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 Post subject: The five-thousandth H500 Trans-Oceanic restoration thread
PostPosted: Mar Wed 06, 2019 4:10 am 
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Hello all,

I've owned a Zenith H500 TransOceanic for over 10 years now, and might finally attempt a restoration on it. I am a beginner to repairing electronics, so I've been doing a lot of reading, starting with the basics like electrolytic vs non-electrolytic capacitors, which capacitors to replace (all of them except for mica) etc. I've also done a lot of research on restoring TransOceanics specifically, and have gotten my hands on the very helpful "Badrestorer’s Illustrated Guide to Restoring the Zenith Trans-Oceanic H500" as well as read through most of the relevant information on antiqueradio.org, among other sites. But I still have some questions that I need to actually ask people who know.

About the radio I have:
It is in excellent cosmetic shape (pictures below). I honestly don't know what I would restore on it cosmetically other than removing three scuffs on the case and wiping it down. There's no corrosion at all anywhere, no peeling of the leatherette, no cracks in the plastic face. It has what I imagine to be all of the original paperwork - the operating guide, a pamphlet with a list of stations, and the schematic with a list of parts and prices. So I know this radio has never been abused, or stored poorly.

It also doesn't work at all. (I know it was unwise to just plug it in, but I was a kid when I bought it and couldn't resist) When I first bought it, the volume was very very very low when plugged in, and I was only ever able to receive one AM station, faintly. I don't recall any hum really, just weak reception and low volume. A few days ago I plugged it in again, because I'm no smarter than when I was 15 apparently. This time around I wasn't able to pull in any stations at all, and the only sound it made at all was a faint crackle from a scratchy spot on the volume pot.


What I know:
I know that I'll have to go through everything and replace all the caps, check resistors and more. I'm hoping that no tubes are blown, as I'm aware that the 1L6 is very expensive and rare, though I'm also aware there is a solid-state replacement available too. I'm on a very tight budget, so I want to do this right, but I also can't just go dropping $30 here and $30 there.

I'm confident in my ability to find the correct capacitors and resistors, and that I'm smart enough to solder and not mix wires up. But I also am not able to read a schematic well enough to confidently make modifications based on it, which leads to the next part...

What I don't know, or what I need opinions on:
I've read a lot about the power supply on this radio and modifications that should be done to it like adding fuses, replacing the selenium rectifier using zener diodes and resistors, etc. But everything I've read seems to have a different opinion on how to do it, I'm a little confused by what I've read, and I don't know how confident I am in making modifications that substantial from scratch.

I have however come across this contraption on ebay made for 500 and 600 Oceanics called the "FILT-R-PAK+" that supposedly solves the power supply issues and upgrades in one simple and easy to install module. Obviously because of my newness to all of this, the "solder and go" nature of that appeals to me. Am I a fool if I spend $40 on it though? Could the things it does be accomplished easily by me, with beginner skills and $1.00 worth of components?
Link to the FILT-R-PAK+: https://www.ebay.com/itm/ZENITH-TRANS-O ... ctupt=true

The repeated testing and swapping of components that people have talked about doing when modifying the power supply intimidates me, and if the FILT-R-PAK+ saved me from that I think it might be worth it.


My second question is, after recapping and replacing any broken components, how likely is it that the radio will need to be re-aligned? I do happen to own a Heathkit signal generator that was my grandfather's, but it is probably as old as the TransOceanic itself and would likely need to be restored to be accurate. It generates tones, but I have no idea how accurate it is.

What is the general price range for having someone re-align the radio for me if it is necessary?
Am I dumb if I don't re-align it after finishing the other repairs?
Should I just check my signal generator against a digitally tuned AM radio, and assume that if it's accurate within the AM band that it will be close enough on the shortwave bands too?


I'll be super thankful for any answers anyone has!

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Last edited by GreyHawkins on May Sun 19, 2019 9:50 pm, edited 1 time in total.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 06, 2019 5:00 am 
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Location: USA
I'd suggest invest $20-$40 on a simple five-tube set to start. While you may be confident about your abilities, you don't know what might trip you up. TO's power supply circuit and multiple bands are extra complications. While 1L6 tube may cost relatively more than most other tubes, it's not outrageous when compard to when the tube was sold new back in the 1950's (accounting for inflation); that should not be a significant factor....you should take care not to damage components anyway.

