Heathkit 10-10 Oscilloscope repair/usage - Page 1
Forum section: electronics / repair

author: electronics-whiz
author_rank: Regular Contributor
timestamp: June 23, 2017, 01:52:45 am
content: So I scored my first scope last weekend cheap at an auction. I got it home tried it our and I get no output on the display. It did come with the manual and I tried a few things with that with minimal luck. This appears to be from like the 1970s era and uses tubes and what looks like carbon comp resistors. All of the main tubes do glow, with the exception of V8 IV2. V11 is really bright when I put one tube in either the V2 or V6 socket (both are 12Bh7 in the manual) which makes me think I have a shorted tube. Also, the manual refers to these as 12BH7 tubes, the tubes in my unit are actually 12BH7A I don't know if that matters or not.According to the manual if you don't get a trace remove the vertical tube then the horizontal tube. I don't recall now but V2 is one of them, and V6 is the other. If I remove one it is still dead, if I remove both when I power on I will get a spot on the display with a small pulse to it, the neon power pilot light does the same. Other times it will show a spot then it will move right or left and then vanish.All of this is with no input on the vertical input on the scope, I have tried turning up the focus and intensity. I also see trimmers inside for both directions and for astigmatism. I have a friend that is an electrician/teacher I will try and ask also as this is something totally new to me.Digital manual for Heathkit model 10-10http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_IO-IP/IO-10/IO-10.pdf

author: oldway
author_rank: Super Contributor
timestamp: June 23, 2017, 06:48:53 am
content: We often discuss the choice of a beginner oscilloscope, a digital or analogue oscilloscope.Speaking of analog oscilloscope, we mean a modern version transistorized and in good working order.Here you have bought a brontosaurus vacuum tube technology oscilloscope and in a not working condition ...Do not you think you exaggerated in the absurd?This oscilloscope can at most appear in the showcase of a museum and is no longer of any use at the present days.In addition, tube technology is too dangerous for a beginner because there are high and lethal supply voltages.Put this device in the dumpster or resell it and buy a modern oscilloscope that is in good working order.Unless you are a collector, do not waste your time with such an antiquity.Anyway, if you are a collector, here some informations about restauration of this kind of oscilloscope:

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 23, 2017, 05:26:04 pm
content: Quote from: oldway on June 23, 2017, 06:48:53 amI think this guy got shocked by a tube once and is freaking out over nothing. Don't waste your time listening to this hater, there is nothing wrong with old tech. If properly repaired it'll still function perfectly fine. While there are high voltages everywhere (be careful), and heathkit scopes are not the best quality, they are simple and easy to understand how the circuits work. This is more 50s to 60s tech, anything starting from the 70s onward, if you buy it broken, they are hopelessly complicated to repair for a beginner. If you can, find a cheap (working) tube tester. Also, replace any electrolytic or paper capacitors (which are usually tubular shaped) and make sure the resistors read close to what they are supposed to.EDIT: here's some more stuff on tube scopes:https://www.eevblog.com/forum/repair/barn-find-oscilloscopes/

author: Paul Moir
author_rank: Frequent Contributor
timestamp: June 23, 2017, 06:39:46 pm
content: Be careful operating this oscilloscope without it's full compliment of tubes installed. With one of them out and therefore the power supply less loaded, the voltage increases. To prevent this getting too high, it's absorbed by the regulator tube which is V11 in this case. If you look at the schematic, V11 pretty much shorts across the B- line as it turns on. That's why it glows brightly.First step is to turn it on letting it warm up a minute or two. Turn the intensity all the way up. Turn the focus to mid point. Turn the frequency to Horiz In (all the way to the left). In a darkened room, now sweep the Horiz Center and Vert Center controls and see if you see even a dim glow from the screen.

author: electronics-whiz
author_rank: Regular Contributor
timestamp: June 23, 2017, 10:44:42 pm
content: If V11 is the regulator tube then I don't understand how if I have all of the tubes in it glows, but if I remove the one it dims to a low glow just like the others.I have even left it on for like 5 minutes to warm up and still nothing.I was able to get in touch with a friedn/ electronic teacher at the college I went to he said in a couple weeks he'd be available and said he had some spare tubes from something and seemed to think it may be repairable. I may just leave it as is until then while I know a good bit about electronics, transistors, etc tubes, scopes are pretty much a new animal to me. I know what scopes do, some of the attenuation adjustments, etc, but usually most things I see show digital scopes.

