Re: 7704A Vertical Amplifier Issues


Albert Otten
 

On Sat, Sep 25, 2021 at 05:15 AM, Mark Vincent wrote:
The reason I specified 1W for the 33 ohm resistor is because I measured 3,13V
across the 33 ohm resistor. The base voltage is 14,4 and the emitter voltage
is 17V. I measured this in mine that is working fine at the time of this post.
I know the EB voltage is not standard ,6-,7V.
Hi Mark,
Something must be wrong here. For comparison, in one of my 7704As, at Q20 I measured Ve = 15.45V, Vb = 14.86 V, Veb = 0.59 V.
Across R4419 I found merely 0.125 V. (BTW this resistor was 39R 1/8W, clearly a replacement soldered in later. Original 33R also burned??).
Is your A44 board an early version at which Q20 etc. have been added later on? With possible mistakes? All my boards are later versions.
Albert

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