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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Sun 17, 2019 9:13 pm 
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Joined: Mar Thu 15, 2018 2:23 pm
Posts: 238
Superretrodyne wrote:
mr.fabe,

I have a 34401A. On the upper ranges it agrees with my Siglent SDM 3045X and the DMMs in both my Tek 2236 scopes. The low end is a disaster, so there is obviously something wrong. I haven't bothered to look into it because when I got a manual and looked at the specs of the 34401A, the error range on the low end is almost +/- 3%. The Siglent's error range is +/- 0.27%. My source was set to 1.41 mv at 20 kHz on the low end.

The rated AC spec range for the 34401a is 100 mV to 1000 V...

Attachment:
34401a specs.jpeg
34401a specs.jpeg [ 239.44 KiB | Viewed 161 times ]


An article regarding this issue was documented by another user as well..

Attachment:
34401A AC zero.pdf [196.33 KiB]
Downloaded 5 times


Regardless.. it's still a good meter and exercise caution if you measure AC below 100mV. DC is great.


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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Sun 17, 2019 10:56 pm 
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Location: Littleton, MA
Barry H Bennett wrote:
does anyone perhaps have a LEGIBLE version of the manual? The one up on BAMA is almost unreadable, particularly as far as the schematic is concerned.

Triplett used to have a good scan of the manual for the 850 on their web site, but they have apparently removed the manuals for obsolete equipment and it's not longer available from them.

So, I put it up for download on my site:
https://www.byan-roper.org/steve/manual ... manual.pdf

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Sun 17, 2019 11:08 pm 
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Excellent Hi-Res scan of the manual. This one's a keeper. Thanks.

Now, I have to look for an Triplett 850 to go with it....


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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Sun 17, 2019 11:21 pm 
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Alan S wrote:
Although I have 3 HP 410-Cs and 2 military TS505Ds, I mostly collect unusual VTVMs such as the Weston 669, the RCA WV-65A (a battery VTVM that uses 2 tubes as a differential amp), the American Chronoscope 601 (a battery VTVM that uses 2 tubes as a differential amp and another tube as an AC rectifier), the Simpson 651 260 VTVM adapter, the Phaostron 777, and a number of single range and multi-range AC and DC TRIO panel meters. I have had a couple of Heathkits and one EICO in the past.

Since I last posted in this thread, I've also acquired a few more VTVMs:

Weston 982 battery powered VTVM
Acton Labs 810
GR 1800-A
McMurdo Silver Vomax 900A (I already had a 900)
Simpson 303
Hickok 415 (a VTVM in the unusual case also used by the Hickok 455 VOM)
Triplett 650
Triplett 631
Measurements Corp Model 62
Sylvania Polymeter 134 - minus RF probe :-(
Sylvania Polymeter 221Z - also minus RF probe :-(
RCA WV-97A
{Edited to add] B&K 177

I also have a Trio panel meter, they're pretty interesting little devices. Do you have any schematic data on them?

The Phaostron 777 is definitely on my wish-list, as is their 555 VOM. Also the Dumont 405 VTVM, and an HP 410A.

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Last edited by stevebyan on Nov Mon 18, 2019 5:58 am, edited 3 times in total.

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Sun 17, 2019 11:23 pm 
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mr.fabe wrote:
Now, I have to look for an Triplett 850 to go with it....

Welcome to "Test Equipment Anonymous" :-)

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Sun 17, 2019 11:58 pm 
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Joined: Aug Fri 30, 2019 11:36 pm
Posts: 15
Location: Arizona
I have a VIZ WV-98A that has me scratching my head that i bought new in late '70's. For last 20 years it sat boxed, until now when I decided to use it.

When I touch the probe ground (shield) and the case, I get a mild tingle shock. (4.8 VDC measured)

Unit has a three wire plug and I replaced C6 Electrolytic (10uf, 150v) I also replaced the original D type battery that did not leak.

Any idea where that stray voltage is coming from?

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 1:57 am 
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rgbiker wrote:
...Any idea where that stray voltage is coming from?


Sounds like a leaky isolation cap. The big paper one.

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 2:48 am 
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Joined: Jan Tue 10, 2012 8:39 am
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I would disconnect and trash any components connected to the power line other than the switch and fuse and transformer. No harm in a capacitor across the line but no need either. Any component going to chassis should be removed.


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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 2:59 am 
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The only battery tube VTVMs I collect (other than the VTVM adapter for the Simpson 260) that use a differential amplifier because they have better operational characteristics and are much rarer than the VTVMs that use a single ended amplifier. Since most battery tubes are directly heated (they don't have a cathode) the differential amplifier requires two tubes as contrasted against the single tube differential amplifier in most service grade VTVMs. The weston 669 that I have is one of the earliest VTVMs ever made and uses a type 78 and a type 1V tube.

I also have the matching Phaostron 555 multimeter.

I copy schematics for TRIO meters from the Internet whenever I find them. They are included here:
Attachment:
trio-105.JPG
trio-105.JPG [ 564.55 KiB | Viewed 132 times ]

Attachment:
trio-109 AC.JPG
trio-109 AC.JPG [ 564.25 KiB | Viewed 132 times ]

Attachment:
TRIO-SF680.JPG
TRIO-SF680.JPG [ 553.71 KiB | Viewed 132 times ]


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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 3:20 am 
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Location: Sunbury, Ohio 43074
Steve, thanks so much. Also many thanks to all the other helpful posts on the 850 schematic / manual.

