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 Post subject: RCA WV-87A Master Voltohmyst
PostPosted: Mar Wed 21, 2012 2:56 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2732
Location: Seattle WA US
First a warning: Don't use alkaline D-cells in this meter. The D-cell is mounted above the power transformer and when the cell leaks, the potassium hydroxide electrolyte will wipe out the transformer as well as other damage. And there seems to be a lot more electrolyte in alkaline cells than in traditional carbon-zinc D-cells.

Now, that the public service announcement is done, does anybody have the calibration instructions for this meter ? I found a minimal schematic online, but nothing else. The circuit is slightly different, with more calibration adjustments than other RCA VTVMs having manuals online.

Thanks for your help,
Chuck K7MCG


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Mar Wed 21, 2012 3:36 am 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 2633
Location: Florida
How many cal pots does it have? More than a WV-98C (5)?

One way to identify them is to set the meter for a range and then try the pots one at a time until one has an effect. You carefully turn each one a little and if nothing happens set it back and try the next one. I've done this several times over the years.

RRM


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Mar Wed 21, 2012 4:55 pm 
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Joined: Feb Thu 24, 2011 1:29 am
Posts: 3149
Location: Dallas, TX - in the city but with bobcats and coyotes
Set mechanical zero first.
Warm-up for 15 minutes.

Current:
Set Selector to "Current" & Range to "50mA". Connect black to -Current and red to +mA.
Deliver exactly 25mA to unit and adjust R14 to half-scale (ed - this is probably a superfluous step)
Deliver exactly 50mA and set R14 for 50mA reading.
Check full-scale of all ranges for +/-3% accuracy.
Move red to +1.5Amp
Supply exactly 1.4 Amperes. Should read between 1.37 and 1.43 A.

DC Voltage:
Selector to "+Volts" Check line voltage for 117V, 60 Hz.
Set Zero Adjust for reading of zero. Do not re-adjust during rest of calibration procedure.
Set Range to "50V". Supply exactly 50 Volts to the ground terminal and probe.
Adjust "+DC Cal," R15, for reading of exactly 50V.
reverse lead connections with selector set to "-Volts."
Adjust "-DC Cal," R13, for a reading of exactly 50 Volts.

AC Calibration Check:
Remove the WG-217 DC Probe from the WG-218 Direct Probe and Cable.
Set Selector to "AC Volts." Set Range to "1.5" Volts.
Short direct probe to ground clip and adjust "AC Zero," R47, for a reading of exactly Zero. This pot is at the rear of chassis and is adjustable via an opening at the rear of the cabinet.
Turn "Range" through the scale settings and verify readings are zero. If not, swap or replace 6AL5s.
Set Range to "150." Apply exactly 150 VAC, 60 Hz, to the direct probe. The meter should read within 5%. If not, verify circuit component values.

AC Compensation Adjustment:
Set the Selector to "AC Volts," & Range to "500V."
Zero pointer (ed - should already be there!)
Apply exactly 200 VAC, at approx. 100 KHz, between Ground and Direct Probe.
Adjust ceramic trimmer C2 for a reading of exactly 200V.


Ohms Adjustment:
Note: Battery must be installed for resistance measurements.
Set Selector to "+Volts" and verify pointer is at zero.
Set Selector to "Ohms" and Range to "RX1."
Adjust the Ohms Adjust for full-scale deflection.
Set Range to "RX1MEG." The meter should read above 1000. A reading of less than 1000 indicates excessive leakage in the resistance circuit.
If necessary to readjust "Ohms Adjust" when changing from RX1 to RX1MEG ranges, verify battery voltage.

I have an original manual to go with mine. :wink:

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In a triode, no one can hear you screen.


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Mar Wed 21, 2012 5:08 pm 
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Joined: Feb Thu 24, 2011 1:29 am
Posts: 3149
Location: Dallas, TX - in the city but with bobcats and coyotes
I would take the time to scan manual and send to somebody IF they would be willing to host it online. 8)

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In a triode, no one can hear you screen.


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Mar Wed 21, 2012 7:39 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 2732
Location: Seattle WA US
Mescalero-
Thank you for taking the time to type out the instructions.
--Chuck K7MCG


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Mar Wed 21, 2012 8:14 pm 
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Joined: Feb Thu 24, 2011 1:29 am
Posts: 3149
Location: Dallas, TX - in the city but with bobcats and coyotes
You are welcome. It was a nice lunch-time project for me. I type w/two fingers at my best! :wink:
I really like the blue hammer-tone paint and the big ol' meter face. But, and it's a big but, the battery corrosion can be a beast indeed! :evil:

73 de KB5SHC

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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Sun 17, 2016 6:15 pm 
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Location: Hutchinson,Kansas
mescalero wrote:
I would take the time to scan manual and send to somebody IF they would be willing to host it online. 8)




I could host it on my web server!


