You now have a attenuation of -32.65db should be 6 db lower as the qa401 adds 6 so you want -28.65 or there abouts
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Let me double check my spreadsheet using your numbers and come back to you. PM me your email address again please
You should also make one for your loopback test to attenuate -0.5dBv output to -5dBv input
i pulled a bone head move when doing some testing... I hit the QA testing for a pulse and instead it stayed on steady input. I was moving some leads around and R25 went up like a smoke grenade. 
Dumbazz move on my part, but I know if R25 smoked there was a reason, so just replacing that is unlikely to fix the issue.
What all should I test before firing this thing up again?
Dumbazz move on my part, but I know if R25 smoked there was a reason, so just replacing that is unlikely to fix the issue. What all should I test before firing this thing up again?
this is a 9pair output in a triple Darlington configuration, +-85 volt rails..
this is where i am using my monster power traffo that i made....
i have four 68mf/100vdc cans from ApexJr for psu duties...
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i pulled a bone head move when doing some testing... I hit the QA testing for a pulse and instead it stayed on steady input. I was moving some leads around and R25 went up like a smoke grenade.
What all should I test before firing this thing up again?
with the aid of a dim bulb tester, two steps, first is output offset dco or dc output adjustments, + -100 millivolt is acceptable, but of course closest to zero is what we aim for, the desiderata …..
second is standing output current adjustments, you may notice your dim bulb getting brighter if you over do your bias adjustments...when you are satisfied that there is no crossover distortion at the 1 watt/8 ohm levels then you are done...actually if the dim bulb tester does not turn full bright, you got a viable amp now....and can wean the amp off it for the crossover distortion testing with a scope...
when all okey, you can then proceed to listening tests....
now to your question on r25, it smoked when there was excess voltage across it, the base of the q9 was pulled to ground when poking around....so i will replace q9 and r25 and maybe the VAS itself...then proceed over..
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Thanks for the input Tony. I've thought the same thing and have been working in that direction. I'll post some thoughts and ask for direction tomorrow. It's looking good, but I'm seeing some differences in resistance from the good channel to the one that had problems. I've solved some of those issues, but not all. I don't want to power it up unless I think it's right, even with a bulb. Some of the base-emitter-collector resistances don't jive with the good side.
Anyway, thanks again, i'll get back to it when i get some data I can put down and be more specific.
jT
I've thought the same thing and have been working in that direction. I'll post some thoughts and ask for direction tomorrow. It's looking good, but I'm seeing some differences in resistance from the good channel to the one that had problems. I've solved some of those issues, but not all. I don't want to power it up unless I think it's right, even with a bulb. Some of the base-emitter-collector resistances don't jive with the good side.Anyway, thanks again, i'll get back to it when i get some data I can put down and be more specific.
jT
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welcome.....for grading ang matching trannies i use this tester....
this tester can give you pinouts, Hfe and tells you what device you have or if it is bad....
https://www.lazada.com.ph/products/...MI0P3-la2O8QIV-Z1LBR2ILwojEAQYAiABEgJzaPD_BwE
this tester can give you pinouts, Hfe and tells you what device you have or if it is bad....
https://www.lazada.com.ph/products/...MI0P3-la2O8QIV-Z1LBR2ILwojEAQYAiABEgJzaPD_BwE
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yes its that thing.
...even tells me if i have a depletion or enhancement mosfets...what is not to like?
worked for me and a lot of others, it may work for you....
Hi Tony,
I have a couple different versions of that thing. It doesn't measure leakage properly as it isn't sensitive enough.
I don't use them anymore as my old tools told the truth and were more accurate.
If you are attempting to match transistors, the two must be at the same temperature. Period. So make your own diff pair circuit up. Measure the difference between collector voltages using the meter as a null indicator.
I have a couple different versions of that thing. It doesn't measure leakage properly as it isn't sensitive enough.
I don't use them anymore as my old tools told the truth and were more accurate.
If you are attempting to match transistors, the two must be at the same temperature. Period. So make your own diff pair circuit up. Measure the difference between collector voltages using the meter as a null indicator.
When you don't know any better, it does appear to work well. That's the danger of those silly things. They work fine in a gross sense. Just like the beta tester in a cheap meter. Why ever would you expect them to be accurate??