One step forward, two steps back? Desoldered the optocoupler, it measured good. Track had a solder bridge so I thought I had it solved.
Put it back and now no more connection to ground on pin 4, but still having the same problem that is: current through ps, especially on negative side.
Put it back and now no more connection to ground on pin 4, but still having the same problem that is: current through ps, especially on negative side.
On the good channel I have the Iq set up, having 180mV over the R in CRC. This is symmetric both on the +24V and -24V rail.
On the bad channel with the Iq pot turned all the way down so no conducting OS, you would expect almost no current, but I have as I stated before 120mV or so on one rail and 6V! on the other rail. Large current means still some short somewhere?
On the bad channel with the Iq pot turned all the way down so no conducting OS, you would expect almost no current, but I have as I stated before 120mV or so on one rail and 6V! on the other rail. Large current means still some short somewhere?
explain where you're measuring voltage sag to show Iq?
usual praxis is (say) across R in CRC (cap bank) , or temporary inserted 0R1 in rail(s)
whatever - 120mV sounds reasonable, but 6V sez that something is burned (that resistor?)
even in case that you're monitoring across 0R47, that means 15A .......... and that is unlikely
write and post comprehensive pictures, so I can grasp what your setup is exactly
usual praxis is (say) across R in CRC (cap bank) , or temporary inserted 0R1 in rail(s)
whatever - 120mV sounds reasonable, but 6V sez that something is burned (that resistor?)
even in case that you're monitoring across 0R47, that means 15A .......... and that is unlikely
write and post comprehensive pictures, so I can grasp what your setup is exactly
Either this side as shown or the other group of four on the right. Should give the same reading but they don’t.
check cap bank pcb alone
disconnect amp rails, measure resistors; give it time to get a reading, because they're still in circuit; though, it'll be best to lift one leg of each, then check with ohmmeter
if you find them OK, power on and measure output rails without load; don't forget to bleed caps afterwards
can't see from pic- are these all 0R47?
desolder both mosfet and SIT from pcb, check mosfet for shorts; check with buzzer/diode test both rails on pcb, ref. to GND ( meaning black probe to GND)
point is - if there is no load (speaker) on output, massive current through neg rail means that negative rail is having connection to GND, in some way ........... even if 6V across R group in C bank is hard to understand ...... that's why I'm thinking that Rs in CRC are suspicious
anyhow, now we have situation of several ookups/mistakes/Gremlins accumulated; you had wrong resistors in place ...... short with GND ....... I mean, troubleshooting something as that is hard even with Crystal Ball
disconnect amp rails, measure resistors; give it time to get a reading, because they're still in circuit; though, it'll be best to lift one leg of each, then check with ohmmeter
if you find them OK, power on and measure output rails without load; don't forget to bleed caps afterwards
can't see from pic- are these all 0R47?
desolder both mosfet and SIT from pcb, check mosfet for shorts; check with buzzer/diode test both rails on pcb, ref. to GND ( meaning black probe to GND)
point is - if there is no load (speaker) on output, massive current through neg rail means that negative rail is having connection to GND, in some way ........... even if 6V across R group in C bank is hard to understand ...... that's why I'm thinking that Rs in CRC are suspicious
anyhow, now we have situation of several ookups/mistakes/Gremlins accumulated; you had wrong resistors in place ...... short with GND ....... I mean, troubleshooting something as that is hard even with Crystal Ball
Crystal Ball makes me think of Zappa
Debris is mess I made of my amp and Guru are you 😉
But with the Crystall Ball you have, indeed two resistors of 0R47 from PS have apparantly given up their resistance, it was futile. Now I learned failure mode of wirewounds is closed, not open, shorting coils to shorter path with less resistance.
Going to work on desoldering the mosfet and doing more measurements to find any remaining short before rebuilding.
Debris is mess I made of my amp and Guru are you 😉
But with the Crystall Ball you have, indeed two resistors of 0R47 from PS have apparantly given up their resistance, it was futile. Now I learned failure mode of wirewounds is closed, not open, shorting coils to shorter path with less resistance.
Going to work on desoldering the mosfet and doing more measurements to find any remaining short before rebuilding.
Haha just realised my mistake with some more sleep and another look. One ps (the good side) has 8x 0R47 resistors in as it should. Somehow back when I made these I didn't order the right amount of parts and made an error with the second half of my order and ordered 47R instead. So the bad PS side measuring so weirdly was because it had 2x 0R47 in parallel with 2x 47R and the other rail was filled with 4x 47R in parallel doh! Hope it provided entertainment at least. I have now found 0R1 resistors to use in the negative rail for proper measurement. Now to go and order some more parts, I will succeed eventually.
I took the correct PS and wired it to the other Sissy board with a 0R1 in the negative rail for measuring. For whatever reason it does start with some Iq flowing but I can seem to set it correctly and the offset too so now both output devices are getting nice and warm, all seems to work.
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just wait , when you finish it properly ...... and hear with proper source and speakers .........
This happened to me too. I luckily realized before soldering them, and Mouser just like that threw a bunch of correct ones into my bag. Lucky me.
It's alive, finally. Last time I did manage to fry one IRFP, so had to order some more parts. Today it came, setting procedure took most of the night. But finally both channels working and set.
Now listening with a beer to celebrate and enjoy.
Now listening with a beer to celebrate and enjoy.
By the way, it's version 'R1' with apparently well-behaved SITs from Pras, no need for modifications (I let it cook for long times in between adjustments)