UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

WaveyDipole · 26th May 2018, 1:45 pm

Hmm, I did wonder whether 1kv or higher ceramic caps might be suitable as they often appear as filter caps on the mains input.

It does look like my observations earlier were premature. I have now managed to get the PCB out of its case and can clearly see the underside. The two RIFA's along with the first Rubycon electrolytic cap are already replacements, which correspond to the 'capacitor replacement kit'. The remainder of the PSU looks untouched.

I am genuinely puzzled by the 'capacitor replacement kit' as this PSU has some 10 aluminium electrolytics, but only one (possibly for the oscillator circuit) is supplied along with the two RIFAs. Replacement for the two 250v caps across the rectifier DC output or the smoothing caps across the low voltage DC outputs are not provided or even mentioned as being required. In my unit, one of the 1000uF DC output caps was bulging badly and once removed showed evidence of leaking electrolyte. I replaced all 3 1000u and the two 100u but didn't have the 2200uF to hand.

Why would a replacement kit offer only 1 replacement cap out of the 10 that are present in the unit? I appreciate that the cost would be higher and I don't necessarily agree with blanket replacement, but on a 30 year old SMPSU, since I have already gone to the trouble of removing it and extracting the board I think I would rather play it safe and do just that while I am working on it.

26th May 2018, 1:45 pm	#30
WaveyDipole Nonode Join Date: Mar 2013 Location: Leicester, UK Posts: 2,534	Re: What to replace a RIFA X2 with? Hmm, I did wonder whether 1kv or higher ceramic caps might be suitable as they often appear as filter caps on the mains input. It does look like my observations earlier were premature. I have now managed to get the PCB out of its case and can clearly see the underside. The two RIFA's along with the first Rubycon electrolytic cap are already replacements, which correspond to the 'capacitor replacement kit'. The remainder of the PSU looks untouched. I am genuinely puzzled by the 'capacitor replacement kit' as this PSU has some 10 aluminium electrolytics, but only one (possibly for the oscillator circuit) is supplied along with the two RIFAs. Replacement for the two 250v caps across the rectifier DC output or the smoothing caps across the low voltage DC outputs are not provided or even mentioned as being required. In my unit, one of the 1000uF DC output caps was bulging badly and once removed showed evidence of leaking electrolyte. I replaced all 3 1000u and the two 100u but didn't have the 2200uF to hand. Why would a replacement kit offer only 1 replacement cap out of the 10 that are present in the unit? I appreciate that the cost would be higher and I don't necessarily agree with blanket replacement, but on a 30 year old SMPSU, since I have already gone to the trouble of removing it and extracting the board I think I would rather play it safe and do just that while I am working on it.