huge. It was almost as wide as the chassis. It was part of a dual rectifier power supply. It had a special wiring harness coming out of it. I sold it on EBAY for around $35. It cost about that much to ship it. __________________ MARTY 2009 Gibson Explorer-Hell Raising Machine 1989 Fender Strat Plus USA 2008 Fender Tele USA 2004 Schecter Elite w/DiMarzio's TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers. TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends." DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker. Tubes: Let's just say they are NOS that kick ass.

10-23-2009, 07:34 PM	#56 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Formerly Phoenix, now north of KC Posts: 2,583	Re: Funny sound as note decays? Well hell Major...I didn't know we could include military components. Now I was around some massive power supplies, but the transformers were hardly conventional. I mean to handle that sort of load, they were oil filled with finned outer shells. Have you ever heard of the military "elephant cage?" There are only 7 of them in the world. I was around two of them. They had all sorts of transformers providing power for equipment that was hooked up to the cage. The biggest conventional military transformers I worked around were in some specialized equipment. One ran 660VDC and the other was around 820VDC. Now I was a buck sergeant in Japan and my first-line supervisor went to pull a component card out of this particular gear. Oops! He forgot to power down the gear and take his wedding ring off. The HV blew his finger off. It was laying inside the equipment. As some other people attended to the sergeant, I powered the gear down and pulled his finger out. Bad news, it was overcooked like a Christmas goose. The doctors were not able to use it and they had to surgically cut the bad finger down to the knuckle. Just think, and old Super Lead could do the same thing to you. Yet everyday, I know people are sticking their fingers into a "hot" amp. "Wow! I got zapped!!!" "How could it have happened?" "I pulled the plug." You know that sort of stuff. Little side bar: I noticed that the Ultra-Linear transformer in your mini is rated below the 70 watt output you stated. Does this ever concern you, or can you get away with this? __________________ MARTY 2009 Gibson Explorer-Hell Raising Machine 1989 Fender Strat Plus USA 2008 Fender Tele USA 2004 Schecter Elite w/DiMarzio's TSL100 with custom 4x12 cab. TSL122 with Man 'O War Speakers. TSL602 #1 with JBL D123 Speakers and 602 #2 with Altec 417 Speakers. "Oh so sweet my friends." DSL401 #1 with Red Fang Speaker and 401 #2 with JBL D123 Speaker. Tubes: Let's just say they are NOS that kick ass.

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