Vintage Power Designs 5015-S Power Supply teardown (Large Images Warning)

[don.r]

I received my Power Designs 5015-S and am starting the repair process. Two things I know for sure need to be sorted are A) new power cable and B) current limit works backward i.e. cw lowers limit and ccw raises it (bodged repair? factory wiring error?). Here is a look inside:

Front panel looks good.



Top view, meter at the bottom, main transformer at the top. Smaller transformer to the left... there is a purpose to dual transformers! Very dusty.



Bottom view. Sprague metal can cap goodness. What a monster filter cap! Yes, that is a variac on the left feeding the main transformer, hence dual transformers.



Main board. Point-to-point on standoffs. Look at those gold trimmers! No software cal here. :-)



Rear heat sink with RCA power transistors. You can see the poor state of the power cord.

[Vgkid]

Your pics are not loading.

[don.r]

Sorry. I added all images as attachments. phpBB and Dropbox... urrrgghhh!!!

[bitseeker]

Thanks for the pics, Don. It looks like a slim version of the 3650-S that I have, including the variac and big ol' filter cap. The cap in the 3650 is like a soup can.

[don.r]

Thanks for the pics, Don. It looks like a slim version of the 3650-S that I have, including the variac and big ol' filter cap. The cap in the 3650 is like a soup can.

Indeed it does. This cap is more lake a tin of tomato paste. 2500uF at 100V. Your variac must be bigger to carry the higher amperage since this one has a 2A limit stamped on it. GE branded. Overall, the supply about the same size as the Chinese Tekpower linear supply I have but weighs at least twice as much. No USB on a PD supply! Its just such a beautiful design and 500uVpp ripple too I might just keep this one and give my son the Tekpower. University students wouldn't appreciate the PD aesthetic anyhow. 

I am surprised that given the age (must be early 70's) how well everything has stood the test of time. Caps measure fine, transformer looks factory fresh.

[bitseeker]

Yes, the 3650 is rated for 5A.

These supplies are well-built and will last a good long while. I couldn't blame you for keeping it and passing down a different supply.

[don.r]

With the power cable fixed I verified that the current limit pot was wired in backwards... looks like a factory error! She now runs like a champ and regulates like a rock! Only the slightest hum from the transformer (open case) over 30V. Ready for another 40 years of service. A bargain for $40.

[bitseeker]

Excellent! *guitar riff*

[Barrett2186]

I have a 3650S that's giving me trouble - the behavior is erratic. It'd be really useful to me to get it working - and the schematics are available (http://ftb.ko4bb.com/manuals/73.166.198.39/Power_Designs_3650S_Power_Supply_Schematic.pdf). There are a large number of test points with voltages listed - is there anyone here that if I can better describe the behavior that could help me down what to check?

Thanks!

[bdunham7]

I have a 3650S that's giving me trouble - the behavior is erratic. It'd be really useful to me to get it working - and the schematics are available (http://ftb.ko4bb.com/manuals/73.166.198.39/Power_Designs_3650S_Power_Supply_Schematic.pdf). There are a large number of test points with voltages listed - is there anyone here that if I can better describe the behavior that could help me down what to check?

Thanks!

I just got done cleaning and testing one for someone, but I didn't have too much trouble so I can't speak to troubleshooting it.  Still, tell us what is going on and somebody may have an idea or two.  Are you trying to use the remote programming terminals?