Electronics > RF, Microwave, Ham Radio

#29 Vintage gear I picked up for future teardowns and restore videos

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Radio Tech:
In this video we take a quick look at some vintage ham radios and test gear a friend gave to me today. This is what we have:
Kenwood TS-520 hybrid HF rig
Heathkit DX-20 CW transmitter
Eico model 215 signal generator
Heathkit HP-23 power supply
HP model 410A Volt OHM meter

I will used these in future repair and restore videos



AF6LJ:
In  a Word Cool...

TimFox:
The only piece of equipment that I own that is older than me is an -hp- 410A voltmeter (on the left of your title still).
I had to replace one capacitor (across the line) and clean up the sockets on the RF diode (2-01C).
I replaced the 6SN7 dual triode, but it was not quite dead.
After that, it was easy to calibrate the unit back to factory spec.
I believe there were two options on the diode:  mine used two 2-01C vacuum diodes, one in the probe and the other to balance out the DC offset, but the manual I found showed a solid-state diode in place of the balancing unit.
Note that the DC input resistance is 110 Megohm, with 10 Megohm in the probe.  Normal VTVMs of that era had 11 and 1 Megohm, respectively.
I took a vacation cruise with many people my age a few years ago.  At dinner one night, the husband of the other couple at the table said he had retired from -hp- and I mentioned the 410A.  By coincidence, his first job at -hp- was to write the manual for the 410B.

Radio Tech:

--- Quote from: AF6LJ on February 15, 2016, 11:53:30 pm ---In  a Word Cool...

--- End quote ---
Good word :)

Radio Tech:

--- Quote from: TimFox on February 17, 2016, 09:35:02 pm ---The only piece of equipment that I own that is older than me is an -hp- 410A voltmeter (on the left of your title still).
I had to replace one capacitor (across the line) and clean up the sockets on the RF diode (2-01C).
I replaced the 6SN7 dual triode, but it was not quite dead.
After that, it was easy to calibrate the unit back to factory spec.
I believe there were two options on the diode:  mine used two 2-01C vacuum diodes, one in the probe and the other to balance out the DC offset, but the manual I found showed a solid-state diode in place of the balancing unit.
Note that the DC input resistance is 110 Megohm, with 10 Megohm in the probe.  Normal VTVMs of that era had 11 and 1 Megohm, respectively.
I took a vacation cruise with many people my age a few years ago.  At dinner one night, the husband of the other couple at the table said he had retired from -hp- and I mentioned the 410A.  By coincidence, his first job at -hp- was to write the manual for the 410B.

--- End quote ---

Thanks for that story. Sounds that it was great to meet the guy that wrote the manual.
As far as the 2 diodes mine has both. I slid the cover off the unit last night. Cover is going into the media blaster this weekend due to large amount of surface rust. on it. Inside looked fairly decent. I will take pics before doing anything and add them to the tear down/restore video. Going to have to replace the probe leads. AC lead is very stiff, common lead is cracking up.

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