No worry post at o4undred AM and U are ok.
The DIY audio "KGB" is only active in the morning UK public library time.
Sorry to any KGB member no offence intended. @ this early hour I fail to find words to describe old (1970 ish) OAP. whit Teacher/ primary student attitude
Never the lees WE reserve the right to make as many spelling horrors as possible
Absolutely no idea who/what you are referring to.
(wouldn't you like to stumble on a couple of the Kryuchkov billions in your public park backyard)
Thought Kryuchkov dudes went round in 3. One read one write and one keep eye on intellectuals.
Sort off remember this joke from when I was doing sound engineer duty for the 1977 Biennale
Hey old betamax where blipping heavy to slug round on a trolley
http://kumu.ekm.ee/images/dokumendid/naitused/2007/enrico-crispolt-eng.pdf
Hey guess who asked me to get my sweet 16 years old chicks on a yacht that summer.
Sort off remember this joke from when I was doing sound engineer duty for the 1977 Biennale
Hey old betamax where blipping heavy to slug round on a trolley
http://kumu.ekm.ee/images/dokumendid/naitused/2007/enrico-crispolt-eng.pdf
Hey guess who asked me to get my sweet 16 years old chicks on a yacht that summer.
I don't know...Depressing state of affairs, isn't it?
Spinoza is always comforting: the reality is always perfect, it's only our perception of it that needs improvement...
I built an F5 this winter and after some brief usage something went awry and it´s been shelves since.
I have now replaced the K170/J74/ZTX450/550 and inserted matched Harris 240/9240´s on both channels.
Last nite I wired it back up and started testing, being only 50% successful.
The PSU provide 26,v/-26,2V with 53,4V being measured across V+/V- (400VA 2x18VAC toroid)
The PCB is DiyAudio v3´s and the schematic used is attached below.
P1/P2 is set to zero ohm measured over R5/6
I briefly got channel#1 running but the bias values weren't predictable and offset was measured to -0,6xV most off the time. So I shut it off, reset P1/P2 again to start over. Imideately on power-up R3 fried letting the magic smoke out.
The bulb-test on this channel btw gave only a 50% dimmed light, not completely faded out after the initial start-up surge.
Channel#2 biased nicely with anticipated valued and behaviour, with offset=0,00V
I would appreciate any input and help trying to understand whats going on
I have now replaced the K170/J74/ZTX450/550 and inserted matched Harris 240/9240´s on both channels.
Last nite I wired it back up and started testing, being only 50% successful.
The PSU provide 26,v/-26,2V with 53,4V being measured across V+/V- (400VA 2x18VAC toroid)
The PCB is DiyAudio v3´s and the schematic used is attached below.
P1/P2 is set to zero ohm measured over R5/6
I briefly got channel#1 running but the bias values weren't predictable and offset was measured to -0,6xV most off the time. So I shut it off, reset P1/P2 again to start over. Imideately on power-up R3 fried letting the magic smoke out.
The bulb-test on this channel btw gave only a 50% dimmed light, not completely faded out after the initial start-up surge.
Channel#2 biased nicely with anticipated valued and behaviour, with offset=0,00V
I would appreciate any input and help trying to understand whats going on
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It wasn't, bulb-tester only used on initial power-up test and removed from circuit when amp was being adjusted.
The first adjustment went ok (as in no smoke) so it is likely that Q1 was damaged during that phase then. Then blew on power-up after P1/2 reset.
Thank you Andrew for prompt and concise reply.
Last edited:
I built an F5 this winter and after some brief usage something went awry and it´s been shelves since.
I have now replaced the K170/J74/ZTX450/550 and inserted matched Harris 240/9240´s on both channels.
Last nite I wired it back up and started testing, being only 50% successful.
The PSU provide 26,v/-26,2V with 53,4V being measured across V+/V- (400VA 2x18VAC toroid)
The PCB is DiyAudio v3´s and the schematic used is attached below.
P1/P2 is set to zero ohm measured over R5/6
I briefly got channel#1 running but the bias values weren't predictable and offset was measured to -0,6xV most off the time. So I shut it off, reset P1/P2 again to start over. Imideately on power-up R3 fried letting the magic smoke out.
The bulb-test on this channel btw gave only a 50% dimmed light, not completely faded out after the initial start-up surge.
Channel#2 biased nicely with anticipated valued and behaviour, with offset=0,00V
I would appreciate any input and help trying to understand whats going on
Make sure your k170 j74 are genuine. I was having similar issues but with 2 pair outputs. One channel k170 kept blowing and a attributed it to substandard k170 from a suspect purchase. Luckily I still had a stash of k170 from mouser. Proven genuine BL k170 and I was gtg.
2 pair F5 is something to experience...
