18-12-2023, 01:13 PM
(This post was last modified: 18-12-2023, 01:18 PM by Mike Watterson.)
Good progress.
Makes sense it's from a radiogram, though they must have had old stock of EF41s to use up! However the EF41s are likely fine.
The IF after/at the ECC85 should need hardly any 10.7 MHz drive.
Do check the continuity of the IFTs.
The 75V on EF41 g2 is low, which will dramatically reduce the gain. Should be 85V (min gain) to 135V (max gain). Though proves emission is good!
The screen grid resistor maybe 82K to 120K depending on HT. There should be a capacitor to chassis, any value from 10nF to 100nF 250V (minimum), Pin 5, is it a replaced plastic/poly type, not any kind of paper? The pin 6 is signal, g1.
Sometimes there is a potential divider on g2, but in any case more like 90V to 120V would be normal on g2. Do examine the caps there and measure resistance g2 to HT and chassis with power off and see if a single resistor to HT, or a 2nd one to chassis.
Edit:
Looks like noval magic eye:
Wing pattern: EM80, EM81 and EM85
Bar: EM84 and EM87
https://www.radiomuseum.org/forum/magic_...terns.html
Russian / Ukrainian made USSR NOS (might need small changes) are available from Ukraine. Less problematic and wear better than the older mostly octal round ones like the EM34 etc.
Makes sense it's from a radiogram, though they must have had old stock of EF41s to use up! However the EF41s are likely fine.
The IF after/at the ECC85 should need hardly any 10.7 MHz drive.
Do check the continuity of the IFTs.
The 75V on EF41 g2 is low, which will dramatically reduce the gain. Should be 85V (min gain) to 135V (max gain). Though proves emission is good!
The screen grid resistor maybe 82K to 120K depending on HT. There should be a capacitor to chassis, any value from 10nF to 100nF 250V (minimum), Pin 5, is it a replaced plastic/poly type, not any kind of paper? The pin 6 is signal, g1.
Sometimes there is a potential divider on g2, but in any case more like 90V to 120V would be normal on g2. Do examine the caps there and measure resistance g2 to HT and chassis with power off and see if a single resistor to HT, or a 2nd one to chassis.
Edit:
Looks like noval magic eye:
Wing pattern: EM80, EM81 and EM85
Bar: EM84 and EM87
https://www.radiomuseum.org/forum/magic_...terns.html
Russian / Ukrainian made USSR NOS (might need small changes) are available from Ukraine. Less problematic and wear better than the older mostly octal round ones like the EM34 etc.
