Hickok 209A VTVM Restoration Part 7
I have completed the electrical restoration of one Hickok 209A VTVM. This included:
- Replacing all the paper and electrolytic capacitors
- Replacing all the carbon composition resistors (most were out of tolerance)
- Installing a polarized AC plug, line fuse and proper safety capacitor
- Replacing the meter movement (original was mechanically damaged)
- Rebuilding and restoring the battery holder
- Balancing the bridge tube resistors
- Giving the unit a full check on all modes and ranges
With all of the above complete I can declare the unit ready to use. The cabinet still needs to be cleaned and refinished, but that will have to wait until warmer weather arrives and I can work outside.
The results of my testing were very interesting. I used my lab equipment (see below) to check the 209A on all of its ranges and modes (with the exception of the decibel range). The testing revealed that the 209A is a 5% accuracy instrument in most modes and ranges and perfectly usable. However other modes and ranges were so inaccurate as to be unusable. Resistance, +vdc,-vdc, vac (rms >3v) and zero center vdc are all 5% or better accuracy when compared with modern equipment. DC current, AC peak to peak voltage and capacitance modes are much less accurate, and I probably would not use them.
Where the 209A is most accurate and useful to me is in the zero-center vdc mode where my tests showed it to be within +-3% of my Keysight U1253B from 1.5 to 600 vdc. This, combined with the huge and easy to read meter will be very useful in aligning tube radios.
Equipment used:
- Keysight U1253B DMM
- Keithley 245 HV DC Supply
- HP 3245A Universal Source
- HP 4263A LCR Meter
- GR Resistance Decade Boxes
- GR Capacitance Decade Box
- Type P40106 High Resistance Decade Box
- Siglent SPD3303S DC Power Supply
What remains to be done:
- Clean and repaint the case
- Fit a new carrying handle
- Investigate why the DC current ranges are not very accurate while I know the FSD on the meter is within 2% of specification
Thanks for reading.
