very hot 74 modded superlead

pman · 09-15-2006, 10:49 PM

i recently bought a modded 74 superlead and it seems to be running maybe too hot. What is too hot though? I have an unmodded 74 50w that gets no where near as hot. The 100w has been modded by a guy named dale who used the presence as the MV and has vol 1 and vol 2 as separate gain channels. the amp has been retubed and biased and given a clean bill of health by my tech. It sounds amazing and never has given me any indication of failure. The plates on the power tubes do not turn red. I can only turn the MV to btwn 1-2 for most gig settings, or it's just too loud. I just want to make sure that this is not a transformer heading for failure.

superleadfixer · 09-16-2006, 12:27 AM

Are you saying the amp gets really hot? Where? Can you touch the transformers without getting hurt? How long does it takes to get that "hot"?
Are the trannies base touching the chassis flush? Are you using an Attenuator? Is the amp fully dimed all the time?

pman · 09-16-2006, 07:09 PM

I AM NOT USING AN ATTENUATOR. IT DOES NOT MATTER IF THE VOLUME (GAIN) CHANNELS ARE AT 1 or 10 the amp gets hot. i have notices other modded amps have fans installed.

***Guv'nor*** · 09-16-2006, 07:18 PM

I think you're mixing things pman.

I am sure if you reply superleadfixer's questions you'll get the point faster and probably you'll find a way to solve your problem.

pman · 09-16-2006, 09:07 PM

the amp gets hot on top. i touch the back where the speaker ports are at and they are not hot. no power brake. the mv (presence) is at about
1-3. the gains are at at 50-75%. i have not touched the tranny's. at the top buy the grill you can feel the heat from about 2 feet away. the grill on top is hot. i can smell the amp as well. I hope this helps

superleadfixer · 09-17-2006, 02:02 AM

Heat will be radiated/comming from the transformers for the most of it and a little from the power tubes.

If you can fry an egg on top of the PT, then it's too much

If it is really hot like you say, it doesn't look good, I would get this amp check for:

- Huge leakage current of the filter caps
- Drifting output tubes (Check voltage drop across screen Resistors for less than 7V at idle!) & or check your dc imbalance mismatched, you shouldn't be more then 10/15ma per side or your OT primaries will get hot, the more imbalance the hotter......That will reduce life of the OT for sure if so......
- Creeping short inside the PT, this ain't good at all.....
- Shorted laminations on the PT (if anybody has cleaned the rust off with a file? Don't do that)
- if after all of this you can't find the source let me know, we could go deeper.......

Good luck!!

pman · 09-17-2006, 09:59 PM

Posted: Sun Sep 17, 2006 6:02 am Post subject:

--------------------------------------------------------------------------------
Thank you for the information. Most of what you said goes beyond my technical experience. It will go to the tech. I have been using this amp for the last 4 months after I bought it and had it retubed and serviced. It has never failed me. This is one of the best sounding amps I have ever used. Who ever modded it made is sound like a JCM 800 on steroids. I just know that my other marshall have never gotten this hot before.

I am thinking of sending it to plexi palace (mohave amps.) unless I can find a guru in phx.

Is it ok to touch the PT while the amp is on? I know these have a huge current running through them.

superleadfixer · 09-18-2006, 12:54 AM

You can touch the PT from outside in normal conditions, yes, BUT don't get burn if you think it's so very "hot" etc.... In a "normal situation" the PT will get very hot no matter what after the amp has been played for a few hrs at a gig fully dimmed, in that case you still could touch it but just a little without getting burned, well in most cases. Use your own judgement has you seems to have some experience with amps, and if you feel there is something a little out of the "normality" get this amp checked by a good tech. It might be just ok after all, hopefully!!

Give it some air, remove the back panel, use a fan in the meantime, BUT avoid using it till your are sure if possible, etc...

I know excellent Super Lead tech in the USA, those guys at Mojave are ok also but ain't cheap, try to ask for a quote first...

The very best place for having maintenance on your old MArshall(s) is at Metroamp in Michigan, George is the guy for old Marshalls.

I could do it also if you like (can I say that here already?)........

