Self induced oscillation

[john & Jake the dog]

hi Ian,
Thanks for the compliment, don't get many of them but I did enjoy trying to do it the best I can.
I am known for not finishing things generally.
Shortly after I took that pic I bent the cables at right angles where
they turn and ran them together if they were going in the same direction and then cable tied them.
Is that ok do you think.

[Richard]

John,

The anode wires are marked with the blue splodges. Think in 3 dimensions, lift them clear of the pcb and separate them from each other a small amount (don't tie together tightly).

What are the components and wiring indicated with the ? They are on the R channel and I don't remember them.

[david counter]

oops I was thinking about the ECF80 not the EL84s, sorry

[Ianm2]

its only for visuals, probably not important for operation.

took me ages to work out this sort of thing, I wasn't taught on an apprentiseship, had to work it out for myself.

if you really want to make in nice in future, heatshrink wire terminations, use a hairdryer or air gun ( VERY careful)

I call it wire hygiene, it is a skill that can be learned, sounds like a horrible americanism but I coined it myself, probably already used somewhere

just remember the 3 planes, top to bottom, side to side, and back to front.

if you are ever near blackpool, and want it doing, I will be happy to show you what I mean, wrt the routing, etc

I wondered what the green resistor is...dropper for the led?

[Greg.]

Hi John,

Looking at your board, it might be a trick of the camera, but are you sure you've soldered all your components on both sides of the board where appropriate? This might be a red herring and if so I apologise, but I'd expect some solder on the top of the board around the legs of the diodes on the power supply and what about the fat earth lead from the board back to chassis?

Best wishes,

Greg

[Mike G]

John,

Where you have run screened cable (inputs), have you been careful and made sure none of the fine strands of screen wire are left as whiskers, that could sometimes short out on other connections etc. As a general rule, if the screen is unused, cut it back as far as possible, and either use a tiny rubber sleeve, heat shrink or maybe just a small amout of insulation tape.

The strands can be hard to spot, but cause real problems.

Mike.

[david counter]

Originally Posted by Richard

What are the components and wiring indicated with the ? They are on the R channel and I don't remember them.

I think that's the wiring for the led Richard

could that be a problem?

[Mike G]

Originally Posted by Ianm2

its only for visuals, probably not important for operation.

took me ages to work out this sort of thing, I wasn't taught on an apprentiseship, had to work it out for myself.

if you really want to make in nice in future, heatshrink wire terminations, use a hairdryer or air gun ( VERY careful)

I call it wire hygiene, it is a skill that can be learned, sounds like a horrible americanism but I coined it myself, probably already used somewhere

just remember the 3 planes, top to bottom, side to side, and back to front.

if you are ever near blackpool, and want it doing, I will be happy to show you what I mean, wrt the routing, etc

I wondered what the green resistor is...dropper for the led?

Ian,

I know it has been mentioned several times on various threads, but remember tightly loomed cables running parallel can sometimes have a negative effect on our amps, (picking up cross talk etc) I agree about tidiness etc, and in at work (instrumentation) I see many panels with neatly loomed wiring, but sometimes being just a tiny bit less tidy may not be a bad thing.

Mike.

[Richard]

Originally Posted by david counter

I think that's the wiring for the led Richard

could that be a problem?

Hi David, There seems to be one connection on the cathode and one on the heater. Why are they needed? They didn't use to be fitted and the problem's on that channel. I'd detach and isolate them at least to eliminate the possibility.

[Ianm2]

yes cross coupling/xtalk/capacitive coupling is USUALLY only a problem where there are either big voltage differences, or low signals wrt noise, this of course means to use wire with the best insulation/dielectric possible, too.

so don't put a wire with lots of noise on it by an input.

in a power amp, low signals SHOULDN't be a major problem

but I did say its only for visuals, and not affecting operation, meaning it may not make it better, of course, perhaps worse, as you say.

I just like to make it look professional where possible, but you do have to adhere of course to the accepted wisdom of routing, yes.