If you like old radios, this will not likely be your only restoration. It's better to have easy, early successes and bulid up your experience; avoid unnecessary frustrations along the way. It's a difficult situation when you discover that you need to troubleshoot but can't clearly read the schematic yet.

A new person can easily get lost in discussions about mods people have made to the set; I would not even try to do those until there's basic understanding on how these components work and how they affect the circuit. Don't bother with any component kits; you need to know enough to select components on your own.

Short answer, I'd say a Transoceanic could be your third radio restoration, after two easy successes with simpler radios.

If the radio has not been messed with it may only need minimal alignment adjustment. If you work on two simpler (five tube) AM sets first, then you'll be able to align the TO yourself. Your Heathkit signal generator will be sufficient for the job; restore it/fix it, learn how to use it before you open up the TO.

Just my opinion.


Last edited by AJJ on Mar Wed 06, 2019 2:13 pm, edited 2 times in total.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 06, 2019 7:07 am 
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Location: Mpls, Minnesota
Put your radio away until you know how each section of the radio works, until you learn to read a schematic, until you know how a vacuum tube works, until you know what a resistor, capacitor, inductor, choke, transformer, and all the other associated components are and what they do, until you have working restored test equipment required to do the restoration. If you look at some of the posts on this forum you will see many people have had a terrible experience in trying to restore a transoceanic radio, this is totally due to lack of experience and proper test equipment. It would be a shame to mess up your nice radio.

Dave


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 06, 2019 1:10 pm 
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would suggest Bad Restorer's posts on H500 restoration as excellent reading while contemplating working on yours. its available here http://www.renovatedradios.com/articleP ... nGuide.pdf or just google Bad Restorers H-500 Restoration. Prime areas for problems on these are the power supply and filament circuits. You will need to be able to use a voltmeter and relate the schematic diagram to the parts on the chassis to do that. You may be able to find a local radio group to help you

nice radio by the way! be a shame to damage it.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 06, 2019 4:06 pm 
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fyi... badrestorer/John Kopp has an excellent youtube channel.
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follow the yellow brick road...
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Greg.

oh... I like your book illustrations... :)
Wildfires are an annual event here!


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 06, 2019 8:58 pm 
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Haha, thanks for the compliment on my illustrations Greg! Didn't think anyone would actually look my name up. Coincidentally that's why I have a low budget right now. Believe it or not, two years out of college as an illustrator and I'm not exactly a millionaire yet.

And thanks for tipping me off to John Kopp's YouTube channel, I was unaware of that! If it's as helpful as his guide it'll be a great asset.


I think there is maybe some confusion, or I overstated my level of beginner-ness.

I know how to read a schematic, just not necessarily well enough to feel like I'm smarter than the person who designed it and go blazing off-trail. Regarding the Trans-Oceanic I've read of several different approaches to solving issues with the power supply (for example I've seen people do things that seem like errors to me like replacing the large sand capacitor with a regular capacitor and no fuse, even though from what I understand the sand capacitor's secondary function was to act like a last-resort fuse) I just wondered if anyone had their own opinion on that matter since I assume most of you would know a better approach than I do.

I'm familiar all of the basic electronic components, and have simply been reading up more on the differences between their different constructions (eg. carbon film versus carbon composition resistors, which types are in old radios and why they've gone bad) and specific details and things to be aware of. I know how to use a multi-meter and have done simpler projects in the past without anyone else's guidance, like adding an aux input jack to the original AM radio on my daily driver '68 Ford Falcon. Or troubleshooting difficult ignition system problems on that same car, including deciding to make my own ignition condenser (the guts are just a capacitor, cars use old terminology) for the points ignition when I realized all of the new ones I could buy from the auto parts store were very low quality and failed every few months. I re-packed the condenser shell with an appropriate capacitor (sourcing an appropriate condenser capacitor from outside the auto parts industry is something I've never heard of anyone else doing) and it ended up being a ≈.3µF one rated for high heat and something like 8,000 volts so I'd feel comfortable with it being around the large voltage spikes in an ignition system. That was a few years ago, and until I replaced it with a hall effect sensor it outperformed and outlasted the regular autoparts store bought capacitors (which in disassembly I discovered were just very poorly made paper capacitors). None of that is super relevant, but I think at least shows that I'm not stupid.

My concern over the cost of the 1L6 tube isn't because my plan is go through blowing up tubes by overpowering their filaments, it's because the consequences of accidentally damaging a tube are higher when a NOS one costs $100, a used one is still $40, and my "fun stuff" budget for the week is $30.

