UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

allan · 14th May 2020, 1:08 am

I have a slightly better diode, a 5082-2835 which I could try, otherwise I'll order an SM type.

I have a few bits of test gear David, including an HP 431C and a DSA-815TG, but when I reassembled the oscillator, and the switch on the back of the attenuator, the meter dropped to near zero output although I can still see 180mV at the PA and 2v at the driver.
I think I muddled up the wiring and the modulator circuit must be switching off the output to the PA. I found the vernier pot wiring was wrong and its possible the wipers for one or two functions are not making decent contact. The fault I was trying to fix ie. alternately lighting the 0-3/0-10 scale lamps is now working perfectly though! Pity the meter reading is zero.
A bit more testing is due Thursday.
I'm now clear about the tuning problem so that's on the list.
Allan

14th May 2020, 1:08 am	#91
allan Pentode Join Date: Oct 2005 Location: South coast near Ringwood/Christchurch, Dorset, UK. Posts: 230	Re: HP8640B Signal Generator I have a slightly better diode, a 5082-2835 which I could try, otherwise I'll order an SM type. I have a few bits of test gear David, including an HP 431C and a DSA-815TG, but when I reassembled the oscillator, and the switch on the back of the attenuator, the meter dropped to near zero output although I can still see 180mV at the PA and 2v at the driver. I think I muddled up the wiring and the modulator circuit must be switching off the output to the PA. I found the vernier pot wiring was wrong and its possible the wipers for one or two functions are not making decent contact. The fault I was trying to fix ie. alternately lighting the 0-3/0-10 scale lamps is now working perfectly though! Pity the meter reading is zero. A bit more testing is due Thursday. I'm now clear about the tuning problem so that's on the list. Allan