Zenith TO H500 - Printable Version
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+--- Thread: Zenith TO H500 (/showthread.php?tid=19365)
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RE: Zenith TO H500 - morzh - 01-06-2019
Has been some time, I went to FL and back, and after having received the alignment instrument I went back to the radio. After having aligned the IF I started aligning the BC band when my reception faded out. Came back after a few second power cycle.
First I thought it was a tube, and the tube lineup happened to be 100% identical to the Stromberg Carlson AWP-8, so I changed the tubes one by one to no result.
Then I checked B+ and found it drooping so I figured it was the selenium rectifier.
I changed it for the 1N4007 plus 47 ohm resistor, shich seems to be the recommended combination.
It works but the voltage on the output plate is about 10V higher than indicated (the resistor drops just 3V). Everything works but I will use a larger resistor, maybe 80 to 100 ohm, 10W or so.
Then finish the alignment.
RE: Zenith TO H500 - Arran - 01-07-2019
Mike;
I would go with something between 47 and 80 Ohms resistance, with 80 at the high end, I'm not sure about the 1LN6 but the 1R5s are very fussy about how much voltage they receive, sometimes they will stop oscillating if the voltage is cut down too much, especially on the filament side.
Regards
Arran
RE: Zenith TO H500 - morzh - 01-07-2019
47 seems too little even though it is (40-50) is the recommended range.
I doubt 100V is a problem, plus the radio will mostly be used with the battery. Plus large resistance will dissipate proportionately more power.
So maybe I will leave it at 47.
RE: Zenith TO H500 - morzh - 01-12-2019
Today the 82 ohm resistors arrived, put it in in series with the 1N4007 and have a 6V dropout bringing the 90V plate voltage to 95V from 101V. Good'nuff.
Gave it full alignment tonight, tomorrow will put it together and shelf it.
Buying them batteries for every radio is becoming a tad expensive.
RE: Zenith TO H500 - morzh - 01-13-2019
After having assembled the radio I found out the radio has some sort of anenna connection problem. The antenna is the one in the front cover.
So I had to pull the chassis out and take the top apart.
Looks like this:
The separation of the wire from the hings could be seen.
I soldered it back.
Seems to work.
Now need to buy thd battery.