author: tpowell1830
author_rank: Frequent Contributor
timestamp: June 23, 2017, 11:32:38 pm
content: Keep in mind that you need to run this in low light in order to see the trace on that old scope. The CRT is not top of the line to begin with and then factor in the age. I have to turn the lights out in order to see the trace on mine.

author: electronics-whiz
author_rank: Regular Contributor
timestamp: June 24, 2017, 12:15:47 am
content: HMM that is interesting. I will have to try that, but unless it's really dim I would have thought I could see it indoors in my workshop/closet.

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 24, 2017, 01:12:29 am
content: Also, it's IO-10 not 10-10. Just in case you need to search for it.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: June 24, 2017, 02:46:48 am
content: I misunderstood. You said V11 glows brightly when you put a single tube into either V2 or V6. I assumed it glowed normally when you had tubes in both. If one particular tube is behaving differently than the other, then something is clearly going on.Also V8 should be glowing quite brightly. The 1V2 in my IO-12 (much older design) is almost lightbulb like. It has had trouble in the past with making good contact with the socket pins, requiring a little wiggle to coax it back to life. I finally gave up on it and put in a high voltage diode. Note to others: this is the tube that rectifies the 1250v high voltage for the CRT, so if it isn't glowing, there's not going to be any hint of a trace.

author: WastelandTek
author_rank: Frequent Contributor
timestamp: June 24, 2017, 03:05:30 am
content: Quote from: oldway on June 23, 2017, 06:48:53 amhogwashdo NOT dumpster this fine piece of equipment...ffsI have a PILE of scopes here, I still use my restored O-10 quite frequently, do not listen to this puffery.Replace ALL paper and electrolytic caps per the Carlson video linked above.

author: floobydust
author_rank: Super Contributor
timestamp: June 24, 2017, 03:12:49 am
content: I would recap the unit, change out all electrolytic capacitors, they don't last this long.V8 HV rectifier filament glow, there is a shield inside so hard to see. If you're getting a trace, it's working.I would check the +150V and -72V regulated power supply voltages.With no tubes driving the CRT deflection (pulling V-deflection V3,V4 and horizontal V5,V6) you should get a centered dot.

author: oldway
author_rank: Super Contributor
timestamp: June 24, 2017, 06:10:36 am
content: This is absolutely not a fine piece of equipment...that's an useless bullshit....You can't measure nothing with this oscilloscope, it has no calibrated input attenuator, not even a calibrated time base...There are a lot of cheap analog oscilloscopes to buy....Buy some decent analog oscilloscope in working condition as Tektronix 465B, 2235, HP1740A or Hameg HM605....

author: oldway
author_rank: Super Contributor
timestamp: June 24, 2017, 07:19:32 am
content: Quote from: WastelandTek on June 24, 2017, 07:15:18 amTry to post something more clever....As I said, it may be o collector item, (but of very low value because they are not rare at all), but useless even for basic electronics.Don't loose your time and money with it....Problem with this oscilloscope is not that it is a vacuum tube technology, but that it has been made to be the cheapest vacuum tube technology possible.In this time (years 60), Tektronix was making very good vacuum tube oscilloscopes....but these Heathkit oscilloscopes had nothing to do with this...It was a copy of old WWII era technology and fully outdated in the sixties.I had one when I was a kid because it was all what my little money could pay.

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 24, 2017, 01:02:45 pm
content: Quote from: oldway on June 24, 2017, 07:19:32 amHave you ever thought that since he is a beginner maybe all he wants to do is see the signals?

author: oldway
author_rank: Super Contributor
timestamp: June 24, 2017, 01:59:10 pm
content: Quote from: Cyberdragon on June 24, 2017, 01:02:45 pmYou are kidding ? Do you really think that you can see a signal with a one channel 200Khz bandwith oscilloscope, with a multivibrator time base (not triggered base time), the worst sincronisation you can imagine, no calibrated input attenuator, no BNC input connector, the most bullshit oscilloscope you can find on the market.... and a beginner should use this in the actual technology....SMPS, Arduino, FPGA, even to test a 555 circuit, it does not serve...?You can only be kidding....

