Hartke HA5500

[Smokerx]

Update:On the HA5500.. I replaced another old Transistor on the rails that cooked off and Q308 for the 2nd time. Its dim bulbing, now and the fans are running, but the safety relay wont pass the signal to the amp. I dont hear the usual relay clicking on and off from the power amp board. So I got it working enough to take measurements off. A thing I noticed is the HA5000's Volume and Preamp pots feel different. When you turn the knob theres a feeling of slight wiper resistance. When you turn these knobs on the HA5500 it feels like theres no resistance whatsoever. Too smooth and too fast.

Also the solder is so old and dodgy its hard to melt and seems to want to take its landing trace with it. Its like the landing trace is poorly adhered and the solder is mostly oxidized.

This all took me a minute because I left my only tube in the HA5000 (still working fine) and had to get a new tube to continue on the HA5500.

TLDR: HA5500 has gone from "Blows fuses" issue to "relay wont pass signal"

[g1]

IC301 is the protect IC that turns the relay on and off. If there is DC at the output (R334), the relay will not turn on.

[Smokerx]

False positive: Relay wont turn on because Q312 was blown open. No Continuity. Usually the transistors have blown closed. Once Q312 is replaced its right back to square 1 with no fans running and a bright glowing dim bulb. I guess thats good, since the issue obviously lives down stream from Q312.

Q308 was replaced. It then passed signal to Q312. which cracked open...(Q312 was also replaced on attempt 2 or 3 tho. So Im cooking fresh, possibly fake parts off) I did measure VDC on the entire "low amp side" btw. (Q319 rail)

Low amp High Amp markings on the amp board are weird to me. Since I looked up Class AB amp and it looks like its handing signal back and forth across those rails in a wave form. So half the signal reached Q319 I guess.

Seriously wouldnt be surprised at this point if all my parts are fugazi and the rails backs got blown out again. Will take it apart and start testing transistors again. never give up. never surrender.