OnlyTwin

Just got this amp used. I've played with it for a week or so, maybe less, and I'm having this problem with it now.

Sometimes when I'm playing on either of the two overdrive channels, I get a sudden decrease in gain. Just out of the blue. As if I've just rolled back the volume knob on my guitar considerably. It's not the guitar; I switch to the clean channel and it seems to be unaffected in volume/gain.

No idea what it could be. Any help with this is greatly appreciated.

R45VT

What year is it?

Could be a tube, when was the last time you changed them? Any time gain drops it sounds like a preamp tube.

Also keep in mind the early ones had too much heat from the tues cooking the rectifier diodes. There were a few modes to fix it.

OnlyTwin

I'm not sure what year it is, how do you check? And I've never changed them, bought it off someone used about a week ago. But from what I understand, the amp has rarely been used and they are the original tubes.

R45VT

Preamp tubes are easy to replace. The amp does have to be biased. Try new tubes first. If you get power tubes a tech would need to bias, and they could easily see if the diodes/PCB area was over heating.

The cheap way first would be to replace your preamp tubes as you can do that yourself.

And I don't know how to check the year, I'm sure it has to do with the serial number. Don't worry about that yet. Preamp tubes first.

Cathbard

The DSL401 is the only EL84 amp I can think of that isn't cathode biased. They are pretty easy to bias though which is good because who the hell owns a 9 pin bias probe?

Anyway, here's how. If that document doesn't tell you all you need to know to bias the amp then you probably shouldn't be doing it yourself.

I must say this 100 times a day but retube the whole amp with JJ's. JJ's are good in most amps but in Marshalls they are up there with most NOS tubes in terms of sound quality. I build EL84 Marshalls and have a reasonable collection of tubes but this is my day to day drawer in my workbench.


In a DSL401, any DSL for that matter, it's JJ or gtfo. The ones you want for that are normal JJ ECC83S and a matched set of their EL84's.

__________________
Gilchrist custom guitar
Yamaha SBG500
Telecaster
Ibanez Iceman
Roland GP-8
Quadraverb
Abbey Harmonic II
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Marshall 1960A

Cathbard Amplification

nickdohle

Hes not kidding. I swapped mine out for JJs via his suggestion. I dont think Ill ever go to another brand for this amp again.

OnlyTwin

What exactly do you need to know to install/bias them? Because I'm guessing that if it requires knowing electronics and circuitry, I shouldn't be doing it.

And an update, it appears that the volume has also experienced a drop. I'm hoping I'm wrong about that.

Cathbard

Did you look at the document I posted up there? ^^

If that document doesn't make sense to you then yes, take it to somebody else to do it for you.

__________________
Gilchrist custom guitar
Yamaha SBG500
Telecaster
Ibanez Iceman
Roland GP-8
Quadraverb
Abbey Harmonic II
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Marshall 1960A

Cathbard Amplification

OnlyTwin

Yeah, I don't know electronics. And if there is also a drop in volume, does this also mean power tubes need replacing?

Robbgnarly

since it is used, replace them all and keep the old tubes for spares.

__________________
2002 PRS CE22
197? Sanox Sound Creator LP clone (GFS Fat Pat)
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate

Cathbard

That is one symptom, yes. But that can also be dirty jacks, faulty pots, dodgey cables and any number of other things.
Sounds to me like you need to take the thing to a tech.

__________________
Gilchrist custom guitar
Yamaha SBG500
Telecaster
Ibanez Iceman
Roland GP-8
Quadraverb
Abbey Harmonic II
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Marshall 1960A

Cathbard Amplification

OnlyTwin

Okay, if I go to a shop to get all the tubes replaced/biased/whatever, how much am I looking at spending here (including cost of tubes)? Ballpark it for me please.

Robbgnarly

where do you live?

__________________
2002 PRS CE22
197? Sanox Sound Creator LP clone (GFS Fat Pat)
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate

Robbgnarly

If your in the US you'll be looking at ~$100 for all the tubes and $50+ to have them changed and biased. The extra cleaning for the pots and sockets will ad a few more dollars to the price.

__________________
2002 PRS CE22
197? Sanox Sound Creator LP clone (GFS Fat Pat)
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate

OnlyTwin

Stockton, California.

Robbgnarly

a complete set of JJ's from Eurotubes is $89-$132 for tubes depending on what you want tone wise.

__________________
2002 PRS CE22
197? Sanox Sound Creator LP clone (GFS Fat Pat)
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate

OnlyTwin

Ahh okay, not bad. To cut back costs a bit, should I just replace the preamp tubes myself and leave the rest to a tech? Or should I just leave it all to a tech so I can get everything cleaned as well?

Cathbard

Cleaning a tube socket is a simple matter of spraying some contact cleaner on the tube pins and then working the tube in and out of the socket a few times.

__________________
Gilchrist custom guitar
Yamaha SBG500
Telecaster
Ibanez Iceman
Roland GP-8
Quadraverb
Abbey Harmonic II
Marshall JTM45 clone
Marshall JCM900 4102 (modded)
Marshall 18W clone
Fender 5F1 Champ clone
Marshall 1960A

Cathbard Amplification

OnlyTwin

Kinky. So might as well do preamp tubes myself, ehh?