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 Post subject: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Fri 01, 2016 2:50 pm 
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Location: South Central PA 17055
Just acquired my first vintage transistor radio, which is a Zenith Royal 500H Chassis 8HT40Z2. The radio plays but I am sure the electrolytic capacitors need to be replaced. I located a website with a "most-often needed 1962 radio servicing information" which includes a schematic and circuit board diagram: http://www.transistor-repairs.com/schematics.html

I am elderly, my vision is very poor, and the schematic is very difficult to read, the electrolytics on the circuit board pictorial do not show the working voltage.

Can anyone tell me the value (and recommended working voltage) of the 5 electrolytic capacitors? There are three near the audio driver and output area, and two near the 1st IF area of the board.

Would appreciate recommendations for a source for the replacements.

Also, I assume my old Weller 200 watt soldering gun is way too hot for transistor circuit board work, so would appreciate any recommendations for a good quality adjustable temperature soldering station, where I could adjust the wattage.
Totally new to transistorized circuitry, and am a little hesitant to apply the heat required for replacing circuit components, so any tips along this line would be sincerely appreciated.

Thanks in advance for any tips, recommendations, and suggestions!


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 12:24 am 
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OK, here's what I see on the schematic:

C20 = 8uf @ 3 volts
C21 = 50uf @ 45 volts
C22 = 100uf @ 6 volts
C25 = 100uf @ 6 volts

For some reason I didn't see the 5th one -- it's probably right in front of me.

EDIT: I found it: C6 = 15uf @ 3 volts.


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 12:34 am 
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Joined: Dec Sat 03, 2011 2:58 pm
Posts: 64
Location: South Central PA 17055
Hondo,

Thanks so very much for the capacitor values, voltages, and for the highlighted schematic diagram!

Will order several capacitors of each value from Mouser.

Thanks again for taking the time to share this information!


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 1:24 am 
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Joined: Jun Fri 01, 2007 9:46 pm
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Location: Chattanooga, TN
Could that space between the 4 and 5 be for a decimal point lost in reproduction (4.5V instead of 45V)? The battery is 6V, but I've never heard of a cap voltage rated in volts and a fraction.

Vince


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 3:11 am 
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Joined: Aug Wed 24, 2011 4:35 am
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Location: Sunnyvale CA
VEK wrote:
Could that space between the 4 and 5 be for a decimal point lost in reproduction (4.5V instead of 45V)? The battery is 6V, but I've never heard of a cap voltage rated in volts and a fraction.

Vince


In any case, I would use 16 or 25 volt caps because they are much easier to find and smaller than the originals.

Brett


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 3:12 am 
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Location: Mpls, Minnesota
That must be a misprint. 6 volt for that one should be fine.

Dave


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 9:28 am 
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The PS for the radio is 4 AA cells (six volts), so the lowest working volt caps commonly available, at 16 volts, is actually overkill. :wink:

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 1:43 pm 
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Joined: Dec Sat 03, 2011 2:58 pm
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Location: South Central PA 17055
Thanks for the additional information on the working voltage.

When I check on Mouser, there is a "Life" category (in thousands of hours).

What would you recommend I select. They list categories like 1,000, 2,000, 5,000 etc? Also, do I select "general purpose" or "audio grade"?

There are many brands listed, which would you recommend?

Sorry for all these questions, but a total newbie when it comes to low voltage capacitors and transistor circuits.
Any assistance, recommendations, or additional information will be greatly appreciated!


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 5:36 pm 
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I only use Nichicon and Panasonic brand electrolytic capacitors for unsurpassed reliability and quality based on my experiences.

There is no need need to buy anything more then "general" or "better" grade. Spending money on high end audio grade or high temperature capacitors in hand held transistors simply makes your wallet lighter.

Type this in the mouser search box; an example of what I purchase:

MOUSER part number:

647-UVR0J101MDD

(Those are zeros in the number)

Nichicon VR line of 85*C radial caps.
Not saying this is the exact part you need, just a "line" of caps to focus on.

Don't even try using a Weller "gun" for small circuit board repairs.

I use a Weller WES51 both at home and work. Had good luck with seller for my home bench:
http://r.ebay.com/EDIjYh


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 7:34 pm 
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Location: Sunnyvale CA
Protista_1 wrote:
Thanks for the additional information on the working voltage.

When I check on Mouser, there is a "Life" category (in thousands of hours).

What would you recommend I select. They list categories like 1,000, 2,000, 5,000 etc? Also, do I select "general purpose" or "audio grade"?


