Quad 306 Refresh and Upgrade.

[Light Dependant Resistor]

Setting about solving for you, offsets have a defined reason that are always fun to solve, the good thing it is running.

[M6NTL]

Setting about solving for you, offsets have a defined reason that are always fun to solve, the good thing it is running.

Well, since I've replaced every passive component in there, and tested the 'big' transistors out of circuit, it must be a small signal transistor or the Op Amp that's the culprit!!!

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[Light Dependant Resistor]

Hi Mark
You have omitted r6 a 120k resistor on the channel which has positive offset, this would appear why
solder a 120k in and see how that goes. Cheers / Chris

[M6NTL]

Hi Mark
You have omitted r6 a 120k resistor on the channel which has positive offset, this would appear why
solder a 120k in and see how that goes. Cheers / Chris

R6 is there Chris - replaced with 62K as per Dada upgrade recommendations...

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[Light Dependant Resistor]

Hi Mark
Sorry i was looking at a earlier image where r6 had not been placed in. R13 though should be 9R1 as raising the resistance to 27R as your image shows will make the sensitivity way too high
Try 9R1 at R13 which is on the emitter of TR3, and follows would raise the voltage at TR3 emitter which i think might solve if it was 9R1 - its a fussy part of the circuit.

[M6NTL]

Thanks Chris.
I changed this from 9R1 to 27R to reduce the input sensitivity to 1V - at least that's what Dada detailed. Have they/I got this backwards?

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[Light Dependant Resistor]

Thanks Chris.
I changed this from 9R1 to 27R to reduce the input sensitivity to 1V - at least that's what Dada detailed. Have they/I got this backwards?

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If we refer to a Quad 909 which has 7R5 and as I recall 775mv sensitivity, lowering the value of R13 changes the sensitivity upward
the opposite of the 27R value , If it was me I would restore R6 to 120k and r13 to 9R1 and measure for offset. But it would suggest approx 6R8 would
give you 1v sensitivity.

The R6 change to 62k hmmm it places the TLC271 op amp to have more influence, but R13 at 27R is too high in value and needs to be ideally 9R1
but 6R8 will work

[M6NTL]

Thanks again Chris...

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