Heathkit IM-28 VTVM, Restored and Alignment
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- เผยแพร่เมื่อ 26 ธ.ค. 2018
- In this video, I present the restored IM-28 VTVM. I show what was done in the restore process. I also go over the alignment procedure. This restore also works for the Heathkit IM-5228.
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As you can see in the video thumbnail, I added the matching knobs for the Zero Adj. and Ohms Adj.
What's the part number of the small knobs or the model of the Heathkit that they are off, that you used for this?
@@sw6188 I found a guy ebay selling a lot of heathkit knobs, this is how I got those.
@@ke4est Every time I go looking for knobs like this there either aren't any or they want stupid money (plus hideous postage) for just ONE knob! I'm restoring an IM-5228 which is very similar to your unit.
When buying one of these what do you suggest to check for? (if buying in person)
Very interesting and informative video.
Thank you
@Rob Hernandez Outside appearance is up to you. Even a rough looking unit sometimes will work fine electrically. If it has not been plugged in, in years I would not plug it in. If the person you are buying from already has it plugged in, run it through at least its lower ranges. Make sure it will read, even if it is wrong. Look at the needle and see how fluid it is. The main thing is the meter, if it appears mostly fluid and the unit seems intact, the rest can all be easily fixed.
No bench is complete without one of these. Nice comprehensive video. Thanks and 73 from a South African in France!
Glad you enjoyed it!
Hello Michael! Great video and loved what you did with the LED for the indicator lamp. I have 2 of these Heathkit IM-28 VTVM's! Unfortunately, they need much more help than your VTVM did. Just about all of the resistors are so far out of tolerance that I have no choice buy to replace them. One of them has a 900K resistor that measured at 1.9M!! So, I have my work cut out for these 2 VTVMs. For some reason, I prefer analog meters over digital.....go figure...LOL.
I came across your video and remembered I had picked up one at a thrift store for $3. I opened it up and It looks like it had been gone through. New caps and clean. I fired it up but the ohms scale was wacky. I could not get it to adjust. To make this short I found a wire on the tube socket that had never been soldered. It probably never worked right for the owner. I'm now a subscriber. Maybe I'll make a video about it.
That is so much more common than you think. Just imagine a guy just got a kit and is eager to get it going, so he/she is rushing through it to get it, to get it up and running. I have a came across a few like that! Thanks for subscribing!
Big thumbs up to this video.
Very detailed and informative.
Thank you again!
Glad it was helpful!
Hi Michael, You've opened up a "can-o-worms" here. I've owned and worked on many Heathkit VTVMs. Generally speaking all the portable VTVM's (Compact design with a handle on top) starting with the V-7 & V7A used a PCB. Earlier models and all the Bench models used point to point wiring. Most point-to-points used a Ne2 Neon lamp across the mains as a pilot light. The PCB models used a 6v lamp across the filament line. I think the IM-28 was a work in progress. I've read that it had a PCB and yet yours is point-point. The schematic you are using is for the IM-28u which may have been a prototype. I don't have a schematic for the IM-28 but the manual is on order. I'm pretty sure that the IM-28 should have had a neon pilot lamps like all the other bench VTVM's like the IM-13 & IM-5228. The IM-28U may not have made it to the public and when yours went back to Heathkit they may have substituted that lamp assembly. All the bench VTVM's had a 6.3 filament line. Once I get the IM-28 Manual I'll check back in. But I think that IM-28u schematic showed some planned changes for the IM-28 that never came out. The 5228 was the last bench model before the Heath Schlumberger merger when the 5228 became the SM-21A.
Hi Michael and Subscribers, others. Mystery solved. I received the original Heathkit Manual for the IM-28 originally it was like all the other point to point Heathkit Bench VTVM meters. The Schematic used in this video was for the IM-28u the "u" standing for updated. The IM28u was upgraded to a circuit board layout rather than point-point wiring. The IM28u has all the characteristics of the Heathkit Portable (Plastic handle on top) meters starting with the V7A. The V7 was pt-pt. I am now watching Ebay for an IM-28u meter. But I don't think it ever made it to production. The schematic for your IM-28 is teh same as the IM-13 and IM5228.
