That VTVM is a very useful piece of equipment. I have a Heathkit V-7A VTVM, I restored it and it's in excellent condition. I'm using it to align radios, I too am a ham operator. A good VTVM is as useful as a good oscilloscope.
It has been some time since I last looked at this, but here are some suggestions. You should be able to find a copy of the manual for the V-6 on the Internet (I found one). Refer to it and check all wiring and component values. Check that all resistors are within tolerance and replace any that are out of spec. This includes the 1MEG resistor in the DC test lead. Refer to the In Case of Difficulty section of the manual for more troubleshooting advice. One suggestion there is that if you cannot get a zero adjust you may need to add a 1000 ohm or more resistor in series with either 12AU7 cathode and the zero adjust control. If it has a selenium rectifier you should probably replace it with a modern 1N4004 diode. Page 13 of the manual mentions "ageing" the instrument. Doing that may help with calibration.
Hi, thanks for the video. I learn Heathkit equipment with you for few years! At this time I try to repair the A4-M2 vtvm, which was used at a factory in the SU in 50-60s
Enjoyed your videos. But a minor mistake on this one mentioning the 1M ohm resistor on the AC probe. Not sure you caught that in review. I have one of these my dad built. Unfortunately it was stored with the battery and destroyed the DC Cal pod and part of the circuit board which I have repaired. However I’m getting drift after calibration and I’m not sure where the draft is coming from. It may be possibly the connections in the wiper switches but I just wondered what you ran into on your unit. Thank you so much for all the work you do on your TH-cam‘s.
If it seems to be drift and not an intermittent connection, I would suspect one of the tubes. But let it run for some time to stabilize. If you replaced any of the tubes, let it run for a number of hours to "burn-in" the tubes.
just a note that 12AT7/12AV7/12AZ7 are adequate substitutes for the 12AU7 . 12AU7s are getting expensive and 12AV7 or 12AZ7 can still be found NOS at low cost
Interestingly the V-7 kit manual has some detail on how to repair a cracked circuit board. Heathkit recommended soldering a small piece of wire over the crack and soldering it in place. I have a V-7 with a cracked circuit board. The manual also included full size drawings of the circuit board. One of these days I may try and etch a new board. As you said the V-7A improved upon the PCB design. I've also got a V-6 only to see how the point to point wiring model looked and was wired.
Hi Jeff. Many thanks for the video. I have just completed a total restoration of a model V6. I have tried both the supplied and reverse dual rectifiers. However I cannot quite zero the ac needle. I was wondering if it is possible to modify the V6 by using the V7 circuit topology? Many thanks. 73 Dick N4HAY
I like your channel very much! Unfortunately the display needle on my restored V7-A broke and i am looking for a replacement. Perhaps you could help me find one. I live in Germany thanx.
I think your best option to find a meter movement would be to check eBay or eBay Kleinanzeigen and look for a meter movement or a V-7A that can be used for parts.
That VTVM is a very useful piece of equipment. I have a Heathkit V-7A VTVM, I restored it and it's in excellent condition. I'm using it to align radios, I too am a ham operator. A good VTVM is as useful as a good oscilloscope.
I always enjoy a Jeff Tranter video on Heathkit products..
It has been some time since I last looked at this, but here are some suggestions.
You should be able to find a copy of the manual for the V-6 on the Internet (I found one). Refer to it and check all wiring and component values.
Check that all resistors are within tolerance and replace any that are out of spec. This includes the 1MEG resistor in the DC test lead.
Refer to the In Case of Difficulty section of the manual for more troubleshooting advice. One suggestion there is that if you cannot get a zero adjust you may need to add a 1000 ohm or more resistor in series with either 12AU7 cathode and the zero adjust control.
If it has a selenium rectifier you should probably replace it with a modern 1N4004 diode.
Page 13 of the manual mentions "ageing" the instrument. Doing that may help with calibration.
Hi, thanks for the video. I learn Heathkit equipment with you for few years! At this time I try to repair the A4-M2 vtvm, which was used at a factory in the SU in 50-60s
Enjoyed your videos. But a minor mistake on this one mentioning the 1M ohm resistor on the AC probe. Not sure you caught that in review. I have one of these my dad built. Unfortunately it was stored with the battery and destroyed the DC Cal pod and part of the circuit board which I have repaired. However I’m getting drift after calibration and I’m not sure where the draft is coming from. It may be possibly the connections in the wiper switches but I just wondered what you ran into on your unit. Thank you so much for all the work you do on your TH-cam‘s.
If it seems to be drift and not an intermittent connection, I would suspect one of the tubes. But let it run for some time to stabilize. If you replaced any of the tubes, let it run for a number of hours to "burn-in" the tubes.
just a note that 12AT7/12AV7/12AZ7 are adequate substitutes for the 12AU7 . 12AU7s are getting expensive and 12AV7 or 12AZ7 can still be found NOS at low cost
Thanks Jeff!
Appreciate your dedicated research and explanation about Heathkit products. Thumbs up sir. Keep up the excellent work. 👍.
Interestingly the V-7 kit manual has some detail on how to repair a cracked circuit board. Heathkit recommended soldering a small piece of wire over the crack and soldering it in place. I have a V-7 with a cracked circuit board. The manual also included full size drawings of the circuit board. One of these days I may try and etch a new board. As you said the V-7A improved upon the PCB design. I've also got a V-6 only to see how the point to point wiring model looked and was wired.
Hi Jeff. Many thanks for the video. I have just completed a total restoration of a model V6. I have tried both the supplied and reverse dual rectifiers. However I cannot quite zero the ac needle. I was wondering if it is possible to modify the V6 by using the V7 circuit topology? Many thanks. 73 Dick N4HAY
Thanks for sharing Jeff...love your book that I've had for several years now. 73 - Dino KL0S
I like your channel very much!
Unfortunately the display needle on my restored V7-A broke and i am looking for a replacement.
Perhaps you could help me find one.
I live in Germany
thanx.
I think your best option to find a meter movement would be to check eBay or eBay Kleinanzeigen and look for a meter movement or a V-7A that can be used for parts.
Is there any Heathkit unit you are looking for that you haven't found yet?
From 1/8th to 3/32nds - that would mean smaller.
Angel idea why my v-7a has no ohms?
Nice meter and interface but very unstable.
Nothing compares with the smell of a selenium rectifier loosing its magic smoke! Bah!
Hello Jeff, purchased your book. Can I mail it to you with a return envelope postage paid return for you autograph and greeting? -Don KW4UP