I do have BadRestorer's guide, and have found it very very helpful. I've read it all the way through a few times now, but the part where he described the modifications he made to the power supply were a little confusing. There are a few pages where it basically says "here's what I did" with an arrow pointing to a wad of wires, and a circle that encompasses three completely unrelated capacitors. Regarding the power supply, I'm wondering if anyone else has any experience with the FILT-R-PAK, and if it's a worthwhile time and effort saver, or if I should just take the time to create the same functionality myself with my own workaround for the selenium rectifier & adding fusing.

Without having restored a radio before, I have no way of knowing if replacing all of the capacitors and out-of-spec resistors will require the radio to be fully re-aligned, or if it was last aligned 70 years ago that those adjustments will likely still be good enough once everything else is back in spec. If it's going to be inoperably misaligned right off the bat then I need prioritize testing and repairing my signal generator. If the radio will be "close enough" without an immediate realignment then I'm fine waiting until a later date to rebuild my signal generator.

Basically I'm new to this in the sense that I haven't fully restored a radio before, but I'm not a moron. I learn quick, and prefer jumping into the deep end.

I actually have a simple 5 tube 1937 Zenith that currently works okay, not great. But it's actually much more of a hacked up mess than the H500 is, and for that reason I'd rather start out on a radio that is clean and hasn't been messed up by other people. If there's one thing I've learned from antiques and cars, is that it's much harder to undo other people's "repairs" than it is to repair simple wear and tear.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 06, 2019 10:05 pm 
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First of all, welcome to the forums!

The radio you have chosen appears to be a great candidate for restoration, it's in very nice cosmetic condition. However, from what I can see it is not quite all original, the electrolytic filter can on the top of the chassis appears to be a GE replacement (which as a side note isn't exactly safe as the original had a cardboard cover to protect the user, the can is connected to one side of the AC line, this is irrelevant if you will be replacing the electrolytic capacitors anyway). Also, there appears to be a wooden block added to the back of the coil tower, presumably to prevent it moving backwards because the screw that holds it to the lid of the cabinet was lost. This is not to discourage you from anything, just to prepare you should you find other disturbances under the chassis.

Next, to answer some of your questions:

Fusing/ Sand Resistor-
(note: you said sand capacitor above, I presume this is an error and you do indeed know the difference between a capacitor and resistor.)
The sand resistor that follows the rectifier in this radio is a wirewound resistor much like the modern ceramic type, except that in this application it was deliberately run near its ratings such that in an over-current situation it would burn open and act like a fuse. It also serves to protect the first filter capacitor and rectifier from inrush current on turn-on. I have seen more of these fail due to green corrosion damaging the leads, versus burning open, but if we are going to replace the selenium rectifier than there will need to be an increase in resistance at this point and I often replace these with 5W ceramic resistors and fuse the radio as well. I normally use a 1/4W fast-blo fuse. It is important to keep in mind that the sand resistor was not really designed to protect the radio from damage, but what it was plugged into, and that to prevent nuisance blowing the fuse should be sized with this same goal in mind. I don't operate my radios when I am not in the room as another precaution.

Rectifier/Zener Diodes-
The selenium rectifier in these units is a topic of much discussion, and I won't go into the argument here as that can be found elsewhere by searching the forums. I will let you know that I replace them in all my radios and have never had any issues. If you do replace the rectifier, it is important to choose a diode which is capable of doing the job. The requirements would be a diode which is designed for rectifier use, can stand up to the peak reverse line voltage and can handle the current demand of the radio. Most of us use the ubiquitous 1N4007 diode, because they are cheap and give a good margin of safety. (1N4007 is rated for 1A and 1000V peak inverse voltage, the radio only draws about 0.075A and would see much over 400V.)

If you do replace the selenium rectifier with something like a 1N4007, then it will also be necessary to increase the resistance after the rectifier to compensate for the lower voltage drop of a silicon rectifier diode versus the selenium unit. This is necessary because the tube filament voltages are derived from the rectified line voltage. As alluded to above, this can be done either by adding a resistor in series with the existing sand resistor or replacing the sand resistor with a unit of greater resistance. In either case it will be necessary to start with more resistance than necessary, and work down incrementally while monitoring the filament string voltage in order to have approximately 8.4V across the string with your given line voltage. I would suggest with starting with about 250 ohms total in this position, but my experience has shown that 180-200 ohms will get you in the right place. (Remember that resistors in series add, so if you keep the sand resistor then add another 50-70 ohm resistor in series.)

