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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 4:04 am 
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Is that C14 ? That is why it would measure open, 2.2 pf.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 4:08 am 
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Yes, that would appear to be C14 based on the photo and the schematic. Low value tubular ceramic capacitor, very reliable and rarely is there any reason to mess with them.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 4:18 am 
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I was wondering if it was a really odd looking capacitor, because there is one on the diagram. But I ignored that idea because it looked more like a resistor, and the value still didn't make sense to me as a capacitor. I still don't understand how the two color bands match up with the 2.2 pF value on the schematic, since it seems like the brown+red bands on it would mean either 12 pF or 100 pF.

Not doubting any of you, I just don't understand what I'm looking at.

I'm always impressed by the near-instant responses here!


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 5:41 am 
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Maybe there was another band but color faded after all these years...who knows. Anyway, this is what it supposed to look like. That brown brand is probably the voltage rating (100V). After some experience, you'll start using the schematic more to verify component identity.

From https://thedhtsstore.com/products/capac ... al-striped :


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Last edited by AJJ on Mar Thu 21, 2019 5:46 am, edited 1 time in total.
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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 5:44 am 
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The schematic I have for the Revision D version of this chassis shows C14 as 1.2pF instead of 2.2pF. So I believe that is what you are seeing here. I have not paid much attention to these small value tubular ceramics, so I can not state with certainty the departure from the standard color convention with regard to the multiplier value (I would expect to see a white .1 multiplier band if that were the case). Somewhere, I am sure there is an old chart that explains the convention for these units. Alternatively, perhaps one of the colors has simply faded.

This is a good case of why working with these radios requires knowledge that the variations that occurred in production did not happen abruptly. The manufacturer did not stop production and then start the new chassis variation the next day, instead it was a progression of small changes over time, that as collectors we have grouped based more on external appearances than circuit changes.

Still, at either 2.2pF or 1.2pF, that capacitor should not give you any trouble given its construction.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 5:53 am 
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I'm looking at 11/51 version of Fotofact H500 (5H40). In that version, this capacitor shows up as C17 also at 2.2pf. For this position, I think exact value is not important.


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Thu 21, 2019 5:02 pm 
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Okay, thank you both so much. I don't mean to be asking dumb questions, but when I see a component that doesn't look like what I'm seeing on the schematic I just need to stop and ask someone more knowledgeable rather than make assumptions and do damage. In this case I thought it looked more like a resistor, and the value painted on it didn't match the capacitor on the schematic by almost 100%, so I wasn't sure if it was an added resistor or capacitor that wasn't on the schematics I looked at.

I appreciate the hand holding!


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Fri 22, 2019 5:55 pm 
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You can replace the 1L6 with a 1R5 and do all your testing. I have a TO H500 A revision and the 1R5 I had used its still in the radio, working fine. The 1L6 is still in the spare rack in the TO.

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: Mar Sun 24, 2019 4:42 pm 
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Thanks Alexandru, I'd heard about using a 1R5 for testing, but because of you I actually up purchasing one. I hadn't realized they were only $6 before, so I'll be getting one I guess!


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: May Sat 04, 2019 11:55 pm 
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"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."

What did you use to fill in the deep holes?


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: May Sat 11, 2019 2:48 am 
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My radio was fine, no scratches, but I think ppl are using a filler (not sure what but wood one I think is fine) and some black ink (some say shoe polisher or leather dye).
This is a good guide: http://www.renovatedradios.com/articleP ... nGuide.pdf

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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: May Sat 18, 2019 11:57 pm 
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I'm sure other things could be used to fill holes in the case, but what I had sitting around was some firm JB Weld two part putty. I got it very close to perfectly matching the curve while it cured, and then sanded it to get rid of the edge.

I haven't been disappointed yet with the results I get when I use India ink to dye old leather or faux-leather black. One should use a pigment and shellac based ink I think. The shellac makes it durable, slightly water repellent, and evens out the texture to a semi-gloss - which hides imperfections well. I don't think a dye based ink would have as nice of results because it wouldn't have shellac in it, and I've heard shoe polish turns white and flakes off after a while. The ink I use for this stuff is a big bottle of "Speedball SUPER BLACK."


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 Post subject: Re: Beginner restoring H500 Trans-Oceanic, opinions?
PostPosted: May Sun 19, 2019 9:27 pm 
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Okay, after life getting in the way for a while I finally got to working on this radio again.

