MrVerylongusername
454 posts
Aug 10, 2009
1:13 PM
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Hi
I have the 90s reissue version. Very happy with it. Last gig though I had major problems using the normal channel - both inputs - very crackly and low volume. The bright channel works fine (which got me through the gig).
My first thought was a cooked valve, but swapping bottles hasn't improved things - so what else could it be?
I've found someone locally who does repairs, but I'm the kind of person who likes to go forarmed with a little knowldege.
Any help much appreciated.
Last Edited by on Aug 10, 2009 1:19 PM
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tookatooka
365 posts
Aug 10, 2009
1:29 PM
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Have you tried wiggling all the valves around a little to ensure there are no dirty connections?
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When I'm not blowing, I'm drawing.
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MrVerylongusername
455 posts
Aug 10, 2009
1:42 PM
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All the preamp stage ones have come right out and have been swapped around. They all light up too.
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Kingley
311 posts
Aug 10, 2009
2:15 PM
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As the bright channel is ok. It sounds like it could just be a bad connection on the normal channel jack sockets.
Have you tried spraying some contact cleaner in the jack sockets?
If you can I would recommend making a little audio recording of the problem and asking someone like Mark Burness for advice.
Greg Heumann may also be able to advise you in more detail than I can.
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MrVerylongusername
456 posts
Aug 10, 2009
2:33 PM
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No, but I don't think it's as simple as that. It was a sudden failure between gigs, I think I'd have got more warning if it was just dirty connections.
What would happen if a cap blew or a resistor was fried?
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walterharp
18 posts
Aug 10, 2009
2:51 PM
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Well, the only valve that should matter is the first (V1) because after the two volume controls all the signal from bright and normal channels are the same.
If both inputs crackled, it is probably not in the jacks themselves, but they are electrically connected, so that is not certain.
If you don't know too much about this and how to use a multi-meter to test things without zapping yourself from a capacitor that is not discharged, I would just go ahead and take it to an amp tech. If they start saying the problem is after valve 2, power tubes, power supply etc.. then they may be off.
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MrVerylongusername
457 posts
Aug 10, 2009
3:21 PM
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I think I need to take it in. It needs PAT testing anyway and although I know how to discharge the caps, I don't really know much about electronics past building simple circuits from diagrams. The guy has a reasonable reputation so I reckon I can trust him - I was just concerned around cost, just knowing that bit about the signal path is reassuring. It sounds like a minor component at worst.
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Greg Heumann
122 posts
Aug 10, 2009
6:03 PM
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I agree with walterharp and kingley. Check the input jack, and all leads soldered to it. Could be a cold solder joint that finally opened up, or a bad jack itself. I know it seems sudden - but stuff tends to fail when it fails, not before or after. It could also be the V1 tube socket and a bad connection there, but that should show up if you flick the tube while the amp is hot.
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/Greg
http://www.BlowsMeAway.com
http://www.BlueStateBand.net
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MagicPauley57
55 posts
Aug 10, 2009
6:07 PM
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with any valve amps ,if you're unsure then get it checked over by a pro , it's not worth electrocuting yourself !
but if the valves are playing up then you will hear it ,pop and hiss etc or sometimes with a preamp valve you might get feedback when they go microphonic!
usually when an amp has been used on only one channel then the others gather dust , sometimes spray on some contact cleaner onto a input jack and insert into each input a few times , also give the volume and tone knobs a good rotating ( ooer missus?)
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MrVerylongusername
458 posts
Aug 11, 2009
8:17 AM
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Well I've dropped my baby off the hospital; I hope the docs can fix her 'cos I don't like that bright channel at all. uggghhhh!
Thanks for all the tips. I'm hoping to get a diagnosis and estimate before I go on my hols, I'll try and post before I go.
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walterharp
19 posts
Aug 11, 2009
10:45 AM
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my 5f6a amp just had valve 1 go.. weird, and sucky cause it was an rca nos blackplate and they are not cheap....
but only one side tested bad. the symptom here was feedback early on in the volume up process, not crackling in one side., wonder if your tech is going to say valve 1 is bad.
i have not looked into the bassman ri circuit, do they have those cheap plastic jacks for input? (plastic on the inside). If so you might want the tech to put some better quality ones in for you while mucking around. last longer and easier to service yourself at a later date.
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MrVerylongusername
460 posts
Aug 11, 2009
11:46 AM
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I opened up the back to look for obvious broken connections - the jacks are the open all metal sort you find on guitars - I must have tried 3 different tubes (I have all sorts of odd 12ay7s and 12au7s kicking around from tube swap experiments) none of them helped. The amp's in good hands now... just have to wait and see.
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MrVerylongusername
463 posts
Aug 13, 2009
7:18 AM
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Turns out it was the tube socket itself. New part ordered, full overhall pending!
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tookatooka
372 posts
Aug 13, 2009
7:40 AM
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Hmmm! unusual for a socket to malfunction. Maybe the amp had been stored for a length of time in less than ideal conditions and a little damp crept in causing slight corrosion?
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When I'm not blowing, I'm drawing.
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MrVerylongusername
465 posts
Aug 13, 2009
8:19 AM
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Possibly - last few gigs have been outdoors, and as another Brit I don't need to tell you about our washout summer! This guy comes very highly recommended by some guitarist friends, I doubt he's out to rip me off.
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Kingley
316 posts
Aug 13, 2009
8:32 AM
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Ah the joys of our great British summers!
At least he has spotted the problem, and it's a cheap one to fix.
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MagicPauley57
61 posts
Aug 13, 2009
6:33 PM
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last year , my old drummer put his bass amp ( plays bass as well as guitar and drums) anyway he has an early 70's 100w marshall superbass that had seen a lot of gigs , it was buzzing , humming and farting etc, turned out the valve bases ,the contacts had fused together creating all sorts of problems .
He now has new ceramic bases that have transformed the amp,
Beware , a lot of modern valve amps that may seem expensive have plastic valve bases that are prone to this what with sometimes set into a PCB , when the heat from the valves , warps the PCB and fuses the valve base conatcts together , it also happened to a vox ac30 reissue i had !
If you buy an amp ( modern reissue) check that the valves are set way from any PCB on a separate part of the amp chassis or you will get similar problems , also get it upgraded to ceramic bases .
I hope this helps as i've gone through all this with my amps and pas on any advice when i can to prevent other people getting poor performance from premium priced amps
one more thing keep amps like this out of garages and cellars unless they're dry!
God Luck
Paul
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