jamesadoty
New Member
Hi all:
I'm new here.
I have a Heathkit IM-5228 VTVM that I'm restoring. I replaced the electrolytic capacitor and the paper capacitor. I also replaced the battery.
I brought the meter up on my dim bulb circuit plugged into my variac which in turn is plugged into an isolation transformer.
I was able to calibrate DC and AC volts and I can properly zero the meter.
In resistance mode I can set the meter movement to infinity ohms, and when I touch my AC/Ohms lead to my ground alligator clip the meter goes to zero ohms.
At this point I was feeling good, everything is working as it should. Or so I thought.
I went to test a known good and tested a 1K ohm resistor and no matter what range I set the range knob to it reads zero ohms.
I double checked the battery, and power from the battery going into the meter.
I calculated the series resistance of the resistors on the C and the B pads of the range switch and they add up pretty close, though admittedly I didn't check each resistor individually.
I found a resistor lead near one of the vacuum tube sockets that was shorted to another resistor lead which it shouldn't have been touching and corrected that, but still no go, I'm not getting any impedance readings at all, it just shows zero ohms.
Sometime in the meter's past someone switched out the vacuum tubes for a pair of Fetrons from Heathkit. I ordered replacement vacuum tubes to try, I own a Hickok 6000A vacuum tube tester I recently restored and it works, so I can test the vacuum tubes.
I'm not saying that either or both of the Fetrons are bad, nor am I saying they're the cause of the issue, but honestly the inside of these meters are pretty simple and I'm pretty much out of ideas.
I took two years of electronic engineering classes starting in 1980 but I haven't used those skills a whole lot since then so I'm really stuck and would appreciate some input from those of you in the know.
Thanks.
I'm new here.
I have a Heathkit IM-5228 VTVM that I'm restoring. I replaced the electrolytic capacitor and the paper capacitor. I also replaced the battery.
I brought the meter up on my dim bulb circuit plugged into my variac which in turn is plugged into an isolation transformer.
I was able to calibrate DC and AC volts and I can properly zero the meter.
In resistance mode I can set the meter movement to infinity ohms, and when I touch my AC/Ohms lead to my ground alligator clip the meter goes to zero ohms.
At this point I was feeling good, everything is working as it should. Or so I thought.
I went to test a known good and tested a 1K ohm resistor and no matter what range I set the range knob to it reads zero ohms.
I double checked the battery, and power from the battery going into the meter.
I calculated the series resistance of the resistors on the C and the B pads of the range switch and they add up pretty close, though admittedly I didn't check each resistor individually.
I found a resistor lead near one of the vacuum tube sockets that was shorted to another resistor lead which it shouldn't have been touching and corrected that, but still no go, I'm not getting any impedance readings at all, it just shows zero ohms.
Sometime in the meter's past someone switched out the vacuum tubes for a pair of Fetrons from Heathkit. I ordered replacement vacuum tubes to try, I own a Hickok 6000A vacuum tube tester I recently restored and it works, so I can test the vacuum tubes.
I'm not saying that either or both of the Fetrons are bad, nor am I saying they're the cause of the issue, but honestly the inside of these meters are pretty simple and I'm pretty much out of ideas.
I took two years of electronic engineering classes starting in 1980 but I haven't used those skills a whole lot since then so I'm really stuck and would appreciate some input from those of you in the know.
Thanks.