zenith porthole question

[Electronic M]

I'd try subbing the IF tubes with known good/NOS tubes. If that fails start checking for shorted or drifted capacitors, and open or shorted transformers/chokes.

[stusnyder]

Originally Posted by Electronic M

I'd try subbing the IF tubes with known good/NOS tubes. If that fails start checking for shorted or drifted capacitors, and open or shorted transformers/chokes.

Thanks Tom for the tips. Most of my tubes are still packed away, got to dig them out this weekend.
Most of those dogbone caps are in mmf. How many zeros do you put in the front of the number to convert to mf, for example 500 mmf would be .05mf?

[old_coot88]

Originally Posted by stusnyder

Thanks Tom for the tips. Most of my tubes are still packed away, got to dig them out this weekend.
Most of those dogbone caps are in mmf. How many zeros do you put in the front of the number to convert to mf, for example 500 mmf would be .05mf?

Six zeros.
It would be .0005 mf
(The modern designation for that particular value would be 470 pf or .00047 mf.)

Nowadays, values below .001 mf (1000 mmf) are generally expressed in pf.

[stusnyder]

Well I finally found the problem. One of the 6au6 IF tubes was bad. Put another one in and bingo Some slight adjustments and now got a decent picture. I consider it done!