At this point I've replaced the electrolytic capacitors, every paper capacitor, and every resistor in the radio that was out of spec - so most of them. I've also cleaned the volume potentiometer and all switches and tube sockets with contact cleaner, and fixed one or two loose solder joints I found. I've replaced the selenium rectifier with a 1N4007 diode, added a safety cap, and added a 9.1v zener diode exactly as done in John Kopp's (badrestorer's) restoration guide. The sand resistor and candholm resistors are on spec so I didn't replace them.

After all of that, the radio sounds no closer to functioning than it did before I started, and I actually have to disconnect the zener diode to get it to make any noise at all. Even with no extra resistor added at all to simulate the resistance of the selenium rectifier, I cannot get the filament voltage up to 1.4v where I'm measuring between pins 1 & 7 of the 1L6 tube. With no resistor at all the highest the voltage has gotten is 1.25 volts, and with the regular hundred-ish ohm resistance that is usually suggested added, it sits at 0.9 volts. If I have the zener diode hooked in it seems to be dumping voltage when it reaches 8.9v, at which point the voltage between pins 1 & 7 of the 1L6 is only 0.75 v. I have the zener diode hooked to the same part of the filament string that John does in his guide. I've measured the voltage on the 1L6 by just measuring directly between pins 1 & 7, and also by measuring from each pin to B- and subtracting one from the other, and I get the same readings either way. I measured the resistance across the filament pins of the 1L6, which came out to 7 ohms, but I haven't measured anything else on the tubes themselves because I don't know what to look for.

Even with the filament voltage as high as I feel comfortable pushing it by removing resistance after the diode (knowing that there is clearly something wrong) the radio only receives one regular AM station faintly, the rest of the band is dead silent. There is a fair amount of hum that gets loudest in the middle of the volume knob's sweep, but the volume of the station being received is completely unaffected by the volume knob, it just plays at the same low volume no matter what.

Do these symptoms sound like anything recognizable? I'm at a loss for what to try next considering everything I've done so far hasn't made a bit of difference in the radio's functionality. I suppose I should check the tubes, but I'm not positive of what to look for on them.

Any ideas are appreciated.



To feel a little bit of success I repaired my grandfather's Heathkit C-2 Condeser Checker I had sitting on my desk, replaced all caps and out of spec resistors, cleaned contacts etc. Now it works perfectly, and measures everything on the dot, so at least I've got that going for me haha.


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 Post subject: Re: The five-thousandth H500 Trans-Oceanic restoration threa
PostPosted: May Sun 19, 2019 11:56 pm 
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What is the voltage for the entire string from the bottom of the candohm (also pin 7 of 3V4) to B-, both with and without the zener diode connected?

The symptoms you describe do sound like an antenna that is open or disconnected. Since we have already determined that the loop antenna is intact, possibly there is a bad connection between the antenna and the chassis? I would not expect to hear any SW stations if you do not have the rod antenna connected.

How have you been connecting the loop to the chassis? Through the accessory cable or the connections in the cabinet lid?

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 Post subject: Re: The five-thousandth H500 Trans-Oceanic restoration threa
PostPosted: May Mon 20, 2019 12:34 am 
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I measured these voltages from the bottom post of the candohm to the B- terminal on the electrolytic cap can:

8.96 v with no added resistor and with the zener diode hooked up.
8.92 v with a 50 Ω resistor added to the sand resistor and with the zener diode hooked up.
9.0 v with a 120 Ω resistor added to the sand resistor and with the zener diode hooked up.
(I figured these would be identical but wanted to be thorough anyway)

12.9 v with no added resistor and no zener diode.
11.9 v with a 50 Ω resistor added to the sand resistor and no zener diode.
10.75 v with a 120 Ω resistor added to the sand resistor and no zener diode.

What you just said did make me wonder about the antenna, so I just measured the resistance through the accessory cable and antenna hooked together - the way I've been testing it - and the resistance came out to 1.4 Ω. Is that correct? I have tried tuning through some of the shortwave bands with the waverod connected but haven't heard any signs of life from them at all.


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 Post subject: Re: The five-thousandth H500 Trans-Oceanic restoration threa
PostPosted: May Mon 20, 2019 2:38 am 
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Your voltages for the entire string seem fine if not a bit high without the zener diode. This makes your low voltage on the 1L6 a bit puzzling, I think one of the tubes is not conducting properly.

