HP 400D VTVM circa 1955

Jonathan G · 15th October 2011, 02:30 AM

Cr1 & Cr2 (HP G111A) are bad. I can not obtain info on what to replace them with? They are not listed in the manual I have. Any help would be greatly appreceiated.

hitachi_nut · 15th October 2011, 10:37 PM

On section 4-10 of the manual from here -> http://bama.edebris.com/manuals/hp/400d/ , it says they are silicon diodes. Try a 1N4007(standard recovery 1A 1kV) first, if frequency response is poor go with a UF4007 (ultrafst recovery 1A 1kV). Back in 1955, I don't think a fast silicon diode with high breakdown voltage exists so a 1N60 or 1N4148 might work.

How big are the original CR! and CR2 diode compared to a 1N4007?

If you are stuck, try this group ->hp_agilent_equipment : HP/Agilent Test Equipment

hitachi_nut · 16th October 2011, 02:58 AM

I forgot to mention that you should match the forward drop of the diodes using a DVM (set to diode) test if you want to do it right.

15th October 2011, 02:30 AM	#1
Jonathan G diyAudio Member Join Date: Oct 2011	HP 400D VTVM circa 1955 Cr1 & Cr2 (HP G111A) are bad. I can not obtain info on what to replace them with? They are not listed in the manual I have. Any help would be greatly appreceiated.

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15th October 2011, 10:37 PM	#2
hitachi_nut diyAudio Member Join Date: Jan 2007	On section 4-10 of the manual from here -> http://bama.edebris.com/manuals/hp/400d/ , it says they are silicon diodes. Try a 1N4007(standard recovery 1A 1kV) first, if frequency response is poor go with a UF4007 (ultrafst recovery 1A 1kV). Back in 1955, I don't think a fast silicon diode with high breakdown voltage exists so a 1N60 or 1N4148 might work. How big are the original CR! and CR2 diode compared to a 1N4007? If you are stuck, try this group ->hp_agilent_equipment : HP/Agilent Test Equipment

16th October 2011, 02:58 AM	#3
hitachi_nut diyAudio Member Join Date: Jan 2007	I forgot to mention that you should match the forward drop of the diodes using a DVM (set to diode) test if you want to do it right.

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