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Old 29th Apr 2009, 8:52 pm   #74
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Default Re: Roberts RT7 - problem

Steve.

Quote:
The two resistors R26 & R27:
Checked using the 20k setting, no power, and in situ with the meter points held at each end;
R26 1.05; R27 .08

R26 With battery connected and on, voltage at the 'Gold' end: 9.72 'Red' end: 0.28
R27 'Gold end': 0.28 'Green' end: 0.00

Derek
The resistance figures are meaningless because no units are quoted and the resistors were undoubtedly shunted by other components. The 0.28 at the juction of R26 and R27 doesn't look too bad though, assuming that the units are volts.

Quote:
TR6 Emitter 1.9v; coll. 4.87v; base 1.76v
TR7 Emitter 3.35v; coll. 2.13v; base 2.10v
With TR6 and TR7 fitted the base voltages have risen to the 2 volt region. What can be causing that? It implies a base current of about 1.5mA for each transistor. Even a dead short in a transformer winding shouldn't cause that. 2200*0.003 is approximately 9-2=7 volts.
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