Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Oct Fri 22, 2021 2:27 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 33 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 6:14 am 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
I'm on to another one. For some reason I seem to like the oddball ones with no information available lol. It's an Electronic Designs Inc VTVM. It has a 6X5 tube on the right and 2 6K6 tubes on the left.

Attachment:
20210922_001359.jpg
20210922_001359.jpg [ 3.1 MiB | Viewed 553 times ]


Attachment:
20210922_001457.jpg
20210922_001457.jpg [ 3.23 MiB | Viewed 553 times ]


Attachment:
20210922_001505.jpg
20210922_001505.jpg [ 2.66 MiB | Viewed 553 times ]



The resistance ranges work although not dead on.

Attachment:
20210922_002953.jpg
20210922_002953.jpg [ 3.15 MiB | Viewed 553 times ]


Attachment:
20210922_003203.jpg
20210922_003203.jpg [ 3.03 MiB | Viewed 553 times ]


Attachment:
20210922_003322.jpg
20210922_003322.jpg [ 3.11 MiB | Viewed 553 times ]


Attachment:
20210922_003506.jpg
20210922_003506.jpg [ 2.97 MiB | Viewed 553 times ]


Attachment:
20210922_003641.jpg
20210922_003641.jpg [ 2.93 MiB | Viewed 553 times ]


Attachment:
20210922_003812.jpg
20210922_003812.jpg [ 2.94 MiB | Viewed 553 times ]



The AC ranges look pretty good. The DC ranges are off a bit off. Does anyone have any thoughts or ideas on how to calibrate this meter? Here is the calibration pots inside. It's close but that's only good in handgrenades lol. I'm also looking for a schematic with no luck so far. Any help, thoughts or ideas would be greatly appreciated.


Attachments:
20210922_004953.jpg
20210922_004953.jpg [ 3.36 MiB | Viewed 553 times ]

_________________
Thanks.
Robb
Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 6:20 am 
Member

Joined: Jan Tue 10, 2012 8:39 am
Posts: 2810
The meter looks a lot like the one in the EICO 221.


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 6:26 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 3779
Location: Seattle WA US
From Vacuum Tube Voltmeters, Rider, 1951

Attachment:
Electronic designs 100  a.jpg
Electronic designs 100 a.jpg [ 154.07 KiB | Viewed 549 times ]


Last edited by K7MCG on Sep Wed 22, 2021 6:27 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 6:26 am 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
bob91343 wrote:
The meter looks a lot like the one in the EICO 221.


Yes it's not exact but it's close.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 6:27 am 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
K7MCG wrote:
Attachment:
Electronic designs 100 a.jpg


My God man. Thank you.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 2:42 pm 
Member

Joined: Mar Sat 03, 2007 12:53 am
Posts: 895
Most of the design of the Model 100 VTVM was taken from the RCA model 195-A voltohmist. The model 100 replaced the vacuum tube AC rectifier in the 195-A with a pair of semiconductor diodes. Therefore, the RCA model 195-A calibration instructions which are included in https://bama.edebris.com/manuals/rca/195a/ will apply to the model 100.


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 2:53 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
Alan S wrote:
Most of the design of the Model 100 VTVM was taken from the RCA model 195-A voltohmist. The model 100 replaced the vacuum tube AC rectifier in the 195-A with a pair of semiconductor diodes. Therefore, the RCA model 195-A calibration instructions which are included in https://bama.edebris.com/manuals/rca/195a/ will apply to the model 100.


Thank you.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 3:10 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
The 195-A is close but all the ranges are different. I have a 3VDC scale and a 3VDC adjustment pot. I also have a 10VAC scale and a 10VAC adjustment pot. The last adjustment pot is a 100VAC. It has a 10VAC scale and a 30VAC scale on the meter face. I'm in search of better calibration instructions and possibly the manual?

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 6:45 pm 
Member

Joined: Mar Sat 03, 2007 12:53 am
Posts: 895
Without power adjust the meter so that the pointer is at 0. Then warm up the meter and short the leads together and adjust the front panel 0 adjust pot so that the meter reads 0. Then apply 3vdc to the meter and adjust the 3vdc pot so that the meter reads 3 volts DC, then repeat the front panel 0 adjust procedure and apply 10vac to the meter and adjust the 10vac pot so that the meter reads 10 volts AC, finally repeat the front panel 0 adjust procedure and apply 100vac to the meter and adjust the 100vac pot so that the meter reads 100 volts AC.


