Heathkit IT-28 Capacitor Checker Repair & Restoration

[@TheDefpom]

I’m glad you found my repair video useful, and thanks for the mention.

[@poormanselectronicsbench2021]

@ 27:20 I think you measured a 30pF value cap, not a 3 pF, as according to the manual, that unit will only measure down to 10uuF or 10pF. The power factor knob only comes into use when testing electrolytic caps. as when you get your best "eye opening" with the PF control set to zero, you then adjust the PF to get a maximum opening. The higher the value on the PF setting you show on that max eye opening after adjusting the PF knob, the higher the ESR is. I would also double check your chassis mounted fuse value too, it should be a 1/2A slo-blow, you can't take for granted that it's the proper value, and if something like a main PS electrolytic shorts you can damage the transformer if that fuse doesn't open. Glad you have it functioning well, thanks for the presentation.

[@offkafka]

Good advice on the fuse, I double checked and it is a 1/2A slo-blow. On the 3 pF cap, you're right that the bottom of the unit's range is 10 pF. That cap came from a bag labeled "3 pF" but it could very well be 30 pF. And good to know on the Power Factor knob. I appreciate your insight and thanks for watching!

[@poormanselectronicsbench2021]

The 200pF cap on the range switch, pin 4, may have drifted low and is throwing off the bridge circuit. Even though it is a mica, refreshing it with a new NP0/COG 1% ( try to get a fresh one on your next parts order to a supplier like Mouser or Digikey) cap might help it return to better accuracy, as that is the cap that allows the .0001 range of the bridge to be measured accurately. It is hard for a lot of older test equipment to get a good value measurement under 10pF due to the residual, built in capacitance of wiring, switches, and terminations used to connect the test capacitor to the equipment.

[@graemebrumfitt6668]

Just love old test equipment, Mr Carlsons lab uses loads of them and Paul is a Guru of electronics! TFS, GB :)

[@FireandFrostHVAC]

Good video, glad to see that you’re still producing content. Could you do a video showing your isolation transformer / dim bulb setup on your bench? I’m designing a isolation transformer / variac / dim bulb unit and I’m looking for what other people have done. Thanks.

[@offkafka]

Great suggestion! I designed and built it before I created a YT channel but I'll try to put something together soon!

[@FireandFrostHVAC]

@@offkafka thanks, I would be really interested in how you built it.

[@offkafka]

Just up! kzbin.info/www/bejne/iJjblp6MqZehoq8@@FireandFrostHVAC