PDP 11/34a Console dead, powersupply problem?

[Christian Corti]

On Wed, 11 Jun 2008, Andreas Holz wrote:
> Are there any docs, advices and procedures to check an repair a H7441
> Powersupply?

The docs are in the 11/34 printset. The usual fault (at least with our DEC 
power supply bricks) is the big capacitor having a short and thus blowing 
the fuse. Either replace the capacitor or "repair" it with a high current 
pulse which burns away the short.

> Looking at the bottom side of the PSU untit there are three PSU's, two
> H7441 with a red LED, the LED of one H7441 is lit, and a H755 with a bulb, 
> which is not lit. What is the meaning of these LED and bulbs?

The LED (or light bulb) is connected to the output to indicate the 
presence of the output voltage. The light bulbs are usually broken; I 
replace them with LEDs when I have to repair these power supplies.

Christian