QSXM3 with LTC1050 servo?

[Brambus]

Sorry for a stupid question, but i could not resist... 
 
I'm planning about building  QSXM3.
Before starting I was searching for a good substitute for MAX420 -
I know that it is possible to use OP07 etc. but having found the data sheet of LTC1050-CN8
i was thinking that maybe it would work.

Would it be enough to omit P7 P8 C79 C80 (i.e. the net around terminals 1-5-8) or am i totally out of way?
Thanks in advance.
Paolo

PS
I see now that 18 volts is the total  V+ to V-  power supply rating. Maybe this is the show stopper...

[peranders]

LTC1050 could be used with some redesign but I'll recommend you a non-chopper type, like a medium speed, low noise type, capable of +- 15 volts. 5-15 V/us, 4 nV/Hz or less, 1 mV offset or less. Low input bias currents.

[Nugman]

Hi Per-Anders,

I'm also looking for a substitute for the MAX420 in QSXM3. In another topic regarding the QSXM2 you were suggesting an OP07 instead. Would this work in the QSXM3 as a drop-in replacement with the same circuit around as with the MAX420? Could I use the OP07 just instead of the MAX420?

Many thanks in advance  for your advice.
Roland

[peranders]

OP07 will work fine.

[Nugman]

Hi Per-Anders,

thanks for the quick reply. I'm a little bit embarrased because I found that you already mentioned the OP07 in the original documentation. I was so focused on looking for a MAX420 and how to replace it, that I somehow missed that. 
You write that when using the OP07, P3/P7 should be used as well. How should the pot be adjusted then? Is there a measurement point that should have a certain voltage or current?
What value should the pot have? The datasheet of the OP07 recommends 20k, while the schematics show a 10k?

Thanks, Roland

[peranders]

Start to use the OP07 without any trimming. I think it will work good. If you add a trim pot then the offset drift will be higher so it's good if you can avoid it. If you anyway want this pot use the recommended value in the datasheet.

[Nugman]

Many thanks!