All pre amp tubes in Marshall suddenly not working!??

[wantsa58]

Went to play my DSL 201 today and when I plugged in... nothing happened. No sound what so ever, looked at the tubes and noticed that all three pre amp tubes where not working! The power tubes and phase inverter light up as usual. What does this mean? Could it be a fuse? All of the tubes are only 4 months old except the power tubes. When I turn it on there are no burning smells or odd sounds, just silence.

Any suggestions?

UPDATE: Just took out the old tubes and they are in great shape, no signs of over heating, and the pins are fine. The sockets are fine as well.

UPDATE 2: Just checked the fuses and they look fine to me. I assume that since the wire is still intact the fuse has not blown, no corrosion etc. I also replaced all three tubes and that did not work.

So confused.

[PINKBITS]

Originally Posted by wantsa58

Went to play my DSL 201 today and when I plugged in... nothing happened. No sound what so ever, looked at the tubes and noticed that all three pre amp tubes where not working! The power tubes and phase inverter light up as usual. What does this mean? Could it be a fuse? All of the tubes are only 4 months old except the power tubes. When I turn it on there are no burning smells or odd sounds, just silence.

Any suggestions?

UPDATE: Just took out the old tubes and they are in great shape, no signs of over heating, and the pins are fine. The sockets are fine as well.

Stuffed if I know, have you checked the fuse? I would have thought you would still get some sound from the power tubes at least

[wantsa58]

Originally Posted by PINKBITS

Stuffed if I know, have you checked the fuse? I would have thought you would still get some sound from the power tubes at least

Fuses seem fine to me, I can't get any sound at all. I have no clue as to what is going on. I mean I would at least expect a warning before this kind of thing happened. I've done just about all I know to do now..

[PINKBITS]

Originally Posted by wantsa58

Fuses seem fine to me, I can't get any sound at all. I have no clue as to what is going on. I mean I would at least expect a warning before this kind of thing happened. I've done just about all I know to do now..

Mate I hope someone much smarter than me can help you out. If not just take it a tech.

If you had some spare fuses or tubes I would certainly try putting them in anyway. Can't hurt. Certainly seems odd that it just stopped working with no pop, bang, smoke no nothing

I'm sorry mate, good luck.

[wantsa58]

Originally Posted by PINKBITS

Mate I hope someone much smarter than me can help you out. If not just take it a tech.

If you had some spare fuses or tubes I would certainly try putting them in anyway. Can't hurt. Certainly seems odd that it just stopped working with no pop, bang, smoke no nothing

I'm sorry mate, good luck.

Thanks man, hopefully someone will chime in. I really think the fuses are fine from the looks of it. I doubt it's the tubes unless power tubes can make the pre amp tubes do that.

[PINKBITS]

Originally Posted by wantsa58

Thanks man, hopefully someone will chime in. I really think the fuses are fine from the looks of it. I doubt it's the tubes unless power tubes can make the pre amp tubes do that.

Have you pulled out any of the preamp tubes and taken a look at the pins, maybe show something?

What I can't work out is that there is no sound at all. I would still expect sound even if all the preamp tubes shit themselves.

[knievel]

Wansta, If they are visibly not lighting up, then you're probably not getting power to the heaters. Its pretty easy to check if you have a volt meter.

[wantsa58]

Yeah the sockets and tubes look great. I don't have a voltmeter here at my apartment so I can't verify any current issues.

I'm probably going to have to bend over and take it to a tech. My reverb has never worked so maybe these will be easy fixes. With my luck the whole damned board will be toast.

[Last]

Seems like a silly question but I've done this before on an amp that I knew worked but suddenly stopped the next time I tried to turn it on.

It turned out that a GFC Switch in our Master Bathroom had tripped disabling the outlets in the Master Bedroom.

Have you tried a different outlet?

edit: just re-read your first post & you seem to be getting some power. Hmm... this is weird. Some fuses may look fine but actually be blown too bad you can't do a continuity test on the fuses.

[wantsa58]

Originally Posted by Last

Seems like a silly question but I've done this before on an amp that I knew worked but suddenly stopped the next time I tried to turn it on.

It turned out that a GFC Switch in our Master Bathroom had tripped disabling the outlets in the Master Bedroom.

Have you tried a different outlet?

Ha yeah I did, but if that where the case NOTHING would turn on. The power tubes, phase inverter, channel light, and power led still light up. In fact the amp itself still hums. I'm going to shoot the breeze with the local tech to see how much it would cost for him to look at it after my physics 2 final in the mourning. Yeah my life is that awesome.

[Blind Lemon]

You got another tube amp? Swap tubes, On some 12AX7s the heaters are hard to see if they're lit. The Tung Solskees(Russian Tung Sols) are that way, good tubes though. What do you have loaded. If the amp is making noise but no guitar noise I would check the input jack. What Marshall you got.


BL

[wantsa58]

Originally Posted by Blind Lemon

You got another tube amp? Swap tubes, On some 12AX7s the heaters are hard to see if they're lit. The Tung Solskees(Russian Tung Sols) are that way, good tubes though. What do you have loaded. If the amp is making noise but no guitar noise I would check the input jack. What Marshall you got.


BL

Tubes are fine, and swapping did nothing. The hum I was talking about is just the noise the amp makes when its on. It doesn't come through the speaker or anything. Another guy on a marshall forum said it could be the BR which supplies the heater voltage as a member here suggested. Does any one know how much this fix would cost?

[Blind Lemon]

I though you said the power tubes and PI were lit? If the bridge rectifier (BR) were bad you wouldn't see any FILS glowing........................... I bet you got a bad plate riz and a pre isn't conducting (he said after taking another long pull of his beer)

BL

[wantsa58]

Originally Posted by Blind Lemon

.......................... I bet you got a bad plate riz and a pre isn't conducting (he said after taking another long pull of his beer)

BL

I don't know what the BR looks like but couldn't one end of it be messed up causing only the pre amp tubes to not light up? Sorry all of this is over my head... I mean I know how to do general trouble shooting but anything inside is a complete mystery to me.