On the tubes used in the Trans-Oceanic the filaments pass 50mA for the filament itself plus the plate current for each tube. However, the plate current is not the same for each tube, thus there is a resistor across the tube filament socket pins to balance the voltages across each filament. Assuming all of the resistors are in tolerance, which you said have been checked, then I would surmise that one of the tubes is weak or the bias voltages are off causing the uneven voltages.

I would check the voltages on the other tube pins against the schematic to see if anything is seriously amiss which could help point out an issue.

Also, your antenna sounds fine as far as I can tell, mine ohms out at about 3.1 ohms through the accessory cable, however the tolerances between multi-meters especially on the low range can vary and I would not think this would suggest an issue with your antenna.

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 Post subject: Re: The five-thousandth H500 Trans-Oceanic restoration threa
PostPosted: May Mon 20, 2019 4:11 am 
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It's helpful to have the differences in filament voltages explained, I've been wondering why exactly there were resistors across some of the filament pins. I'll do some poking around myself with voltages, but it sounds like I should go to my local place that can actually test tubes and get them tested. Unfortunately they're on vacation for the next 10 days so I'll be waiting again, oh well! Thanks a bunch for the help.


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 Post subject: Re: The five-thousandth H500 Trans-Oceanic restoration threa
PostPosted: Apr Wed 08, 2020 9:24 pm 
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I had a similar issue with an L600. Voltages were all about right, but no to very weak reception. I cleaned/polished all tube pins and used Dexoit on the tube sockets. Inserted tubes several times, dried everything off and the TO came to like. Apparently there was enough dirt/corrosion about that it caused problem.


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 Post subject: Re: The five-thousandth H500 Trans-Oceanic restoration threa
PostPosted: Apr Thu 09, 2020 11:23 pm 
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As a thanks for the help I received here I think I owe you all an update on the Trans-Oceanic project!

I honestly can't remember how many months ago I finished it now, but all the tubes tested good, I put them in, buttoned everything up and figured out the power resistor values, and it worked! I haven't done any sort of alignment on it since I haven't gotten around to restoring the signal generator I own yet. I also mocked up a temporary battery using 6 D cells and 9 9volt batteries, and that worked well for a long time and only recently ran down enough to stop working.

I'm very pleased with the sound quality from this radio, I'm sure there are better sounding radios out there, but from my small personal sample-size it's the best sounding AM radio I've heard. Reception on AM is great, reception on the shortwave bands is fine, I've picked up stations on all of them, but it definitely seems like some of the bands are weaker than others.

Here's a quick clip of it playing AM radio: https://youtu.be/K22qOAU5ijI
And this is something on the 31 meter band: https://youtu.be/2AjYng4FHO0

Over the last few months the shortwave bands have started exhibiting some weird intermittent behavior when the radio is plugged in to wall power. All of the shortwave bands will be completely quiet when I switch to them. One day when I switched back to the AM band after shortwave it was also quiet, until I tuned to over 1100, at which point the AM band came back on and worked across the whole dial. I experimented more and it did the same thing a few times in a row; AM working, switch to shortwave and it goes quiet, switch back to AM and it's still quiet, tune to over 1100 and the whole AM band comes back to life. WEIRD. My hope is that I might've been too cautious with the power resistor values, because the shortwave bands also go quiet when the battery voltage starts to get low. That's my hope, and that there's not an issue with the 1L6 tube or something expensive like that. I haven't dug into troubleshooting it yet though, and the first thing I'll do is put together a fresh battery so I can see if shortwave still works on battery power, if I get stumped I'm sure I'll be back with more questions.


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 Post subject: Re: The five-thousandth H500 Trans-Oceanic restoration threa
PostPosted: Apr Fri 10, 2020 12:41 am 
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GreyHawkins wrote:
...My hope is that I might've been too cautious with the power resistor values... and that there's not an issue with the 1L6 tube...

I think you're on the right track. Check the voltages to see if there's room for a slight boost before opening up the wallet for a new tube.

I had the same symptom on my RCA Strato-World. In that instance I had to buy a new 1L6. Considering how nice these radios are, it's probably worth it. 1L6 is not that expensive if you consider the tubes' price when they were new (inflation adjusted).


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