Ashdown Peacemaker 60 Head

[lordnikon]

I finally got new preamp tubes yesterday and after installing them to my dismay I had a slight problem. Every so often the audio would cut down or just clip out for a brief moment. then one time it got this high frequency squeal from nowhere ( I was just standing and no playing ). I'm hoping it is just the input because that seems to be where it is originating from. If I could recieve any suggestions that would be great.

thanks,

[Mars Amp Repair]

I've had quite a nightmare with one of these, the least of which is just getting the stupid thing apart!

BTW, the best way to get the chassis out of its box is to 1st remove the 4 screws holding the front panel on from the inside. Then you have to slide the chassis & that front panel out simultaneously...then tilting the front panel down so you can get the front metal escucheon & meter to clear that front panel piece.

It is very poorly designed that way.

As for the squealing & intermittent sound...could be connections on the main pcb, too.

Also, you might make note of how brown the circuit board looks at the two green 390ohm 3 or 5 watt cathode resistors. If it looks very brown, you will probably have to remove those resistors and replace them with one 10watt cement block resistor of about 250 - 270 ohms (the 2 390ohm resistors are in parallel) & get the resistor up off the board. I added a terminal strip.

BTW, the reason for increasing the value of those resistors is that these tubes will eventually self destruct if allowed to continue to idle at the extreme current the original design creates (about 160ma for the pair!).

Also, there is an add-on afterthought circuit that appears to be a bias circuit, but this is a self-bias design. The add-on afterthought according to Steve at Ashdown is to stablize the bias until the tubes have warmed up enough for the self-bias to take over. It adds about -6 volts to the grids.

Anyway, I guess that might not help your current issue except tubes running extrememly hot can cause all kinds of weird problems...glen

[lordnikon]

yea when I when i pulled the chassis out I looked through the board for any markings and the first thing that popped out to me was the brown around those two resistors. I'm gonna have my friend get me the parts from his work and we'll go through hopefully it wil all go well. Thanks for the help and I'll get in touch if anything else happens.

[Mars Amp Repair]

yeah,
You ought to first measure the idle current in those tubes...putting an ammeter in series with the red center-tap on the output xformer is the easiest method in that amp. Then if the current is too high (remember you're measuring the current for BOTH tubes at the centertap), then try a 250 ohm 10watt & if still too high, go for the 275ohm etc. g

[Mars Amp Repair]

yea when I when i pulled the chassis out I looked through the board for any markings and the first thing that popped out to me was the brown around those two resistors. I'm gonna have my friend get me the parts from his work and we'll go through hopefully it wil all go well. Thanks for the help and I'll get in touch if anything else happens.

OK, here is the schemo...glen