My 2205 has fallen, whos got a crutch!?

Deadbolt

Deadbolt

New member
Hey guys,
Its been sometime since i've posted here. Been pretty busy with other things but recently my marshall is out of commision and i thought i may be bale to get some insight here first as to what i should do.

So, its a 1989 marshall jcm 800 2205(50 watta dual channel) It has some fairly fresh jj's preamp tubes all the way across. The power tubes have never been changed since i bought the amp.in 2003 the whole IC for the overdrive channel was replaced by an amptech an this thing roard finally (picked it up cheap because somebody didn't take care of it)that was sometime ago now.
So last staurday we had a gig i moved the amp from where my band practices to the car went to the show and played all was well. back in the car brought it back to where we jam. on tuesday we jammed again at our usual spot. The amp was working fine just like the soldier that it has always been.
So yesterday we head out and i go to turn the amp on so she can warm up while i unpack my case get the axe ready, but no power the switch won't light up and the amp is not turning on. i tried a different plug and a different power cable. nothing different cab guitar cables still nothing.
SO what could this be? will a bad power tube cause this to happen? transformer?
thanx in advance i'm probably ging to geta hold of the tech who repaired it to have a look again
Thanx guys
 
Re: My 2205 has fallen, whos got a crutch!?

I had the same thing happen to my 1985 2205 ... turned out to be a leaky power cap.
 
Re: My 2205 has fallen, whos got a crutch!?

The only thing I can think of is a fuse maybe?

A friend of mine had a mesa single rec head that died on him, turned out it was only a fuse...

Other than that I'm no help :blackeye:
 
Re: My 2205 has fallen, whos got a crutch!?

If it's not lighting up at all I'd check the fuses first. If it lights up and stays running you are good to go but chances are you'll pop another fuse. I'm guessing that you have a bad power amp tube and if they are the originals and you have 15 years on them they are overdue to be changed. While it is possible to cook a tranny and filter caps do go bad over time the vast majority of problems with tube amps are caused by bad tubes.

If you think the amp was hot with the old tubes, I think you are in for a pleasant suprise.
 
Re: My 2205 has fallen, whos got a crutch!?

Thanx guys. Robert. i don't think the tubes are actual originals but definatly have some life on them. fuses are still a-ok. I am going to have to pick up some new power tubes so i can take it somewhere to be biased and see how that goes.

It was pretty surprising just because when it was turned off everything was working fine. Come back and it wouldn't do anything. there was no warning really i guess just nothin.
Thanx again keep them replys comin!
 
Re: My 2205 has fallen, whos got a crutch!?

I would hold off on buying tubes until you get a proper diagnosis of the problem. I'd also test the fuses with an ohm meter because sometimes fuses can fail and not show visual signs of failure.

There are often two fuses in tube amps. The supply fuse is usually rated in the area of 1 amp and the fuse that protects the mains voltage is 3-4 amps. Since you aren't lighting up at all I'd have to suspect something in the power supply. In some amps if the mains fuse blows (larger value fuse) you won't get sound from the amp but it will still light up.

You may need tubes or you may not. No use spending the money on new power tubes if it is a power supply issue. Fortunately for you though it's probably not a tranny failure. Those usually stink to high heaven when they burn up. Filter caps and other smaller components usually aren't bank breaking to have repaired.

At least thats been my experience. Remember though I'm not an amp tech, I've just blown up a couple amps.......
 
Re: My 2205 has fallen, whos got a crutch!?

I have a 900 combo, and had a similar problem. It turned out to be corrosion on the plugs in my effects loop!
 
Re: My 2205 has fallen, whos got a crutch!?

Bludave, when if first picked up the amp the clean channel was good, but with overdrive it would crackle and just crap out on me. took it to a tech and he told me IC for the overdrive channel was fried, he found a few cold solders and the effects loop was slightly corroding. everything that was problematic he knew of at the time was replaced. (for free because he mis-diagnosed the first time but a great guy !)