Zener diodes are something different, instead of a rectifier which turns alternating current into direct current, a zener diode is a voltage limiting device much like a pressure valve on a water heater. When the voltage goes above a certain point the zener diode turns into a short and allows the voltage to bypass a point. In this radio, they are normally installed in parallel with the filament string as it is possible to damage the tube filaments if one is pulled and re-inserted with the radio on. If the tubes are only removed and replaced when the radio is off and unplugged, then I do not find zener diodes necessary.

Filt-r-Pak, Etc.-
Now, there is nothing inherently wrong with these units, they do work, and I have heard good things from people who have used them. However, the sales pitch given from the manufacturer makes the process of installing these much easier than it is in actuality. The filt-r-pak is actually an entire replacement power supply, with capacitors, resistors and a rectifier mounted to a circuit board. To install it, you still need to detach all the old components from the radio and solder the new leads from the filt-r-pak in the place of the old components. Given that this is the same amount of work as just installing new discrete components (which can be had at much less cost) I do not see any benefit of this unit.

Alignment-
Unless somebody has been messing with the adjustment slugs in your radio, you do not strictly need to perform an alignment. Your radio will likely work just fine, but may not have peak sensitivity or tracking that it would have after an alignment. If you have a signal generator, then you are a step ahead. You can check it with an AM radio for accuracy as you said. You can also check it using the Trans-Oceanic when you are ready to align by checking the output against a known SW station like WWV which broadcasts at 2.5MHz, 5MHz, 10MHz and 15MHz.

The alignment procedure for these radios is not particularly difficult but it is lengthy and repetitive and requires a special hex wrench for tuning the IF transformers. I would see how your radio performs before any alignment attempt is made.

-Hunter

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 06, 2019 10:07 pm 
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GreyHawkins,

You got some opinions on a less painful path to successfully fix a TO. No one is questioning your intelligence or abilities. Most of us started in this hobby from exactly where you are now with no prior formal training. You'll get no negative comments if you decide to start on the set right away; and many will patiently help and support you here when you need it.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 07, 2019 7:18 am 
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Hunter, thank you so much for the very thorough response, typing this stuff up takes longer than you'd expect. You answered every question I can think of at this point, certainly enough that I feel ready to order parts and start cautiously digging into things. Your information on replacing the rectifier, and the reason for adding a zener diode, made them both finally "click" in my brain and make sense. I definitely agree with you on the filter can, I hadn't noticed before that it didn't match photos I've seen. Sounds like I won't be buying the FILT-R-PAK, since I've got a grasp on how to do what it does on my own now. I will be replacing the selenium rectifier, since replacing it sounds easier than what I've read of cleaning one up after it's blown.

I do plan on realigning the radio at some point, I'd like for it to perform at its best. But it's good to know I might not need to get my signal generator totally sorted out before getting to enjoy the radio a bit. It hadn't occurred to me to compare the accuracy of the signal generator against a known shortwave station, now it seems so obvious.

And yes, I definitely meant sand resistor. Trying to type quickly over a lunch break didn't help my case for trying to claim some intelligence, haha.

AJJ, I'm not trying to be rude or anything. I honestly appreciate you replying at all, because the worst thing would have been for my post to go completely unanswered. Sometimes it happens when I first join specialized forums like this that I get poopooed as a noob and my actual questions get ignored, I just wanted to nip that in the bud in case that was happening on this thread here. I really appreciate any helpful feedback I get, I just don't want to be told to not try because it's assumed I won't be able to figure something out.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 12:19 am 
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Alrighty, here's where I've gotten to on the H500...

I ordered new caps, some resistors (based on a quick glance to see if there were any that looked especially suspect, but not based on actual testing yet), a diode and resistors for the power supply, and a zener diode to protect the tube filaments.

Right now I've replaced the selenium rectifier, installed the zener diode, and replaced all of the paper and electrolytic capacitors. I tested the candohm and sand resistors, and they both check out - 1005Ω, 1004Ω, and 135Ω respectively.