Steve, would you be willing to shoot that higher Rez manual to BAMA so they can replace the one they have up there now? Or I can do it if you wish but won't without your ok.

Barry

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 3:34 am 
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Barry H Bennett wrote:
Steve, would you be willing to shoot that higher Rez manual to BAMA so they can replace the one they have up there now?

I just did. I've not had much luck uploading to BAMA, perhaps because until now I didn't know that the ftp userid should be blank, rather than "guest".

You should start a thread on your 850. I opened mine up tonight. The Tiny Chief capacitors are of course leaky (1.2MΩ according to my GR 1862-B), and almost every carbon composition resistor under the chassis is out of tolerance. I haven't checked the range resistors yet.

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Last edited by stevebyan on Nov Mon 18, 2019 3:48 am, edited 1 time in total.

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 3:39 am 
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While uploading the manual to Didier's site (k04bb.com), I found that he already has a hi-resolution scan of a manual for a late-model (triple-T Triplett logo) 850. See here:
http://www.ko4bb.com/getsimple/index.ph ... t/Triplett

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 3:43 am 
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Alan S wrote:
I copy schematics for TRIO meters from the Internet whenever I find them. They are included here:

Thank you Alan

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 5:14 am 
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Posts: 6727
Location: Liberty, Missouri
I only have one real VTVM, an RCA 98C.

Image
clickthepic
--------
However, I have several analog and digital volt meters.
HP-334A
HP-410C
HP-427A
HP-3400A
HP-3456A
HP-3490A
Three selective volt meters, a few VOMS, and half a dozen or so hand held DVMs. Interestingly, I've never had an HP-400, nor any kit built meter.

I think I finally beat the need for the biggest stack of meters, but I still have quite a few.

------------
Steve, yours is only the second GR1806 I've EVER seen on anyone's bench. I had one for several years and if I had had the rack mount version I'd still have it today. Those are the finest VTVMs ever built I think.

Image
clickthepic

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Last edited by Mikeinkcmo on Nov Mon 18, 2019 5:42 am, edited 1 time in total.

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 5:32 am 
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Mikeinkcmo wrote:
Those are the finest VTVMs ever built I think.


Not to mention one of the best-looking.

Even though I’ve been really thinning the herd, I’d have to grab one of those given the opportunity.

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 5:44 am 
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Joined: Feb Fri 01, 2019 11:35 pm
Posts: 271
Location: Riverside Ca. 92504
Maybe we should all get together for a intervention ( swap meet ) so we can compare our problems ( buy sell swap ) and ease our conscious ( lighten our wallet) ….It would enlighten us (We could get that sought after VTVM ) and ease the burden on our soul ( happy days are here again I got it) Amen Tom


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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 5:57 am 
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Mike, your WV-98C looks like it just came out of the box. Nice!

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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 11:17 am 
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Interesting to see this discussion revived. Like Steve, I have added a lot of VTVMs to my collection since then, including an excellent Measurements 62 and a Weston 982, as well as a couple of Sylvania Polymeters. In addition, though I have mentioned them in other discussions, are the following General Radio voltmeters:

726-A (from 1937 and possibly the first VTVM with a vacuum tube probe to rectify high frequency signals)

1803-A (A.C. volts only)

1230-A (electrometer)

1806-A (early variant with jewelled D’Arsonval meter and somewhat different circuit)

I have also acquired some of the Trio Laboratories panel VTVMs. Most have subminiature tubes, but one that operates directly off the mains uses standard miniature tubes. They are extremely well made.

Like Steve, I am very keen to acquire a Dumont 405, especially because it matches a Dumont oscilloscope that I have owned for decades, and which holds a very special place in my collection. I would pay very well for a 405 VTVM.

With regard to the General Radio 1806-A, which I agree is the finest VTVM ever made, I noticed that both Steve, and Mike when he owned the late-style example above, removed the cover of the Flip-Tilt case entirely, presumably because it takes up a fair amount of bench space. I have always liked General Radio’s Flip-Tilt case design, but I wonder how popular it was.

I have never seen an example of the rack-mount GR 1806-AR, and Mike’s 1806-A is the only example I have seen in General Radio’s late “modern” style. Another instrument for which I would pay well.


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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 12:08 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5345
Location: Sunbury, Ohio 43074
Mikeinkcmo wrote:
I only have one real VTVM, an RCA 98C.


That's a nice one too, Mike. I've got perhaps 5 of that one, but I decided I just liked the face of the Triplett better. It is a very occasionally used instrument anyway.

Steve, I'm not going to "restore" mine in the truest sense of the word. I'll recap it, but I don't think I'm going to bother with the resistors. These things had a limited accuracy to begin with, and truthfully I don't need it to be accurate anyway. I've got the DMM for that. I like the needle approach for peaking things, and it's handy for extremely high input impedance in RF circuits of course, which I seldom get into anyway. When I do, I generally use the scope regardless.

Besides, it looks cool on the bench. ;-)

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https://www.bbtvtestequipment.com


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 Post subject: Re: I have a VTVM addiction....
PostPosted: Nov Mon 18, 2019 12:32 pm 
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Quote:
...Mike, your WV-98C looks like it just came out of the box. Nice!...
You guessed it, it did, maybe 50 years ago. :wink:

Actually I got it from the estate of a SK friend, for that very reason, plus as a keepsake.

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