author: electronics-whiz
author_rank: Regular Contributor
timestamp: June 24, 2017, 02:17:07 pm
content: This scope has BNC input, external horizontal input, a few other things I don't yet know what they do. Figured $10-15 for a first scope is not bad, if I screw up and blow it up I'm not out much. Right now I'd just like to look at some signals, maybe see if I have clean DC off a rectifier, mess around and see if I can see the bus frequencies on an old Pentium 3 motherboard.There is no point dropping $$$ on a fancy scope when I still have to figure out the beginner part. I have no real plan to use in any real complicated testing, etc. I don't see how this wouldn't be worth at least trying to fix. If it's a $15 scope and $150 to fix it then maybe not worth it. Seems even older scopes online still sell for like $100+

author: oldway
author_rank: Super Contributor
timestamp: June 24, 2017, 02:31:44 pm
content: http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_IO-IP/IO-10/IO-10.pdfQuoteOnly if it has been modified or if it is not an IO-10 heathkit oscilloscope.QuoteAnd how do you do to measure if the ripple is in the specifications of the service manual ? No way to measure anything without calibrated vertical input attenuator. NB: no need of an oscilloscope, use your multimeter in AC voltage to know how much ripple you have.QuoteNope...

author: Cyberdragon
author_rank: Super Contributor
timestamp: June 24, 2017, 04:16:47 pm
content: Most old scopes have been modified (really only get them if they have been). Again, he is new to scopes, he needs to learn how to view signals fist before he can measure them. So a 200Khz untriggered viewing only scope is plenty good enough. Yes, he will eventually need to upgrade, but wait till he's ready before shoving a bunch of buttons and knobs at him. That is far from the worst "oscilloscope" ever made. Look up the Waterman Electronics Pocketscope and be afraid. Now that heathkit looks fancy.But no, it won't work on any computer motherboards. It'll be fine for simple breadboard circuits, audio, and PWM stuff though.

author: oldway
author_rank: Super Contributor
timestamp: June 24, 2017, 04:29:44 pm
content: QuoteYes, using his CRT to make a clock....and nothing moreQuote...To sincronize that oscilloscope on a PWM signalTwo channels and 20 Mhz minimal bandwith recomended for a beginner.

author: mcinsand
author_rank: Newbie
timestamp: October 04, 2017, 09:55:37 am
content: Any update on the scope project? I've always liked the simplicity of the IO-10, and it's useful for some of the things at my bench, such as sweeping a VCO and looking at resonant circuit responses.

author: bd139
author_rank: Super Contributor
timestamp: October 04, 2017, 10:39:52 am
content: Indeed. Interesting thread. It's either been abandoned or OP killed himself on itMy second scope (the first one doesn't count as it wasn't actually really mine) was an IO-12 which could just about slew to 5MHz if you pushed it. Perhaps surprisingly if you know a few tricks you can actually get these as usable instruments into the 100MHz+ range with some compromises but not a lot of people know that (down-conversion, sampling, demod probe, power detector etc). Relative measurements are quite useful too which it's capable of as well. There's a whole education in bending low specification tools to get the information you need out

author: mcinsand
author_rank: Newbie
timestamp: October 05, 2017, 12:04:32 pm
content: >>Perhaps surprisingly if you know a few tricks you can actually get these as usable instruments into the 100MHz+ range with some compromises but not a lot of people know that (down-conversion,>>sampling, demod probe, power detector etc).Don't forget about using inductive compensation to increase interstage bandwidth. Your IO-12 might have enough room under the hood for such tinkering.>>There's a whole education in bending low specification tools to get the information you need outMy first tutor was a near-nonagenarian when I met him in the 1990s. He wastheperson for HF and VHF radio repair in Western NC, and he got his start working on the very early radar systems for the military. He was a tremendous help when I was working on my first project: a Heathkit HW-101 transceiver. I remember noticing an ancient DuMont scope on his bench during one of my first visits, and I'd learned enough to know that it had a bandwidth of maybe 1 MHz. So, I asked if it was there just for decoration. He laughed and said that, no, it was his workhorse scope. No doubt that he learned how to do more with limited bandwidth during his radar days, but he did know how to diagnose, design, and repair like I doubt that I ever will. Scopes and test gear with electronics are definitely like tools in other fields; better to have a skilled person with limited tools than an unskilled person with top of the line.

