Marshall 1974x - transformer failure going on?

mary04 · May 31, 2011

Got my new used 2004 Marshall 1974x in the house yesterday, and I couldn`t wait to try it out. What a big disapointment it was. The amp sounded thin and buzzy, completly lacking mids and bottom. I swapped out all the tubes including the EZ81 rectifiertube. Now I have JJ all over. Another try, and this time I could somehow understand some of the excitement over this amp. But I still found it very low on volum, and not as great soundings I had expected. Everybody talking about how loud this amp is, but mine isn`t like that. I can easily have an normal conversation sitting next to it with volum on 10 even after swapping the tubes.

After 10-15 minutes of playing (volum set on 10 off course), the amp started to weaken out. The sound became thin and buzzy, and I can only describe it as horrible. I have off course heard about the tranny problems with this amplifier, and since mine is a 2004 it could easily be one of the bad ones. Anyone recognize the symptoms on my amp? Can it be the trannys once again? What else could it be?

If it is the trannys - any recommadations on replacement? Mercury Magnetics? I reckon Marshall don`t offer me a warranty repair since I`m not the original buyer, and its been seven years since production time.

Any tips and info will be much appreciated!

Best regards Mary

LowWatt · May 31, 2011

I'm no tech, but I've blown OTs before and that sounds like a blown Output Transformer.

phsyconoodler · May 31, 2011

Jumping the gun a bit,eh? You may be right but the amp needs to be checked over first.there may be something else causing your woes,like a burned screen resistor or something like that.
the voltages need to be checked and if you are not comfortable inside tube amps,you need a tech.
What about the speaker?There are a few things to consider and check before condemning the transformers.And when I say transformers,it could be either the power or the output if it ends up being that issue.

LowWatt · May 31, 2011

phsyconoodler said:
Jumping the gun a bit,eh? You may be right but the amp needs to be checked over first.there may be something else causing your woes,like a burned screen resistor or something like that.
the voltages need to be checked and if you are not comfortable inside tube amps,you need a tech.
What about the speaker?There are a few things to consider and check before condemning the transformers.And when I say transformers,it could be either the power or the output if it ends up being that issue.

I just play them ...this man builds and repairs them. That sounds like some good advice. Still, budget for it. The early versions of that model had significant OT blowing issues.

mary04 · May 31, 2011

Hmm, thanks guys! But the symptoms can be caused by a bad tranny then?

phsyconoodler · May 31, 2011

Yes indeed.I'm just saying get other things checked first.
You may very well be right but the don't just throw money at it without knowing.
I suggest Heyboer transformers from Graydon Stuckey or Trinity amps.Trinity has a killer output transformer that makes the original sound lame,made for them by Heyboer.

mary04 · May 31, 2011

phsyconoodler said:
I suggest Heyboer transformers from Graydon Stuckey or Trinity amps.Trinity has a killer output transformer that makes the original sound lame,made for them by Heyboer.

Thanx! I`ll take it to a tech first thing tomorrow, and if it is the trannys I`ll contact Trinity amps. Mercury Magnetics are fine too, but maybe the Trinity Heyboer are just as good for less money.

phsyconoodler · May 31, 2011

Quote:"but maybe the Trinity Heyboer are just as good for less money."

Actually 'better' for less money.

rockinlespaul · May 31, 2011

I had Dean Zink put in the stock Marshall upgrade replacement and have never looked back. Actually, that was his recommendation.

donnyjaguar · May 31, 2011

Hmmm... are you sure the speaker isn't whipped? I can see a partially melted down voice coil having the same symptoms.

mary04 · May 31, 2011

donnyjaguar said:
Hmmm... are you sure the speaker isn't whipped? I can see a partially melted down voice coil having the same symptoms.

Very sure, because I hooked up a 2x12 65 amps cab just for the test, and the same miserable thing happend all over again.

mary04 · Jun 7, 2011

Well, the tech has reported back that my 1974x has a malfunctional output transformer. I`ve already been in touch with Stephen at Trinity amps, but sadly their out of trannys for several weeks. So I found a German made tranny that costs about $190 that I know nothing about. I could of course buy a set of Mercury Magnetics, but have decided not to spend that kind of money at the moment.