There is one spot I've come across so far where what I've found in the radio doesn't match the schematic. Capacitor C20 which goes between pin 5 of the I.F. 1U4 tube and the second I.F. transformer is different. I discovered that the one in the radio right now is a .0033mf, and the one that I ordered based on the schematic is a .0047mf. The capacitor looks exactly like all of the others, so I don't think it was replaced, and I'm a little confused. I'll be finding a new one to match the one already there, but I don't know why there's a mismatch.


Here's where things stop going well, because I slowly powered up the radio while watching the filament voltage on the 1L6, and to get the filament voltage on the 1L6 up to 1.3 volts I had to disconnect the zener diode, and reduce the resistance after the 1N4007 diode down to just that of the sand resistor (120-130Ω) which is obviously way lower than it should be. Basically, the zener diode was already getting 9v by the time the 1L6 filaments were only seeing 0.7v. The radio acts exactly the same as it did before I started; there is a slight hum that gets louder in the middle of the volume knob's sweep. It can faintly pick up two stations on BC around 1400, but the volume of the actual stations is completely unaffected by the volume knob, they just play at a constant quiet volume. It also occasionally will make wind-chime sounds from the speaker, and they're clearly coming from the radio itself. The tube's filaments all seem okay, as they have continuity.

From those who know more than I do, does it seem like I'm on the right track? I think what's up next will be me going through and testing more resistors, since I haven't done that yet. Do any of the symptoms I've described sound like something else obvious that I don't know about?

It was a little disheartening to try powering it up and have it behave identically to how it did before I did any work at all, even though I know that without having touched hardly any resistors yet I'm not actually very far along in the repair process. I just thought there would maybe be some noticeable difference in functionality at this point.




On a side note, I did some light restoration on the case. I filled a couple deep holes, and painted the whole thing with India ink. I've discovered that cheap Shaeffer India ink works well on pretty much anything with fading black leather or non-vinyl leatherette; it ends up water repellent, shiny, and durable. I used it on a leather camera case a few years ago and it still looks like I just finished it. Anyway I think the radio looks pretty good now.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 12:39 am 
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- Except for the candohm resistor. Don't spend too much time worrying about resistors until you got the paper capacitors replaced; chances are the radio will work fine even if few old ones are out of tolerance. Except for components that are outright fried, external appearance doesn't tell you if it's good or bad.

- 0.033 versus 0.047...Don't spend too much time worrying about it for now.

Don't expect the set to start working right away. This is your first radio repair and it's not a simple one. Go slower than you thiink you need to. Plan to spend lots of time with it.


Last edited by AJJ on Mar Wed 20, 2019 12:50 am, edited 2 times in total.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 12:47 am 
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It looks like you are on a good track.

You do appear to have C20 identified correctly. I would not worry too much about the value of C20, its purpose is to neutralize the grid to plate capacitance of the IF 1U4 in conjunction with R12. There are assorted production changes to the H500 that occurred without any official nomenclature change by Zenith. Looking at my assorted schematics, it appears that C20 was initially .0047uF and then later changed to .0033uF. I would not expect the value to be particularly critical and either of the parts would work fine.

With regards to your filament voltages, it looks like your power up test went well and nothing was damaged. It would be helpful however, to know what the voltage of the entire filament string was in addition to that of the 1L6, as well as to know what the breakdown voltage of the zener diode you chose was. We do not want the zener diode to conduct unless there is a fault. As such its breakdown voltage should exceed the operating voltage of the set under normal conditions. Some people like 9.1V zeners, however if wired a certain way these can conduct under normal operation and artificially reduce the filament string voltage. Depending on how it is wired, a zener diode with lower breakdown voltage can also partially deplete new batteries. Best practice would be to use something over 10V as the tubes can withstand that voltage for a short period until the zener conducts.

If you can hear a couple of stations, that likely means that the converter, IF, detector and audio stages are working, at least to some extent. As a double check, it would be good to make sure that you have the BC band button depressed (I have forgotten to do this before) and that the loop antenna has continuity and is connected to the chassis. With the antenna fastened to the lid or extension cable, check between the two pins on the three pin plug that have the larger gap. Expect to see 3-5 ohms if the loop is in good condition.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 12:52 am 
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It's hard to attach pictures of the schematic because of the resolution limit on attachments, but here's the general section of the schematic with the mismatch capacitor. The schematic says .0047mf, the original looking one in the radio is a .0033mf. I assume I should stick something close to .0033mf in. I put an arrow pointing to the suspect.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 1:02 am 
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Here is a cropped version of a later H500 schematic showing the change to .0033uF. As said, you can likely use either value without noticing any difference in performance.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 1:12 am 
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Hcompton79, sorry you replied as I was typing my own response!

If the value of C20 isn't super critical then I guess I'll stick the .0047mf cap in there, at least until I get the radio working and I feel like finding the correct one. Thanks for posting that part of the later schematic!

The breakdown voltage of the zener diode I bought is 9.1v, I have it hooked up the same way badrestorer / John Kopp has it in his guide. From the lowest voltage end of the canholm to one of the B- busses, with the cathode / (-) towards the canholm resistor.

The BC button is pressed, haha. And I've given all of the band switches a good soaking and workout in contact cleaner a few times now. I just measured the loop antenna's resistance and it came out to 1.4Ω.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 1:18 am 
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To alleviate future confusion, I want to elaborate on the H500 versions alluded to earlier. The Trans-Oceanic H500, experienced several production changes. Unfortunately, Zenith did not really do a good job of documenting these changes and the receivers did not receive any nomenclature in model numbers indicating the changes (all had chassis 5H40).

In the collectors world we have grouped the receivers based on general features, however as most of these production changes were running it is possible to have smaller circuit variation that matches a different schematic than the outward features of the radio would dictate.

Here are the five chassis variations, courtesy of Badrestorer's H500 guide:

Introduction, baseline: Uses a 1S5 tube for the Det/AVC/AF. Has a dual-pin earphone jack.

Revision A: Uses a 1U5 tube for the Det/AVC/AF. Tube socket is wired differently from the 1S5. Also has a dual-pin earphone jack.

Revision B: Uses the 1U5 and earphone jack has been changed to a single 1/4-inch jack.

Revision C: Uses the 1U5 and has a single earphone jack. Low voltage switch was added for line voltages less than 110vac.

Revision D: Uses the 1U5, has single earphone jack and low voltage switch. A socket was added for an optional 50A1 ballast tube.

I would like to add that I do not believe that the Revision D description is correct, I have never seen and do not believe that Zenith ever made a H500 that had both a low voltage switch and 50A1 regulator tube as the latter would make the former redundant. If anyone has an example that has both, I would be most interested in seeing it.

Based on the photos you have included of your H500, it would appear that you have a Revision B chassis. Unfortunately, I could not find a digital copy of the schematic available for this particular revision, otherwise I would post it here.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 1:25 am 
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I just checked the actual resistance on my H500's Wave-Magnet and it measures 2.1 ohms, so I guess I had remembered it being a bit higher. Nonetheless, It appears yours is in good shape.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Wed 20, 2019 2:47 am 
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Good idea posting the descriptions, at least for the sake of anyone arriving on this page via Google. The schematic I'm working from does seem to be the revision B one, hence my confusion at the capacitor mismatch.

Thanks for the help! I'll keep picking at this.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 3:40 am 
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I started checking more resistors, and so far every one I've checked has been pretty far out of tolerance (something like an 800 Ω 10% resistor that tests as 920 Ω), so they're definitely my culprit.

But I hit another snag quicker than I expected. There is a resistor between the detector coil and the third pin of the 1L6 tube that is measuring infinite resistance, and it is coded with only two color bands (the ends are just body color). The two bands are brown and red, which I interpret could mean either 100 Ω or maaaybe 12 Ω.

Once again I'm confused, because again what I'm seeing on the schematic doesn't seem like it matches what I'm seeing in the chassis, and I can't find any reference online on how to read a resistor with only two color bands so I can be sure I'm interpreting it right.

The confusing resistor:
Attachment:
IMG_4630 copy.JPG
IMG_4630 copy.JPG [ 217.88 KiB | Viewed 1583 times ]


The section of the schematic I'm looking at:
Attachment:
Screen Shot 2019-03-20 at 8.14.57 PM.png
Screen Shot 2019-03-20 at 8.14.57 PM.png [ 1.02 MiB | Viewed 1583 times ]


Thanks again for any help, I wouldn't be attempting this if I wasn't able to ask questions here.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 3:54 am 
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That's C14, a capacitor. No need to replace it.


Attachments:
Screen Shot 2019-03-20 at 8.01.24 PM.jpg
Screen Shot 2019-03-20 at 8.01.24 PM.jpg [ 64.47 KiB | Viewed 1574 times ]


Last edited by AJJ on Mar Thu 21, 2019 4:08 am, edited 1 time in total.
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