JCM 900 6l6 to EL34 Conversion problems - Page 2

American Viking · 07-01-2009, 04:01 PM

Yeah dude, I would get the 900 fixed, definitely with a Mercury Magnetics transformer. This will fix your problem AND improve the tone. I don't have anything with that brand in them but MM makes a great product.

Just don't listen to Ken. A DSL is more problematic in the long run. It's got way more that can go wrong with it and the tone isn't as good.

I'm just going to have to outright say it, I have a DSL and I think they suck compared to other products in the Marshall line. The only people I really hear stand up for the DSL/TSL is if that's all they own by Marshall. Sorry Ken, don't mean to bust your balls but there's a huge chance he can buy a DSL and have something go wrong with it even more expensive to fix. I think the JCM2000 is good for a cheap backup and the weekend warrior. Mine collects dust since I got a real amp.

The 900's are going up in price too, a year and a half to two years ago they were selling at a pathetic $400 and now they're going for almost $900 and up. You'll be seeing the price steady at a higher rate since Marshall has reissued the 900. I'd be holding on to it for sure if I had one.

MartyStrat54 · 07-01-2009, 04:32 PM

An SLX is going to sound different than any other 900 amp, because it is a completely different design, but they kept the 900 moniker. All other 900 models used diodes to provide "clipping." But you knew that already.

Marty

American Viking · 07-01-2009, 05:03 PM

yeah, I was surprised when I saw they reissued the 4100 High Gain Dual Reverb over the 4100 SL-X. I would have surely thought it would be the SL-X.
Even with the JCM800 RI they did the 2203 with the vertical inputs over the horizontal which is internally designed much better. So thinking they would RI the ones that people wanted more I would have put my money on the SL-X.

I'm sure that one sounds great anyway but I have no use for reverb.

harp · 07-02-2009, 10:49 AM

Well I've ordered the OT (80 bucks from Weber VST). I'll keep you guys posted. I'm installing it myself so it won't cost anything but the parts. Yes, I'll bleed the caps. No I won't kill myself too much.

American Viking · 07-02-2009, 04:00 PM

let us know how it goes my brother

MartyStrat54 · 07-02-2009, 05:49 PM

Wow! That's cheap for an OPT. You got it from Weber? Can you post a link so I can look over their prices? That is, if you got it handy. Otherwise, I can look it up myself. I just want to make sure I get the right page.

Marty

harp · 07-03-2009, 09:43 AM

Weber Speakers - Making the world a bit louder each day.

The OT will be in next Wednesday. I'll post as soon as I get it installed.

MartyStrat54 · 07-03-2009, 03:01 PM

Thanks, I reviewed the information. Did you get the "ballsy" model, or the one with cleaner headroom? I'm familiar with Weber speakers. I didn't know they expanded into amp parts. It's good to know.

Marty

harp · 07-03-2009, 04:01 PM

Ballsy of course. I couldn't figure out why someone would want to try to get clean headroom out of a Marshall. Kinda defeats the purpose. Plus, at 100 watts, I've got way more headroom than I need anyway.

harp · 07-09-2009, 09:41 PM

So I just got the new Output Transformer in today. I installed it and re-biased again. Plays just fine but still gets freaking hot. So hot I can't turn the knobs after about 30 minutes of playing. Somebody please help me. I can't figure out what's going on!!!!!!!!!!!!!!!!!

pleximajor · 07-10-2009, 01:02 AM

better hope your power transformer has enough heater current to run el34s
4 -6L6 need .9 amp each tube thats 3.6 amp on 4-6L6
4-El34 need 1.5 amps each tube thats 6 amps on 4- el34s
thats almost double the amount of current the power transformer may not be overrated by that much

gemather · 07-10-2009, 08:46 AM

Hello,
in my JCM 900 MK3 from 1991 there is missing the the extra grid fusees inside.
I do not mentioned what them for - and placed 6550 Tube´s to run my amp.

Quite funny and strong sound.
Yust some of the United States in my room.
... Until a year later one of the tube´s kicked of.

It burned my whole amp,cause the mostlys in there is for maximal 500volts.
The Grid of an 6550 Tube´s got upon to 670volts.
The Grid of an 5881 Tube´s got upon to 470volts.
In fact of loosing one, there is a lot damage to be done by 670volts trespasing up to mainfuse.

Today,after repair,i use 5881 better.Sounds also good enough for angry cats.

Jesstaa · 07-10-2009, 09:14 AM

Geeze, how'd you manage to get 6550's running for a whole year? 670volts should've killed it in no time.

Btw, which country in Northern Europe you from?

gemather · 07-10-2009, 09:24 AM

hello,
just the transformer got a bit hot after a while playing...