***Guv'nor*** · 09-18-2006, 03:27 AM

Quote:

Originally Posted by superleadfixer

I could do it also if you like (can I say that here already?)........

Please, do it. No problem at all.

I'd send my amp right to you.

superleadfixer · 09-18-2006, 09:02 AM

Quote:

Originally Posted by Guv'nor

Quote:

Originally Posted by superleadfixer

I could do it also if you like (can I say that here already?)........

Please, do it. No problem at all.

I'd send my amp right to you.

Very nice of you Guv'nor, thanks you so much, would be happy to help out anyone around here on mods, repairs, full amps replica builds, etc.. 8)

The white Super Lead on my Avatar is not an actual real Marshall, it is a replica.....btw

pman · 09-21-2006, 10:49 PM

Thank you for your information. I found a marshall guy in Phx who took it in to his shop. I do appreciate the information. I wish that I was more technically inclined about amps, but that is way beyond my scope. It turned out that the amp was biased incorrectly. Do you make amps? Like a small 5watt for home and studio.? I want something more friendly for the neighbors?

thanks

Pete

superleadfixer · 09-21-2006, 11:07 PM

I do build/repair/mod amps yes, mainly every Super Lead type you can imagine, you choose the one (era) you prefer, like those 12series ones a la Van Halen, or else.....

JTM45/50/100 also (kt66), 1987, etc...

For the 5w amp I could manage but it would be from scratch as I don't make those.....

As for your Bias did you loose tone? Heat would come from an overbias amp (a lot) or "very" unmatched tubes....

QUICK NOTE ON MATCHED TUBES: Specialy with el34 tubes a little mismatch is better up to 10ma per side. THat will increase your even order harmonics and make the amp sounds more colorfull, the magic even comes from a properly mismatch power section AND a unbalance driver tube (V3)...... All of that will increase your EOH, not the odd order harmonics (those are the bad ones, harsh and unpleasant to the ears..)

pman · 09-22-2006, 03:07 PM

I have been very happy with my marshalls. IS there a major tone difference btwn the PTP and PCB. I am just wondering if it is worth getting a hand wired amp. I recently bought and sold a 76 50W 2x12 non-master volume. I thought it sounded like shit compared my other earlier models. I was told in 76 Marshall started cutting corners with parts. Both channels sounded more like a bassman Vs. 1 bright 1 Low. What I really would like is a Fender Vibrolux Custom w/1 channel, no trem and no reverb. I think those are one of the greatest amps for the money.

superleadfixer · 09-22-2006, 11:24 PM

Yes they are differences. First a PTP circuit board is much stronger/solid BUT the biggest difference is the total capacitance from a PTP board versus a PCB board, with all those big turrets you have on PTPs you get completely different capacitance values at the end of the line giving your amp a different feel in a better way usualy. Also they look better and easier to mod/repair/etc...So yes it is better to have a PTP board instead of a PCB.......

I do board swaps (ex. specially for those SLPs reissues...)

Parts were still good up till the early to mid 80's (Philips Mustard, etc..) ususaly...After that is goes down real fast..........trannies, caps, tubes, etc...

zeusecho · 11-03-2008, 03:22 PM

Quote:

Originally Posted by superleadfixer;

[u

QUICK NOTE ON MATCHED TUBES[/u]: Specialy with el34 tubes a little mismatch is better up to 10ma per side. THat will increase your even order harmonics and make the amp sounds more colorfull, the magic even comes from a properly mismatch power section AND a unbalance driver tube (V3)...... All of that will increase your EOH, not the odd order harmonics (those are the bad ones, harsh and unpleasant to the ears..)

Hi Superleadfixer...

So for a DSL50 with only two EL34s do they need to be mismatched by design or can you intentionally mismatch with the bias adjustment?

Thanks.