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 7:13 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
Alan S wrote:
Without power adjust the meter so that the pointer is at 0. Then warm up the meter and short the leads together and adjust the front panel 0 adjust pot so that the meter reads 0. Then apply 3vdc to the meter and adjust the 3vdc pot so that the meter reads 3 volts DC, then repeat the front panel 0 adjust procedure and apply 10vac to the meter and adjust the 10vac pot so that the meter reads 10 volts AC, finally repeat the front panel 0 adjust procedure and apply 100vac to the meter and adjust the 100vac pot so that the meter reads 100 volts AC.


Thank you. I've actually done this. Lol. It made sense to me. But then you see other calibration procedures and it's set to 4VDC on the 5VDC scale.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 9:13 pm 
Member
User avatar

Joined: May Wed 18, 2011 2:40 am
Posts: 5746
Location: Littleton, MA
Alan S wrote:
Without power adjust the meter so that the pointer is at 0. Then warm up the meter and short the leads together and adjust the front panel 0 adjust pot so that the meter reads 0. Then apply 3vdc to the meter and adjust the 3vdc pot so that the meter reads 3 volts DC, then repeat the front panel 0 adjust procedure and apply 10vac to the meter and adjust the 10vac pot so that the meter reads 10 volts AC, finally repeat the front panel 0 adjust procedure and apply 100vac to the meter and adjust the 100vac pot so that the meter reads 100 volts AC.

This meter is unusual in that the AC section is simply a VOM rather than a VTVM. In the AC position, the panel meter is disconnected from the VTVM electronic circuitry and connected to what is essentially the AC portion of a VOM. So in AC mode, the front panel zero adjust control shouldn't have any effect on the meter.

in my reading of the schematic, the two AC adjustments shown there should interact, so it's not clear to me what procedure should be followed to adjust them. One adjustment controls the shunt resistance across the meter. The other controls the calibration of the 10 Volt scale, with proportionately smaller effects on the higher scales.

I think I'd start by adjusting R33 so that the series combination of R33 and R34 is 10,000 Ω. (This is clearly a 1,000 Ω/V AC meter.) I'd then apply 100 Volts AC and adjust R31 until the meter reads 100 Volts. Next, I'd apply 10 Volts and adjust R33 so that the meter reads 10 Volts. Then I'd repeat the 100 Volt and 10 Volt adjustments.

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


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 9:26 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
stevebyan wrote:
This meter is unusual in that the AC section is simply a VOM rather than a VTVM. In the AC position, the panel meter is disconnected from the VTVM electronic circuitry and connected to what is essentially the AC portion of a VOM. So in AC mode, the front panel zero adjust control shouldn't have any effect on the meter.

in my reading of the schematic, the two AC adjustments shown there should interact, so it's not clear to me what procedure should be followed to adjust them. One adjustment controls the shunt resistance across the meter. The other controls the calibration of the 10 Volt scale, with proportionately smaller effects on the higher scales.

I think I'd start by adjusting R33 so that the series combination of R33 and R34 is 10,000 Ω. (This is clearly a 1,000 Ω/V AC meter.) I'd then apply 100 Volts AC and adjust R31 until the meter reads 100 Volts. Next, I'd apply 10 Volts and adjust R33 so that the meter reads 10 Volts. Then I'd repeat the 100 Volt and 10 Volt adjustments.


Your correct in that in AC mode the front panel zero adjust has n9 effect on the needle. The above procedure gets me close on all scales but not dead on. I will try your procedure after I get home from work at 1130 and let you know. Thanks.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 10:01 pm 
Member
User avatar

Joined: May Wed 18, 2011 2:40 am
Posts: 5746
Location: Littleton, MA
K7MCG wrote:
From Vacuum Tube Voltmeters, Rider, 1951

Robbdoe1, you seem to be interested in restoring VTVMs, so you'll probably be interested in these links to scans of the two most common books written about them.

First, Rider's Vacuum Tube Voltmeters is available from the excellent tubebooks.org site:
http://tubebooks.org/Books/rider_VTVM.pdf

Second, Rhys Samuel's excellent The VTVM is available in several editions:
First printing, 1956: https://worldradiohistory.com/BOOKSHELF ... l-1956.pdf
Eighth printing, 1962: https://worldradiohistory.com/BOOKSHELF ... 7-1956.pdf
A nice hi-res scan of the Fifth printing, 1960: http://www.vacuumtubeera.net/The-VTVM-R ... l-1956.zip
ARFer ncwalz's nice scan of the Second printing, 1957: http://www.mediafire.com/file/abz95ndxa ... l.pdf/file

Rider's book is especially valuable because it includes schematics for many commercial VTVMs, along with calibration instructions for some of them.