It named Schleswig Holstein cause in

former times

them got the biggest Stones together angering dwarfs.

gemather · 07-10-2009, 10:01 AM

...so i put some kiloohms here and there...
...to gridvoltage and powergrid...

gemather · 07-10-2009, 10:21 AM

today,with my new 5881, i only deplaced the capacitor upon to R6 in my amp,biased to temperature.thats all.

harp · 07-19-2009, 04:18 PM

So out of desperation I decided to replace the caps. Since they are now 13 years old. It made absolutely no difference. Still banging my head against the wall. Anyone?

American Viking · 07-19-2009, 07:35 PM

it's time to take this thing to a qualified tech. i wouldn't bring it back to the same guy that told you about the OT.
if the chassis is getting hot, you need to play this amp with everything exposed so you can locate the source of the heat. the chassis shouldn't get hot at all and it leads me to believe that maybe something drawing current is either arcing or touching part of the chassis. it's hard to say without being able to experience this up close but if we're running low on ideas.

on the positive side, atleast you have up to date caps and a new transformer.

harp · 07-19-2009, 09:13 PM

Thanks man,
I'm going to have to agree with you. I'm in over my head. It's just that I hate giving up! Thanks for all the help though.

American Viking · 07-20-2009, 07:10 AM

i know how you feel! good luck though. let us know what happens

RobS · 07-20-2009, 07:35 AM

Harp,
I know this is a bit late but I just had my 900 4100dr retubed 2 weeks ago and when I dropped it off I enquired about the EL34 mod, mine is a 6l6/5881 model.
The tech said he has worked on both type amps and did not recommend doing it. He works for Marshall and said that he cannot really hear any difference in these amps with the two tube types. Now I have not heard an EL34 model but took his word for what it was worth. Needless to say after the retube I find that mine has far more bottom end to the point where I run the bass at 5.5 now, used to be between 8 and ten. With the chB Vol at 5-6 and gain at about 14 it sounds pretty much identical to my mates 800 at near full gain and with a Les Paul going through it I cannot be happier.

If the fatter sound is what your after then I suggest reversing the mods done and put 6L6WGC's in like I did. As others have said the tones are there, it's just a matter of spending alot of time tweaking the EQ to find the right sound.
Have a look at the Duncan Amps tone stack calc and it will give you a good idea of how the interaction of the eq works. I always thought high bass, middle on the mids and high treble, but the eq when I had a look at the tone stack gizmo I really understood how to get the best sound out of the amp.

Rob

American Viking · 07-20-2009, 09:01 AM

Quote:

Originally Posted by RobS

The tech said he has worked on both type amps and did not recommend doing it. He works for Marshall and said that he cannot really hear any difference in these amps with the two tube types.
Rob

Considering to switch between EL34 and 6L6 only requires a simple bias adjustment. There's an out of this world chance that you may need to change the bias resistor but it's extremely unlikely.
Does this guy really work for Marshall? If there's no audible difference between tube types then we're all wasting money and should just go to solid state.

Ken · 07-20-2009, 10:26 AM

Quote:

Originally Posted by harp

Thanks man,
I'm going to have to agree with you. I'm in over my head. It's just that I hate giving up! Thanks for all the help though.

Maybe my advice wasn't so bad after all? *S*

Seriously, I know you're really frustrated and I'm sorry about that! I know you want that amp working.

ken

American Viking · 07-20-2009, 04:37 PM

lol

Procter2812 · 07-20-2009, 05:08 PM

.

RobS · 07-21-2009, 12:48 AM

Quote:

Originally Posted by American Viking

Considering to switch between EL34 and 6L6 only requires a simple bias adjustment. There's an out of this world chance that you may need to change the bias resistor but it's extremely unlikely.
Does this guy really work for Marshall? If there's no audible difference between tube types then we're all wasting money and should just go to solid state.

Viking...Yes he does work for Marshall and I'm only passing on what he said.
As I said I have not heard an el34 4100 and was only passing on what he told me.
Bottom line is if you want an EL34 amp get an EL34 amp
I'm very happy with mine. However it really comes down to the guitars used, eq and guitar tone controls. Lots of mucking around but all the more fun

harp · 08-13-2009, 09:59 PM

Just thought I would update everyone. After taking the amp to the amp tech I found out that the "matched" quad of tubes that I got from JJ was not so matched. Because I was only checking the bias on one of the tubes, I had it biased way to hot. The amp tech switched the tubes around so that both sides were more or less balanced, then re-biased. The thing still runs pretty hot, but it's not near as bad as it was. Thanks for all the helpful advice.

ekkybedmond · 09-03-2009, 12:37 PM

Hi,
owner of an old JCM900 50W combo; this is the EL34 version and a.t. Bob at Eurotubes it plays on 6L6, KT77 and also JJ's 6V6. Tried them all, no problems. Just measure the PLate Voltage beforehand to find a suitable tube.
The 6V6's are great, starts cranking before the roof takes off. Of course a Weber Silver Bell Alnico 75W helps .. instead of the G12T-75 Celestion which is horrible in this amp.

