Solartron 7075. - UK Vintage Radio Repair and Restoration Discussion Forum

paul larner · 22nd Jan 2024, 4:06 am

I have the solartron 7075 volt+ohms meter,its display doesent change when fed with any voltage or any resistances on its inputs,i have replaced a couple of faulty caps on the psu pcb,all power rails are in spec and ripple free,any ideas what to check next?

Diabolical Artificer · 22nd Jan 2024, 7:58 am

I had to replace just about all the capacitors on an older AC meter, I'd start by checking the ones in yours. also check for out of spec resistors.

Andy.

Oldtestgear · 22nd Jan 2024, 11:27 am

The best way to check this is from the input terminals though to the ADC & check if the input circuits are actually working. These old DMMs are not the easiest things to fault find but can be repaired fairly readily as most of the parts were off the shelf.
Try with either a 10V or 1.0V DC signal at the input terminals. At least this is how I would start fault finding on these.

Phil

paul larner · 23rd Jan 2024, 12:22 am

Would anyone know what board deals with the sampling? I don't fancy trawling thru 200+ pages of the service manual to find out. It's on the round tuit pile at the moment as busy making an SWR bridge to fit a twin needle meter to my new homemade HF L match ATU.

73

Did try uploading the manual but the file is too large! 13Mb.

paul larner · 23rd Jan 2024, 1:02 am

I replaced the input terminals with banana posts as the original FIscher connector was a crazy price like over £60! So they are OK.

factory · 23rd Jan 2024, 8:33 pm

Did it work before you replaced the connector? There was no need to replace it until you get it working, as was mentioned in one of the "dozen" or so threads you created on eevblog.

Also, there is no need to upload manuals here that are available elsewhere, a weblink to the relevant archive would have been fine.

David

dave cox · 25th Jan 2024, 1:52 pm

I've found the U1899 jfets to not be beyond reproach!

IIRC, the 'A to D' is a timed integrator, working quad slope (up / down on ref then up /down on unknown) with the input / reference switched by JFETs (or IC analogue switches in some models, but not this one AFAICS).

The simplest path is for dc measurement !

dc

paul larner · 26th Jan 2024, 7:22 pm

I will ask againe,does anyone know what pcb deals with the input sampling?.

paul larner · 3rd Feb 2024, 1:13 pm

anyone?

Oldtestgear · 3rd Feb 2024, 2:08 pm

As you have been advised on the EEVBLOG, read the manual. I found the relevant page in a couple of minutes. I am sure that you could do the same. Trying to get others to do the basics for you will not go down well on any forum.

If after reading the manual you are still stuck then I am sure people will be willing to help.

Phil

factory · 3rd Feb 2024, 3:00 pm

Normally people read the manual, take some measurements (as mentioned in post 3), post the results and then ask questions.

David

paul larner · 3rd Feb 2024, 6:41 pm

I have not found it in the manual,this is why i am asking ok.

factory · 3rd Feb 2024, 9:20 pm

I wish you luck with repairing this, but in the words of Shango066 "I'm done".

https://groups.io/g/HP-Agilent-Keysight-equipment/message/120903
https://www.vintage-radio.net/forum/showthread.php?t=185578
https://groups.io/g/Solartron_Schlumberger_Equipment/message/137

David

22nd Jan 2024, 7:58 am	#2
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,925	Re: solartron 7075 I had to replace just about all the capacitors on an older AC meter, I'd start by checking the ones in yours. also check for out of spec resistors. Andy. __________________ Curiosity hasn't killed this cat...so far.

22nd Jan 2024, 11:27 am	#3
Oldtestgear Hexode Join Date: May 2008 Location: Devon, UK. Posts: 307	Re: solartron 7075 The best way to check this is from the input terminals though to the ADC & check if the input circuits are actually working. These old DMMs are not the easiest things to fault find but can be repaired fairly readily as most of the parts were off the shelf. Try with either a 10V or 1.0V DC signal at the input terminals. At least this is how I would start fault finding on these. Phil

23rd Jan 2024, 12:22 am	#4
paul larner Banned Join Date: Jan 2024 Location: Northampton, Northamptonshire, UK. Posts: 41	Re: Solartron 7075. Would anyone know what board deals with the sampling? I don't fancy trawling thru 200+ pages of the service manual to find out. It's on the round tuit pile at the moment as busy making an SWR bridge to fit a twin needle meter to my new homemade HF L match ATU. 73 Did try uploading the manual but the file is too large! 13Mb.

23rd Jan 2024, 1:02 am	#5
paul larner Banned Join Date: Jan 2024 Location: Northampton, Northamptonshire, UK. Posts: 41	Re: Solartron 7075. I replaced the input terminals with banana posts as the original FIscher connector was a crazy price like over £60! So they are OK.

23rd Jan 2024, 8:33 pm	#6
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,884	Re: Solartron 7075. Did it work before you replaced the connector? There was no need to replace it until you get it working, as was mentioned in one of the "dozen" or so threads you created on eevblog. Also, there is no need to upload manuals here that are available elsewhere, a weblink to the relevant archive would have been fine. David

25th Jan 2024, 1:52 pm	#7
dave cox Nonode Join Date: Jan 2009 Location: Bristol, UK. Posts: 2,081	Re: Solartron 7075. I've found the U1899 jfets to not be beyond reproach! IIRC, the 'A to D' is a timed integrator, working quad slope (up / down on ref then up /down on unknown) with the input / reference switched by JFETs (or IC analogue switches in some models, but not this one AFAICS). The simplest path is for dc measurement ! dc

26th Jan 2024, 7:22 pm	#8
paul larner Banned Join Date: Jan 2024 Location: Northampton, Northamptonshire, UK. Posts: 41	Re: Solartron 7075. I will ask againe,does anyone know what pcb deals with the input sampling?.

3rd Feb 2024, 1:13 pm	#9
paul larner Banned Join Date: Jan 2024 Location: Northampton, Northamptonshire, UK. Posts: 41	Re: Solartron 7075. anyone?

3rd Feb 2024, 2:08 pm	#10
Oldtestgear Hexode Join Date: May 2008 Location: Devon, UK. Posts: 307	Re: Solartron 7075. As you have been advised on the EEVBLOG, read the manual. I found the relevant page in a couple of minutes. I am sure that you could do the same. Trying to get others to do the basics for you will not go down well on any forum. If after reading the manual you are still stuck then I am sure people will be willing to help. Phil

3rd Feb 2024, 3:00 pm	#11
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,884	Re: Solartron 7075. Normally people read the manual, take some measurements (as mentioned in post 3), post the results and then ask questions. David

3rd Feb 2024, 6:41 pm	#12
paul larner Banned Join Date: Jan 2024 Location: Northampton, Northamptonshire, UK. Posts: 41	Re: Solartron 7075. I have not found it in the manual,this is why i am asking ok.

3rd Feb 2024, 9:20 pm	#13
factory Octode Join Date: Jul 2009 Location: Cheshire, UK. Posts: 1,884	Re: Solartron 7075. I wish you luck with repairing this, but in the words of Shango066 "I'm done". https://groups.io/g/HP-Agilent-Keysight-equipment/message/120903 https://www.vintage-radio.net/forum/showthread.php?t=185578 https://groups.io/g/Solartron_Schlumberger_Equipment/message/137 David