Sweet Linda came home today.

[Oldskoolfan]

Got another Linda today. Beautiful condition. Nary a scratch on the face. Seller said she is blowing fuses. Has 3 service tags on it. Last one dated 10/4/89. I'll have to find out how she comes up on the variac and dbt. Interior and exterior is very clean. Well cared for if nothing else.

 

[Oldskoolfan]

By the way, anybody got a top panel they want to get rid of? Only issue is the top panel is missing.

 

[Oldskoolfan]

Well, I fired it up on my DBT just to see.... didn't blow any fuses, DBT worked like it should. No magic smoke. All seemed well so I checked rail voltages.
Positive rail was 60.2 vdc. Negative rail was -60.2 vdc.
AC input was 50vac both sides of secondary to center tap.
No dc on the output terminals.

I knew these voltages were low so I took out the rail fuses and read voltages again.
Rail voltages were 75.9 and -75.9vdc
AC voltages were 57.2vac both sides to center tap.

Something is loading it down pretty good. This should be educational.
Feel free to offer suggestions. I think I need to start pulling power transistors so here is my first question.
Do I start with the driver row or start with the top row?

 

[J!m]

Test the condition of the main filter caps first. I presume they are original issue? Leaning that way since it doesn't blow coming up slow. In-rush is another story...

Those being bad would drag it down pretty hard, but sketchy output devices would vaporize fuses at any reasonable volume.

 

[Skratch]

Looks like you have a few different outputs. They should all be same if possible. Also what is the bias voltage. Also the drivers are different. Looks like who ever repaired it was not familiar with Phase Linear specs

 

[Oldskoolfan]

Looks like you have a few different outputs. They should all be same if possible. Also what is the bias voltage. Also the drivers are different. Looks like who ever repaired it was not familiar with Phase Linear specs

I've got plenty of like drivers if that might be dragging down the rail voltage. Will the bias voltage be valid at this point? With the rail voltage down 20%?