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Old 20th Aug 2013, 10:32 pm   #5
ukcol
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Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
Default Re: Roberts R200- Distorted Output

Hi Josh

Yes check R22 as Ron suggests, it is very likely to be the problem. Then remove the 1N4148 and replace it with an AC128 with collector and base joined together. X2 provides bias stabilisation with variations in temperature and a silicon diode is not suitable in this set.

You will see (from the Trader sheet) that the early versions of this set did not employ temperature stabilisation of the output bias, so presumably they suffered from thermal run away.

Colin M
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