Samlex 1223 (& 21/35) Power Supplies

The Samlex 1221/1223/1235 series power supplies are billed as a good quality, low RF switching power supply. Low RFI, and switching power supply typically don't go hand in hand. These power supplies are lightweight, and are rated for 13.8v (you can adjust that if needed).

These power supplies have also gone under these models from ham radio manufacturers:

Yaesu FP-1023
Kenwood KPS-15

C21, C22, C23

The most common failure you will come across is these three capacitors. They will bulge from the top when they have (or will) fail. When you buy a used Samlex, open it up and check for these three capacitors. If any are bulged, replace all of them to be safe. Be sure to use a quality part, preferably Japanese or something other than Chinese.

What tends to cause these failures is two fold - They were probably pushed to their limit quite a bit, and also, the part is apparently “just enough”. Repair notes I've seen state to take the 2200uF/25V capacitor, and replace it with anything higher than 2000uF and use one rated for 50v to avoid this issue.

Q1, Q2

The other common failure that tends to be seen is the main pair of Mosfets. Once again, probably being pushed too much. Easy way to tell if they are bad is to test each leg with an ohmmeter. They will all short to each other if they are bad. The ones I had replaced had a little burn discolouration at the top heatsink portion.

R6, R9

Along with the toasted Mosfets, typically these two resistors will probably go in conjunction.

Fuses

You'll want to buy spare 6.3A “Slo-blow” fuses, especially if you are repairing one of these power supplies. These are your insurance policy so if you screw something up, hopefully the fuse protects it.

Other spare components to think about

Here is a spare parts kit that comes with more components that are likely to fail at some point, depending on your situation. I've replicated this parts list on Mouser, and the price with shipping barely competes with the eBay listing