Re: 7603 working .... then blank


tinkera123
 

Hi Roger,

Yes, I had assumed that the “+50v” power to the +130v transistors was Unregulated …. and that has proved to be incorrect.
My checking this morning shows that whilst the +50v Unreg Supply is okay, the Regulated +50v Supply is not. Therefore, the 'feed' to the +130v Supply must be the +50v Regulated.
Below are voltages with ribbons connected :-

Unregulated Supplies … P890 pins in order, measured value, correct value (vdc) ….
1 -68.4, -53; 2 -24.5, -18; 3 +13.0, +8; 4 +25.2, +18; 5 +67.1, +53; 6 +97.0, +130; 7 -7.8, +40; 8 0, 0; 9 0, 0; 10 0, 0.
…. Only +130v Unreg Supply is not working

Regulated Supplies …. P900 pins in order, measured value, correct value (vdc) …
1 0, 0; 2 -49.8, -50; 3 -14.9, -15; 4 -0.6, +5; 5 -0.7, +15; 6 +0.7, +50 7 & 8 0, 0.
…. -15v and -50v Regulated Supplies are okay.
….. +5v, +15v and +50v Regulated Supplies are not okay.

I also measured the Voltage feedback to these Supplies (Sense), P901, and got the same result.

My next steps ….
... Check the transistor connections as per Adrian’s “Screw loose?” Thread on Jan 30.
... Have a look at the transistors etc you mentioned

Cheers,
Ian

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