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I'M Back, PDP 11/40..

Hi All;
I have gotten out the PDP 11/40 out and seeing if I can get it doing what it did before I put it away..
I have to hook up the Power Supply and make another AC and DC Lo startup circuit board, like I did for the PDP 11/45..
THANK YOU Marty
 
Backplane readings
-15v = -15.06
LTC = 2.29
+15v = 16.10 (input TO regulators)
+5v = 4.76 *
+5v = 4.76 *
ACLO = 1.727v
DCLO = 3.46v

* Something in the backplane (a card I assume) is bringing down the +5v? What causes the ACLO to be 1.727v? I read that it should be closer to DCLO.

I don't want to copy and paste from my blog, but there are more details/thoughts.
http://vintagecomputer.org/browse_thread.cfm?id=178

Let me know what you think. It's tough to work on this given my house and space, so work has gone slowly. If this was a PC I'd have fixed by now.
 
Hi All;
Bill, Unfortunately, I know almost nothing about the Old Dec Power Supplies.. Someone like Lou, would have a more knowledgeable answer..
Having said that, IF and I say IF, you want to put in the time and the effort, you could, Unplug All of the PDP 11 Power supplies, and for now attach in a more modern PC type of supply, and compare your readings, If the Readings look more normal across the Board, then you need to look at the DEC Power Supply units.. Otherwise, the problem lies in one of the Boards that you have plugged into your Backplane.. Now remember that for your + and - 15 voltages, you would be using + and - 12 volts instead.. but, that will work..

THANK YOU Marty
 
I am going to complete the items on my to do list (as described on my site) with orig power supply first. Maybe try a modern power supply if all else fails.
 
A big thanks from me, too. I'm a long, long way from getting my /05's running but I am sure this guide will be of immense help when the time comes.
Thanks again

Steve.
 
Notable quote from above guide (p 81):

CAUTION

Be extra careful that you put the ground
lead on the correct backplane pin. Otherwise
you may short something to ground
which could cause considerable damage
to the machine and your pride.

Never let it be said that DEC Field Service didn't have a sense of humor!
 
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