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Just taken in a Peavey Chorus 400, which has recently had the footswitch rewired/repaired by someone else. Problem is: when any function i.e. reverb, chorus, channel 1/2, stereo/mono is switched in the volume levels of the amp rise considerably. The footswitch repair ( which consists of new 7 pin din socket plug and cable) looks correct from previous dealings with Peavey footswitches. The owner has apparently taken the amp back to the tech who did the job and he says there is nothing wrong. I have tested the amp and I would not be happy to gig the thing. I have mailed Peavey for a schem for the amp and footswitch but was wondering has anyone out there come across this prob?
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What problem? That someone miswired a footswitch? Sure.
The problem could well be in the amp. Maybe the amp is not decoding the FS properly. I don't see how the reverb control could affect the gain though.
When you click the combiner switch, do both channel lights come on? And when the combiner is off, does the select switch move to one light or the other? Do the reverb and chorus switches affect the lights in any way?
And louder and such aside, does the reverb control actualy turn the reverb off and on? And does the chorus switch actually turn the chorus off and on?
Your amp gets louder when chorus is selected? FInd out if the channel controls - gain, volume - affect this. In other words is the chorus button actually turning on the boost channel instead? or something.
There are two speakers, and each one has its own power amp. Are both speakers producing sound at all times? Or is one of them switching off and on?
If the FS has had trouble, it is possible the 4028 IC in there has failed.
By the way, is that a Stereo Chorus 400? I don;t know a CHorus 400. Unless it was an export only model.
On the Stereo CHorus 400 schematic the FS wiring is included.Education is what you're left with after you have forgotten what you have learned. -
Hi Enzo,
yes it'd deffo a Chorus 400. Must be an export model as you said. The footswitch operates all the controls correctly, just that it also increases vol. You switch the rev or the chorus on and sure they come on, but it's as tho you've hit a boost pedal too.
Thanks for the advice, I'll check it out!Comment
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Hi again,
ok, first of all just to clarify: The amp is definitely stereo although it's just labeled Chorus 400 on the front panel! Had the amp fired up tonight and I've checked the things you recommended yes it's possible to control the volume of one channel with the other. Also if I select ch1 and turn the gain up on ch2 I'm getting cross talk between the channels, i.e. very fizzy distortion underneath ch1's normal voice. The sound is coming out of both speakers at all times and when you switch the chorus in you hear it appear on just one side and the other side is dry as it should be.
I've not yet received the schematic from peavey.
CheersComment
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Oh I knew it was stereo even without the name. I am even assuming for discussion that it is the same as the Stereo CHorus 400.
All your observations support my theory the switching circuit is confused. A shorted diode in the matrix after that 4028 maybe or a stuck JFET or an open resistor.Education is what you're left with after you have forgotten what you have learned.Comment
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Once again thanks for your help, I'll let u know what i find.Originally posted by Enzo View PostComment
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Ok, problem sorted, but first I have to appologise to you Enzo. The Amp is clearly a STEREO chorus 400! It does say: Stereo chorus 400 on the front panel. when I fist saw the thing the Stereo bit was obscured by the overhang of the cabinet. Let me explain: I find myself with a garage full of amps because the tech who normally reapirs for my friends shop was taken ill a month or so ago. I was asked to look at a couple of amps, and it's escalated to 1 out 2 in. All this on top of a full time job and a family!
Anyway, dispite the schematic not arriving yet from Peavey, I've pulled the thing apart tonight and had a good look, traced, pulled and probed and could find nothing wrong. So, after making a lasting impression of the heatsink on my forehead I decided to take another look at the footswitch. I removed the cover from the 7 pin din whilst still sending a signal through the amp (Purely cuz I couldn't be arsed to turn it off!) and plugged the footswitch back in. Signal became stayed normal, no distorted crosstalk, the chorus just normal no jump in vol when switched. if i push the cover back over the plug, no prob, but inset the retaining screw into the plug and everything goes haywire.
Thanks for your help.Comment
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I just posted the schematic over at www.ampix.org in the Enzo gallery. You can download it from there for your reference.Education is what you're left with after you have forgotten what you have learned.Comment
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Thanks for that!Comment
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