09-15-2006, 10:49 PM	#1 (permalink)
pman Junior Member Join Date: Sep 2006 Posts: 7	very hot 74 modded superlead i recently bought a modded 74 superlead and it seems to be running maybe too hot. What is too hot though? I have an unmodded 74 50w that gets no where near as hot. The 100w has been modded by a guy named dale who used the presence as the MV and has vol 1 and vol 2 as separate gain channels. the amp has been retubed and biased and given a clean bill of health by my tech. It sounds amazing and never has given me any indication of failure. The plates on the power tubes do not turn red. I can only turn the MV to btwn 1-2 for most gig settings, or it's just too loud. I just want to make sure that this is not a transformer heading for failure.

09-16-2006, 12:27 AM	#2 (permalink)
superleadfixer Senior Member Join Date: Sep 2006 Location: CANADA Posts: 99	Are you saying the amp gets really hot? Where? Can you touch the transformers without getting hurt? How long does it takes to get that "hot"? Are the trannies base touching the chassis flush? Are you using an Attenuator? Is the amp fully dimed all the time? __________________ I\'ll mod your SLP (or anyother...) Marshall to REAL plexi specifications/with real replica trannies/etc... http://myspace-332.vo.llnwd.net/0145...52020332_l.jpg

09-16-2006, 07:09 PM	#3 (permalink)
pman Junior Member Join Date: Sep 2006 Posts: 7	hot amp I AM NOT USING AN ATTENUATOR. IT DOES NOT MATTER IF THE VOLUME (GAIN) CHANNELS ARE AT 1 or 10 the amp gets hot. i have notices other modded amps have fans installed.

09-17-2006, 02:02 AM	#6 (permalink)
superleadfixer Senior Member Join Date: Sep 2006 Location: CANADA Posts: 99	Heat will be radiated/comming from the transformers for the most of it and a little from the power tubes. If you can fry an egg on top of the PT, then it's too much If it is really hot like you say, it doesn't look good, I would get this amp check for: - Huge leakage current of the filter caps - Drifting output tubes (Check voltage drop across screen Resistors for less than 7V at idle!) & or check your dc imbalance mismatched, you shouldn't be more then 10/15ma per side or your OT primaries will get hot, the more imbalance the hotter......That will reduce life of the OT for sure if so...... - Creeping short inside the PT, this ain't good at all..... - Shorted laminations on the PT (if anybody has cleaned the rust off with a file? Don't do that) - if after all of this you can't find the source let me know, we could go deeper....... Good luck!! __________________ I\'ll mod your SLP (or anyother...) Marshall to REAL plexi specifications/with real replica trannies/etc... http://myspace-332.vo.llnwd.net/0145...52020332_l.jpg

09-18-2006, 12:54 AM	#8 (permalink)
superleadfixer Senior Member Join Date: Sep 2006 Location: CANADA Posts: 99	You can touch the PT from outside in normal conditions, yes, BUT don't get burn if you think it's so very "hot" etc.... In a "normal situation" the PT will get very hot no matter what after the amp has been played for a few hrs at a gig fully dimmed, in that case you still could touch it but just a little without getting burned, well in most cases. Use your own judgement has you seems to have some experience with amps, and if you feel there is something a little out of the "normality" get this amp checked by a good tech. It might be just ok after all, hopefully!! Give it some air, remove the back panel, use a fan in the meantime, BUT avoid using it till your are sure if possible, etc... I know excellent Super Lead tech in the USA, those guys at Mojave are ok also but ain't cheap, try to ask for a quote first... The very best place for having maintenance on your old MArshall(s) is at Metroamp in Michigan, George is the guy for old Marshalls. I could do it also if you like (can I say that here already?)........ __________________ I\'ll mod your SLP (or anyother...) Marshall to REAL plexi specifications/with real replica trannies/etc... http://myspace-332.vo.llnwd.net/0145...52020332_l.jpg

09-16-2006, 07:18 PM	#4 (permalink)
*Guv'nor* Moderator Join Date: Aug 2006 Posts: 243	I think you're mixing things pman. I am sure if you reply superleadfixer's questions you'll get the point faster and probably you'll find a way to solve your problem.

09-16-2006, 09:07 PM	#5 (permalink)
pman Junior Member Join Date: Sep 2006 Posts: 7	the amp gets hot on top. i touch the back where the speaker ports are at and they are not hot. no power brake. the mv (presence) is at about 1-3. the gains are at at 50-75%. i have not touched the tranny's. at the top buy the grill you can feel the heat from about 2 feet away. the grill on top is hot. i can smell the amp as well. I hope this helps

09-17-2006, 09:59 PM	#7 (permalink)
pman Junior Member Join Date: Sep 2006 Posts: 7	Posted: Sun Sep 17, 2006 6:02 am Post subject: -------------------------------------------------------------------------------- Thank you for the information. Most of what you said goes beyond my technical experience. It will go to the tech. I have been using this amp for the last 4 months after I bought it and had it retubed and serviced. It has never failed me. This is one of the best sounding amps I have ever used. Who ever modded it made is sound like a JCM 800 on steroids. I just know that my other marshall have never gotten this hot before. I am thinking of sending it to plexi palace (mohave amps.) unless I can find a guru in phx. Is it ok to touch the PT while the amp is on? I know these have a huge current running through them.

09-21-2006, 10:49 PM	#11 (permalink)
pman Junior Member Join Date: Sep 2006 Posts: 7	Thank you. Thank you for your information. I found a marshall guy in Phx who took it in to his shop. I do appreciate the information. I wish that I was more technically inclined about amps, but that is way beyond my scope. It turned out that the amp was biased incorrectly. Do you make amps? Like a small 5watt for home and studio.? I want something more friendly for the neighbors? thanks Pete

09-21-2006, 11:07 PM	#12 (permalink)
superleadfixer Senior Member Join Date: Sep 2006 Location: CANADA Posts: 99	I do build/repair/mod amps yes, mainly every Super Lead type you can imagine, you choose the one (era) you prefer, like those 12series ones a la Van Halen, or else..... JTM45/50/100 also (kt66), 1987, etc... For the 5w amp I could manage but it would be from scratch as I don't make those..... As for your Bias did you loose tone? Heat would come from an overbias amp (a lot) or "very" unmatched tubes.... QUICK NOTE ON MATCHED TUBES: Specialy with el34 tubes a little mismatch is better up to 10ma per side. THat will increase your even order harmonics and make the amp sounds more colorfull, the magic even comes from a properly mismatch power section AND a unbalance driver tube (V3)...... All of that will increase your EOH, not the odd order harmonics (those are the bad ones, harsh and unpleasant to the ears..) __________________ I\'ll mod your SLP (or anyother...) Marshall to REAL plexi specifications/with real replica trannies/etc... http://myspace-332.vo.llnwd.net/0145...52020332_l.jpg

09-22-2006, 03:07 PM	#13 (permalink)
pman Junior Member Join Date: Sep 2006 Posts: 7	custom made amp I have been very happy with my marshalls. IS there a major tone difference btwn the PTP and PCB. I am just wondering if it is worth getting a hand wired amp. I recently bought and sold a 76 50W 2x12 non-master volume. I thought it sounded like shit compared my other earlier models. I was told in 76 Marshall started cutting corners with parts. Both channels sounded more like a bassman Vs. 1 bright 1 Low. What I really would like is a Fender Vibrolux Custom w/1 channel, no trem and no reverb. I think those are one of the greatest amps for the money.

09-22-2006, 11:24 PM	#14 (permalink)
superleadfixer Senior Member Join Date: Sep 2006 Location: CANADA Posts: 99	Yes they are differences. First a PTP circuit board is much stronger/solid BUT the biggest difference is the total capacitance from a PTP board versus a PCB board, with all those big turrets you have on PTPs you get completely different capacitance values at the end of the line giving your amp a different feel in a better way usualy. Also they look better and easier to mod/repair/etc...So yes it is better to have a PTP board instead of a PCB....... I do board swaps (ex. specially for those SLPs reissues...) Parts were still good up till the early to mid 80's (Philips Mustard, etc..) ususaly...After that is goes down real fast..........trannies, caps, tubes, etc... __________________ I\'ll mod your SLP (or anyother...) Marshall to REAL plexi specifications/with real replica trannies/etc... http://myspace-332.vo.llnwd.net/0145...52020332_l.jpg

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