R21 and R22 both measure 176K colour bands are very faint cant read and cannot find any Manual Change
Interesting. These two resistors are both 24.9K on my schematic. No worries. Let's repeat a VM test from a while back: if you place VM leads between TP1 and U3C pin 9, difference should be less than 10 mV. Same should be true at TP2 vs. U5D pin 9.
Sorry to hear of continuing troubles.
TP2 obviously not working, highly probable TP1 not working either. It you'd like to trouble shoot without resorting to component removal, we try.
As a check for at least partial opamp health, try measuring U3B (i.e.TP1) by using meter probe to join pins 7 and 6 simultaneously. This will produce unity gain and you should see 0V on meter if that opamp section is operable. Try same procedure at U5B.
If these checks look good, would you report opamp U3C voltages at +,-, and output pins, and Q1 base and emitter voltages? Similary, U5D and Q2?
TP2 obviously not working, highly probable TP1 not working either. It you'd like to trouble shoot without resorting to component removal, we try.
As a check for at least partial opamp health, try measuring U3B (i.e.TP1) by using meter probe to join pins 7 and 6 simultaneously. This will produce unity gain and you should see 0V on meter if that opamp section is operable. Try same procedure at U5B.
If these checks look good, would you report opamp U3C voltages at +,-, and output pins, and Q1 base and emitter voltages? Similary, U5D and Q2?
ooops, my mistake counting pins the wrong way rou.
TP1 to pin 9 3mv. Tp2 to pin 9 jumping up and down from zero to 300mv
!!! found broken track between U5 and TP2, now TP2 to pin 9 3mv
TP1 to pin 9 3mv. Tp2 to pin 9 jumping up and down from zero to 300mv
!!! found broken track between U5 and TP2, now TP2 to pin 9 3mv
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Test 3-52 can now be performed, only the very low frequencies are unstable. The null with ext osc for 1kHz comes in at 1,100Hz. It more or less works now, how well is another thing
Progress!
Don't hesitate to follow your own instincts, but I would suggest post #138 as a possible pursuit.
Don't hesitate to follow your own instincts, but I would suggest post #138 as a possible pursuit.
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