General Radio 1001 sig gen modulation stage seems dead

These instruments were quite reliable in their day. You can download a copy of the GR 1001A model from ftp://bama.edebris.com/bama/gr/1001a/1001a.djvu. It might have a few differences from the model 1001, but is probably close enough to give you some help. You'll need the DJVU browser plug-in to view and print the manual, but it's free and works well. Follow the link on the BAMA page to get it.

From your symptoms, I'd assume that the RF side is working, and you should concentrate on the modulation circuitry. My first suspects would be the switches... the modulation switch and the meter switch. If either of those has bad contacts, the instrument would have no modulation. Get a small vial or spray can of DEOXIT contact cleaner (available from web vendors like

Another thing to check would be the modulation level pot, and resistors R11 and R14. Diodes D1 and D2 are less likely suspects, but you should check them as well. Finally, check for broken wire(s) from the modulation pot, through C14, R11, C15, L1, C20 and R14.

HTH,

--
Dave M
MasonDG44 at comcast dot net  (Just substitute the appropriate characters in the 
address)

Never take a laxative and a sleeping pill at the same time!!