Results from measuring resistors in-circuit (power off) below.
Deviations from the schematic:
I’m working on identifying all the little bjts…
Deviations from the schematic:
- R107 measured 5K (10K in schm)
- R207 5K (working channel)
- R108 measured 5K (10K)
- R208 5K
- R111 measured 30R (51R)
- R211 25R
- R112 measured 25R (33R)
- R212 23R
- P101 measured 60R to 0.8R (200R)
I’m working on identifying all the little bjts…
Attachments
all of these resistors are pretty much irrelevant for Iq
continue with everything right from R114, looking at schm in posts #44 or #188
continue with everything right from R114, looking at schm in posts #44 or #188
one pic all "1-B"
second pic all "3-B"
so, my OCD still functional
try checking all resistors in situ, primarily comparing to same measurement on proper channel pcb
be sure to have probes same oriented on both channels
even if in some cases you can't get valid measurements ( resistor being in circuit), comparison with proper channel can give us some idea
second pic all "3-B"
so, my OCD still functional
try checking all resistors in situ, primarily comparing to same measurement on proper channel pcb
be sure to have probes same oriented on both channels
even if in some cases you can't get valid measurements ( resistor being in circuit), comparison with proper channel can give us some idea
Understood. I’ll check all resistors from the good channel and compare.
To confirm, do you mean measuring resistors with power off? I hope so. It’s tight in there and getting the resistance measurements with the board out was challenging enough. 😀
To confirm, do you mean measuring resistors with power off? I hope so. It’s tight in there and getting the resistance measurements with the board out was challenging enough. 😀
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Just want to sneak a question in-between troubleshooting von Ah's board...
Would any modifications be needed if feeding Scryer +/-28vdc?
Would any modifications be needed if feeding Scryer +/-28vdc?
dissipation of P channel mosfet is main obstacle
for cozy sleep, nice wide green - 40W
45W even so
50W reserved for all Papa-Wannabies
those, who are crying in solace, boasting in public
Keratherm ( torqued to 0.9Nm) or Alumina oxide pad + goop
you'll live and boast
though, if you're using less than 4U/400, enjoy in consequences ...... in solace
you'll live and boast
though, if you're using less than 4U/400, enjoy in consequences ...... in solace
Apologies for going off script, but I changed out the SIT in the errant channel. 
Biased up fine. Cooking in now with ~ 180mV across R141. DC offset drifting around less than 10mV.
Woo hoo!
Biased up fine. Cooking in now with ~ 180mV across R141. DC offset drifting around less than 10mV.
Woo hoo!
Starting now! I’ll let you all know. 
(Edit: the hum is gone while connected in the main system)
(Edit: the hum is gone while connected in the main system)
Attachments
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Great news !!Apologies for going off script, but I changed out the SIT in the errant channel.
Biased up fine. Cooking in now with ~ 180mV across R141. DC offset drifting around less than 10mV.
Woo hoo!
So the issue was a defective SIT ?
Was it bought from a reliable source?
Thanks
Eric
Correct, the SIT appears to have been the problem.
I luckily got 10 from a dubious source right when the original thread about the K2087C started here. They were obviously pulls from older equipment.
I didn’t spend a lot, and ended up with two pair that have worked for me. Two other lucky forum members got a pair of K2087Cs from me.
I luckily got 10 from a dubious source right when the original thread about the K2087C started here. They were obviously pulls from older equipment.
I didn’t spend a lot, and ended up with two pair that have worked for me. Two other lucky forum members got a pair of K2087Cs from me.
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