Finally got around to replacing the old corroded soldered-in D cell in the RCA Voltohmyst with a new battery today.
1.5V Battery
Snipped the wires off the battery and into the trash it went. Had to drill out a rivet to remove the battery holder clip.
Voltohmyst battery removed
The battery holder is a little on the big side and just fits into the space vacated by the old battery and clip. Soldered the wires onto the battery holder and fastened it to the Voltohmyst using some double sided tape.
New battery holder
Now it’s got a new battery that can be replaced whenever it’s needed.
New battery installed
Next thing to do is go through the manual and read up on how to calibrate the meter.
Saw someone at the TARC swap meet with one of these little Tektronix 222 DSOs for sale, so I bought it. Terrific timing since my Hitachi oscilloscope died a while back and I still haven’t gotten around to looking into it.
Tektronix 222 oscilloscope
It’s little, and doesn’t have a lot of capabilities but I think it will do pretty much everything I need (at the moment). It comes with two scope probes that are permanently attached. It’s designed to be powered with an 8V SLA battery, but it looks like batteries with the right form factor and voltage aren’t readily available anymore. I did find a promising looking battery replacement project though. This one didn’t come with a battery, but a standard sized power jack lets you power it with wall power. It’s even got a RS-232 serial port!
The scope seems simple enough to figure out how to use without a manual, and I was even able to find a service manual online to download.
Here I’ve got one of the channels measuring the output from one of my EtherkitSi5351 breakout boards. I don’t remember what I have my RedBoard making the Si5351 do, but I seem to be getting a pretty good signal out of it.
The RCA WV-98C Senior Voltohmyst (SN 201001 1104)I picked up at the hamfest yesterday looks to be in pretty good working order.
RCA WV-98C Senior VoltOhmyst
No smoke, popping or other unusual sounds/odours when I plugged it in. Some initial testing with batteries and some resistors suggests a bit of recalibration or maybe a bit of repair might be needed though.
Removing four screws from the back lets you take the back cover off (a fairly substantial chunk of cast aluminum) revealing the innards of the meter.
Back of the RCA Voltohmyst
Voltohmyst circuit board
The blue adjustment screws are trim pots used for adjusting the meter calibration.
One thing that surprised me was the presence of a soldered in D cell.
Top part of the Voltohmyst. Badly corroded 1.5V D cell and transformer
1.5V Battery
No idea what vintage the battery is or what it’s used for (at the moment), but my multi-meter showed it still had 1.4 V across it. The battery has definitely seen better days. I think I’ll see about replacing the battery with a battery holder so it can be removed and replaced in the future. Fortunately it looks like the wires have enough slack to work with.
The rest of the meter looks to be in pretty decent shape, and pretty clean. Without taking off the face of the meter, it’s a little hard to get in there to check out the middle. There are two tubes in the unit, a 12AU7 and 6AL5.
Lots of colourful wires at the range selector and mode selector switches.
Range selector switch
Mode selector switch
The probe for the meter is a big chunky thing, about the size of a Sharpie marker.
Voltohmyst probe
Next step will be to go through the manual and read a bit more about the meter works before I try to dive in and replace things.
