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Author Topic: Heathkit VTVM Model 5  (Read 1982 times)
W4UTI
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« on: August 16, 2015, 06:02:27 PM »

Confusion! I'm trying to redo the Heathkit VTVM Model 5 I built while in the Air Force on Guam in 1952. No schematic or manual. I have found schematics on the Internet but they show the tubes as 7A6 and 12AU7. My Model 5 uses 6H6 and a 12AU7 like the Model 6. It reads "Model 5" on the front, and the switch positions are all Model 5. (6 voltage ranges while the model 6 has one more position). Where, how, can I get a Model 5 schematic? I would like to have a manual as well.

Thanks and 73,
Karl - W4UTI
W4UTI@arrl.net
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W9GB
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Posts: 3021




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« Reply #1 on: August 17, 2015, 02:37:37 PM »

Quote from: W4UTI
It reads "Model 5" on the front, and the switch positions are all Model 5.
 (6 voltage ranges while the model 6 has one more position).
Where, how, can I get a Model 5 schematic? I would like to have a manual as well.
Karl -

You need to remember the history of that 1951-1952 period at Heath.  
When you stated the year 1952, in Guam -- that was a "key year".
Bob Eckweiler fills in the history details for you.  
You actually have the Heathkit VTVM Model V-5A (1952).
====
Heathkit VTVM History
courtesy of Bob Eckweiler, AF6C
http://www.w6ze.org/Heathkit/Heathkit_019_V7a.pdf

The Heathkit V-5 VTVM
The V-5 replaced the V-4A in September of 1951.
Again the size of the meter was increased to 4-1/2" almost filling the width of the front panel. The cabinet itself also changed radically. Instead of a flat front panel that screws into a flange on the cabinet. the front panel, rear panel and cabinet are "formed" aluminum with rounded edges. There are no front panel screws; instead the front and rear panels and chassis are held to the cabinet by screws at the back of the cabinet, making a neater appearance and allowing the meter to fully extend from edge to edge. The jeweled pilot light remained on the front panel.

Internally the tube lineup changed; the octal 6SN7 tube was replaced with the smaller miniature 9-pin 12AU7 dual triode and the 6H6 was replaced by a 7A6 dual diode in an attempt to improve AC accuracy.
The 7A6 is a "loctal" based tube and has a different pin-out than the 6H6.
The tube socket and socket wiring were changed to accommodate the new tube.

In the Ohms circuit the two batteries (3V) were replaced with a single 1.5 volt cell,
and one of the Ohms divider resistors was changed to compensate.
Meter ranges remained the same as the V-2 through V4A.

The Heathkit V-5A VTVM
The V-5A replaced the V5 in 1952. It remained on the market until replaced by the V-6 in 1954.
The V5A is almost identical to the V-5 except the 7A6 AC to DC circuit tube was changed back to a 6H6, as was the tube socket and wiring.

Heathkit V-5A VTVM Manual (Assembly & Operation)
http://www.ko4bb.com/manuals/50.158.136.69/Heathkit_V-5A_Vacuum_Tube_Voltmeter.pdf

Heathkit V-5A VTVM Schematic Diagram
http://www.ko4bb.com/manuals/50.158.136.69/Heathkit_V-5A_VTM_Schematic.pdf
« Last Edit: August 17, 2015, 02:53:24 PM by W9GB » Logged
W4UTI
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Posts: 33




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« Reply #2 on: August 17, 2015, 06:22:36 PM »

WOW! What a great reply. Yes, with all that info it looks like I have a 5A. It has the "new" front, larger meter, and the tubes are 6H6 and 12AU7. With the manual in your reply, I can order the parts I might need to replace and just about rebuild it from scratch. YOU HAVE BEEN MOST HELPFUL.

Incidentally, I got my first ticket in 1950 while I lived in Southern Illinois, West Frankfort. Drove to St. Louis for the General exam, and, after much nervous shaking during the CW test, I did settle down and I passed it. 13 WPM-HOORAY!

Graduated from SIU in June, 1951.

I spend most of my time on the low ends of 40 and 30. I only operate CW. Listen for me.

Check my webpage at www.KG6FAA.com and my bio on www.QRZ.COM.

I do thank you so much. You have been such a great help. I had no idea I would get such a helpful response.

73,
Karl - W4UTI
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WI8P
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« Reply #3 on: August 18, 2015, 07:06:22 AM »

Gregory, for some reason I'm getting 404 File not found on this server errors when I click on the manual and schematic pdf links.  It's not that I need them, but I do like to look at this stuff.  Grin 
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G3RZP
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« Reply #4 on: August 18, 2015, 09:17:37 AM »

Me too.
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KE0EFX
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« Reply #5 on: August 18, 2015, 11:01:49 AM »

Try here...

http://www.ko4bb.com/manuals/index.php


73,
Scott
ke0efx
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KE0EFX
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« Reply #6 on: August 18, 2015, 11:04:19 AM »


Sorry,

Then under "Search term" enter V-5A and click Go.  That takes you to the page I attempted to post the above link to...



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G3RZP
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« Reply #7 on: August 18, 2015, 12:39:19 PM »

My Heath VTVM - which I totally rebuilt, is, IIRC, an IM10. It has the 1500 volt DC range but frankly, 1500 volts on a phenolic switch rated for 350 frightens me.
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KB1WSY
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Posts: 1183




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« Reply #8 on: August 18, 2015, 03:28:05 PM »

My Heath VTVM - which I totally rebuilt, is, IIRC, an IM10. It has the 1500 volt DC range but frankly, 1500 volts on a phenolic switch rated for 350 frightens me.

I have a similar issue. I totally rebuilt my Eico 232, including restoring a very fragile phenolic switch, and it has a 1500V range. It is about 60 years old. (I added the neon light on the front panel to remind me to switch the meter off after use; so it's not a "factory spec" unit.)





73 de Martin, KB1WSY
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WI8P
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Posts: 509




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« Reply #9 on: August 19, 2015, 06:14:41 AM »


That worked!  Thanks!   Grin

BTW: Great site - lots of old manuals there!
« Last Edit: August 19, 2015, 06:21:41 AM by WI8P » Logged
W9GB
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Posts: 3021




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« Reply #10 on: August 20, 2015, 02:41:15 PM »

KO4BB moved his web page.

Here is the main page, select from the Manuals section.
http://www.ko4bb.com/getsimple/index.php?id=manuals
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