American Viking · 09-04-2009, 01:26 AM

Quote:

Originally Posted by ekkybedmond

Hi,
owner of an old JCM900 50W combo; this is the EL34 version and a.t. Bob at Eurotubes it plays on 6L6, KT77 and also JJ's 6V6. Tried them all, no problems. Just measure the PLate Voltage beforehand to find a suitable tube.
The 6V6's are great, starts cranking before the roof takes off. Of course a Weber Silver Bell Alnico 75W helps .. instead of the G12T-75 Celestion which is horrible in this amp.

+1
Bob is the man.

Jesstaa · 09-04-2009, 05:11 AM

Wow, 6V6's in a 6L6/EL34 type amp, sounds interesting, maybe I'll have to try it after I've had my amp completely fixed.

And harp, maybe that could've been my problem, I had a quad of JJ KT77's and my amp got really hot (And the bias wouldn't stay put). They ended up red plating, and I took it to the tech with the suspicion something was broken, he said it was fine and it just needed some 6L6's (Apparently he also had to look up the info on the internet to find out of KT77's would work)...
I need a better tech, he also checked over my amp (With the obvious noise problem) and said there's nothing wrong with it.
Didn't charge me at least.

07-01-2009, 04:01 PM	#31 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,044	Re: JCM 900 6l6 to EL34 Conversion problems Yeah dude, I would get the 900 fixed, definitely with a Mercury Magnetics transformer. This will fix your problem AND improve the tone. I don't have anything with that brand in them but MM makes a great product. Just don't listen to Ken. A DSL is more problematic in the long run. It's got way more that can go wrong with it and the tone isn't as good. I'm just going to have to outright say it, I have a DSL and I think they suck compared to other products in the Marshall line. The only people I really hear stand up for the DSL/TSL is if that's all they own by Marshall. Sorry Ken, don't mean to bust your balls but there's a huge chance he can buy a DSL and have something go wrong with it even more expensive to fix. I think the JCM2000 is good for a cheap backup and the weekend warrior. Mine collects dust since I got a real amp. The 900's are going up in price too, a year and a half to two years ago they were selling at a pathetic $400 and now they're going for almost $900 and up. You'll be seeing the price steady at a higher rate since Marshall has reissued the 900. I'd be holding on to it for sure if I had one. __________________ "TOO LOUD" can only be applied to shitty bands.

07-01-2009, 05:03 PM	#33 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,044	Re: JCM 900 6l6 to EL34 Conversion problems yeah, I was surprised when I saw they reissued the 4100 High Gain Dual Reverb over the 4100 SL-X. I would have surely thought it would be the SL-X. Even with the JCM800 RI they did the 2203 with the vertical inputs over the horizontal which is internally designed much better. So thinking they would RI the ones that people wanted more I would have put my money on the SL-X. I'm sure that one sounds great anyway but I have no use for reverb. __________________ "TOO LOUD" can only be applied to shitty bands. Last edited by American Viking; 07-01-2009 at 10:46 PM.

07-02-2009, 10:49 AM	#34 (permalink)
harp Junior Member Join Date: Jun 2009 Posts: 18	Re: JCM 900 6l6 to EL34 Conversion problems Well I've ordered the OT (80 bucks from Weber VST). I'll keep you guys posted. I'm installing it myself so it won't cost anything but the parts. Yes, I'll bleed the caps. No I won't kill myself too much.

07-02-2009, 04:00 PM	#35 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,044	Re: JCM 900 6l6 to EL34 Conversion problems let us know how it goes my brother __________________ "TOO LOUD" can only be applied to shitty bands.

07-03-2009, 09:43 AM	#37 (permalink)
harp Junior Member Join Date: Jun 2009 Posts: 18	Re: JCM 900 6l6 to EL34 Conversion problems Weber Speakers - Making the world a bit louder each day. The OT will be in next Wednesday. I'll post as soon as I get it installed.

