Heathkit IO-102 Repair, Mods & Demo

After decades languishing in my basement, I rescucitate my IO-102 scope which no longer worked. How I troubleshot it, and made a couple of mods.
Finally, I demo it using an IG-18 & ID-101, and then test its bandwidth response.

[@edgeeffect]

"we're going to be horizontal.. promise" really made me smile. Woah... it's so cool that you've still got it... all I've got left from the 1970s is a broken toy spaceship. ;)

[@dtss_smudge]

I wish I had saved even more stuff from the 70's! Thanks for watching and for the comment!

[@fredcailloux2526]

Thank you! You just save me hours of research! I have owned one since 1978 (serial number 138107) and a none working one for spare parts (serial number 05220).Both collect dust for almost 40 years? I retired last year and buy a new workbench, plenty of new and old trusty "Toys". Since my IO-102 was the first instrument I own, he stay on my vintage shelf until I die!

[@dtss_smudge]

Glad you found the video helpful. Other than the power transformer and the CRT, pretty much everything else in the scope is repairable/replaceable. Good luck, and thanks for commenting!

[@ghramsey1681]

Nice video. A while ago I saw a craigslist ad for a Heathkit IO-4510 scope for $50. Dual channel. I was messing with building tube amps for guitar playing at the time and wanted a scope to testing. I went to buy it and upon power on test by the former owner something broke. It would not power on. He was the orignal builder, but didn't want to mess with it further and gave it to me for free. Upon bringing it home it was a single diode 1n4001 or maybe 4003 that had blown. The PSU caps were OK but I replaced them just the same due to them being original. I went and purchased an expensive 20kv rated DMM probe for about $50. The last such item in stock at Frys at the time. I seem to recall changing the voltage regulator circuit built from discrete transistor arrangement to a 7505(I think). Worked well, but I ran into a block while calibrating it. A trimmer capacitor for the vertical trace circuit which is broken. It turns but does not make any change on the trace. For some reason too they made it super hard to fix because the cap is under the massive stepper switches. I had to get a super long length non-conductive screwdriver just to even attempt to adjust it only to find it was really mushy when adjusted and finally the top portion fell apart. Sadly, there's no way to replace that cap without major surgery. I'll have to desolder 25 pins of the switch to even get my hand in there to remove the old part much less position a new one. I still have the scope gathering dust. My own electronics hoarding. I might get around to repairing it one day. I think one of the reasons I never did though other than the location was being unable to find the same type trimmer cap. It's been probably a dozen years now since I shelved that scope. I noted recently though that someone selling Heath replacement parts. Maybe I can get that part now... I might revisit this scope.

[@dtss_smudge]

The 1980s IO-4### series scopes succeeded the 1970s IO-1##. Nice scope, especially just before Heathkit started really cheapening out their test equipment (IG-5282, IB-5281, etc I'm looking at you). The vertical compensation trimmer caps that appear to have failed you aren't critical, they're just in parallel with the input attenuator resistors. Unless shorted, they should not prevent a waveform from displaying. In fact, most quality scope probes have long had such trimmers built into them. Your IO-4510 certainly deserves a new life. Thanks for sharing its story.

[@ghramsey1681]

@@dtss_smudge I really went all out at the time. I scratch built a 4505 scope calibrator. Made a 1:1 PCB and everything but I reworked the 5v regulator which uses discrete transistor regulator circuit to use a normal 75xx . 7505 probably. I made it into a tank compared to the kit version I've seen. The power transformer is I think over sized but was probably what I found in a local electronics / surplus shop here in Houston. The logic chips were cheap at maybe a dolllar or two each. Was a fun build. I forget what I was doing in the calibration steps of the scope, but I was probably using the 4505 I built in lieu of something more expensive. I am sure that trimmer was actually broken. I want to say the whole top came off so it was open maybe. I know it was a major road block to calibrating it per the manual.

[@rfburns3472]

Great video! I have the equivalent, mint condition with manual, Heath/Schlumberger SO-107A which was a factory wired unit. My father bought it back in 1973 for his FM broadcast radio station. I went through the whole thing as you did, replacing all the old electrolytic caps and some resistors mainly in the power supply section. Not the best 5 MHz scope but good enough for audio and low frequency RF work. Sorry to say I will be putting it up on eBay soon as its time to part with it. I hope someone can use it and not e-waste it.

[@dtss_smudge]

Obviously, 5Mhz was good enough for a FM station! Make sure to mention on your listing that it was factory and refurbished, Include pics of what must be awesome factory wiring! Thanks for the comment!

[@rfburns3472]

@@dtss_smudge Thanks for the advice!