Thanks for you're help though maybe this will turn out to be a simple fix..

[b-squared]

I haven't seen this yet...you check the rectifier?

BB

[wantsa58]

Originally Posted by b-squared

I haven't seen this yet...you check the rectifier?

BB

Not liking the fact that no one has heard of this happening . I might get it to a tech tomorrow and have him look at it. It's just weird that there wasn't any warning for this. Worked fine this morning and then it just dies all of the sudden??

[mrpesca]

I have a DSL 401 and it won't make any sound sometimes due to a bad solder joint. Apparently it's pretty common with these amps. Do a google search for dsl 201 problems and you'll see others having problems too.

[wantsa58]

Originally Posted by mrpesca

I have a DSL 401 and it won't make any sound sometimes due to a bad solder joint. Apparently it's pretty common with these amps. Do a google search for dsl 201 problems and you'll see others having problems too.

Yeah I have heard of such things, I just don't know how my pre amp tubes could do this while the out put tubes are working fine??

[dondoucette]

Yep... gonna have to get the board out of the chassis and check the solder joints...SIGH... My money is you are going to find some cold solder joints on this amp.

Good luck.

Don

P.S. be safe and discharge the electrolytics first before you dig too deep or you may be in for a nasty shock.

[wantsa58]

Yeah I know those caps have A LOT of charge stored in them. I'm going to let a tech do it though. I have limited experience in this kind of thing sadly and only tinker with pedals and the like. I'm hoping that with time I will be able to do this kind of thing.

[Splattle101]

The power to your pre-amp valves is the 6.3 V line. I don't know about your Marshall, but I do know that in my Bassman the only things on that line are the filaments for the preamp valves and the on/off lamp. It comes directly from the power transformer.

You may be up for a bill. But it needs to go to a tech.

[wantsa58]

Yeah I'll go talk to the guy tommorow, if it's going to be expensive I'll have to wait and that's going to suck.

[wantsa58]

Talked to the tech today and he said that it sounds like something related to a fuse to him. He didn't think it was the BR or transformer since my other tubes where working fine. He's going to check it out tomorrow and if it's a major problem I'll have to send it off. Hopefully something simple happened.

[Big John]

The bridge rectifier on this amp has a tendency to get so hot that it actually affects the solder joints. You are not the only 201 owner with this problem. If the rectifiers aren't fried, just re-touch the recitifier diodes' 4 solder joints (big circle) and re-touch the solder joints for the filaments on V3 (small circle) because the next tubes in line are the V2 & V1.



A little advice with this amp: either mount a heatsink right on top the rectifier diodes or run a fan into the back of the amp if you plan on using it for extended periods.

[Big John]

Don't forget to check/set the power tube bias while you're in there.

[wantsa58]

Thanks for the pics Big John. So I checked the fuses with an ohm meter and believe they are indeed good. I set the meter to the lowest ohm rating and found that the mains fuse read at 0.5 ohm and the HT fuse read at 1.7 ohm. These readings mean they are fine correct?

[wantsa58]

I actually found a site that details what to check for on my amp when this happens. It has lots of pics so I am going to disassemble my amp tomorrow. I know that I need to "drain the caps" and don't see any harm in me taking a look see. With my limited funds due to my 4 k tuition I can't take it to a tech any time soon. I'm also hunting down an old heat sink to attach to the bridge rectifier.

I just have one question... How exactly do you drain the caps? The tech around here does not look at amps so I would have to send it off to even get it checked. If it's simple I'll just look at it my self, touch up 5 solder joints and hope for the best.

EDIT : Just talked to a friend and he said to just get some pliers with a rubber handle and use a resistor that is bent to touch the leads and hold it there for a while. After about 30 seconds he thinks it would be safe to work on. He also said that all the caps should be in parallel so draining one will drain the others. Is this right?

[Liam]

I normally drain the filter caps by connecting pin 1 of the first preamp tube socket to ground with a wire with croc clips at both ends. Pin one is the first one clockwise after the gap looking from the wire side of the tube socket.

That way you drain the caps slowly, as you are draining them through the plate resistor on V1. Check the caps with a meter after a couple of minutes, if they are down to less than 5 volts you are safe to start work on the amp.

Remember to take the wire off again before you fire the amp back up. Doesn't kill anything, but you get no signal out of the amp.

Hope that helps

Liam

(Draining the caps directly with rubber handled pliers sounds a bit dangerous to me. Try to stay clear of them until you have drained them. Work with one hand in your back pocket at all times, so if you do get a shock it doesn't go across your chest and stop your heart. Bic biro tubes or plastic chopsticks are the best things to touch stuff with until you are sure that ALL lethal voltages are out of the amp. Pin 1 of V1 gives you some protection as there is plenty of resistance between it and the filter caps. Tube amps have killed people, and will no doubt do so again. Don't be that person.)

[wantsa58]

Thanks, but I meant draining the caps with a resistor HELD by rubber handed pliers lol. My physics teacher that would be a quick and easy way. He also gave me a large resistor that would allow the current to slowly leak off. Or would that still be a bad way? I got that method off of a Fender site. He also said that if the current was low ( don't have the number he gave to me right now ) to not worry about it.

Kind of curious to see how much current is in the caps, several people on other sites found that their caps had very little current in them.

I plan on taking it apart tonight and getting some pics.

[Liam]

There's no current in the caps, just voltage. Varies, some will hang onto a few hundred volts when they've been turned off for days. Others leak down in 1/2 an hour.