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


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 10:08 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
stevebyan wrote:
K7MCG wrote:
From Vacuum Tube Voltmeters, Rider, 1951

Robbdoe1, you seem to be interested in restoring VTVMs, so you'll probably be interested in these links to scans of the two most common books written about them.

First, Rider's Vacuum Tube Voltmeters is available from the excellent tubebooks.org site:
http://tubebooks.org/Books/rider_VTVM.pdf

Second, Rhys Samuel's excellent The VTVM is available in several editions:
First printing, 1956: https://worldradiohistory.com/BOOKSHELF ... l-1956.pdf
Eighth printing, 1962: https://worldradiohistory.com/BOOKSHELF ... 7-1956.pdf
A nice hi-res scan of the Fifth printing, 1960: http://www.vacuumtubeera.net/The-VTVM-R ... l-1956.zip
ARFer ncwalz's nice scan of the Second printing, 1957: http://www.mediafire.com/file/abz95ndxa ... l.pdf/file

Rider's book is especially valuable because it includes schematics for many commercial VTVMs, along with calibration instructions for some of them.


Yes VTVMs and analog multimeters that are vintage. Thank you so much for the links. I will dl them tonight.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 11:36 pm 
Member

Joined: Jan Tue 10, 2012 8:39 am
Posts: 2810
The reason behind calibrating at, say, 4V on the 5V scale is to average the nonlinearity. If you calibrate zero and full scale, the long stretch between may not be very linear. When you set it at maybe 80% of full scale, the space between known points is smaller and thus has less chance of losing accuracy.

I didn't explain that too well but maybe you can get it.


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 22, 2021 11:50 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
bob91343 wrote:
The reason behind calibrating at, say, 4V on the 5V scale is to average the nonlinearity. If you calibrate zero and full scale, the long stretch between may not be very linear. When you set it at maybe 80% of full scale, the space between known points is smaller and thus has less chance of losing accuracy.

I didn't explain that too well but maybe you can get it.


Yes I understand. It makes sense if you think about it....it may also be why the meter is off a little using the above common sense method. 10VAC scale and 10VAC pot calibrate to 10VAC lol. Your only getting zero and 10VAC calibration and the in-between....or linearity may be off. Thanks for the insight.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Sep Wed 29, 2021 11:48 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
stevebyan wrote:
Alan S wrote:
Without power adjust the meter so that the pointer is at 0. Then warm up the meter and short the leads together and adjust the front panel 0 adjust pot so that the meter reads 0. Then apply 3vdc to the meter and adjust the 3vdc pot so that the meter reads 3 volts DC, then repeat the front panel 0 adjust procedure and apply 10vac to the meter and adjust the 10vac pot so that the meter reads 10 volts AC, finally repeat the front panel 0 adjust procedure and apply 100vac to the meter and adjust the 100vac pot so that the meter reads 100 volts AC.

This meter is unusual in that the AC section is simply a VOM rather than a VTVM. In the AC position, the panel meter is disconnected from the VTVM electronic circuitry and connected to what is essentially the AC portion of a VOM. So in AC mode, the front panel zero adjust control shouldn't have any effect on the meter.

in my reading of the schematic, the two AC adjustments shown there should interact, so it's not clear to me what procedure should be followed to adjust them. One adjustment controls the shunt resistance across the meter. The other controls the calibration of the 10 Volt scale, with proportionately smaller effects on the higher scales.

I think I'd start by adjusting R33 so that the series combination of R33 and R34 is 10,000 Ω. (This is clearly a 1,000 Ω/V AC meter.) I'd then apply 100 Volts AC and adjust R31 until the meter reads 100 Volts. Next, I'd apply 10 Volts and adjust R33 so that the meter reads 10 Volts. Then I'd repeat the 100 Volt and 10 Volt adjustments.


I'm back at it again. I tried this procedure above but the meter will not adjust to 100 Vac. 10 Vac with the 10 volt pot is no issue. It reaches about 80 to 90 percent of it's way to 100 Vac when adjusting the 100 volt pot. The pot reaches it's mechanical stop before I can reach 100 volta on yhe AC scale.

Any ideas?