Robert, i will definatly be patient but can be hard and frustrating with many gigs coming up. I'm going to try some other fuses. when you mentioned it before i checked them over and they "looked" good but i will try some new ones and see if it helps.

Edit: roberti just checked the fuses again for there ratings. One has marked 250v\2.5a The other is only marked 250v. so i assume there both 250 volts at 2.5 amps. Are these correct? it was definatly working fine on them before thanx
 
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Re: My 2205 has fallen, whos got a crutch!?

Never assume a fuse rating, you need to be sure.

It should be posted somewhere on the amp chassis, but I'll do a little research and let you know what i find out.
 
Re: My 2205 has fallen, whos got a crutch!?

as far as the power tubes go, if the amp isn't lighting up, I seriously doubt it's the tubes, but if you have a lot of gigs coming up, you need another set to carry with you and a preamp or two for that "just in case" emergency that will likely pop up at some point.

thought i'd throw my 2 cents in.
 
Re: My 2205 has fallen, whos got a crutch!?

tube or solid state rectifier? if it's a tube rect, that might be it. no rectifier, no turning ac volts into dc volts, no lights, no nothing.
 
Re: My 2205 has fallen, whos got a crutch!?

Well, I do believe I shall chime in on this one!!!

Deadbolt, I'm 99% sure the problem is as simple as the power switch....they are notorious for failing after awhile, and since they switch both sides of the PT primary, (to allow for 220/240v use...even though you're probably running 120v)...doubly so

The entire 800 series is reasonably bulletproof, and if the heaters aren't even coming on, this would be an indication that the PT isn't even getting AC...Drake tranny's rarely fail....

It is SS rectifier, just so you know

FWIW....

Jeff Seal
 
Re: My 2205 has fallen, whos got a crutch!?

Robert- There is a sticker on the rear of the amp above where the fuses go. it states exactly what you said in your post i never knew it was fuse ratings. the ones i posted were straight from the fuses themself.

Scott f- i thought forsure that since none of the tubes were lighting it would have nothing to do with them. But i was unsure wheter a blown power tube would cause this. thanx for your post and it is a ss rectifier like jeff has already stated.

Jeff- I remember your name from the marshall forum and mildy from around here but good to see your still around because i remember your posts being always helpful.
Like i said this amp has been a soldier for me and you stating it was bullet proof brought a smile to my face knowing i found "MY" so called(i know not everybody elses) diamond in the rough.
My question would be how could i diagnose the switch properly? or how could i forsure prove it was the switch? obnviously i can change it but i would have to take it to a tech and time is money. Thanx again guys as always helpful as ever.
 
Re: My 2205 has fallen, whos got a crutch!?

Simple, my friend...... looking at the power switch, you should have the following........... five terminal's with the following color codes.... the top two (with the chassis upside down) should be brown and blue side by side, then yellow and orange, and then a lonely black wire on the bottom right side...for the neon bulb.

UNPLUG AMP and then....(sorry, standard disclaimer..)

Simply jumper (connect together) the brown and yellow together and separately the blue and orange together.....be careful and the black wire should not be jumpered to anything......

Let us know.....

Jeff Seal
 
Re: My 2205 has fallen, whos got a crutch!?

I actually first thought the power point you were using mighthave just broken down ;)
 
Re: My 2205 has fallen, whos got a crutch!?

Hopefully Deadbolt will report back and is not now a deadbolt from futzing inside a tube amp!
 
Re: My 2205 has fallen, whos got a crutch!?

Thanx jeff i willl take a peak right now, and scott your post made me laugh. just so you know i am aware of the danger that may lurk inside but i feel comfortable enough i will probably check it out thanx again. i will let you guys know what happens!

edit:well turns out the culprit was the switch as stated above. i jumped the wires from the switch leaving the black. plugged the amp in and the tubes were starting to glow. i appreciate all the help guys. now i just need to grab a switch somewhere.
glad to see me still kickin scott? :)
 
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Re: My 2205 has fallen, whos got a crutch!?

NIce, I'm trying to remember the factory direct place you can buy them from. Ebay might be of some help.
 
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