Thanks Tom. Yes, I saw this comment the other day, but with a sickness in the family, I have been doing a lot of running. Thanks for the update and the research! It is much appreciated! As far as the neon lamp. Yes, I chose to purposely replace it with an LED. 🙂
Hi Michael, Family is always first of course. It will be very interesting if we find an IM-28u for sale one day. I've also got a big interest in Heathkit. I built many of their test equipment kits and there was a Heathkit Store a few miles from my residence. Take care, Tom
Looks like brand new in side and out ! Should the triodes every run down too low (unlikedly), you can sub a 12AT7 or 12AY7 if 12AU7 isn't handy
Thanks for the alignment my heath kit vtvm IM- 5258 firing on all cylinders. Best alignment I've seen yet God bless from KG4GCX NC
Bryan, thanks for the kind words!
Hi Mr. Graves, First time view to your channel, great video on the Hearth VTVM. I am a proud owner of serval Heathkit products, I have a IM5284 VOM, an IM2260 digital meter, and my favorite IO 4235 oscilloscope, these are used about everyday and work like new, Heathkit did make good equipment... Have a nice day!!
Thanks for the kind words! I hope you subscribe for more. Yes, they did. You will have guys that are biased, but for what they are(not 10,000 dollar stuff), they make mostly good equipment. I too use a few of their products on a daily basis.
I just got one and I’m happy I found this video ! Thanks ! Take care! 73 de ve3hip in welland Ontario Canada 🇨🇦
Thanks for the kind words!
Sure is a handsome piece of test gear for the workshop bench. Cleaned up really good. It's good to see a very useful piece like that get to be back in service... I look forward to seeing you get to use it on future projects. That is one piece of gear likely to survive an EMP... Looks great Michael. Keep after it...
Thanks for the kind words Brian. Yes, you will see it in future videos! 🙂
time to replace the caps in mine! Love mine - I built it :)
That is always the best! You know where it has been. 🙂
The service manual that i have is for the IM-28 and the electrolytic capacitors that it calls for are 0.047uf 1600vdc, 0.05uf 400vdc and 20uf 150vdc. Is that what the manual that you have calls for?
Thank you
What's the difference between the -28 and the -5228? They look identical
I think it is just mainly where they changed styles.
So you replaced the original ceramic with electrolytic capacitors?
No, those are not ceramic that I replaced.
@@ke4est Ah ok.
Thank you
Hey Michael I'm looking for a ste of probes what kind do you have i like the fact i can use one for ac and dc mine is old worn out thanks for reply. Ans merry christmas to you and yours.
Hello Byran. The ones I am using on that meter I got from a seller on eBay. Have bought from him a couple times and chatted with him, good guy he sells a completed set and also has a kit a bit cheaper if you want to assemble them yourself. www.ebay.com/itm/Heathkit-VTVM-Probe-IM-11-IM-13-IM-18-IM-28-IM-5218-IM-5228-Assembled/232008436470?hash=item3604c7caf6:g:WboAAOSwDw9bQpFW
do you do Heathkit im-28 restorations?
I do sometimes. Usually over the winter. Too busy during the summer.
Where can you buy the capacitors needed for the IM-28? anyone know?
And what type? just regular axial electrolytic capacitors? or do they have to be a certain type?
Thank You
Sorry for late reply, I get mine at Digi-Key. There are many fakes out there these days. Digi-Key is a reputable source.
@@ke4est Thank you for replying back. I will look for them there.
Cheers
More good info, thanks. DE N3ELZ
Thanks for the kind words.
Very helpful OM! kn7sfz
Glad it helped!
@@ke4est Yep, I'm getting ready to start using the one my dad (SK) put together in January '73, quit ham a few months later and has been sitting unused for 47 years, still in new shape. I'm enthusiastic! kn7sfz
@@vocalrehab Would love to hear how it turns out.
@@ke4est OK. I hope to open it up today. By the way, did you mention Digikey as your source for caps? I'm just getting my feet wet in restorations of old equip and wonder which is the best supplier for low quantity parts and inexpensive shipping (I don't see me meeting the $99 free shipping target..hi hi).
@@vocalrehab Yes, I use Digi-Key mostly. I use Illinois Capacitor Brand caps to replace the paper and foil caps and rubycon for the electrolytic caps mostly. There are others also, but that is the main ones. Don't buy caps off of ebay, too many fakes. Yeah, I know what you are thinking, but yeah they fake capacitors too, like everything else.