Please HELP! w/ 50W board install

[gtrbarbarian.]

Hi guys,

I started this 50w Metro Amp board install last June after successfully completing a 100w board install (now my main amp), but before I could get the 50w up and running, a cross country move put this on hold

I figure there is enough expertise on this forum to help me w/o bugging George, although he has always been very helpful!

Anyways, I got to the point where everything was wired up, but when I turned it on, there was the smell of charred plastic As you can see in the first pic, two resistors that make up the bias circuit are charred...I think it might be the wire that is running from the bias circuit to the standby switch....

any ideas on how this is supposed to be wired?

Thanks in advance!
-Jon



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[jj jafar]

that white wire should go to the bias of the power tranny.

[Billy Batz]

that white wire should go to the bias of the power tranny.

Is there a Bias tap on a RI 1987 PT? Traditionaly the bias in a 50W is tapped from the secondary AC. You could take it from the standby switch.

[Flames1950]

Billy's right, the reissue is just like the older 1987's in that the bias is tapped off the PT secondary. The white wire's in the right place.
I can't read the resistor values in the pic but the bias caps are going the right way and I think the bias diode is too, it's a little tough to tell in a picture.
Maybe a starting point would be to replace the burned resistors, and then pull the power tubes. Fire it up and let's see what you're getting for voltage on pin 5 of each of the power tubes. You shouldn't be pulling much actual current without the tubes in unless there's a short. If the resistors still toke up we'll have to find the short (but it's not obvious where a short would be from the pics), otherwise we'll go from the voltages you get.

[gtrbarbarian.]

Thanks guys for your replies!

Flames, I will replace the resistors and then check the voltage, and then report back.

Thanks

Jon

[jj jafar]

i looked at the wire picture and not the fact it was a 50 watter,my bad.i need to be slapped from time to time. jason