I found a dead Krell FPB 200 on sale for cheap. The seller wrote that it goes into protection immediately.
from past experience i knew, its gotta be a short somewhere in the output drive.
what too heavy and those handles at the back make no sense, it messes up the front frace when placing it down.
the fins are also quite pointy and sharp, you cant grab it there.
So i started taking it apart.
Its well built, easy to take apart. a few screws here and there, and everything comes off in modules.
but its huge, its heavy. and its overbuilt as heck.
i mean what you need so many transistors to drive the output stage?
and its microprocessor controlled (biasing trough optocouplers that switch in and out resistors. it measured the rail and output voltage and currents at all time.
If its one of these, i might be screwed. Unobtanium TO-3's
i didnt wanna do this to it, if possible:
But after measuring several spots, i found no short.
so i kept digging, taking apart this PCB sandvich, comparing Left and Right for meter readings
and found a reading that wasnt equal on one so i looked whats hooked it to.
a shorted transistor, but after lifting the legs i noticed the short was still on the PCB
turned out to be a shorted silver Mica capacitor (1100pF)
after replacing it (all eight), it started working again!
for good measure i gave it a new set of electrolytics, the old ones where still good but the new ones are slightly lower esr and may last a while longer now.
After listening for a while.. i noticed this thing is a damn room heater.
60W in Standby!
180W when turned on..
1600W when theres a signal going in without even a load connected.. Class-A of course.
i listened a few hours and my room went to 35c.. nothing i want in my room 24/7.
it sounded good, nothing that immediately kicked me off my chair but alright for an class-a amp. may not have the right speakers for it.
i found my "jaboost" opamp-amp that ive built afterwards sounding slightly less fatiguing over long sessisons. and you dont want to leave the room afterwards.
https://www.diyaudio.com/community/...her-dont-expect-miracles.423889/#post-7929116
Its gonna find its place, someday, somewhere.
from past experience i knew, its gotta be a short somewhere in the output drive.
what too heavy and those handles at the back make no sense, it messes up the front frace when placing it down.
the fins are also quite pointy and sharp, you cant grab it there.
So i started taking it apart.
Its well built, easy to take apart. a few screws here and there, and everything comes off in modules.
but its huge, its heavy. and its overbuilt as heck.
i mean what you need so many transistors to drive the output stage?
and its microprocessor controlled (biasing trough optocouplers that switch in and out resistors. it measured the rail and output voltage and currents at all time.
If its one of these, i might be screwed. Unobtanium TO-3's
i didnt wanna do this to it, if possible:
But after measuring several spots, i found no short.
so i kept digging, taking apart this PCB sandvich, comparing Left and Right for meter readings
and found a reading that wasnt equal on one so i looked whats hooked it to.
a shorted transistor, but after lifting the legs i noticed the short was still on the PCB
turned out to be a shorted silver Mica capacitor (1100pF)
after replacing it (all eight), it started working again!
for good measure i gave it a new set of electrolytics, the old ones where still good but the new ones are slightly lower esr and may last a while longer now.
After listening for a while.. i noticed this thing is a damn room heater.
60W in Standby!
180W when turned on..
1600W when theres a signal going in without even a load connected.. Class-A of course.
i listened a few hours and my room went to 35c.. nothing i want in my room 24/7.
it sounded good, nothing that immediately kicked me off my chair but alright for an class-a amp. may not have the right speakers for it.
i found my "jaboost" opamp-amp that ive built afterwards sounding slightly less fatiguing over long sessisons. and you dont want to leave the room afterwards.
https://www.diyaudio.com/community/...her-dont-expect-miracles.423889/#post-7929116
Its gonna find its place, someday, somewhere.