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2m KL150 PA repair

18 April, 2023 - Reading time: 4 minutes

The KL150 I took from my stock for the new VK7RVP 2m repeater seemed to be in good condition, until I tested it.

As usual, the low power mods were performed, channel frequency programmed, controller installed, etc.  Next the alignment was done, and it was then that it became apparent that the PA had issues.  The PA struggled to produce 47W, and power level wouldnt regulate properly.

Careful visual inspection revealed what seemed to be some missing parts around the base of the final device.  Next we refer to the schematic diagram for the PA.

According to the schematic there should be 4 capacitors on the base, I can only count 2.  Hmm...

Seems someone has decided to remove some for some reason.  Checking a known healthy and working KL150 confirms this.

The rest of the PA checks out fine.

I went searching all of the usual suppliers for what seems to be unobtainable mica SMD capacitors. Either they weren't listed, weren't stocked, or had minimum order quantities.  So I settled for next best, some AVX SQCB, expensive, but seemingly worth it.

No sooner had the package from Digi-Key arrived, I had the appropriate parts installed.

I had a bit of a clean up around the base. Some desoldering braid to mop up, acetone and cotton tips to dissolve and remove the excess flux gives it that nice clean factory look.  I installed the new capacitors as pictured, and prepared the unit for test.

Results are pleasing with the transmitter making an easy 70+ watts, good power regulation at 50w, and nice spectral purity.

Thats it, fixed.  Almost ready for installation, needs soak testing, and I might give it a 5DJ voice board to make it a bit nicer on air.