author: bd139
author_rank: Super Contributor
timestamp: October 05, 2017, 12:22:08 pm
content: Exactly.High bandwidth scopes are a relatively new thing as well. If you look at the Saturn V Instrument Unit, it uses C-band transponders on it (4-8GHz) back in the early 1960s. No oscilloscopes that fast then! It was all frequency domain and you can get your SA output on 1 MHz DuMont fine and he knew it

author: oldway
author_rank: Super Contributor
timestamp: October 06, 2017, 02:46:34 pm
content: It should not be exaggerated.We are on a forum where some people do not hesitate to say that an analog oscilloscope is totally useless.I do not agree with that.But come to argue that an oscilloscope whose technology dates from the WWII is usable by a beginner, there is an exaggeration.When Dave is looking for an analog oscilloscope of less than US $ 50 on Internet, he is looking for modern decent oscilloscopes of 20 or more Mhz, not this kind of antique crap scope that no longer belongs in an electronics workshop at the moment.Yes, it can be a museum piece and I leave it to collectors the right to waste their time and money on this kind of apparatus .... It serves, yes, to show it still works to the visitors of the museum and nothing else.I can write about it because I had a IO-12E in the past and the first thing I have done was to buy a 7 Mhz BEM 003 MBLE when I had enough money to replace this piece of shit.

author: bd139
author_rank: Super Contributor
timestamp: October 06, 2017, 02:52:37 pm
content: Yeah it’s shit and you’ll replace it if something better comes along but there’s still mileage in it which is the point.

author: oldway
author_rank: Super Contributor
timestamp: October 06, 2017, 03:26:57 pm
content: There is no mileage in such an old oscilloscope anymore...It is dead...it has nothing to do with modern technology.If you want to learn electronic, you need basic decent modern test equipment....Not the least state of the art, but some decent equipment...And this shit oscilloscope was not even the state of the art in the years 60...It was a WWII technology....It has helped a lot of beginners in the years 60, I agree....But this is more than 50 years ago....

author: bd139
author_rank: Super Contributor
timestamp: October 06, 2017, 06:21:05 pm
content: Some of us like the smell of shit

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 06, 2017, 10:04:45 pm
content: There's no arguing the scope is crap, it's a Heathkit, but just because it's useless for your line of work doesn't mean it's useless to everyone. There are several youtubers who show how to use these types of un-triggered scopes, you just have to know how to fiddle. If you are an inexperienced fiddler who is spoiled by auto-triggering, well tough bananas.I've personally diagnosed an odd distorting transistor with a bad junction in an old Hi-Fi set with a vacuum tube sig-gen and a manual trigger tube scope.Just because you have lost touch with the McGyvver ways of using the bare minimum tools to diagnose a problem, doesn't mean it's impossible.Not saying anyone should ever use this as a main scope, but yes, it is possible to teach someone how to use a scope with a tube un-triggered scope. It is even possible to use it for audio work,you don't need a triggered scope for basic audio. P.S. You said a BEM 003? You do realize that there really isn't much difference in actual functionality other than that seems to have auto-trigger and maybe a few more tubes.Sure, it's higher quality, but to a beginner, that probably doesn't matter, it'll last them until they get a new one.

author: bd139
author_rank: Super Contributor
timestamp: October 07, 2017, 08:15:10 am
content: Yep. The best scope is the one you have that works.My old Heathkit scope was used to repair its successor successfully. No signal on either channel. I injected the output of a 555 astable into the input BNC and used the heath scope to trace it out. Eventually found a dry joint after the channel switch. Bingo it paid for itself. That scope was used to repair my old 465B and so forth.Also the old tube scopes are virtually impossible to blow the front end up on.

author: oldway
author_rank: Super Contributor
timestamp: October 07, 2017, 09:10:24 am
content: If you want to waste your time with an oscilloscope launched on the market in 1956, which has only one channel, with a bandwidth of barely 200Khz, with a non-triggered/recurrent sweep and an uncalibrated vertical input, this is your right.The video shows that the time base has not even a basic linearity....It was perhaps valid in the 60s, but not anymore.If you are not able to understand this, I think I no longer have to waste my time answering in this topic.Dave has shown that decentWORKING2 channels 20Mhz modern CRT oscilloscopes are easily found for $ 50 or less.So, buying aFAULTYdinausore from 1956 to use it in 2017, it sounds like pure insanity.I can understand that it can be purchased for collecting, but not for use in learning electronics.

