warm feet for free.

[space cowboy]

a friend of mine came across a box of his old radio stuff. the stuff he thought he could sell went to ebay, this came to me - bad transistors.

I opened it up, pills look ok, no burn marks or smell...

so I hooked it up and there's no signal to the radio with the box on or off. I'm no tech, but I'm thinking it's not the transistors...

turned out there were 3 broken connections to the relay. fixed two and thought I had it. reconnect it and I've got signal to the receiver. key up and nothing.
I break out the magnifiers and catch the third disconnect, a little bit of solder and it looks good.
key it up on AM and it shuts down the 350W computer supply, switch to ssb and it works as long as I keep the mod low.

can anyone tell me what that screw in the middle is for?

 

[pcpackrat]

Its to adjust the capacity on the output transformer. Not why someone would leave that behind. Usually its used like that during design and a component is chosen in the end.

Tune for maximum smoke and minimum harmonics.

 

[Robb]

10-12w PEP into the amp w/2290 transistors should see around 160w/less PEP output. 30A supply should keep it happy. Leave the adjustable capacitor alone unless you want to mess with the internal impedance and take what comes with it. You fixed it - congrats; take it as a win and leave the rest alone - IMO . . .

Keep it clean . . .

 

[space cowboy]

cool, thanks for the info guys. after 100 looks and no answer i was starting to get worried.

what effect would changing that setting on the variable cap have? knowing the friend, I wouldn't be surprised if he cranked the screw a couple times to see if it would cure the "bad transistors". anything that could cause issues with the radio driving it?

 

[psycho]

I am willing to bet that the amp didn't use 2290s when new.