zenith 6A229..need help
Hello dear members
greeting every one
a friend sent me a zenith radio model 6A229 as a gift.....the thing is that somebody tried before me to repair it....the band switch is in mess all the wires is been cut but this is not the current problem for me
(at least for now)...so i started with changing the paper and electrolytic caps.all were out of specs.
the problem is when you connect the speaker plug to the back of the radio(which have a field coil with 820 ohms DC resistance and the primary of the out put transformer is 570 ohms and i did not find any shorts in the speaker assembly) the voltage drops from 270-280 DC to 60-70 volts DC on the electrolytic caps.....i reviewd all the caps. that i have changed for any mistakes in the connections several times and all looks ok...my next thought was that there might be a problem with the canohm resistor so i checked the resistance and it measures 300 ohms(from C18 to R10 170 ohms,from R10 to C19 30 ohms and from C119 to ground 100 ohms)..the rest of the resistors are ok
is that normal for the canohm resistor? i could not found the value of this resistor any where
is it possible the the cause of the voltage drop id due to low resistan of the candohm resistor.
thank you very much and any kind of help is appreciated
- zenith 6a229 (113 KB)
Nice gift if you can get it working OK. The schematic is very bad and I have trouble reading the component codes. I will try to get a better print from a friend who has Riders. It may take a couple of days.
Something odd when you connect the speaker plug. Field Ohms measure the right sort of value as does the output transformer. Electrolytics +ve to the field coil and -ve to the centre tap and the Candohm. Some of those values sound low to me?
Have you any power resistors you can make a dummy load with to work with no tubes fitted? Something to load the HT by about 30mA so need a 10W resistor. Value, with HT about 250V, then 7.5 to 8K.
Not good to run the HT without some sort of load. If you can do this then disconnect all the Candohm connections and see what hppens also with no tubes in. You would need to connect the second smoothing electrolytic -ve to the first one and the centre tap. You will made a simple full wave rectifier circuit. The HT should stay high when you connect the speaker. If not something is pulling the the HT down.
You could also join the Antique Radio Forum who have many Zenith experts who are helpful.
Sent you better copies of the schematic and have asked on the Antiques Radio Forum if anyone knows the value of the Candohm resistor R14.
Antiques Radio Form (ARF) John gave the values for the Candohm
Starting from the transformer the Candohm values are thought to be 300, 27, 125 Ohms.
thank you very much for your help
i found the cause of the voltage drop accidentally....it was caused by a short circuit in the first IF can
a slight amount of smoke came out from it...i opened it and i put a thin sheet of plastic and it fixed it..
the audio section is working know but i found that the oscillator is not working...most probably due to a bad 6j5 tube the oscillator coil is ok....so im looking for a replacement..
any how thank you very much for your advice