Heathkit IM-28 VTVM, Steps Needed for Restoration

In this video, I look at a Heathkit IM-28 VTVM. I go over what needs to be done to it to make it dependable and ready for daily use. This restore also works for the Heathkit IM-5228.

[@TheTheo58]

A very detailed, informative video of the IM-28 I build one years ago. Was in the process of starting to update several yrs ago new cabinet, and updated jacks BNC etc. And replacement of the capacitors. 73

[@michaeldavidheit]

Nice video, years ago I built the same VTVM as part of an NRI electronics course. I used it in my TV / Radio repair shop until I sold the shop. Just recently I started into restoration of old radio gear as well as some ham gear so I bought one off Ebay. I plan to restore it; your video helped. Thank you and 73 AD7VV

[@ke4est]

Glad it helped you out!!

[@emylrmm]

just a note that 12AT7/12AV7/12AZ7 are adequate substitutes for the 12AU7 . 12AU7s are getting expensive and 12AV7 or 12AZ7 can still be found NOS at low cost

[@EntropicRemnants]

Thanks for this. I just picked one of these up myself so this is a nice overview.

[@ke4est]

Glad it helped!!

[@brianheise2675]

Hey Michael, I really like the big meter that this 47 year old Heathkit has, It should look and work really nice on the test bench... Thanks for posting, I'll be glad to see it working in tip top shape on your bench...

[@ke4est]

Your welcome Brian. Yes, I should have it up in a couple of days. I have all the video shot, just got to finish the editing. I do have it mounted on the bench now, and it is very nice to have for sure!

[@garybevis8691]

I Michael, I love the Heathkit VTVMs.. I have a V-6, I think it is circa 1953-54 it has the meter that is full width of the case...I started back into the electronics hobby a little over a year ago after about 30 years off for raising kids and such. Take care and share more vids, I like your style. 73s KI7TWX

[@ke4est]

Thanks for the kind words Gary! I did a restore on a V-6 too that is a few months old if you look back on my channel. If not subscribed please do so, I am working on the next one right now. Probably be next week sometime. May be a delay as I have to go out of town a bit, but hope to have it up next week.

[@SDsailor7]

How good are these vtvm 's specifically this IM-28 anyone know? Thank you

[@rosshollinger8097]

Nice job. I'm hoping to get mine up and running soon. I picked up two of these, one with manual and probes. The 9.1 Ohm 2W resistor is out of spec at 9.68 Ohms. The parts list calls for a precision resistor and both the ones I have are 5%. I see yours is also 5% (unless the color on my computer is off). I haven't found anything during research to contradict the manual. Do you know what the deal is with these?

[@ke4est]

Modern resistors from a reputable supplier will hold their value pretty good within operating temperature(room temp). If you can source some 9.1 ohm 5% resistors, get a few and ohm them out yourself to find one that is closest to actual 9.1. You can get some at digikey. The reason you want it to be precise is so that the meter tracks correctly. 9.68 will work, but the accuracy of the meter reading may be off. For example if you are on the 15V scale and your resistor is off a bit, 5 volts may read 5 volts, but 10 volts may read a needle width higher than dead on 10V and 15 volts may read even off more. Sometimes you have to take some resistors you have and make your own precision resistor so that the meter tracks correctly. This will involve some calculations and trial and error with some series and/or parallel-series resistor combinations.

[@rosshollinger8097]

@@ke4est Thank you for your reply. I'm playing with that now and will let you know how it goes.

[@ke4est]

@@rosshollinger8097 Sounds good!

[@joer5000]

what is an average cost to restore one of these?

[@ke4est]

It all depends on stock on hand. But if you have the tools you need, I would say around 50USD.

[@MANIX204]

ok, I have a fault, restore one, but I can't find the problem, the needle runs backwards

[@ke4est]

Maybe it is as simple as the meter wires are installed backwards??

[@MANIX204]

@@ke4est I don't know, because I don't have a way to see where each end goes, but I'll try to change them, I've never restored something like a tester, I have more than 40 old restored radios in my house for decoration and an 80-disc jukebock, thanks I'll do that and see what occurs

[@eugenetheodore2956]

Hello Michael, I rerstored one of these & it worked well for a while. It now won't read on the r x 1 scale. Do you know what might cause this?

[@ke4est]

Check your range switch to make sure no contacts are broken. Check for broken wires and cold solder joints on the range switch. Also, check the precision resistors on the wafer switch.

[@tubeDude48]

Since batteries are now made overseas; they're CRAP and they LEAK quite quickly, it's best to put a Battery Eliminator in! ALL the roundy resistors need to be changed. At 11:06, there's a resistor tied to a wire!

[@ke4est]

Yes, I agree, that is why I said personal preference. 🙂 No roundy's in this one, all Allen Bradly and all well within tolerance. No that is an optical illusion. 😉

[@tubeDude48]

NE-2 Neon's are cheap, and it keeps the unit original.

[@ke4est]

I agree if I were going to make it a shelf queen. I use this as a daily driver. Yes, I have a drawer full of them. :)