I just picked this blue sparkle beauty up! Normal Channel is fine. Bright Channel DOA!
I tried the Bright switch trick - cleaning, etc. to no avail.
I do get a slight popping when activating the Bright knob and I get hiss when turning up the treble. Otherwise is dead?
Anyone care to point me in the right direction on next steps?
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
9 times out of 10 the first transistor off of the input Jack has been popped by being hit by too much signal level!
These transistors cost 25 cents and the shipping cost are 500% more, lol!
Of course if the amp has been worked on and screwed up then things could get deep real fast !
Have you worked on circuits before other then soldering wires and such?
Yeah, old hand wired stuff and I have built a few.... but nothing solid state.
Guess I better pull a schematic and figure out the value of that transistor?
If I got you right, that one is right on top of the board after an orange drop and ceramic disc cap?
stevem Messages: 4733 Registered: June 2004 Location: NY
Senior Member
The Transistor has a 47 pf cap across its base and collector , the Emitter leg is the one on the schematic with a arrow on it and the volume control is in the Emitter leg also!
Well. I replaced the PET 8002 with a 2N3904..... while it DID bring the BRIGHT channel back to life, its clearly either not right or there are further issues.
The dead Bright channel now works, However,
It works best in the LOW input, the Bright input is weak and thin
Also
when you engage the BRIGHT Boost, the volume drops significantly.
Finally, there is also a lot of HISS, particularly the higher the TREBLE is turned up?