Welcome to Australia's only Vintage Radio and Television discussion forums. You are not logged in. Please log in below, apply for an account or retrieve your password.
Australian Vintage Radio Forums
  Home  ·  About Us  ·  Discussion Forums  ·  Glossary  ·  Outside Links  ·  Policies  ·  Services Directory  ·  Safety Warnings  ·  Tutorials

Workshops, Tools and Test Equipment

Forum home - Go back to Workshops, Tools and Test Equipment

 Help with Cossor 1044k VTVM
« Back · 1 · Next »
 Return to top of page · Post #: 1 · Written at 10:06:33 PM on 6 November 2014.
Kxdniu's avatar
 Location: Melbourne, VIC
 Member since 19 May 2014
 Member #: 1577
 Postcount: 92

Hi,

I got a Cossor 1044K VTVM from eBay.

After replaced rectifier and filter cap, it works.

However, it is not very accurate.

I couldn't find a circuit for it. I know it is similar to Heathkit V-7A, but the AC input is different.

Does anyone has some info about it?

I try to fix it and use it for my radio works.

Regards

Kevin


 
 Return to top of page · Post #: 2 · Written at 11:33:01 PM on 6 November 2014.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 4013

It may be poorly calibrated, however are you allowing it time to warn up and stabilise before using it?


 
 Return to top of page · Post #: 3 · Written at 11:40:29 PM on 6 November 2014.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 2747

It also may be like an AVO 7X and a huge variety of radios & have wax paper capacitors in it as well, and they will have to go. I mentioned 7x as had paper caps & one was common to DC 400V range which was thrown off accuracy swiftly by it.

Marc


 
 Return to top of page · Post #: 4 · Written at 7:38:47 AM on 7 November 2014.
Kxdniu's avatar
 Location: Melbourne, VIC
 Member since 19 May 2014
 Member #: 1577
 Postcount: 92

Yes, I did let it warmed up for half an hour. There is only one capacitor in it that may be a paper one.
It is the ac input capacitor. I haven't replace it, as I don't have a high voltage rating one. By the way, any info about from where to get a 1500v capacitor?

Thanks guys.


 
 Return to top of page · Post #: 5 · Written at 9:54:23 AM on 7 November 2014.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 2747

You can get a "red" green cap at 2KV and there are TV types that go into KV. Try RS components. I nobbled the old Heathkit CRO here when refitting by raising the input caps to 2KV.

What we do need to know is if the voltage is correct on the valve/s and these can get tired & loose emission and are not as yet confirmed as being the right ones.

It was a Kit so is likely just a re-badged Heathkit

http://www.radiomuseum.org/r/cossor_valve_voltmeter_1044k.html

I have the circuit of the Heathkit.... what is different about the AC input? Viz electical or cosmetic?

Marc


 
 Return to top of page · Post #: 6 · Written at 11:22:18 AM on 7 November 2014.
Kxdniu's avatar
 Location: Melbourne, VIC
 Member since 19 May 2014
 Member #: 1577
 Postcount: 92

Hi Marc,

The common VTVM ac input circuit has one dc blocking cap in front and then three resistors for different input voltages.

This VTVM uses a low rating cap. For 1500v ac, the circuit has a 2.85m resistor in front, then the cap, next are two resistors.

Also it uses two extra caps in the bridge circuit.

That's why I hope someone can give me some info about it.

It's similar to v-7a, but not the same.

I will try RS components, thanks

Kevin


 
 Return to top of page · Post #: 7 · Written at 4:46:12 PM on 7 November 2014.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 2747

One option is to have a look at the Heathkit circuit print it & then make the mods to suit yours.

This is a Kyoritsu or something variant...

Marc


 
« Back · 1 · Next »
 You need to be a member to post comments on this forum.

Sign In

Username:
Password:
 Keep me logged in.
Do not tick box on a computer with public access.