Todd


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Sun 17, 2016 6:19 pm 
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Joined: Nov Tue 18, 2008 8:34 am
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Location: Hutchinson,Kansas
I am curious as to what the forum thinks a very nice WV-87A is worth that has been restored? A friend of mine has one for sale.............


Todd


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Mon 18, 2016 3:52 am 
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Joined: Nov Wed 28, 2012 4:25 am
Posts: 122
Location: Muskoka Ontario
mescalero wrote:
I would take the time to scan manual and send to somebody IF they would be willing to host it online. 8)


What about BAMA? Isn't that their raison d'ĂȘtre?


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Mon 18, 2016 9:09 am 
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Location: Littleton, MA
torch wrote:
mescalero wrote:
I would take the time to scan manual and send to somebody IF they would be willing to host it online. 8)


What about BAMA? Isn't that their raison d'ĂȘtre?

I've never gotten them to accept a test equipment manual scan. You can upload one, but in my experience it never shows up on the site.

Didier's site:
http://www.ko4bb.com/manuals/

and Ebaman:
http://www.ebaman.com/

do seem to accept contributions. It might take a while, but they do show up eventually.

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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Mon 18, 2016 7:29 pm 
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Joined: Jan Sun 15, 2012 4:20 pm
Posts: 478
Location: Lawton Oklahoma
I made an offer of 100.00 for one on ebay that isnt restored and he wouldnt even aknowledge the offer. He is asking 200.00 BIN but Im not gonna pay that when I have a boatload of VTVMs already.


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Tue 19, 2016 10:01 pm 
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Joined: Feb Thu 24, 2011 1:29 am
Posts: 3149
Location: Dallas, TX - in the city but with bobcats and coyotes
Presently here: http://www.ko4bb.com/manuals/index.php?dir=10%29_Recent_Uploads
In short order, it will make it to the RCA section.

Interestingly, I don't seem to be able to post .pdf files, or any files, in the photo gallery anymore. :cry:

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In a triode, no one can hear you screen.


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Wed 20, 2016 2:46 pm 
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Joined: Nov Thu 07, 2013 3:29 am
Posts: 120
Location: Leesburg, Virginia
fordtech wrote:
I made an offer of 100.00 for one on ebay that isnt restored and he wouldnt even aknowledge the offer. He is asking 200.00 BIN but Im not gonna pay that when I have a boatload of VTVMs already.


My experience also when BIN or BO price is silly high. IMHO $100 is max pristine condition as a collectable.

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W0MPM


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Thu 21, 2016 7:27 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 9782
Location: Mpls, Minnesota
Bama has it.
http://bama.edebris.com/manuals/rca/wv87a/

Dave


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Thu 21, 2016 8:11 am 
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Joined: Feb Thu 24, 2011 1:29 am
Posts: 3149
Location: Dallas, TX - in the city but with bobcats and coyotes
Thanks, Dave. They do now! They did not have it back when this thread originated. I notice that BAMA's copy seems to have been cleaned up. Nice stuff, this modern technology.

_________________
In a triode, no one can hear you screen.


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Fri 22, 2016 2:08 pm 
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Joined: Jan Sun 15, 2012 4:20 pm
Posts: 478
Location: Lawton Oklahoma
Anyone with a copy of the WV87B manual or at least know if they are the same mechanically?

Thanks for the tips and info in this thread, will be very helpful when I get my B.


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Mon 25, 2016 4:30 am 
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Joined: May Wed 18, 2011 2:40 am
Posts: 2563
Location: Littleton, MA
mescalero wrote:
I would take the time to scan manual and send to somebody IF they would be willing to host it online. 8)

It's now available on my site:
http://www.byan-roper.org/steve/manuals ... WV-87A.pdf

as well as the afore-mentioned KO4BB and BAMA sites.

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Steve Byan http://www.byan-roper.org/steve/steve-at-play/


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 Post subject: Re: RCA WV-87A Master Voltohmyst
PostPosted: Jan Mon 25, 2016 4:57 am 
Member

Joined: Feb Thu 24, 2011 1:29 am
Posts: 3149
Location: Dallas, TX - in the city but with bobcats and coyotes
Thanks, Steve! 8)

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In a triode, no one can hear you screen.


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