Hello all,
I got this tester with the ground probe and AC test probe. I made a DC test probe with your help. Decided to change the filter cap which is something i do on anything this old. Only change made.

Cleaned all the contacts on the rotary switches and pots, checked for any component or wire damage. Looks good.

Powered the tester up and went through the initial steps of operation according to the manual (which the forum was kind to send to me). Started my first test of the tester with controlled AC measurement with a Variac that has a voltage meter. Tester meter is free and adjusts to zero. Paralled my DVM to the Variac output and connection to the VTVM.

On all properly selected scales of the VTVM, if Variac outputs 100 Vac meter reads 50 Vac, DVM 100 Vac. Variac 50 Vac, Tester reads 25 Vac, DVM 50 Vac. I am reading exactly half the voltage on the VTVM as the Variac is outputing and the DVM is reading.

Compared all of this with my RCA WV-77E Voltohmyst, measured all voltages correctly.

Tested the tubes, all looked good on the tester. But, is the 6SN7 my problem, or another cap?

I know its long but thanks for any help
Mitch

:Hello all,
:I got this tester with the ground probe and AC test probe. I made a DC test probe with your help. Decided to change the filter cap which is something i do on anything this old. Only change made.
:
:Cleaned all the contacts on the rotary switches and pots, checked for any component or wire damage. Looks good.
:
:Powered the tester up and went through the initial steps of operation according to the manual (which the forum was kind to send to me). Started my first test of the tester with controlled AC measurement with a Variac that has a voltage meter. Tester meter is free and adjusts to zero. Paralled my DVM to the Variac output and connection to the VTVM.
:
:On all properly selected scales of the VTVM, if Variac outputs 100 Vac meter reads 50 Vac, DVM 100 Vac. Variac 50 Vac, Tester reads 25 Vac, DVM 50 Vac. I am reading exactly half the voltage on the VTVM as the Variac is outputing and the DVM is reading.
:
:Compared all of this with my RCA WV-77E Voltohmyst, measured all voltages correctly.
:
:Tested the tubes, all looked good on the tester. But, is the 6SN7 my problem, or another cap?
:
:I know its long but thanks for any help
:Mitch
:

::Hello all,
::I got this tester with the ground probe and AC test probe. I made a DC test probe with your help. Decided to change the filter cap which is something i do on anything this old. Only change made.
::
::Cleaned all the contacts on the rotary switches and pots, checked for any component or wire damage. Looks good.

::
::Powered the tester up and went through the initial steps of operation according to the manual (which the forum was kind to send to me). Started my first test of the tester with controlled AC measurement with a Variac that has a voltage meter. Tester meter is free and adjusts to zero. Paralled my DVM to the Variac output and connection to the VTVM.
::
::On all properly selected scales of the VTVM, if Variac outputs 100 Vac meter reads 50 Vac, DVM 100 Vac. Variac 50 Vac, Tester reads 25 Vac, DVM 50 Vac. I am reading exactly half the voltage on the VTVM as the Variac is outputing and the DVM is reading.
::
::Compared all of this with my RCA WV-77E Voltohmyst, measured all voltages correctly.
::
::Tested the tubes, all looked good on the tester. But, is the 6SN7 my problem, or another cap?

::
::I know its long but thanks for any help
::Mitch

The 6SN7 is in a bridge circuit, and if the D C works the tube is probably OK. The DC prpbe has a one meg resistor in the probe, in case of a shorted co-ax. The resistor has to be shorted out for AC or the resistor and the capacity of the probe lead will cause low AC readings. Check to be sure the probe, in the AC position has continunity to the connector.
Lewis

::
:

:::Hello all,
:::I got this tester with the ground probe and AC test probe. I made a DC test probe with your help. Decided to change the filter cap which is something i do on anything this old. Only change made.
:::
:::Cleaned all the contacts on the rotary switches and pots, checked for any component or wire damage. Looks good.
:
:
:
:
:
:
:::
:::Powered the tester up and went through the initial steps of operation according to the manual (which the forum was kind to send to me). Started my first test of the tester with controlled AC measurement with a Variac that has a voltage meter. Tester meter is free and adjusts to zero. Paralled my DVM to the Variac output and connection to the VTVM.
:::
:::On all properly selected scales of the VTVM, if Variac outputs 100 Vac meter reads 50 Vac, DVM 100 Vac. Variac 50 Vac, Tester reads 25 Vac, DVM 50 Vac. I am reading exactly half the voltage on the VTVM as the Variac is outputing and the DVM is reading.
:::
:::Compared all of this with my RCA WV-77E Voltohmyst, measured all voltages correctly.
:::
:::Tested the tubes, all looked good on the tester. But, is the 6SN7 my problem, or another cap?
:
:
:
:
:
:
:
:
:::
:::I know its long but thanks for any help
:::Mitch
:
:The 6SN7 is in a bridge circuit, and if the D C works the tube is probably OK. The DC prpbe has a one meg resistor in the probe, in case of a shorted co-ax. The resistor has to be shorted out for AC or the resistor and the capacity of the probe lead will cause low AC readings. Check to be sure the probe, in the AC position has continunity to the connector.
:Lewis
:
:
:
:
:
:::
::
:
While making the AC volt tests the DC probe was not inserted in the meter. From what i read it needs to be?
Mitch

The DC probe does not have to be plugged in when making AC readings. The function switch has the DC input switched out anyway. In the instruction manual there is a block diagram for the AC input circuit, and the AC calibration. Make sure all the controls are working correctly.