Do I have to replace both the power and output tranny, or is it ok just to swap the output one? And which have the greatest impact on the sound - the power or output tranny?

phsyconoodler · Jun 7, 2011

The output has the most to do with the sound.Try GDS amps.They have Heyboer transformers and were the original guys who reverse engineered the first reproduction 18 watt transformers.

RussB · Jun 7, 2011

Doug Hoffman has Heyboer 18 watt OT's in stock.

http://www.hoffmanamps.com/MyStore/...late&thispage=Transformers&ORDER_ID=197586333

twangbanger · Jun 7, 2011

phsyconoodler said:
The output has the most to do with the sound.Try GDS amps.They have Heyboer transformers and were the original guys who reverse engineered the first reproduction 18 watt transformers.

gldtp99 · Jun 7, 2011

RussB said:
Doug Hoffman has Heyboer 18 watt OT's in stock.

http://www.hoffmanamps.com/MyStore/...late&thispage=Transformers&ORDER_ID=197586333

I've used these Heyboer OT's from Hoffman with no problems--- great sound and very fast shipping !!

vibroluxious · Jun 8, 2011

I have built several 18 watt style amps with GDS output transformers. I can't recommend them enough.

ked · Jun 8, 2011

I've also used GDS transformers in 3 builds and they are very good transformers. The last time I bought an OT they were $69.00 each.

Ken

soundguruman · Jun 9, 2011

mary04 said:
Got my new used 2004 Marshall 1974x in the house yesterday, and I couldn`t wait to try it out. What a big disapointment it was. The amp sounded thin and buzzy, completly lacking mids and bottom. I swapped out all the tubes including the EZ81 rectifiertube. Now I have JJ all over. Another try, and this time I could somehow understand some of the excitement over this amp. But I still found it very low on volum, and not as great soundings I had expected. Everybody talking about how loud this amp is, but mine isn`t like that. I can easily have an normal conversation sitting next to it with volum on 10 even after swapping the tubes.

After 10-15 minutes of playing (volum set on 10 off course), the amp started to weaken out. The sound became thin and buzzy, and I can only describe it as horrible. I have off course heard about the tranny problems with this amplifier, and since mine is a 2004 it could easily be one of the bad ones. Anyone recognize the symptoms on my amp? Can it be the trannys once again? What else could it be?

If it is the trannys - any recommadations on replacement? Mercury Magnetics? I reckon Marshall don`t offer me a warranty repair since I`m not the original buyer, and its been seven years since production time.

Any tips and info will be much appreciated!

Best regards Mary

Probably not the OT. Probably an arcing tube socket, or the bias has gone out of adjustment, or failed completely.
In which case the tube socket might need to be replaced.
Other than that, when it gets fixed and the bias is adjusted correctly, it should work just fine.
Changing the output tubes without adjusting the bias is going to lead to problems. You should not do that.

Then, change the preamp tubes to Chinese (Sino) 12AX7 which is also sold by groove tubes as 12AX7CH. These preamp tubes will give the amp an amazing kick in the pants. The gain will be much higher, and it will then sound like a Marshall is supposed to sound. This will make the amp crunchy and crispy.
Most do not realize what a difference the right preamp tubes will make, it's big.
There's also a couple of tweaks for this amp, but don't do them until the amp is all working correctly first.
In any case you need a tech, this is not a do it yourself repair.

RussB · Jun 9, 2011

soundguruman said:
Probably not the OT. Probably an arcing tube socket, or the bias has gone out of adjustment, or failed completely.
In which case the tube socket might need to be replaced.
Other than that, when it gets fixed and the bias is adjusted correctly, it should work just fine.
Changing the output tubes without adjusting the bias is going to lead to problems. You should not do that.

Then, change the preamp tubes to Chinese (Sino) 12AX7 which is also sold by groove tubes as 12AX7CH. These preamp tubes will give the amp an amazing kick in the pants. The gain will be much higher, and it will then sound like a Marshall is supposed to sound. This will make the amp crunchy and crispy.
Most do not realize what a difference the right preamp tubes will make, it's big.
There's also a couple of tweaks for this amp, but don't do them until the amp is all working correctly first.
In any case you need a tech, this is not a do it yourself repair.

That amp is cathode biased

Marshall 1974x - transformer failure going on?

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