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Old 9th Aug 2017, 4:56 pm   #4
Mike1948
Diode
 
Join Date: Aug 2017
Location: Chippenham, Wiltshire, UK.
Posts: 5
Default Re: SRP51/SRP52 problem

OK an update to this. I've replaced the AC176 & AC128. Also replaced R8 & R9 both of which had become out of spec. R13 & R14 both replaced with new 2.2 ohm resistors. Removed RV5 and replaced it with a fixed resistor. This required a surprising low value to produce a reasonable quiscent current. 12 ohms produced a current of 8.8ľa measured as per test procedure. Half rail voltage set up as per test procedure. (24.5 input giving 12.2). All voltages on diagram generally a little under that specified, (0.9v is 0.8v, 12v is 11.8).
So now the circuit is no longer failing as described, in fact seems to now have one problem - fairly pronounced distortion, mostly noticeable on lower notes
Any suggestions please? Very grateful for anyone's help.
Thanks,
Mike
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