Bare Knuckle Pickups Forum
Forum Ringside => Tech => Topic started by: gamesandy135 on February 14, 2008, 04:45:10 PM
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Hello everyone, you may have sen in the guitar, amp section of the board, I got myself a Laney VC30 (2nd hand, not brand new).
The amp was working absolutely fine (and still is to a degree) until today. Here's the problem. Every time I turn the reverb up, I get no reverb and the amp seems to get louder and harsher. If I turn it up past 4 (the reverb) I start getting nasty feedback/squeels.
At first I thought that maybe the reverb tank had broken (it does look old and battered) so I swapped the old one out and put in the reverb tank from my Valveking which I know is working, the same thing happened.
When the reverb is turned off, the amp seems fine to me.
Now, I would use a pedal for reverb anyway, but I don't know if this indicates something worse happening. I suppose the cable connecting the amp the to the reverb tank may have gone, but I don't know how to change it.
Thanks for any help guys.
(On another note, is it possible to use a 16ohm speaker in an 8ohm amp, or not really recommended?)
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Difficult to assess the specific cause from a distance, but I've just looked at the schematic over on freeinfosociety.com - and it verifies that the reverb ( and effects loop ) are handled by solid state circuitry on a seperate circuit board - as are a couple of other Laneys I have seen ( including my own ).
As such, there is no valve shared by both pre - amp and reverb.
If you are prepared to use a reverb pedal into the front of the amp, then just go ahead and keep the 'Reverb' control turned off - as the low voltage circuitry dealing with the internal reverb is effectively by-passed with it turned down.
It would be interesting to see if any effects pedals put in the F.X send/ return loop are affected as well ( that too flows in and out of the solid state side panel ). This information would not aid with a long distance fix, but would perhaps offer your local friendly techie more clues.
Your fault does not sound like the onset of a greater problem, rather that the reverb buffer circuitry is already problematic , but has no capability of creating further problems. As for the connecting cable to and from the circuit board and reverb tray, it is a normal screened stereo phono cable, as you might use to connect your Hi-Fi seperates together.
I cannot imagine this being damaged, as it is robust cable.
Be VERY careful if you lift the chassis out for a look, as even when unplugged from the mains, high voltages remain in the mains smoothing capacitors for a while after switch off.
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Thank you very much for the informative reply, and going out of your way to help out., very much appreciated. It's put my mind at ease.
I have my EHX holy grail in the loop along with a couple of other pedals and they seem to be working fine. That said, I noticed when I first hooked the amp up and tried it that effects in the loop were a bit quieter that when used on my valveking, but I've seen other people comment on this and was expecting it.
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My pleasure !
Don't worry about your effects sounding a bit quieter in the FX loop than your other amp, for in more expensive amps ( like the Fender Twin ) - there is a selector switch to + or - decibels of gain to the effects in the loop. A cheap pedal left on clean boost at the end of the chain will give it a 'lift' if you need to ensure a predictable volume match. I am thinking of a Marshall BB2, EHX LPB 1 or any cheap overdrive that either has a clean boost switch, or allows the distortion to be turned right off whilst still having the gain knob up a bit.
There are of course more expensive and smoother sounding pedals just to give a line driver function, but careful experimentation could save you some cash.
I am happy to hear that the FX loop is functioning -as at the very least it gives you the option of leaving your reverb pedal on top of the amp / in the loop - then setting and forgetting so you have less pedals to trip over / tap dance with on the floor.
The frustrating thing is that the cause of this could be something real simple, like perhaps a bad solder joint. I was looking at an LC15 combo recently, and in that where a couple of strips of adhesive foam on the circuit board, which ( according to Laney technical support ) go from insulating to conducting over time ! I am not saying that is your problem, as that was a feature of the LC15 layout / design - but I am saying that the causes of these things can be very surprising, and defy oodles of amp theory.
:D
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Here's an update on the situation - it's working!
I was changing the speaker in the amp from the eminence to a celestion G12H and to do this I have to take out the whole chassis/controls bit (you'll know what I mean if you've seen a VC range amp).
Anyway, doing this enabled me to have a good proper look at the wiring and I followed the reverb cable up to the pcb and found that it was hanging loose. It's a little plastic thing that just sort of hooks onto/plugs into the pcb. It's hard to describe but anyway, pushed that back on and it seemed to fit snugly enough. Everyhting back together, fired up the amp and hey-presto, working! (well, once I'd swapped around the red/white connections to the reverb tank, always forget which way they go).
On another note, the speaker sounds fantastic through this amp. I thought it would be a bit quieter than the eminence but it seems louder (next purchase, THD Hotplate).
So anyway, you were right, something very simple was the cause. Thanks again Fourth Feline
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Here's an update on the situation - it's working!
I was changing the speaker in the amp from the eminence to a celestion G12H and to do this I have to take out the whole chassis/controls bit (you'll know what I mean if you've seen a VC range amp).
Anyway, doing this enabled me to have a good proper look at the wiring and I followed the reverb cable up to the pcb and found that it was hanging loose. It's a little plastic thing that just sort of hooks onto/plugs into the pcb. It's hard to describe but anyway, pushed that back on and it seemed to fit snugly enough. Everyhting back together, fired up the amp and hey-presto, working! (well, once I'd swapped around the red/white connections to the reverb tank, always forget which way they go).
On another note, the speaker sounds fantastic through this amp. I thought it would be a bit quieter than the eminence but it seems louder (next purchase, THD Hotplate).
So anyway, you were right, something very simple was the cause. Thanks again Fourth Feline
That is brilliant news !
To have not only the pleasure of a more appropriate speaker and to have the satisfaction of restoring your amp's full functionality must have made you a very happy chappy :D
Have a great weekend with your improved VC30 ! :wink: