Quote:
Originally Posted by DavGoodlin
After getting used to putting my Fluke 177 on everything, I started to wonder why most voltages I was measuring were too high compared to the schematics for the tube sets.
The WV77e responded well to a new top-hat diode replacing the selenium and new B+ filter. Four .18 uf in series replace the .047 The 12AU7 was also gassed, likely the reason this VTVM was cast aside.
Attachment 191180
The older WV97a is on the left, has the second 6AL5 for a B+ rectifier and AC calibrate. It needs a .1uf @ 1.8kV, so three .33 uf @ 630 v in series make this value.
Those leaky batteries are pretty hard on these meters. It may be worth adding an internal bleeder supply using a resistor and 1.55 volt zener diode.
Both of these need a set of lead-probes. The Heathkits are really beat up and need them too. |
The WV-77 meter only needed a 22K dropping resistor in series with the rectifier diode and it calibrated as per the manual with good accuracy when compared to the Fluke.
The WV-77 was in production for many years and the WV-97 actually pre-dated it. The Senior Voltohmyst WV-98 has the larger meter and was more expensive.
The RCA WV-97 has some issues with DC measurement, due to several drifted resistors as it is over 60 years old. After repairing the meter initially, I decided it was not worth further troubleshooting after making this discovery. Anyone need some parts?