Bare Knuckle Pickups Forum
Forum Ringside => Guitars, Amps and Effects => Topic started by: bucketshred on December 12, 2010, 09:38:34 PM
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Sorry, just venting, I only found out when I had an audition yesterday :(
Luckily I got through though :D
Paddy
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Symptoms?
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Oh that's bad. Bad tubes? Overheating?
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Symptoms?
It says 'Marshall' on the front.
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Think the OT has blown on the amp and the cab doesn't work with anything :( going to test it all next weekend with a friend though.
I've had a TSL and a JCM800 now which have all blown on a yearly basis. Bugger that! I'm getting it fixed, flogging it and getting something reliable. Any suggestions?
Paddy
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JCA50 or 100 :)
blackstar? seeing as you like marshall?
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Well if the cab doesn't work with anything, that may be a good place to start. Do you have another cab to test the amp with? Have you opened the cab to check for loose connections or tested the tip and ring connections of the cabinet jack for continuity? You have a multimeter on hand?
Get a Peavey if you want something you can ride down a flight of stairs like a bobsled and still work.
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Or and lovely orange brick built amps, well I know the english one seem to be
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Tried my head with another cab and tried my cab with another head. Nothing. Bugger :(
Right, I guess I'm amp shopping in the new year. Always wanted an Orange, guess I can get one now :)
Paddy
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You didn't you use the same speaker cable by any chance?
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Can you check whether or not the preamp is putting out signal or if the power amp section is working? If you have an effects loop, you can you plug straight in the return hooked up to the cab that's known to be working. Help separate some problems. Have you taken the chassis out of the case to look for problems? Bubbly caps, burnt resistors, browned molex connectors.... Are the tubes lighting up? Any sound whatsoever? Crackles, pops, buzzing....
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You didn't you use the same speaker cable by any chance?
Good point!
Do all the valves fire up and glow? Are all the fuses OK?
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Most times when an output tranny or power tranny go, they will actually smell burnt to a degree. Put your sniffer on em, dude.
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Tried my head with another cab and tried my cab with another head. Nothing. Bugger :(
Right, I guess I'm amp shopping in the new year. Always wanted an Orange, guess I can get one now :)
Paddy
If you open your cab you should be able to test if the speakers are ok by using a cheap multimeter.
the speakers, depending on how they are wired, might cause a problem with fault finding.
but a good speaker has a + to - resistance similar to the impedance of the speaker. I think i used to get 6 or 7ohms from an 8ohm speaker. The different reading is just because impedance is frequency dependent and not like standard passive resistance. I think!
that would you should be able to find what has blown, or if it is a wiring issue.
as for the head.
As for the amp... plugging in the FX return is usually a good way to test only the power amp. might be loud. depends if a master vol is pre or post loop.
if you get sounds there then the issue is in the preamp. If you get nothing still... then it is the power amp.
You can check transformers using a multimeter. checking resistance on the primary of the OT by measuring right across the winds, and then each side to the common. each side to the common should be equal i think. If you have a short or really weird reading it is a sign your OT is messed up. It isn't a very accurate or 'be all, end all' test and it is never safe to poke around in amps, but it is something I read about once when I needed to check one.
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You didn't you use the same speaker cable by any chance?
Good point!
Do all the valves fire up and glow? Are all the fuses OK?
None of the valves glow at all.
Paddy
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TBH, I've wanted a new amp for a while so this seems like a good opportunity to get one. I'm not impressed with Marshall at all at the moment.
Paddy
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Not all OTs are balanced. Some will measure way off and that's OK. It's one of those little things no one tells you on those valve sites that go on and on about matched phase inverter tubes. What's the point when even matched power tubes aren't matched perfectly? It's snake oil.
To the OP: Yeah I got the feeling you didn't want it anymore, but a working Marshall is worth a lot more than a dead one when you're trying to cut your losses. I love picking up dead amps, but it makes me feel guilty at the same time. Most of the time it's something real cheap and easy to get it back to a deserving price. Open that sucker up and follow the leads coming off of the power tranny. Do you see anything funny in that area? Bubbled out capacitor, bad connector, cold/broken/bad solder joints or burnt up resistors? Don't touch anything unless you've drained the filter caps, cuz that'll solve your amp problems for good.
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Mate, I know nothing about amps. My plan is to take it to Marshall, complain, get it fixed and then flog it to fund a new amp.
Bloody cr@p timing too considering I've just joined a new band.
Humph.
Paddy
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Sell it and buy a Splawn Quick Rod or Pro Mod. Bye bye Marshall!!!
That being said, I finally got a chance to (extensively) play a 4 channel JVM with some good volume through a Soldano cab. That thing killed. Very very good sounding head, and great cleans. Still not on par with my Quick Rod though.
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if your tubes aint lit, then there is no heater voltage going to them. that is usually a separate feed from everything else.
it usually feeds your indicator light too but not always!
you might have a bad valve that has blown the heater fuse, or something similar to toe-knees problem. that could be it.
Is your amp is under warranty? marshall charge £25 an hour + parts to diagnose and fix a fault I think.
JacksonRR. yeah, that measuring test is defo not a dead cert. I had to check my old O'netics OT that way, it measured the same each side... but really low readings compared to other trannies, but I checked it was in spec with the builders and they told me it was. You can't do a proper check on transformers unless you have special kit I think?
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Yeah if you do decide to save the cash and open her up and you find a blown fuse, first thing is yank those power tubes. Fuses are awesome when they work out, but sometimes they don't and when you're valve fails in an awesome light show(I peed a little my first failure, jk), it may take out more components. But if you'd rather take it to a tech and be done with it, you may be better off selling it broken. Well I wish you best of luck finding the new amp, man.
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I had a similar problem to this a while back and it just turned out to be the heater fuse that had blown.
Nice cheap & simple fix not had a single problem since
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Yep, if no valves are lighting I'd check the heater/mains fuses. If one or both have gone try a fresh one and see if that pops too.....
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What about the on/off button? I had mine once broken.
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So what's going on with it Bucketshred? Any news?
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Well there is the possiblity of me getting it fixed for a very low price in the new year by a mate of mine. He is out of the country at the moment. Once that is done then I'm flogging it and going amp shopping :D
Paddy
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Sounds good man. When it gets fixed can you post what had happened with it? I'm curious....
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You didn't you use the same speaker cable by any chance?
Good point!
Do all the valves fire up and glow? Are all the fuses OK?
None of the valves glow at all.
Paddy
That means 98% it's a fuse that has blown. Could just have blown because of an electricity spike or because of a bad tube, resistor or whatever.
Check fuses.
Replace blown fuse.
Try and see.
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is there ANYTHING powering up in the amp at all?
you say that the valves don't glow, but does the mains on/off switch light up?
if NOTHING is lighting up, it could just be the mains fuse - they do occasionally pop even without anything being 'wrong'.
if the mains lights up but the heaters don't, then it'll be a fuse on the heaters like others have suggested.
it'll not likely be very much wrong.
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is there ANYTHING powering up in the amp at all?
you say that the valves don't glow, but does the mains on/off switch light up?
if NOTHING is lighting up, it could just be the mains fuse - they do occasionally pop even without anything being 'wrong'.
if the mains lights up but the heaters don't, then it'll be a fuse on the heaters like others have suggested.
it'll not likely be very much wrong.
Had this on a Laney GH50L. Replaced the fuse, fired it up, EL34 lit up with sparks, took out a resistor and both mains fuses. First fuse saved the surrounding components when the tube failed, second time not so lucky. Is there any sign of power tube failure or old age?