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Oct Tue 05, 2021 2:33 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
I'm making a dedicated DC probe for this meter. Can anyone tell me IF it uses a series resistor? If it does, what size? Some of my VTVM's use a 1M ohm resistor and others use a 6.8M ohm. Is there a way to tell without a manual? Thanks guy's.

_________________
Thanks.
Robb


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Oct Tue 05, 2021 4:25 pm 
Member
User avatar

Joined: May Wed 18, 2011 2:40 am
Posts: 5746
Location: Littleton, MA
Robbdoe1 wrote:
I'm making a dedicated DC probe for this meter. Can anyone tell me IF it uses a series resistor?

A series resistor in the DC Volts probe is an essential feature in service-grade VTVMs. (Some laboratory grade VTVMs don't have it, though.) So yes, it almost certainly uses a series resistor.

Robbdoe1 wrote:
If it does, what size? Some of my VTVM's use a 1M ohm resistor and others use a 6.8M ohm. Is there a way to tell without a manual?

If it's not shown on the schematic, and you don't have the specification for the DC input impedance, there's no way to be certain of its value.

You mentioned that the DC volt ranges were a little off when you first tested it. How much were they off, and in what direction? And what is the resistance of the DC Volts range divider, from the connector to ground (i.e. the sum of R-1 through R-6)?

If they were about 10% high, and the total resistance of the DC volts range divider is 10 Megohms, then the probe almost certainly had a 1 Megohm resistor in it.

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


Top
 Profile  
 
 Post subject: Re: Electronic Designs Inc Model 100 VTVM
PostPosted: Oct Wed 06, 2021 4:18 pm 
Member

Joined: Aug Wed 04, 2021 3:43 pm
Posts: 124
stevebyan wrote:
Robbdoe1 wrote:
I'm making a dedicated DC probe for this meter. Can anyone tell me IF it uses a series resistor?

A series resistor in the DC Volts probe is an essential feature in service-grade VTVMs. (Some laboratory grade VTVMs don't have it, though.) So yes, it almost certainly uses a series resistor.

Robbdoe1 wrote:
If it does, what size? Some of my VTVM's use a 1M ohm resistor and others use a 6.8M ohm. Is there a way to tell without a manual?

If it's not shown on the schematic, and you don't have the specification for the DC input impedance, there's no way to be certain of its value.

You mentioned that the DC volt ranges were a little off when you first tested it. How much were they off, and in what direction? And what is the resistance of the DC Volts range divider, from the connector to ground (i.e. the sum of R-1 through R-6)?

If they were about 10% high, and the total resistance of the DC volts range divider is 10 Megohms, then the probe almost certainly had a 1 Megohm resistor in it.


Hello and thank you.

The sum of R1-R6 is 11M ohm. The DC readings are low to start my test. 2.6VDC on the 3VDC scale, 8.7VDC on the 10VDC scale and 25VDC on the 30VDC scale using my adjustable power supply and confirming with my Fluke. The DC probe I used has the ability to add a 1M ohm resistor in series with the probe tip or short the tip directly. The above reading were taken with the tip shorted directly. When I added in the 1M ohm resistor the readings dropped even lower. If I attempted to calibrate it on the 3VDC range I ran out of adjustment on the 3VDC pot and could not achieve calibration.

I then calibrated the DC via the 3VDC pot in the rear of the meter. I set the power supply to 3VDC and the meter to the 3VDC range. I adjusted the pot to achieve exactly 3VDC with the probe tip shorted directly. So obviously on the 3VDC check it was dead nuts, on the 10VDC check it was above the 10VDC tic on the meter face (see pictures) and on the 30VDC check it was slightly below the 30VDC tic on the meter face (see pictures). I have no way yet to verify the 100VDC, 300VDC or 1000VDC ranges currently.

Attachment:
20211006_110434.jpg
20211006_110434.jpg [ 2.82 MiB | Viewed 227 times ]


Attachment:
20211006_110520.jpg
20211006_110520.jpg [ 2.88 MiB | Viewed 227 times ]


What would you make of this? Is there anything I'm missing? The only other adjustment pots are 10VAC and 100VAC which when turned had no affect on the DCV readings. For clarification I zeroed the meter with power off mechanically. I also zeroed the meter in every DC range I went to.

_________________
Thanks.
Robb


Top
 Profile  
 
Post New Topic Post Reply  [ 33 posts ]  Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: KB4QAA and 22 guests



Search for:
Jump to:  


































Privacy Policy :: Powered by phpBB