View Full Version : 5150 PSU - Efficiency and Cleaning Up

July 28th, 2011, 10:15 PM
Good morning, I was wondering about the above. 5150 I've recently aquired draws 102W at the plug (132W with the 5151 connected), hence wondering how close to the 65W output this is likely to be.

Also it's shiney case is a bit corroded on the air outlet, so I was wondering how (if) this could be polished up?


July 29th, 2011, 07:37 AM
60-70 percent efficiency is not atypical for switch-mode power supplies of the early 80s vintage.

However, you didn't say how the 5150 was equipped.

July 29th, 2011, 08:14 AM
That's what I was expecting - and it's well loaded, so I'm wondering if it's delivering at or over it's rated output:

- 5150 256k system board, MDA, FDD controller + 1 FDD drive
- Quadram with another 256k (and leaking battery of course)
- 5251 terminal card (twinax jobbie)
- ST11M 8-bit MFM and ST-251-1 HDD

July 29th, 2011, 08:22 AM
You might want to look for a 135 watt power supply, with the MFM hard drive in there. :)

July 29th, 2011, 08:31 AM
Yeah I was surprise, but it seems to have done quite a few miles as it is already :)

Do you know anything about the finish on the later-spec shiney PSUs?

July 29th, 2011, 09:02 AM
Are you sure you have a 5150 65 watt PSU? ISTR that the ST251+controller combo amounts to about 30-35 watts of consumption.

July 29th, 2011, 09:45 AM
"finish on the later-spec shiney PSUs"
Chrome or zinc plated, I think. Does it look like the plating is peeling off or rusting from underneath?

July 29th, 2011, 10:10 AM
not sure where you measure but the 5151 is just looped from the mains

July 29th, 2011, 11:13 AM
Thanks for all the input. 102W measured at the socket, at DOS prompt, 5151 not connected. PSU itself is marked "CEAG IBM PN 8 529 342", dated wk.47 '83, and stickered "63W 220VAC".

ST-251-1 is rated at 36W on startup according to the spec sheet (http://vintage-blog.peacon.co.uk/wiki/Seagate_ST-251)!

Finish just looks dull on the vents. Bright and shiney elsewhere. A little metal polish perhaps?

August 1st, 2011, 01:12 PM
Hmm although it was working perfectly OK, the strain is showing inside:


August 1st, 2011, 01:23 PM
Nah, that's just a Rifa Type X metallized paper capacitor doing its job of making a mockery of Swedish quality control. It's used in power line filter circuits. Just replace with a polypropylene or polyester capacitor of the same ratings. I have a bucket of these things NOS. Many years ago, one of the surplus places was selling them for $0.25 a pound, all assorted types.

August 1st, 2011, 01:25 PM
Thanks for the pointers on this - much appreciated!

August 2nd, 2011, 12:22 AM
Seems these Rifa Type-X's are 'change-on-sight' components - I'll be checking my other machines before next use!


August 2nd, 2011, 08:33 AM
Since they're no longer made, the Rifa X caps are prized by audiophile cultists of the thermionic sort. Suum cuiquae. :sigh:

August 2nd, 2011, 09:03 AM
The 5154 EGA monitor has very similar X2 capacitors in the power supply.
I've had a couple cases where these went bad, they will produce lots of smoke :-)

August 4th, 2011, 04:59 AM
Slight problem, the only 20.3mm pitch 100nF X1's I can find are made by... guess who...


Any other suggestions!?

August 4th, 2011, 09:42 AM
How about this series? (http://www.farnell.com/datasheets/51268.pdf)

22.5mm pitch; polyester.

August 4th, 2011, 11:07 AM
Thanks. Actually it looks like IBM solved this for me already... the PSU has pairs of pads for these, the inner set being 15mm :)

August 7th, 2011, 02:00 PM
it's shiney case is a bit corroded on the air outlet, so I was wondering how (if) this could be polished up?

For the benefit of the search, the air flow/dust/contaminants from the RIFA X2 caps exploding had damaged the finish, some kind of plating. So I decided to sand it back and re-finish with a 'chrome' spray - here are the results:


And, fitted:



August 7th, 2011, 03:52 PM
Looks nice.

If you run into this again, remember that some of the domestic US PSUs for the 5150 were black. So there's another option for you.

August 8th, 2011, 12:02 AM
Thanks, I've seen that mentioned now you menion it. Was that the 63W in the 5150 alone (i.e. not the later XT supplies)?

August 8th, 2011, 05:56 AM
I think the original PC was the only one to ship with the 63W supply. 63W is just enough to run a stock 5150 with two floppy drives, but if you want a hard disk, you need a little more oomph. The XT was commonly shipped with a hard disk and therefore would require a larger supply. I've never seen one with a 63W supply.

I've seen lots of PC's upgraded with aftermarket power supplies too. Just the other day someone dumped another 5150 on me, and it's got the original dual floppies, with a "hardcard" (Standard WD disk controller, metal plate, and 3 1/2" form factor MFM drive bolted together) - and an aftermarket power supply. So, either the original supply broke at some point, or it got upgraded to handle the load of the hard disk.