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 Post subject: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Sun 03, 2019 5:17 pm 
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Joined: Feb Sun 03, 2019 4:47 pm
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HELLO,
I AM RESTORING A RCA VOLTMETER WV-73A. DOING IT BLINDLY AS I CANNOT FIND A SCHEMATIC.
I TESTED ALL THE TUBES THEY CAME OUT GOOD. I SAW NO CORROSION ON ANY OF THE PINS, THEY ARE SHINY SO I DIDNT CLEAN PINS. I REPLACED ALL THE PAPER CAPS WITH NOPOLAR PP DAYTON CAPS, A FEW WHERE OFF QUITE A BIT, AND ONE PAPER CASING LYCTIC THAT WAS OUT OF SPEC. THERE WAS ONE PAPER .005UF I DIDNT HAVE REPLACEMENT FOR.
I DEOXIT THE SELECTOR SWITCH AND THE PHONE JACK, AC PLUG.

POWERING IT UP THE NEEDLE JUMPS TO MAX ON THE SCALE. AFTER 5 MIN WARMUP NOTHING CHANGES. WHEN I PUT IN HEADPHONES IN JACK THE NEEDLE GOES TO 0 AND I HEAR A LOUD FIZZING LIKE HUM FROM THE PHONE OUT AND CHANGES PITCH ON EACH SELECTOR SWITCH. WHEN I TOUCH THE INPUT CLIP OR THE CHASIS THE BUZZ GETS LOUDER.

I WONDER IF ANYONE CAN GIVE ME ACCESS TO SERVICE MANUAL AND ANY SUGGESTIONS ON HOW TO GET THIS TUBE UNIT WORKING PROPERLY. I AM LEANING TOWARDS CHECKING ALL THE RESISTORS, IM SURE SOME HAVE DRIFTED OUT OF SPEC THRU THE YEARS. I AM NOT SURE WHERE TO CHECK B+

THANK YOU FOR ANY INSIGHT.


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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Sun 03, 2019 7:05 pm 
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I highly recommend you quit replacing parts until you locate a manual :) You can easily make it worse.

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Sun 03, 2019 8:45 pm 
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In addition Barry's comments, I might suggest you DROP THE CAPS KEY. it makes reading your posts more difficult.

----

As for the manual, if you do a search "RCA WV-73A PDF", without the quotes, you'll get plenty of hits.

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Tue 12, 2019 6:50 pm 
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No dice on searching web for wv-73a pdf. unit is from 1946-1947.
No dice searching through catalogs on americanradiohistory.com for this unit.

Since i couldnt locate a schematic after a year of looking I did consult with some tube experts regarding the capacitor replacements i selected as i only have experience in restoring solid state gear.

I replaced
1 x 0.25 200v wax-dipped paper cap with 0.22 400v PPT-film
2 x 0.5 200v wax-dipped paper cap with 0.47 400v PPT - film
1 x 0.1 1200v wax-dipped paper cap with 0.1 1200v Illinois polypropylene metallized-film
1 x paper lyctic 20uf 25wv with 22uf 50v Muse

Attachment:
ppt.jpg
ppt.jpg [ 70.49 KiB | Viewed 337 times ]


original 0.1uF measured 0.2uF
20uF measured 23nF
0.5uF measured 1.9uF

I guess i could step back and put in the out-of-spec caps back in but i'd prefer not to.
I wonder if it was calibrated to the out-of-spec caps.
There are two calibration pots HCAL and LCAL. Would it hurt to adjust LCAL?


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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Tue 12, 2019 7:09 pm 
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Location: The Old Dominion VA 23518
eizner23 wrote:
HELLO,


POWERING IT UP THE NEEDLE JUMPS TO MAX ON THE SCALE. AFTER 5 MIN WARMUP NOTHING CHANGES. WHEN I PUT IN HEADPHONES IN JACK THE NEEDLE GOES TO 0 AND I HEAR A LOUD FIZZING LIKE HUM FROM THE PHONE OUT AND CHANGES PITCH ON EACH SELECTOR SWITCH. WHEN I TOUCH THE INPUT CLIP OR THE CHASIS THE BUZZ GETS LOUDER.


THANK YOU FOR ANY INSIGHT.


EDIT (2) RCA put a headphone/speaker jack on the instrument......

https://www.radiomuseum.org/r/rca_marin ... v_73a.html

EDIT: Only accessories are probes.

Attachment:
RCA Audio Voltmeter.jpg
RCA Audio Voltmeter.jpg [ 69.88 KiB | Viewed 331 times ]

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Tue 12, 2019 7:18 pm 
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Location: The Old Dominion VA 23518
Surplus Sales of Nebraska has the manual:

https://surplussales.com/Manuals/man_rca.html

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"Capacitor Cosmetologist since 1979"
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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Tue 12, 2019 11:03 pm 
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PM me with your email and I will send the schematic. But in the meantime wash all that deoxit out of the selector switch.

Dave


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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Wed 13, 2019 5:04 pm 
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Appreciate the link Findm-Keepm I purchased the manual- you made my day. Nice site.
Thank you for the kind offer Dave.

I've been reading opinions on why Deoxit on selector switches is a not desirable. Thanks for pointing that out it makes sense. I will clean it out.

