Another Zenith "bugeye" restoration

[bandersen]

Yes, I'm working on another bugeye set. This time it's a 16Z25 chassis and a 14XP4A CRT.





There are some odd old repairs. Like two fusible resistors where only one is needed.
Also found a ceramic also in the AGC/IF shorted to ground and resistor added in parallel with the HOT bias resistor. I guess someone was trying to improve the brightness or contrast ?




I restored the circuits to their original values and wiring using a Sams and another, restored 16Z25 for a reference.

After a quick recap, I bypassed the CRT filament with a power resistor, popped the HOT cap off and powered it up. B+ seems fine, but I only get sound for a few seconds before it cuts out.


I figured it's and AGC issue and tried adjusting the AGC control but nothing happened. I unmounted it for a closer inspection and found it's shot just like in the other bugeye I'm working on.


I temporarily tacked in a new control, but it made little difference.
Next, I did a resistance check on the tuner and IF and sound tubes and compared to the table in Sams. The only odd values were on pin1 of the RF tube and pin1 of the 1st IF tube. Both are about 40% high and part of the AGC buss. I'll start check the associated resistors.