Stanford Research SR715 LCR Meter Teardown

[barnacle2k]

Because of all the recent talk of LCR Meters, here my newest acquisition fresh from ebay:
A Stanford Research SR715 LCR Meter, it boasts a 0.2% base accuracy rating.
It came with the full manual in a binder, as always with Stanford Research gear the manual contains the full schematics. 
Also included a nice pair of Kelvin clips.
Did some basic measurements to test it out, but I don't have any capacity or inductance standards.
It has a RS232 interface for PC connectivity, the GPIB option is not fitted.
Another nice feature is the external bias connection via banana plugs on the back for up to 40V or 100mA.

Measuring 100n 5% Wima:


Small hand-wound inductor 100µH calculated:


1.000K resistance standard:


100.00K resistance standard:


How well does it measure LOW ESR? (Yes that is a 1000µF 1200V foil CAP)


A big old inductor (rated 4.7H @ 100mA):


1000µF standard capacitor:


The very nice manual:




Original cal certificate included:


TEARDOWN time (4 Screws later:)

Boring switch matrix:


The money shot:


Beefy protection circuitry and filter caps: (Nichicon of course)


The only SMD part I could find on that board:


Dale precision resistors:


CPU is a Zilog Z80:


Under the input:

[Lightages]

Thanks for the look inside. It is always interesting to see how different designs of the cases have converged over the years. That is a very different looking case. Also interesting is the neon lamp being used as a "spark gap".

[AF6LJ]

Thanks, nice tour through that LCR meter.

[Vgkid]

Thanks for the teardown, i guess i will post the insides of my bridge.

[Salas]

Very nice pictures. The form factor reminds of cash registers though. Weird choice for test gear.

[TiN]

Nice LCR. And that cap is enormous..

[barnacle2k]

The form factor is a downside, its not rack or stack-able.
But i recall a lot of bench, LCR meters had this kind of formfactor, the Telemeter Electronic LCR Databridge units for example.
It might be due to the manually operated LCR bridges being a flat tabletop kind of deal.

And that cap is enormous..

Its quite a beasty
Specs:
RMS: ripple current 100Amps
short circuit current: 35kAmps
ESR: 400µOhm
ESL: 50nH
energy content: 666Joules (demon capacitor out to kill me?  )

[commie]

One of the nicest boards I have ever seen. Take note the use of Z80 microprocessor(Von Nuemann) whilst PIC/AVR are Harvard. Nice!

Cheers
Commie

[HighVoltage]

The form factor is a downside, its not rack or stack-able.
But i recall a lot of bench, LCR meters had this kind of formfactor, the Telemeter Electronic LCR Databridge units for example.

A long time ago, I owned a Wayne Kerr 421- LCR meter
It had also a similar strange form factor.
As I see, they are also around for sale....

Nice tear down, btw.
Thank you for sharing those great pictures.

[PA4TIM]

This was is the GR digibridge. Looks like these calculator/typewriter style cabinets were populair in the 70's

[PaulAm]

I was looking at one of those for a while, but ended up with an HP 4262a.  It's a little easier to stack.

[cnqhdszq]

I need the diagrams of SR715 ,may you take photos of it  and Email to me ?  E-mail : qhdszq@126.com  thanks

[JonM]

I need the diagrams of SR715 ,may you take photos of it  and Email to me ?  E-mail : qhdszq@126.com  thanks

You can download the manual from SRS:

http://www.thinksrs.com/downloads/PDFs/Manuals/SR715720m.pdf

[JonM]

I need the diagrams of SR715 ,may you take photos of it  and Email to me ?  E-mail : qhdszq@126.com  thanks

You can download the manual from SRS:

http://www.thinksrs.com/downloads/PDFs/Manuals/SR715720m.pdf

However, I now see that the manual ends with the parts list on page 7-12 and no schematics included. Now I know that I may be missing information in the mis-placed paper copy of the manual for my SRS560.
 

[cnqhdszq]

Yes The manual does not have diagram in.

[guenthert]

One of the nicest boards I have ever seen. Take note the use of Z80 microprocessor(Von Nuemann) whilst PIC/AVR are Harvard. Nice!

Cheers
Commie

Well, barnacle wrote "Z80", but in the picture you can clearly see a Z8, which happens to be a (Harvard architecture) microcontroller (quoting Wikipedia here, as I've not encountered that chip myself.  It's a bit, er, dated).

[bluesystems]

I see by your post you have the schematic diagrams in your pictures of the manual for the SR715.
My SR720 has started producing "Out Error 1" on power up and I could use a set of schematic diagrams to sort it out.

In the past Stanford Research has supplied schematic diagrams on request for a moderate fee. This seemed fair.
When I requested this time service documents including the schematic diagrams their response was disappointing .  I received.
"
We don't supply schematics with the SR720. You will probably want to send the product back to SRS for service.
"
For me it is uneconomic as the unit will have to be shipped internationally.
Stanford Research seems to be no longer interested in allowing their customers to support their own equipment. I find this very disappointing and short sited.
I wonder if you would consider sharing your copy of the schematic diagrams so I can get my SR720 back up and running.
Thanks for any reply. Bob J

[korlatos]

For some reason, SRS now includes schematics in the manual posted on their web site.

[korlatos]

File now attached.

[coromonadalix]

few years ago  they wanted 125$ usd to get a manual copy + schematics  lolll

thks

[Kosmic]

They also added the Calibration, Troubleshooting and Maintenance section of the manual 

[maxwell3e10]

It looks like they posted manuals with schematics for a majority of their products!

[coromonadalix]

are they gonna close ??     strange behaviour ??

[Kosmic]

I think they just updated the manuals on their web site and for some reason decided not to lose time by creating stripped down versions.

It's not like the added (not removed) sections were not in the manual in the first place.