Valve amp only playing out of one channel

[wack]

Just bought a used Yaqin MS 6V6 valve amp

Set it up and, it only plays out of one channel, not a speakers or input problem as I've tried swapping them over , no balance control so not that, both speakers working

Seller is fine about it ,offered to take it back or part refund £100 which is 1/3 of what I paid for it

The only issue I can see is the 4 valves on the working channel get much hotter than the 4 on the non working channel but I assume that's load related, they all light up so none of them are actually dead

Anyone know anything about valve amps , is it likely to just need new valves

It sounds great out of the working channel

 

[dannnielll]

Valves are very robust,about the only thing that can damage them is over voltage and current in the heater. So if you are happy that the heaters are correct, you can swop the valves over and see if the problem swops over.
The circuits used are also simpler than in solid state units and the only expensive part, besides the valves will be the transformers.

 

[wack]

Thanks I'll try that first

 

[dannnielll]

Thanks I'll try that first

Common sense would be to remove the good valves and put the potentially bad valves where the good valves are. ..That at least ensures that the ancillary circuit are ok. So the "bad " valves, are the only variable. Then if it does not work, replace two of the suspect valves with two of the known good ones ,and process of elimination. Hopefully you will find that it is a valve,as a transformer failure would be catastrophic.
Just two warnings. If the valves have a plastic base,that is the part you should touch as the wiring to this base from the glass bulb is delicate. If it is an all glass envelope, then removal and insertion needed to be by very delicate rocking,the pins must not be put under sideways pressure, or the glass can crack. As a valve might have 8 or 10 pins you need to be careful
The second warning is that even reseating the valves and moving the wiring can solve the problem by removing oxides on poor or dry joints..or indeed create a problem on what appeared to be the good channel. Visual inspection and poking the wiring with a pencil can sometimes show these faults.

 

[Hixs]

Valves have a limited lifespan (like a lightbulb), so they're probably knackered if reseating them doesn't work.

 

[wack]

I swapped them over and the problem remained , still only working on the left channel so the valves are ok

I'm taking it for repair , a guy at work has recommended somebody for the repair in Wigan so I'm going to drop it off off tomorrow if he's in

Thanks for the advice I'll update what it was when it's fixed because when I need something fixing I find threads on various forums just left dangling with no solution

 

[MIKEVO]

It could be several things, such as heater voltage (6.3v) may be low on one channel, the Cathode Bias resistors may have overheated, a dry joint (common as valve amps run hot), or even a connector plug has come loose inside (there are a couple in that amp). There are also relays on the inputs, I guess you have tried the other inputs with no success?
As mentioned, the output Transformer will be worse case. The Main Power supply is common to both channels and uses a solid state rectifier, so no problem there.
Good luck, I hope its an easy fix.

 

[wack]

Yes I tried the other inputs , all the same , the only thing I didn't try was headphones as it uses a full size connector and I've only got headphones with an iPod socket

 

[wack]

Said I'd update , got it back from being repaired, one of the valves must've got damaged in transit because it blew it within 2 minutes of turning it on , guy repaired it FOC , new valves, worked for 4 hours then blew a capacitor , he thinks it's got multiple problems so has had it for a month to soak test it before letting me have it again

I've said if it starts smoking again push it out into the garden to see if it goes up in flames

 

[MIKEVO]

Said I'd update , got it back from being repaired, one of the valves must've got damaged in transit because it blew it within 2 minutes of turning it on , guy repaired it FOC , new valves, worked for 4 hours then blew a capacitor , he thinks it's got multiple problems so has had it for a month to soak test it before letting me have it again

I've said if it starts smoking again push it out into the garden to see if it goes up in flames

That's a real shame. Did the guy that repaired it say what the initial fault was?

 

[wack]

I didn't ask, it would've gone over my head , the last time he knew what it was as soon as I described what it did, a pop followed by a whistle then smoke, a capacitor burning out
Apparently It'll be modified when I get it back, the guy fixing it designs and builds amplifiers so he knows what he's doing

 

[dogfonos]

I hope this gets sorted, wack, and doesn't end up costing you a small fortune.

he thinks it's got multiple problems

I get the impression that the seller sold this item as 'working condition'?

 

[wack]

He did but did offer a full refund , it ended up costing me £200 after we renegotiated the price so I took a chance on it ,some you win some you lose, I'm 100% confident the guy fixing it can get it working properly , he seems to think it could be very sensitive to voltage , ie in china 220-230v means just that where here it can be 230-240v and some of the components might not be up to the extra volts

I think he's changing parts that will cope with 240v or higher