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-   -   310B prototype 710mmfd temp coefficient capacitor needed. W0XO (https://www.radiobanter.com/boatanchors/110951-re-310b-prototype-710mmfd-temp-coefficient-capacitor-needed-w0xo.html)

Dale December 5th 06 11:55 AM
310B prototype 710mmfd temp coefficient capacitor needed. W0XO
 
On 4 Dec 2006 23:10:40 -0500, (Scott Dorsey) wrote:

I assume this is a capacitor with a particular TC that is used to
compensate for the drift of some other parts with temperature?

If so, you need to know both the value and the TC, and then you can
order what you want out of the AVX catalogue.

The note drawn on the schematic in Jonathan pictures says "0 temp
coefficient, 710 mmfd". The parts list in the manual doesn't list the
parts internal to the 70E-8A PTO- it just says to send it to Collins
for service.

I've popped the covers off a spare 70E-8A, and the cap says
"Merlec Corp. 913 009 6 00" on one side, and "710 mmf +/- (?) 1%"
on the other.

So, is 0 TC and 710 pf enough to order a replacement? It's a stud-
mounted ceramic disc cap.

I'd like to finally solve the amazing drift problem with my 310 B-3
as well. I asked about it months ago, and a couple of people
took the time to suggest ideas (thank you!), but still no luck...

Thanks,
Dale

KJ7SL

P.S. If anybody has the parts list for inside the PTO, it would
be helpful.

Scott Dorsey December 5th 06 02:03 PM
310B prototype 710mmfd temp coefficient capacitor needed. W0XO
 
Dale wrote:
On 4 Dec 2006 23:10:40 -0500, (Scott Dorsey) wrote:

I assume this is a capacitor with a particular TC that is used to
compensate for the drift of some other parts with temperature?

If so, you need to know both the value and the TC, and then you can
order what you want out of the AVX catalogue.

The note drawn on the schematic in Jonathan pictures says "0 temp
coefficient, 710 mmfd". The parts list in the manual doesn't list the
parts internal to the 70E-8A PTO- it just says to send it to Collins
for service.

Oh, use any modern NPO or COG dielectric ceramic capacitor. That's close
enough to zero. Probably closer than the original.

Try Digi-Key part P4859-ND. That's a 100V, 680 pF NP0 ceramic.
If 680 pF isn't close enough, add a 33 pF in parallel. Fifty cents each,
discount if you buy ten.

Avoid the high density Y5P Z4V, etc. dielectric types like the plague
because they will have a very high temperature coefficient.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."


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