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Old 20th Aug 2013, 6:33 pm   #1
JoshWard
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Join Date: Dec 2005
Location: Near Stowmarket, Suffolk, UK.
Posts: 1,962
Default Roberts R200- Distorted Output

Hi folks,
I have an R200 on my bench at the moment but I am struggling a bit overcoming a problem with distorted output.

I am working from Trader sheet 1602, the set has a serial number above 70,000.

My problem appears to lie within the bias circuitry. With X3 removed or reversed I can easily adjust the bias to the required 4mA and the output seems fine but when in it's correct position (it is actually a PNP transistor wired as a diode, base and collector are the cathode and the emitter is the anode) I cannot get the bias above 3.4mA (that is with the pot maxed out) and the output is distorted.

X3, TR4, TR5 and TR6 have all been replaced with AC128s but to no avail.

I must be missing something obvious here but not sure what it is...!!

Thanks in advance,
Josh.
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