In this application, the requirements are particularly undemanding. You are going to end up running 16V caps at most 6 volts and most of them much, much less than that (hundredths or tenths of a volt for the coupling capacitors). And, you are operating at <100 deg f, usually much less than that, so even the 85 deg C rated caps will have their lives extended immensely. There are calculators that use the service temperature and working voltage to determine the actual life in service, but I will save you the time - you are probably looking at hundreds of thousands to millions of hours at the operating conditions in a 500H even for the "1000 hour" capacitors. That's an absurd number of course, because with that kind of time plain old aging or evaporation of the electrolyte will kill them long before operating them will, or something else (like the transistors or the switch/volume control pot) will die first, But we are talking 50+years, so, nothing to worry about. Age is what got the caps in the current radio, not the ratings, and the original capacitors were of very low quality compared to anything you can get today.

I would echo the comments about the Weller temp-controlled station, but if you are only doing the one radio, then a cheapie 15 watt pencil iron will do. You do have to be *extremely careful* when desoldering, as the boards in the 500H were among the worst of the early PC board era, with exceptionally thin plating that is prone to delamination or hairline cracks with even light handling or manipulation. Many 500Hs do not work properly for long because of the tendency to cracks, and when you try to find and fix it, the manipulation of the board cracks *other* traces in an endless spiral. You eventually catch up, but the radio might look like it is wired point-to-point after a few cycles of finding cracks and jumpering them (I use #32 magnet wire and glue the jumper along the original path with model cement).

Don't let this scare you off of doing it, it's well worth it when it works correctly and pretty much unchallenged in terms of performance in a pocket portable radio. You just need to be careful.

Brett


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 11:17 pm 
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Joined: Dec Sat 03, 2011 2:58 pm
Posts: 64
Location: South Central PA 17055
Brett and Doc,


Thank you so very much for taking the time to share this valuable information!

I will get a very low wattage soldering pencil, and be especially careful handling the circuit board.

Your suggestions and information are sincerely appreciated!


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sat 02, 2016 11:41 pm 
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Joined: Aug Sat 16, 2014 2:19 am
Posts: 794
Protista_1 - When I first started collecting vintage transistor radios, I went to my local Radio Shack and bought their 30 watt soldering iron kit for $10.99:

https://www.radioshack.com/collections/ ... 5717865349

So far, I've had good results with my Radio Shack soldering iron! - Mark


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jul Sun 03, 2016 12:51 am 
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Location: SoCal, 91387
Hondo wrote:
OK, here's what I see on the schematic:

C20 = 8uf @ 3 volts
C21 = 50uf @ 45 volts
C22 = 100uf @ 6 volts
C25 = 100uf @ 6 volts

For some reason I didn't see the 5th one -- it's probably right in front of me.

EDIT: I found it: C6 = 15uf @ 3 volts.

For C20 use a 10uf
C21, 47uf
C22 & C25, 100uf
C6, 22uf
Those are the modern equivalent values.

If you go to Rat Shack for the iron, see if they have the caps there, so you can save a delivery charge on them.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement Upd
PostPosted: Jan Wed 18, 2017 5:05 pm 
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Joined: Dec Sat 03, 2011 2:58 pm
Posts: 64
Location: South Central PA 17055
I finally got up the courage to order the components from Mouser, carefully remove the circuit board, and replace the electrolytic capacitors. Thanks to everyone for all the helpful advice, cautions, as well for the schematic enhancements. Having never soldered solid state components before, I was very fearful of doing damage, but went ahead carefully at the lowest possible temperature settings, being careful not to hold the iron tip for a prolonged period of time.
Anyway, when I got everything back together, I could not believe the difference! This radio is amazingly sensitive, and the audio is incredible, considering the size of the radio/speaker!

This is by far the best performing set I own, and I wanted to thank everyone once again for all the help, advice, and encouragement, without which I would never have attempted the recapping!

Amazing radio!


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jan Wed 18, 2017 9:12 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
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Location: Indianapolis, IN
Glad you got it done & working ! They are excellent radios...

And thanks for posting and letting us know how it turned out !

John


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement
PostPosted: Jan Wed 18, 2017 9:17 pm 
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Location: SoCal, 91387
Yes, congrats on getting the recap done, and no surprise that it outperforms all your other radios. This is probably the best "pocket size" Transistor radio ever made.

_________________
\\\\\\\\\\\\\\\\\\\\\\\\He Who Dies With The Most Radios Wins//////////////////


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 Post subject: Re: Zenith Royal 500H Electrolytic Capacitor Replacement Upd
PostPosted: Jan Thu 19, 2017 7:38 am 
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Location: Sunnyvale CA
Protista_1 wrote:

This is by far the best performing set I own, and I wanted to thank everyone once again for all the help, advice, and encouragement, without which I would never have attempted the recapping!

Amazing radio!



Congratulations! You will not likely find a higher-performance pocket radio from any era.

Brett


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