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07-03-2009, 04:01 PM	#39 (permalink)
harp Junior Member Join Date: Jun 2009 Posts: 18	Re: JCM 900 6l6 to EL34 Conversion problems Ballsy of course. I couldn't figure out why someone would want to try to get clean headroom out of a Marshall. Kinda defeats the purpose. Plus, at 100 watts, I've got way more headroom than I need anyway.

07-09-2009, 09:41 PM	#40 (permalink)
harp Junior Member Join Date: Jun 2009 Posts: 18	Re: JCM 900 6l6 to EL34 Conversion problems So I just got the new Output Transformer in today. I installed it and re-biased again. Plays just fine but still gets freaking hot. So hot I can't turn the knobs after about 30 minutes of playing. Somebody please help me. I can't figure out what's going on!!!!!!!!!!!!!!!!!

07-10-2009, 01:02 AM	#41 (permalink)
pleximajor Member Join Date: May 2009 Posts: 61	Re: JCM 900 6l6 to EL34 Conversion problems better hope your power transformer has enough heater current to run el34s 4 -6L6 need .9 amp each tube thats 3.6 amp on 4-6L6 4-El34 need 1.5 amps each tube thats 6 amps on 4- el34s thats almost double the amount of current the power transformer may not be overrated by that much Last edited by pleximajor; 07-10-2009 at 08:51 AM.

07-10-2009, 08:46 AM	#42 (permalink)
gemather Member Join Date: Jul 2009 Location: northern europ Posts: 56	Re: JCM 900 6l6 to EL34 Conversion problems Hello, in my JCM 900 MK3 from 1991 there is missing the the extra grid fusees inside. I do not mentioned what them for - and placed 6550 Tube´s to run my amp. Quite funny and strong sound. Yust some of the United States in my room. ... Until a year later one of the tube´s kicked of. It burned my whole amp,cause the mostlys in there is for maximal 500volts. The Grid of an 6550 Tube´s got upon to 670volts. The Grid of an 5881 Tube´s got upon to 470volts. In fact of loosing one, there is a lot damage to be done by 670volts trespasing up to mainfuse. Today,after repair,i use 5881 better.Sounds also good enough for angry cats.

07-10-2009, 09:14 AM	#43 (permalink)
Jesstaa Senior Member Join Date: Apr 2009 Location: Gippsland, Vic, Australia. Posts: 1,477	Re: JCM 900 6l6 to EL34 Conversion problems Geeze, how'd you manage to get 6550's running for a whole year? 670volts should've killed it in no time. Btw, which country in Northern Europe you from? __________________ GEAR LIST Guitar Marshall JCM900 4100 (6L6) (1995) Marshall Valvestate 1965A cab (????) Cort VX-2V (2008) Bass Stagg BC300 (2008?)

07-10-2009, 09:24 AM	#44 (permalink)
gemather Member Join Date: Jul 2009 Location: northern europ Posts: 56	Re: JCM 900 6l6 to EL34 Conversion problems hello, just the transformer got a bit hot after a while playing... It named Schleswig Holstein cause in former times them got the biggest Stones together angering dwarfs.

07-10-2009, 10:01 AM	#45 (permalink)
gemather Member Join Date: Jul 2009 Location: northern europ Posts: 56	Re: JCM 900 6l6 to EL34 Conversion problems ...so i put some kiloohms here and there... ...to gridvoltage and powergrid...

07-10-2009, 10:21 AM	#46 (permalink)
gemather Member Join Date: Jul 2009 Location: northern europ Posts: 56	Re: JCM 900 6l6 to EL34 Conversion problems today,with my new 5881, i only deplaced the capacitor upon to R6 in my amp,biased to temperature.thats all.

07-19-2009, 04:18 PM	#47 (permalink)
harp Junior Member Join Date: Jun 2009 Posts: 18	Re: JCM 900 6l6 to EL34 Conversion problems So out of desperation I decided to replace the caps. Since they are now 13 years old. It made absolutely no difference. Still banging my head against the wall. Anyone?

07-19-2009, 07:35 PM	#48 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,044	Re: JCM 900 6l6 to EL34 Conversion problems it's time to take this thing to a qualified tech. i wouldn't bring it back to the same guy that told you about the OT. if the chassis is getting hot, you need to play this amp with everything exposed so you can locate the source of the heat. the chassis shouldn't get hot at all and it leads me to believe that maybe something drawing current is either arcing or touching part of the chassis. it's hard to say without being able to experience this up close but if we're running low on ideas. on the positive side, atleast you have up to date caps and a new transformer. __________________ "TOO LOUD" can only be applied to shitty bands.

07-19-2009, 09:13 PM	#49 (permalink)
harp Junior Member Join Date: Jun 2009 Posts: 18	Re: JCM 900 6l6 to EL34 Conversion problems Thanks man, I'm going to have to agree with you. I'm in over my head. It's just that I hate giving up! Thanks for all the help though.