The cable I have only has one clip, seems like its missing the ground clip (connected to the shielding i assume).

Any thoughts on what the "plugs" are?


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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Wed 13, 2019 5:22 pm 
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eizner23 wrote:
Any thoughts on what the "plugs" are?

A good photo of them would help. But from the radiomuseum.org listing, they look like Amphenol single-button mic connectors: Amphenol 75-MC1F or Switchcraft 2501F. Amphenol doesn't make them any more, but Switchcraft still does.

$7.31 from Mouser:
https://www.mouser.com/Search/Refine?Ke ... raft+2501F

Edited to fix the link. Thanks Don.

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Last edited by stevebyan on Feb Fri 15, 2019 5:11 pm, edited 1 time in total.

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Feb Fri 15, 2019 3:26 pm 
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Try this:

https://www.mouser.com/Search/Refine?Ke ... raft+2501F

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Sat 02, 2019 4:40 pm 
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Got the schematic, took some readings:
1st amp tube v1
pin 8 -> 5v, reads 4v
pin 6 -> 21v, reads 12v
pin 3/5 -> 1v, reads .9v
2nd amp tube v2
pin 8 -> 23v, reds 22v
pin 6 -> 30v, reads 26v
pin 5 -> 1.3v, reads 1.2v
3rd amp tube v3
pin 8 -< 200v, reads 230v
pin 6 -> 195v, reads 114v
pin 5 -> 5.8v, reads 0v
rectifier tube v6
pin 8 -> 440v, reads 305v
C14, 17, 18 (multisection cap) NOTED FLUID LEAKING WHEN HOT, MAKING FIZZING NOISE, TEMP READ 150F
c17 -> 10uf, reads 14uf voltage out 40-60v
c18 -> 30uf, reads 18uf voltage out 40-60v
c14 -> 10uf, reads 20uf voltage out 115v

i suspect multi section cap is bad causing v3 to be under powered. also suspect issues with c2, c13 causing pin 5 of v3 to be 0v and pin 6 of v1 to be under powered.
i would appreciate any of your opinions. schematic here.


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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Sat 02, 2019 4:59 pm 
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Replace the multi-section cap C14 C17, C18 IMMEDIATELY. DO NOT apply power to the unit until it is replaced. Damage to the rectifier tube and transformer WILL result.
Let it cool down. You were very close to that cap blowing up in your face!!!

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Last edited by joelandjoyce on Mar Sat 02, 2019 5:24 pm, edited 1 time in total.

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Sat 02, 2019 5:04 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
+100. The very first thing that needs to be done with instruments such as this, is to at the very LEAST, disconnect and test the electrolytics. Most of us don't bother with this type of instrument... they just get summarily replaced. Please do that and then recheck your voltages.

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Mon 04, 2019 6:10 pm 
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The caps seems fine testing with my multimeter. What method is recommended to test caps under high voltage?
I plan on replacing the mutli-sections with Nichicon UCA, maybe reuse the cans if the replacements will fit in.


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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Mon 04, 2019 6:17 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Eizner, if it was sizzling, hot, and fluid leaking out, no testing is required. It's bad, replace it.

That said, rather than re-write books on capacitor testing, do a search on this forum. There's days, literally, of reading past discussions.

Simple answer: An old Heathkit IT-11 or IT-28, or Sprague TO4, 5, or 6, or similar capacitor tester. Modern ones do NOT repeat NOT test a cap at anything close to rated voltage.

The two heathkits cited btw are essentially identical except for the case colors and knobs. The Spragues are upgrads of the previous model. CDE made a few, as did others such as Solar (a real oldie but goodie).

The best tester, for THIS kind of work, is a well stocked new parts assortment. They all need replacing or will soon, except in lab grade instruments.

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Last edited by Barry H Bennett on Mar Mon 04, 2019 10:31 pm, edited 1 time in total.

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Mon 04, 2019 10:00 pm 
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Joined: Jan Mon 17, 2011 8:57 pm
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From the schematics, C17 has 440 volts on it, C18 has 430 volts on it and C14 has at least 195 volts on it.

As others have said, replace those before continuing on.

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Tue 05, 2019 12:01 am 
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eizner23 wrote:
What method is recommended to test caps under high voltage?


place trashcan under bright light, if it makes a sound hitting the trashcan, it is bad.

Seriously, no testing needed, toss and replace, don't even waste time checking, you'll spend more on testing gear than the costs of just replacing them anyways, a DMM cannot make that determination. You don't need audio grade caps either. Electrolytic s get same, minding +/- polarity and voltage rating.
Paper caps do not matter for +/-. Good quality yellow caps will work fine, see sidebar vendors for same. MICA caps probably good, check range resistors, etc

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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Wed 06, 2019 6:18 pm 
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EICOKnight wrote:
From the schematics, C17 has 440 volts on it, C18 has 430 volts on it and C14 has at least 195 volts on it.

As others have said, replace those before continuing on.


Nichicon UCA V rating is 450v, would that be sufficient?


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 Post subject: Re: RCA VOLTMETER WV-73A RESTORE
PostPosted: Mar Wed 06, 2019 7:10 pm 
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Location: Sunbury, Ohio 43074
If it really has 430V on it, I'd opt for a 600V cap. Too close otherwise.

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