author: med6753
author_rank: Super Contributor
timestamp: October 08, 2017, 10:50:24 am
content: Quote from: oldway on October 07, 2017, 09:10:24 amIf you want to continue to spread the hate at least get your facts straight. The Heath IO-10 has a bandwidth +2 to -5db from 2Hz to 5Mhz. Not 200Khz. It was specifically designed to service color TV's and the 3.58Mhz colorburst signal. And it does have good linearity if everything is working correctly. Is it old and out dated? Agreed. But you can still learn from it. I certainly did.

author: oldway
author_rank: Super Contributor
timestamp: October 08, 2017, 11:47:42 am
content: bandwith of 200Khz, not 5Mhz...http://tubularelectronics.com/Heath_Manual_Collection/Heath_Manuals_IO-IP/IO-10/IO-10.pdfNB: nonsense is not hate....even if I would spread hate against a crap Heathkit IO-10 from 1956, what's the matter with this ?

author: med6753
author_rank: Super Contributor
timestamp: October 08, 2017, 12:04:23 pm
content: I stand corrected. I confused the O-10 with the IO-10. They are totally different. Yes, 200KHz bandwidth.But it still could be a tool to learn how to design directly coupled (DC) vacuum tube amplifiers.

author: oldway
author_rank: Super Contributor
timestamp: October 08, 2017, 12:37:47 pm
content: Quote from: med6753 on October 08, 2017, 12:04:23 pmYour avatar's picture is a 2465B Tektronix, with a bandwidth of 400MHz, sensitivity of 2 mV at 400MHz, and risetime on all channels of 0.875 ns.And you are saying that a beginner can use a FAULTY Heathkit IO-10 of 200Khz bandwith....You are kidding ?Or you are hating beginners?

author: med6753
author_rank: Super Contributor
timestamp: October 08, 2017, 02:00:03 pm
content: Quote from: oldway on October 08, 2017, 12:37:47 pmSince we're in the mood for correctness that's a 2465, not a 2465B. 300Mhz, sensitivity of 5 mv at 300Mhz. Risetime 1.17ns.QuoteIf they have an interest in audio 200Khz bandwidth is more than enough. And as I mentioned before since it's a DC coupled scope there's very few leaky coupling capacitors to replace. And again, if there's an interest in vacuum tube circuits it's a perfect project. If I had that scope I'd fix it up.QuoteNo hate at all. Always willing to help beginners. Obviously you feel very strongly that this is a lousy project to take on. That's OK, you're entitled to that. I just think you need to tone down the rhetoric a few octaves.

author: oldway
author_rank: Super Contributor
timestamp: October 08, 2017, 02:26:44 pm
content: You give very bad advice to electronics-whiz ... Not only very bad advice but also very dangerous advice, which is much more serious.The multimeter and the oscilloscope are two basic and essential instruments.The first advice to give to a beginner is to never buy a faulty meter nor a faulty oscilloscope.There you are already in error.Then, you should not ignore that in a tube technology gear there are dangerous voltages with currents that can be greater than 30mA .... Such currents can be lethal....This is really not what must be recommended to a beginner.Finally, a beginner has enough things to understand in the circuits so as not to have to worry about erroneous waveforms (for example, sinusoid instead of a square wave) due to the major imperfections of the oscilloscope he use.So, there is only one advice to give to electronics-whiz: sell or put in the cellar this faulty antiquity IO-10 and buy a modern oscilloscope that works.

author: med6753
author_rank: Super Contributor
timestamp: October 08, 2017, 02:53:19 pm
content: Holy crap! How did I ever survive the 1960's when I was a beginner!I got my father'sFAULTYO-10 scope out of storage and learned to fix it. I'm still here.Same withFAULTYVTVM and fixed that too. I'm still here.Back then all we had were vacuum tube circuits. Lethal voltages and all. Of course if you are going to work on these circuits you needed to understand the high voltages involved. If the Op is really interested in fixing up what you describe as a pile of junk then wouldn't it be better to help rather than shitting on his parade?THAT'Swhat this forum is all about.