07-20-2009, 07:10 AM	#50 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,044	Re: JCM 900 6l6 to EL34 Conversion problems i know how you feel! good luck though. let us know what happens __________________ "TOO LOUD" can only be applied to shitty bands.

07-20-2009, 07:35 AM	#51 (permalink)
RobS Senior Member Join Date: Apr 2009 Location: Melbourne - Australia Posts: 464	Re: JCM 900 6l6 to EL34 Conversion problems Harp, I know this is a bit late but I just had my 900 4100dr retubed 2 weeks ago and when I dropped it off I enquired about the EL34 mod, mine is a 6l6/5881 model. The tech said he has worked on both type amps and did not recommend doing it. He works for Marshall and said that he cannot really hear any difference in these amps with the two tube types. Now I have not heard an EL34 model but took his word for what it was worth. Needless to say after the retube I find that mine has far more bottom end to the point where I run the bass at 5.5 now, used to be between 8 and ten. With the chB Vol at 5-6 and gain at about 14 it sounds pretty much identical to my mates 800 at near full gain and with a Les Paul going through it I cannot be happier. If the fatter sound is what your after then I suggest reversing the mods done and put 6L6WGC's in like I did. As others have said the tones are there, it's just a matter of spending alot of time tweaking the EQ to find the right sound. Have a look at the Duncan Amps tone stack calc and it will give you a good idea of how the interaction of the eq works. I always thought high bass, middle on the mids and high treble, but the eq when I had a look at the tone stack gizmo I really understood how to get the best sound out of the amp. Rob __________________ JCM900 4100 DR + 1960 A + B + Powerbrake JCM800 2203x Ibanez PS10CL Paul Stanley Custom Gibson LP Traditional Epiphone LP Custom

07-20-2009, 04:37 PM	#54 (permalink)
American Viking Senior Member Join Date: Jan 2009 Location: RICHMOND, VIRGINIA Posts: 2,044	Re: JCM 900 6l6 to EL34 Conversion problems lol __________________ "TOO LOUD" can only be applied to shitty bands.

07-20-2009, 05:08 PM	#55 (permalink)
Procter2812 Senior Member Join Date: Mar 2009 Location: Manchester!! Posts: 1,037	Re: JCM 900 6l6 to EL34 Conversion problems .

08-13-2009, 09:59 PM	#57 (permalink)
harp Junior Member Join Date: Jun 2009 Posts: 18	Re: JCM 900 6l6 to EL34 Conversion problems Just thought I would update everyone. After taking the amp to the amp tech I found out that the "matched" quad of tubes that I got from JJ was not so matched. Because I was only checking the bias on one of the tubes, I had it biased way to hot. The amp tech switched the tubes around so that both sides were more or less balanced, then re-biased. The thing still runs pretty hot, but it's not near as bad as it was. Thanks for all the helpful advice.

09-03-2009, 12:37 PM	#58 (permalink)
ekkybedmond Junior Member Join Date: Sep 2009 Posts: 3	Re: JCM 900 6l6 to EL34 Conversion problems Hi, owner of an old JCM900 50W combo; this is the EL34 version and a.t. Bob at Eurotubes it plays on 6L6, KT77 and also JJ's 6V6. Tried them all, no problems. Just measure the PLate Voltage beforehand to find a suitable tube. The 6V6's are great, starts cranking before the roof takes off. Of course a Weber Silver Bell Alnico 75W helps .. instead of the G12T-75 Celestion which is horrible in this amp.

09-04-2009, 05:11 AM	#60 (permalink)
Jesstaa Senior Member Join Date: Apr 2009 Location: Gippsland, Vic, Australia. Posts: 1,477	Re: JCM 900 6l6 to EL34 Conversion problems Wow, 6V6's in a 6L6/EL34 type amp, sounds interesting, maybe I'll have to try it after I've had my amp completely fixed. And harp, maybe that could've been my problem, I had a quad of JJ KT77's and my amp got really hot (And the bias wouldn't stay put). They ended up red plating, and I took it to the tech with the suspicion something was broken, he said it was fine and it just needed some 6L6's (Apparently he also had to look up the info on the internet to find out of KT77's would work)... I need a better tech, he also checked over my amp (With the obvious noise problem) and said there's nothing wrong with it. Didn't charge me at least. __________________ GEAR LIST Guitar Marshall JCM900 4100 (6L6) (1995) Marshall Valvestate 1965A cab (????) Cort VX-2V (2008) Bass Stagg BC300 (2008?)

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