Whoops. The 221 DC probe resistor should be 15 megs, not 1 meg. AC readings exactly 50% of normal is suspect. Has the circuitry been modified?

:The 6SN7 is in a bridge circuit, and if the D C works the tube is probably OK. The DC prpbe has a one meg resistor in the probe, in case of a shorted co-ax. The resistor has to be shorted out for AC or the resistor and the capacity of the probe lead will cause low AC readings. Check to be sure the probe, in the AC position has continunity to the connector.
:Lewis
:
:
:
:
:
:::
::
:

:Whoops. The 221 DC probe resistor should be 15 megs, not 1 meg. AC readings exactly 50% of normal is suspect. Has the circuitry been modified?
:
:
::The 6SN7 is in a bridge circuit, and if the D C works the tube is probably OK. The DC prpbe has a one meg resistor in the probe, in case of a shorted co-ax. The resistor has to be shorted out for AC or the resistor and the capacity of the probe lead will cause low AC readings. Check to be sure the probe, in the AC position has continunity to the connector.
::Lewis
::
::
::
::
::
::::
:::
::
:
The only change made was a replacement of the filter cap. By inspection of the chassis all wiring and components are original, they have the old odor. I did not try the AC cal pots but will and post results.
Thanks
Mitch

::Whoops. The 221 DC probe resistor should be 15 megs, not 1 meg. AC readings exactly 50% of normal is suspect. Has the circuitry been modified?
::
::
:::The 6SN7 is in a bridge circuit, and if the D C works the tube is probably OK. The DC prpbe has a one meg resistor in the probe, in case of a shorted co-ax. The resistor has to be shorted out for AC or the resistor and the capacity of the probe lead will cause low AC readings. Check to be sure the probe, in the AC position has continunity to the connector.
:::Lewis
:::
:::
:::
:::
:::
:::::
::::
:::
::
:The only change made was a replacement of the filter cap. By inspection of the chassis all wiring and components are original, they have the old odor. I did not try the AC cal pots but will and post results.
:Thanks
:Mitch
:
All,
Went through the calibration steps as if it were a new unit, after inital setup. DC and AC Cal and zero pots were frozen in place. Lubricated them and freeded them up. AC volt measurements are within 3 to 5 %. DC volt measurements are within 10 to 20 %. Ohms are prety far out even with new battery for full scale reading. Takes 1.7 VDC to reach full scale with no room for adjustment. Seems that the 6SN7 grid needs more voltage. I will replace this tube when i get one. This tube also appears to effect the DC volt calibration.
Comments welcome
Mitch

Another 6SN7 may indeed fix the ohms problem. Some 6SN7's just do not have enough gain to go to full scale with a 1.5 volt battery. It will affect DC and AC cal also since the bridge is used for all measurements. There is at least one write up on the 221 in which EICO recommended adding another battery and using 3.0 volts for the ohms scales if all else failed.

The dc probe needs to be 15 megs. It will be a miracle if the all multiplier resistors are still within tolerance unless they have been changed from the originals.

The older units used sceened carbon comp series pairs to arrive at the correct values. These will probably have drifted all over the place.

Modern 1% metal films will be the best choice. Or you can use a modern DVM to screen 5% carbon film types and make them up in pairs like the originals. These will be very stable and if carefully screened will be better than the originals as to accuracy and stability.

148.82.121
:All,
:Went through the calibration steps as if it were a new unit, after inital setup. DC and AC Cal and zero pots were frozen in place. Lubricated them and freeded them up. AC volt measurements are within 3 to 5 %. DC volt measurements are within 10 to 20 %. Ohms are prety far out even with new battery for full scale reading. Takes 1.7 VDC to reach full scale with no room for adjustment. Seems that the 6SN7 grid needs more voltage. I will replace this tube when i get one. This tube also appears to effect the DC volt calibration.
:Comments welcome
:Mitch
:

:Another 6SN7 may indeed fix the ohms problem. Some 6SN7's just do not have enough gain to go to full scale with a 1.5 volt battery. It will affect DC and AC cal also since the bridge is used for all measurements. There is at least one write up on the 221 in which EICO recommended adding another battery and using 3.0 volts for the ohms scales if all else failed.
:
:The dc probe needs to be 15 megs. It will be a miracle if the all multiplier resistors are still within tolerance unless they have been changed from the originals.
:
:The older units used sceened carbon comp series pairs to arrive at the correct values. These will probably have drifted all over the place.
:
:Modern 1% metal films will be the best choice. Or you can use a modern DVM to screen 5% carbon film types and make them up in pairs like the originals. These will be very stable and if carefully screened will be better than the originals as to accuracy and stability.
:
:
:148.82.121
::All,
::Went through the calibration steps as if it were a new unit, after inital setup. DC and AC Cal and zero pots were frozen in place. Lubricated them and freeded them up. AC volt measurements are within 3 to 5 %. DC volt measurements are within 10 to 20 %. Ohms are prety far out even with new battery for full scale reading. Takes 1.7 VDC to reach full scale with no room for adjustment. Seems that the 6SN7 grid needs more voltage. I will replace this tube when i get one. This tube also appears to effect the DC volt calibration.
::Comments welcome
::Mitch
::
:
Thanks all,
I will change the tube and begin the process for the resistors as i plan on using this meter as a back up and confirmation for measurements.
Mitch