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177 Microvolt DMM - parts

200, 210, 220, 486/7, 60x, 61x, 64x Electrometers
409, 41x, 42x, 44x, 48x -
14x, 18x, 1801 Nanovoltmeters
15x, 18x Null Detectors/Microvoltmeters
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Joined: January 4th, 2011, 1:07 pm
Country: United States

177 Microvolt DMM - parts

Post by manorth » January 4th, 2011, 1:53 pm

I need to get a replacement part for Q104 - Dual P-Chan Mosfet
Keithley P/N TG-94
Do you know where I kind find these, or a generic equivalent p/n?

Dale C
Keithley Applications
Keithley Applications
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Joined: June 10th, 2010, 6:22 am
Country: United States

Re: 177 Microvolt DMM - parts

Post by Dale C » January 17th, 2011, 1:22 pm

The part number TG-94 was originally obtained from
General Instruments Corp.
And the part number was 955
This was in 1972.
This looks like an analog front end input component. Probably low leakage transistor.
The Model 177DMM was obsolete in 1992. And last repaired in 2000.
Not sure if General Instruments is still in business or has this part.
Hope this helps.

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Re: 177 Microvolt DMM - parts

Post by irata358 » September 4th, 2019, 8:25 am

Please find attached datasheet for 955 dual mosfet transistor. From General Instruments 1977 Data Catalog
(63.1 KiB) Downloaded 65 times

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