Location: Leicestershire
Posts: 317
I'm Mark.
Location: Leicestershire
Posts: 317
I'm Mark.
Play Time!
Out come all the old carbon resistors!
Found a resistor (R8) not shown on the schematic or Quad's parts list - drew where it goes!
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Location: Leicestershire
Posts: 317
I'm Mark.
Now with all the resistors and capacitors I'm changing removed, and all output transistors removed to clean up the heatsink. Got some new insulators with better thermal properties to fit.
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You're doing a grand Job Mark. I must bung a meter across the innards of mine some time.
It is impossible for anything digital to sound analogue, because it isn't analogue!
Location: cheltenham
Posts: 746
I'm matt.
Just remembered - In the service manual supplied ba Dada R11 is 47R but mine measured 120R.
Location: Leicestershire
Posts: 317
I'm Mark.
Location: Leicestershire
Posts: 317
I'm Mark.
Location: cheltenham
Posts: 746
I'm matt.
Ahh, that explains it. I'll have to see what revision my board is...
Location: North Island New Zealand
Posts: 1,757
I'm Chris.
Hi Mark
Concerning R8 resistor , it is placed on the pcb layout drawings between the collector and base of TR1.
rather than as you show hand drawn as 10 ohms heading toward the base of T9.
If placed it solves the traditional method of biasing a PNP , however what is interesting is that the PNP works happily anyway without it.
and it would appear the value of R6 at 120k creates ability for TR1 to be turned on just enough with tiny contribution by C4
These components are coming from different points to bias TR1 , so maybe R8 was excessive - it suggests a high value of resistance
if it was going to be used - maybe 68k
I changed TR1 to a 2N5087 and TR2 to 2N5088 in mine. I am willing to give R8 a go so will report back.
Cheers / Chris
.
Location: Leicestershire
Posts: 317
I'm Mark.
Hi Chris,
I believe that I have drawn the position of R8 correctly, as it is fitted on my PCB.
The value I'm changing R26 to is 62k.
Please do correct me if I'm being stupid!!!
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