Hello All,
It's been quite some time since I've had the opportunity to post here as my DIY audio life has been fairly inactive since completing my beloved Bijou. Unfortunately I am experiencing issues with what has quickly become my hands-down favorite amp.
A bit of brief background info: there has always been a slight audible hiss with my Bijou. I've completed a number of dead silent p2p speaker tube amps and vinyl pre-amps and consider myself at least somewhat experienced in the wiring/grounding area. No matter what I did I couldn't get rid of the hiss in the Bijou. Two weeks ago I implemented Ampheads mods per the Bijou website; I removed R9 and C7, left R10 in and added the new heater biasing resistors. No change. For grins I decided as a last resort to try a different set of tubes in the 6n6pi position. The hiss was gone! All was well...for a day or two. Listening at work (my usual headphone setup) and without warning there was quite a set of sparks and smoke from the R10 area of the board. That resistor was cooked and there was a considerable scorching of the circuit board.
I happened to have another power supply circuit board and last night I finished swapping components from the old board to the new. I added R9 and C7 back in and removed the modified heater biasing resistors. I switched it on to test and within seconds of powering on there was a funny hum followed immediately by the catastrophic failure of C7. I replaced C7 (in case perhaps I had the polarity reversed, though I checked twice) and the same thing happened again.
I'm beginning to think that possibly one of the voltage regulators was damaged in the first failure which is now causing the new problems. It's a challenge to diagnose as I can't safely have the amp on to test.
Thoughts? Any help would be very much appreciated!
Thanks!
Charlie