author: bd139
author_rank: Super Contributor
timestamp: October 08, 2017, 04:09:57 pm
content: When you have no money you use what you can find. Sometimes when we find something we like it even if it’s shit by modern standards. So what?Back in the 1920-1970 period you were faced with tubes. I was on the tail end of that when my measly allowance at the age of 8 allowed me to purchase discarded tube radios and repurpose them. I was 8 and working with HT with a shitty micronta meter. Thanks to the education I got, from my father, I knew what the hell I was doing and worked safely.Really, education is #1 way before tools. Agree with med6753 here. We can be elitist or we can help. Let’s help. I think we need to help people solve the problem they have, not tell them they have another problem.Oldway I’m not disagreeing with you entirely for reference just the approach. Perhaps OP likes that scope. So what!?

author: oldway
author_rank: Super Contributor
timestamp: October 08, 2017, 05:11:36 pm
content: Quote from: med6753 on October 08, 2017, 02:53:19 pmYes and - in 1960, we did not use a seat belt in the cars, we did not have a differential circuit breaker in the electrical installations, the cars did not have to go through the crash test, etc ...You have to be stupid to want to use security rules of 1960 !!!If you have repaired tube gears in 1960 and nothing happened to you, so much the better for you ....But the times have changed and the security rules too.To advise a beginner to start with repairs on circuits at 250 or 300V dc, today, it is not only irresponsible, but also criminal ...There are enough interesting circuits to experiment in low voltage so as not to take unnecessary risks.Moreover, in the age of computers, tubes technology, this is no longer of interest to a beginner.

author: oldway
author_rank: Super Contributor
timestamp: October 08, 2017, 05:17:17 pm
content: Quote from: bd139 on October 08, 2017, 04:09:57 pmIf you don't have 50 bucks, better not to begin with electronics !!! Money to buy the last Smartphone, yes, people find it....If he likes electronics, OP will find 50 bucks to buy a modern decent oscilloscope, that's basic, as well as a multimeter. What you have done when you was 8 years old does not matter....times have changed a lot, nobody came back to the past....

author: oldway
author_rank: Super Contributor
timestamp: October 08, 2017, 08:26:12 pm
content: From tggzzz in another topic:Quote

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: October 09, 2017, 04:40:22 pm
content: One of the main issues with faultfinding on valve gear is the temptation to 'jockey' them.It is normally quite OK to take a valve out and see if that clears a fault (except for a voltage regulator of course) but swapping them around is a bad idea. Valves do sometimes develop shorts, and if you swap a shorted one you will then have two stages with burned-up feed resistors instead of one. The majority of faults are passive components, anyway. I know it's hard to convince people of that, but it's true!All CRT oscilloscopes have some quite dangerous voltages on the CRT, so you still need to take care when working on a newer unit with solid state amplifying stages. One gotcha is that the cathode and grid are at a high negative potential, sometimes a couple of kV which might be enough to fry a cheap meter. This is so the deflection plates can be at a relatively low positive voltage.When all is said and done though this is a very, very old unit, and it might take a fair bit of work to get it going well. Plus, it will probably have rather limited perfomance compared to a later model. It could be a project for later to refurb it, but for now if you want to learn scopes I'd look for something a little less ancient.

author: mcinsand
author_rank: Newbie
timestamp: October 09, 2017, 08:32:22 pm
content: >> It was all frequency domain and you can get your SA output on 1 MHz DuMont fine and he knew itThat's why I have my IO-10. The horizontal amplifier DC input goes very well with the voltage input to a VCO, with the vertical taking in the response signal.My first scope happened to be my second electronics project, and it is still a great scope: a Lavoie LA-239C with the Federal Property tag still fixed to the front. Another former Navy radar alumnus gave me two carcasses with a challenge to use the parts to make one working scope. That was fun, and I don't think that I could have taken a course that taught me so much so quickly. As I remember it, horizontal sweep and Z-axis modulation took the most time, but was still just a matter of tracing back through the schematic.

