Farnell TM39 Microvoltmeter schematic. - UK Vintage Radio Repair and Restoration Discussion Forum

WaveyDipole · 26th Jun 2019, 2:28 pm

I have just recently acquired a Farnell TM39 Microvoltmeter. It seems to a quite well made if rather large instrument and seems to be in working order. Interestingly is has provision for two internal PP9 batteries and has a logging feature, although I'm not sure what this connects to? On the rear there are two sockets for a 'pen recorder'? The movement seems operate freely and does centre correctly when no power is applied. A quick test on the 10v range shows that the deflection is about correct in both directions, but I can't get it to zero when power is applied. The indicator is stable and there is a certain adjustment range of around one major scale division available, but it always stays to the left of the centre position between the 4 and 2 mark.

The fault is probably nothing major (faulty pot perhaps or leakage), but I have been unable to find a manual or schematic online. I did come across a manual for the TM2 which seems to be an older but similar instrument and a TM4 which is an RF version of the instrument, but I can't find anything for the TM39. Does anyone have a circuit diagram for this by any chance or come across a user/service manual?

Station X · 27th Jun 2019, 9:55 pm

Thread title edited at OP's request.

Several posts moved to a new thread here:-

https://www.vintage-radio.net/forum/...d.php?t=157617

Julesomega · 3rd Jul 2019, 1:12 am

I too would like to go on the record as looking for service information for the TM39, also the TM1 and TM2

short wave · 3rd Jul 2019, 10:07 am

Hi Julian TM2 here..
https://elektrotanya.com/farnell_tm2...wnload.html#dl
regards S-W

Julesomega · 3rd Jul 2019, 4:57 pm

Thanks so much to Short Wave for the link, and Wavey Dipole for his PM with helpful comments on the TM39

26th Jun 2019, 2:28 pm	#1
WaveyDipole Octode Join Date: Mar 2013 Location: Leicester, UK Posts: 1,597	Farnell TM39 Microvoltmeter schematic. I have just recently acquired a Farnell TM39 Microvoltmeter. It seems to a quite well made if rather large instrument and seems to be in working order. Interestingly is has provision for two internal PP9 batteries and has a logging feature, although I'm not sure what this connects to? On the rear there are two sockets for a 'pen recorder'? The movement seems operate freely and does centre correctly when no power is applied. A quick test on the 10v range shows that the deflection is about correct in both directions, but I can't get it to zero when power is applied. The indicator is stable and there is a certain adjustment range of around one major scale division available, but it always stays to the left of the centre position between the 4 and 2 mark. The fault is probably nothing major (faulty pot perhaps or leakage), but I have been unable to find a manual or schematic online. I did come across a manual for the TM2 which seems to be an older but similar instrument and a TM4 which is an RF version of the instrument, but I can't find anything for the TM39. Does anyone have a circuit diagram for this by any chance or come across a user/service manual? Attached Thumbnails Last edited by WaveyDipole; 26th Jun 2019 at 2:42 pm.

27th Jun 2019, 9:55 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 14,872	Re: Farnell TM39 Microvoltmeter schematic. Thread title edited at OP's request. Several posts moved to a new thread here:- https://www.vintage-radio.net/forum/...d.php?t=157617 __________________ Graham. Forum Moderator Keep the soldering iron hot.

3rd Jul 2019, 1:12 am	#3
Julesomega Hexode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 376	Re: Farnell TM39 Microvoltmeter schematic. I too would like to go on the record as looking for service information for the TM39, also the TM1 and TM2 __________________ - Julian It's good here

3rd Jul 2019, 10:07 am	#4
short wave Pentode Join Date: Mar 2013 Location: Leeds, West Yorkshire, UK. Posts: 223	Re: Farnell TM39 Microvoltmeter schematic. Hi Julian TM2 here.. https://elektrotanya.com/farnell_tm2...wnload.html#dl regards S-W

3rd Jul 2019, 4:57 pm	#5
Julesomega Hexode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 376	Re: Farnell TM39 Microvoltmeter schematic. Thanks so much to Short Wave for the link, and Wavey Dipole for his PM with helpful comments on the TM39 __________________ - Julian It's good here