09-29-2020, 08:42 PM
Not out of the woods yet....
Tonight re-installed the output transformer. Put in my 8-Ohm speaker.....turned on the power with the voltmeter on the cap that was shorted before: the last filter, so if the voltage starts sagging anywhere, I will see it.
Turn-on. First I heard a pop at 70V. OFF!!! Found a piece of solder wire landed in a tube panel. Whew!
Turned it on again. The voltage was stable, and I brought it up to the nominal. The speaker made some raspy sounds. I heard a barely noticeable hum when putting an ear against the speaker. Then I started with the tuning. The band was BC, so I expected to hear the local station at 1160kC. But....no.
Then the speaker made a howl, a one-tone type - something got to generate; I turned down the volume, the howl disappeared.
Then I looked at the voltmeter....the voltage was really down, to 35V (instead of 140V or so) and I started to worry, but before I couold start to worry, I saw a faint white smoke....same general location it came out before. Turned it off.
Then I pulled most tubes out, and started looking. The voltage goes up, and then sags, but within reason.
I re-installed the tubes, one by one....the voltage held. I put the output ones, connected the speaker. Heard noise, and it felt like the radio noise, so I tuned into 1160kC and.....the station came through. I let it play a few minutes. Tried the tone control; when using the top band, the howl returned and disappeared when the volume was reduced.
So.....it is a progress, but I do not like inexplicable smoking. Plus I have not brought the voltage all the way up: it stayed at 90V AC.
I have to tell you: the assembly of this thing is absolutely horrible. Borderline flimsy. The wires are thin, really thin. Many parts have their leads formed and not insulated, relying on the rigidity of the leads to not bend and short to something.
The ERO caps are just bad: I remember using a non-recapped (I left all paper caps in place) Zenith and it in fact worked just fine. I highly doubt this one would. I am not saying I am disappointed, but I expected a bit more sturdiness from the assembly of a good German radio of the 50s.hing
Now...need to carefully bring the voltage up. If sags, find out who does it.
Then find out why it howls. A few tubes have shields: all are installed and grounded (they use soldered wires).
Some tubes used adhesive strips to hold them (fighting microphonics?) - those are no longer used as I do not have them. But I doubt this is them.
Oh.....the rectifier is selenium. But. It works fine. I checked the ripple on it - real small. Rectifies fine, no hum or anything. I am reluctant to replace it. Plus there is no good way of doing it: it is a small job and is on the external side of the chassis.
Tonight re-installed the output transformer. Put in my 8-Ohm speaker.....turned on the power with the voltmeter on the cap that was shorted before: the last filter, so if the voltage starts sagging anywhere, I will see it.
Turn-on. First I heard a pop at 70V. OFF!!! Found a piece of solder wire landed in a tube panel. Whew!
Turned it on again. The voltage was stable, and I brought it up to the nominal. The speaker made some raspy sounds. I heard a barely noticeable hum when putting an ear against the speaker. Then I started with the tuning. The band was BC, so I expected to hear the local station at 1160kC. But....no.
Then the speaker made a howl, a one-tone type - something got to generate; I turned down the volume, the howl disappeared.
Then I looked at the voltmeter....the voltage was really down, to 35V (instead of 140V or so) and I started to worry, but before I couold start to worry, I saw a faint white smoke....same general location it came out before. Turned it off.
Then I pulled most tubes out, and started looking. The voltage goes up, and then sags, but within reason.
I re-installed the tubes, one by one....the voltage held. I put the output ones, connected the speaker. Heard noise, and it felt like the radio noise, so I tuned into 1160kC and.....the station came through. I let it play a few minutes. Tried the tone control; when using the top band, the howl returned and disappeared when the volume was reduced.
So.....it is a progress, but I do not like inexplicable smoking. Plus I have not brought the voltage all the way up: it stayed at 90V AC.
I have to tell you: the assembly of this thing is absolutely horrible. Borderline flimsy. The wires are thin, really thin. Many parts have their leads formed and not insulated, relying on the rigidity of the leads to not bend and short to something.
The ERO caps are just bad: I remember using a non-recapped (I left all paper caps in place) Zenith and it in fact worked just fine. I highly doubt this one would. I am not saying I am disappointed, but I expected a bit more sturdiness from the assembly of a good German radio of the 50s.hing
Now...need to carefully bring the voltage up. If sags, find out who does it.
Then find out why it howls. A few tubes have shields: all are installed and grounded (they use soldered wires).
Some tubes used adhesive strips to hold them (fighting microphonics?) - those are no longer used as I do not have them. But I doubt this is them.
Oh.....the rectifier is selenium. But. It works fine. I checked the ripple on it - real small. Rectifies fine, no hum or anything. I am reluctant to replace it. Plus there is no good way of doing it: it is a small job and is on the external side of the chassis.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
