Updating a HeathKit IT-11 capacitor checker

tombo22247

Member
2016-02-17 12:23 am
Hello, If this post is in the wrong place, I apologize. I have recently found this tester and want to update the required capacitors. There are a total of 11 capacitors in the unit. I have seen comments that say to not change out the .02 ufd and 200uuf as they were matched by the manufacturer and they seldom fail. I did note a .5 ufd 600v tubular capacitor has a crack down the entire side. It's about the size of a roll of dimes. Does anyone have a suggestion about a replacement capacitor for this one?
The list of capacitors are:
200 uuf molded mica (noted uuf rating vs ufd of all the others)
.001 ufd disc ceramic 1400V (2 capacitors)
.02 ufd Mylar (actually 2, .01 waxed units)
.05 ufd tubular
.1 ufd tubular
.1 ufd Mylar
.5 ufd tubular
2 ufd Mylar
40 ufd 350V (2 capacitors)
I'm having some problems locating capacitors that match the ones I plan on replacing. Any advice on what sizes for each of the ones in the above list?
 

rayma

Member
2011-04-29 8:37 pm
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tombo22247

Member
2016-02-17 12:23 am
Hi, Thanks for responding. I will use the 450v but should I stick with the 40ufd? Also, the .5 ufd 600v capacitor in the unit has cracked from the metal lead out to the edge, then down the side of the capacitor. I'm having trouble finding this size capacitor. Do you know of an alternative? I was wondering if they were scarce due to the age of the unit.
I think I'll leave the two .01 waxed units and the 200 uuf mica unit alone. A former HT tech said these should not be replaced unless they fail and need to be matched.
I appreciate all the advice.
Tom
 
the .5 ufd 600v capacitor in the unit has cracked from the metal lead out to the edge, then down the side of the capacitor. I'm having trouble finding this size capacitor. Do you know of an alternative?
It's just a paper-in-oil coupling capacitor. Nothing special. Today most are listed as .47ufd. You might find a NOS .5ufd (new old stock) unit on eBay.
Link to manual download
Here's one
 
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rayma

Member
2011-04-29 8:37 pm

ticknpop

Member
Paid Member
2005-05-28 9:43 pm
toronto
Use a 600 Volt Solen .47 uf Polypropelene
Actually i'd change all the tubular and mylar caps to the 600 volt Solens.
Use 600 volt PPFMX Multicaps for the lowest values if you can't get Solens,

Check your resistors, carbon ones will have drifted off value with temperature and time
 
Some notes on Caps.

I realize that the thread is a bit stale, but thought I would add this for others that come along searching for mods or updates on these really useful tools. If you replace the pair of electrolytic caps, consider replacing both with a single film cap. That way you don't have to worry about finding the Variac when you haven't used it for a few years. It's also likely to be cheaper than the electrolytics. See examples at Mouser . If you choose to keep the pair of electrolytics, then consider placing some ~330K resistors in parallel with each one to "balance" the voltage across them. Also, if you are a safety-minded, you might think about replacing the .001 1400V caps that sit between the AC and ground with modern XY caps. They are pretty cheap. Some IT-11s don't have 3 prong plugs, but you can retrofit with a 3-prong cord wired as shown in the schematic linked from the previous post by rayma.