|
Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
|
Thread Tools |
27th Apr 2021, 5:12 pm | #1 |
Pentode
Join Date: May 2018
Location: High Wycombe, Buckinghamshire, UK.
Posts: 135
|
AVO 8 mk5
Can anyone help with an issue I have with this AVO 8 mk5 I picked up cheap on a famous auction site.
The x100 & x10k ohms ranges do not work at all. No needle movement. low ohms range is fine. I have fitted new batteries and checked values of R2 =2k16ohms. R3=51k which apparently can cause this problem. Values are fine. However. R5 should read 1.8mohm. and it measure nearly 2meg. I am wandering if this maybe the culprit but do not have a 1.8meg resistor at the moment to try. See screen capture of that part of circuit. I am having problems tracking down a 1.8m ohm resistor. does not seem to be a preferred value anymore?? Any ideas ?? Last edited by technotel; 27th Apr 2021 at 5:26 pm. Reason: left text out |
27th Apr 2021, 5:50 pm | #2 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
|
Re: AVO 8 mk5
The value of that resistor won't make those ranges not work. Likely culprit are the printed ribbon cables and their connections if the battery is fine.
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW. |
27th Apr 2021, 6:05 pm | #3 |
Pentode
Join Date: May 2018
Location: High Wycombe, Buckinghamshire, UK.
Posts: 135
|
Re: AVO 8 mk5
Hi Sinewave
Yes I have belled out the ribbon cable and appears to be fine although it looks battered and I see one route has had a wire put in to replace it as it was o/c. Do you think there is any mileage in changing the ribbon cable for a wire loom? would this effect the resistance, totally mess up the calibration?? many thanks |
27th Apr 2021, 6:09 pm | #4 |
Octode
Join Date: May 2016
Location: Oxfordshire/Bucks borders, UK.
Posts: 1,604
|
Re: AVO 8 mk5
If it was totally ruined then cable would be ok, but calibration checks would need to be made. Whilst the ribbon may be ok, the terminations can be dodgy if its been got at before.
__________________
Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW. |
27th Apr 2021, 6:24 pm | #5 |
Pentode
Join Date: May 2018
Location: High Wycombe, Buckinghamshire, UK.
Posts: 135
|
Re: AVO 8 mk5
Thanks for the advise. I think I will rewire it to be sure.
|
27th Apr 2021, 7:27 pm | #6 |
Hexode
Join Date: Oct 2007
Location: Bristol, UK.
Posts: 440
|
Re: AVO 8 mk5
PM sent re mkV for spares.
Don m5aky |
3rd May 2021, 3:03 pm | #7 |
Pentode
Join Date: May 2018
Location: High Wycombe, Buckinghamshire, UK.
Posts: 135
|
Re: AVO 8 mk5
Hi all
quick update on this AVO 8 MK5 repair. I found the x100 22kohm pot was the culprit. I have added a couple of images. The pot was broken but oddly enough still giving a resistance!! Thanks to Don who donated an old AVO mk5 to me. I was able to use a pot from it. The x10 and x100 sprang into life. Many thanks Don. Going to go through set up now with manual. Happy days. I rewired the battered ribbon cable first but this wasn't the problem. Terry |