Heathkit IO 4550 Repair and Restoration

A huge thank you again for all that continue to Join us in the lab for repairs and alignments. The channel would not exist with out all of you so thank you again for dropping by.
Ways to support the channel: / zenwizard_studios
In this video we take a look at a scope that in a round about way started everything for me personally. This is a ONE owner HealthKit scope that is being repaired so it can be moved on to a maker space. Hopefully it will help inspire the next generation to be curious and ask the tough questions of their physical world.
** Repair exposes the Tech to mains electric and should only be done by trained personal. Errors can be fatal. **

[@youtuuba]

The IO-4550 was a pretty nice scope for the money, one of the best that Heathkit ever offered. Decent quality throughout, good design, and good ergonomics. This model was the only Heathkit scope I ever assembled, although I have build at least a couple hundred Heathkits over the years, and done full restorations on much of their test equipment lineup. My only initial issue with it was that a pair of large (2W?) carbon composite resistors on a power supply PCB got so hot that the painted colors rings were bubbling/semi-molten. I asked Heathkit tech support about this and they said it was normal. I asked why it was normal to have resistors running so hot that their surface finish was bubbling, and they said these resistors were running at their specified power distribution, under which conditions they run stinking hot, but non-destructively. They must have been right, because I had that scope for a long time, used it almost every day on my workbench, and never had a problem with it. BTW, those same two resistors appear in THIS video and it looks like they had some surface finish bubbling as well. I finally gave that 4550 to a friend and bought a used Tek 2235A to replace it on my bench, which I still have and use. In my experience, a lot of Heathkit's test equipment lineup over the years was just a bit disappointing, in that so many models never quite performed as well as one might expect or require. But I now have in my every analog and digital multimeter of theirs, and most of those are solid, reliable and perform as well as most others. Also, at least my 4550 scope worked as well as some B+K Precision and Phillips analog scopes I regularly used at work, with the exception that their not having electronic trace rotation was sometimes a bit of a pain.

[@larrybud]

My dad built a heathkit TV around mid to late 70s IIRC. I would have been around 8-10 years old. I remember him soldering all the parts in, adjusting everything etc. It had a front-panel pullout that you have to tune each channel. Similar to a telephone switch board, you'd plug in slot one and call it channel "0 - 2", then another jump to say UHF or VHF, then turn a tuning cap to tune in the actual frequency. I had my hands in that thing all the time. At some point during that time I got my hands on a really old scope. I barely can remember it, has zero idea how to use it, but sure wish I still had it.

[@garynichols1502]

I lusted after this scope when I was in high school. Never could afford one though.

[@PapasDino]

That was my very first scope! Built it (along with loads of other Heath test gear!) and used it for years before I moved up to Tek scopes.

[@ZenwizardStudios]

I like it, for 10Mhz it is a great scope. Especially the trigger works very well. There will be more Heath gear in the future. They did have some wonderful kits at the time.

[@gwc1410]

I had this same scope. I bought it in 1978 for a great price. It served me well, but after about 10 to 15 years it started to fail all the time and I had to constantly fix it. The components inside were poor quality and failed a lot. One day I turned it on and it literally went up in smoke. I opened it up and found many burned up resistors inside. That was too much for me, so on an impulse I threw it away. Also, a friend had the same scope and his quit working. He told me the symptoms, and I said this had happened to my scope, and told him to check a specific resistor. He checked the resistor and it was bad. As I said previously, low quality components.

[@notajp]

I just had one of these given to me that had been sitting in an empty house for years. It had no power, so I determined that power switch contacts were dirty. Cleaned the switch and have power back, but I haven’t went any further yet. Thinking of bringing it back up slowly on a variac to start. I also had a Heathkit IT-17 tube tester given to me just a week before.

[@ZenwizardStudios]

Excellent! I am trying to track down and IT-17 for the lab but have not had much luck yet.

[@OneDamNote]

I've seen the IT-17s sell around 170-225 in auction on epay, as a range.

[@rocketmike4969]

I have one of these scopes. It was a gift from my wife in 1981 when I got my first engineering jobs. I am currently doing a complete restoration on it. How do you cleans the switches without breaking the plastic dust shields that surround the contact rotors. What cleaning chemical do you use? This scope is low mileage and too nice to scrap. It just needs some TLC to live again. My area of engineering was Industrial Automation so I don’t have the restoration experience you have so that’s why I have the cleaning question. I also have a need for this scope as my Tek 2430 died with a non-repairable high voltage power supply problem. You can’t buy, beg or steal that part! Super video, thanks!

[@ZenwizardStudios]

Send me an e-mail and I can send you some information.

[@johnnorton6085]

@@ZenwizardStudios I'm sure I'm not the only one who would like to know how you managed to clean this type of rotary switch. I like your videos but there is too little content on the techniques you use for restoration. That's much more interesting to me that an example of you aligning an instrument.

[@jimdavis6833]

I'm not usually one to criticize, but your hand waving annoys me.

[@poormanselectronicsbench2021]

I would, and am, always more concerned about proper eye protection when handling CRT's of any size, either a good set of wrap around glasses or full protection goggles, as your hands may get cut but will heal much better than a eye cut with a large chink of accelerated glass from an implosion. Long ago, my oldest brother purchased and built a Heathkit IO-103 single trace switch, and also a heathkit 2 channel switch unit. He mostly bought it to hook up to his stereo components, which were all kit versions of a Dynaco ST120, PAT4, and a HH Scott LT112B FM stereo tuner. Although he kept the stereo components when he moved, he abandoned the scope to me as it stopped functioning properly, BUT, when my mom sold off the family house, her and my sister gave me a deadline to grab anything left, but then, she tossed items, including that scope, before her proclaimed deadline. Although it was not a lab grade unit, it did have sentimental value, and it would have been interesting to bring it back into service as well.