• Please review our updated Terms and Rules here

Question about 8/a power supply

S

SEgamer

Experienced Member
Joined
Sep 18, 2011
Messages
97
Location
GA, USA
I'm slowly acquiring parts for a PDP-8a since complete PDP systems are almost non-existant around here. I was wondering what the output voltage(s) and amp ratings of the transformer are for a PDP-8 system.

Or if anyone has a spare then please let me know. I also need a backplane for a pdp8a-400 case.
 
I have a bunch of parts for a PDP8A/U that may be what you need. These computers came off some CNC machine tools that we ran until a couple of years ago. I have a some rack mount backplanes as well as power supplies, spare transformers and a bunch of spare boards. These units were running a K&T 180 CNC horizontal machining center. They used a Shugart SA4004 hard disc drive for the memory. The one computer was running when removed and replaced with a newer system.

John
 
Thanks John, I'll send you a PM soon.

I think I found the secondary voltages on the transformers. After looking through one of the documents off of pdp8online, it looks like the transformers output 5VAC, 15VAC, and 20VAC.
 
I didn't see it on the diagram with the voltages, but here are the amp ratings for each regulator (which I assume the transformer will be around these).

G8016:
+5V @ 20A

+15V @ 0.75A
-15V @ 0.75A (1.5A total on the 15VAC line)



G8018:
+5V @ 25A
-5V @ 2A (possibly 13.5A on each 5VAC line, there are two lines in parallel sharing a center tap on the transformer)

+15V @ 2A
-15V @ 2A (4A total on the 15VAC line)

+20V @ 4A
 
Do you mean 12.5A ?
Anyways, I think it's still 25A, the center tap just tells you that they're doing full-wave rectification, but with only two diodes.
patscc
 
I added the amperage of the -5 and +5 to get 27A then divided it evenly across the two lines = 13.5A. I was thinking that they put the lines in parallel with that center tap so that there wouldn't be as much amperage on one line.

That could be wrong though and one of the lines could be used for the -5V circuit and the other for the +5V circuit. Or as you said they're using only two diodes for rectifying the 5V line.
 
You must log in or register to reply here.
Back
Top