author: TTWhy
author_rank: Newbie
timestamp: October 16, 2017, 12:50:57 am
content: It was one of these I experienced a nasty shock. The "home kit" design and some stupid probing ended with me brushing against the 400V line and making a very memorable involuntary yelp. The thing about these HeathKit products: the fault is with the builder not the company and they flicker with just enough life so you keep going.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 16, 2017, 01:50:23 am
content: Quote from: oldway on October 06, 2017, 02:46:34 pmI have used similar Oscilloscopes, (AWA probably late '40s, early '50s vintage), & although they are sorely limited compared to a more sophisticated device, they will display signals, & sometimes that's all you need.Fault finding an audio amplifier comes to mind.Interestingly, Heathkit, & a number of others persevered with non-triggered 'scopes like this when not only were Tektronix making sophisticated Oscilloscopes in the upper price bracket, but even among cheaper stuff, Telequipment produced the early " Serviscopes", with triggering, calibrated time/div & volts/div, etc.Probably the old style ones were quite a bit cheaper, but the little Telequipment beasties were certainly affordable for small businesses.Not so much for individuals though, as at £200 or so, it was the best part of a year's wage in Oz in the 1950s.

author: mcinsand
author_rank: Newbie
timestamp: October 18, 2017, 12:17:54 pm
content: >> The thing about these HeathKit products: the fault is with the builder not the company and they flicker with just enough life so you keep going.Yes and no, with respect to faults. A fault I have with a lot of the designers from decades ago is that they saved maybe a nickle, but no more, by not adding bleeder resistors. Really, how much would a 4-5 resistors resistor cost in a bulk purchase, back then? Many of the power supplies do not have a purely-resistive path to ground, and just putting a couple of 220 k? resistors in a couple of the B+ connections lets the capacitors discharge prior to work. Always check and double-check, though.If not for the safety concerns, an old analog scope would be the perfect project for a beginner. I've been careful enough (paranoid?) to not have been shocked (yet) after decades of playing with tube gear. However, the 239C scope that was my second project really got me going with reading schematics and tracing through the circuitry. And, at the end of it, I had a useful piece of bench equipment. Actually, that scope is big enough to be a small bench on its ownOld gear is from an age of repair, and, as long as a scope's CRT and power transformer are fine, basic electronics skills and generic parts from Mouser will get you through getting it going again.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 19, 2017, 04:37:24 am
content: Quote from: mcinsand on October 18, 2017, 12:17:54 pmThe omission of bleeder resistors was not primarily motivated by cost.Many designers regarded them as unnecessary "power wasters".This was very much in line with the parsimonious attitude towards power consumption common among Engineers at that time (maybe because the older ones "cut their teeth" on battery operated tube designs back in the 1920s.)Serendipitously, with tube equipment, turning it off does not immediately stop the tubes from drawing anode current.The cathode continues emission until it is no longer hot enough to do soDuring this time, the capacitors discharge via the tubes.In normal operation, this is effective, but if you turn the thing off & immediately delve into the "guts", you may be unlucky enough to get a "bite" from the HT.Large devices with a separate "HT off" switch almost always do have bleeder resistors.

author: rhb
author_rank: Super Contributor
timestamp: October 24, 2017, 01:16:42 am
content: Much of my electronics experience was with a Heathkit 5 MHz, recurrent sweep (IO-18 IIRC). I learned a lot with that scope despite the limitations. I have better gear now and about to do a major upgrade.The IO-10 is only satisfactory for audio repair work. But you can learn a lot just building AF amps and oscillators using the scope even if you can't do RF work.Yes, tubes and especially CRTs require caution. But I've never been bitten. And I'm pretty sure that's true for a lot of people.Checking the capacitors is important. I lost a rectifier tube when a HV capacitor went out by going short.As for whether it's worth your time, only you can decide. In the end it's a bet on the value of what you learn at some time in the future. The scope in itself is not worth much, but the ability to fix it is.If the scope is in good original cosmetic condition, be very careful about what you do.

author: mcinsand
author_rank: Newbie
timestamp: October 25, 2017, 11:55:29 am
content: The battery design perspective would explain a lot, though the guys that trained me stressed bleeders, bleeders, bleeders, just in case there is an open failure to ground anywhere. Also, there are bleeders, and then there are bleeders. For HT, bleeders do consume significant power. I think the bleeders in my 2.5 kV supply draw about 50 watts, but that is more to help build some flux density through the filter choke. The 1 kV supply bleeders also dissipate more power than an IO-10 would draw.