Heathkit Capacitor Tester IT-22 from 1965 - Page 1
Forum section: electronics / repair

author: Spartan1
author_rank: Newbie
timestamp: May 16, 2024, 11:10:48 am
content: Hello fellow techies.I recently bought a Heathkit Capacitor tester it-22.Noticed weird readings from the eye.Decided to pull it apart and basically do some voltage tests first.This transformer in it is a 240v instead of the 125v in the circuit diagram I have posted.The main concern I have, are the outputs of the transformer are different to the circuit diagram.1) My transformer output is 14vShould be 12.6v.2) Next transformer output is just over 600v.Should be 540v.3) Next transformer output is 58v.Should be 55v.Wondering if these wrong readings are acceptable for the 1629 tube.Thanks in advance

author: wasedadoc
author_rank: Super Contributor
timestamp: May 16, 2024, 11:40:36 am
content: I'd be tempted to put a suitable series resistor in the tube heater supply.

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 16, 2024, 01:42:02 pm
content: C1 is likely a "death cap" and should be replaced with a class Y safety cap. Other leaky paper caps probably causing the behavior issues.Might be more like a 220V primary, good enough if it runs cool, though filament/heater should be within 5% for good cathode lifespan. Wasedadoc's suggestion of a dropping resistor for the heater is a good one.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: May 16, 2024, 02:32:26 pm
content: I do not think the filament voltage would cause immediate problems but high voltage here might shorten the tube life. Did you measure across the filament wires? The schematic calls for a VTVM, so I think a high impedance modern multimeter should be adequateAlso take the volt readings with a grain of salt. Notice the primary to the transformer has quite a volt range specified. Quite common for line voltages to be specified this way since they did vary even more than that specified. The secondaries will be affected also although they do not specify a range. I know that you are using 240.What sort of magic eye problems are you experiencing?Edit :https://www.radiomuseum.org/tubes/tube_1629.html

author: Spartan1
author_rank: Newbie
timestamp: May 16, 2024, 04:17:20 pm
content: Quote from: Wallace Gasiewicz on May 16, 2024, 02:32:26 pmHi Wallace,I was getting the same readings using a new electrolytic capacitor, and a faulty swollen electrolytic capacitorShowing good for both capacitors.Not shorted and Not open

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: May 16, 2024, 08:49:58 pm
content: I think your cap tester only shows if something is really bad, Open or Short, Heath had other testers that showed leakage and cap values. Yours does not.

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 17, 2024, 12:43:09 am
content: Yeah, read the manual carefully, this is a very simple reactance based tester, no leakage test, reactance must be over 10 ohms@50/60Hz for the short test to be accurate, open test just tries to push ~19Mhz though the DUT and if something gets through it'll read good.

author: FIXITNOW2003
author_rank: Regular Contributor
timestamp: May 17, 2024, 06:30:20 am
content: AER you using a modern DMM to read these voltages ? the values in the manual would have be done with a much old style of test meter which would have loaded the circuit a little bit giving lower voltages , try using an old AVO 7 or similar test meter

author: TheDefpom
author_rank: Frequent Contributor
timestamp: May 17, 2024, 06:45:13 am
content: I believe the transformers in various Heathkit gear were either 110V or 220V, so on 240V you will see ~10% higher voltages.Also make sure you test all of the resistors, they tend to drift high with age, they are probably 10% types so make sure they are within that tolerance, unless they are 5% of course.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: May 17, 2024, 11:22:49 pm
content: Schematic posted calls for a Vacuum Tube Volt Meter VTVM.The readings should be very close to a modern High Impedance voltmeter, Like a Fluke Multimeter.However the voltages you measures are kinda what I expect. The voltages I measure an old equipment like this are seldom exactly what is stated.

author: TimFox
author_rank: Super Contributor
timestamp: May 18, 2024, 02:15:54 am
content: A VTVM of that era would have 11 megohm input resistance, close to a typical 10 megohm modern DMM.

author: wasedadoc
author_rank: Super Contributor
timestamp: May 18, 2024, 07:06:46 am
content: Quote from: FIXITNOW2003 on May 17, 2024, 06:30:20 amGood analogue meters at that time were 20,000 Ohms/Volt. Even not so good ones were 10,000 Ohms/Volt. So drawing 50uA or 100uA respectively at full scale deflection. Those loadings in that circuit are totally insignificant.