[Radioroslyn]

If you have an AC ma meter you may want check the mains current. 1amp seems rather large,
heater current for the 117Z6 is only  75ma+what ever else radio requires. Or check the wattage rating of the set and figure about 1 amp=100w. Your set is probably around 20-30w= less than a 1/2 amp.

Terry

[klondike98]

Thanks Terry!! Yes, its 20 watt set, so I'll cange that fuse to 0.5 amps and will measure when I fire it up.

[klondike98]

Recapping is almost done.  I've worked my way to the cap that is connected to the antenna connector and frame of the tuning capacitor that broke when I was trying to pull the pin out of the connector (it had gotten soldered in by someone at some point - photo and discussion in post #1)  The first picture is the connector before I tried pulling it apart.   

[Image: https://www.dropbox.com/s/mxdaeixlvlipqd....jpg?raw=1]


John (Eliott Ness) sent me some Molex pins (Thanks!!) to use as a replacement but I was able to get the pin part of the connector unsoldered and its in good shape so I'd like to try and keep that in place.  Female part of the connector is what is broken and it also came unsoldered from the frame of the tuning cap.  I did find a connector that, with a bit of manipulation, will hold the pin nicely.  Now I just have to figure a way to solder the connector to the frame (or connect it in some other way)  That's a darn big heat sink to try to solder to.  Anyone have any ideas on how to go about it?  


[Image: https://www.dropbox.com/s/u9elk3773ctl0r....jpg?raw=1]


[Image: https://www.dropbox.com/s/g7i54aajtw3jgg....jpg?raw=1]



Just for grins, I do have an alternate solution, a little ugly but I believe it would work.  (The Q-tip is simulating the pin connector that would go there.)
[Image: https://www.dropbox.com/s/d6n36hsus2iqxv....jpg?raw=1]

[klondike98]

After all the worry about the antenna female connector, I was able to salvadge the business end of the original and with my 80 watt soldering iron get it soldered to the tuning cap frame.  I just made sure the frame was nice and clean (a little sanding) so the solder would flow.  It not the neatest but actually a bit neater than what was there.  There was just enough of the bottom end of the connector to solder on the cap and wire that also needed to be there.  

[Image: https://www.dropbox.com/s/jz4w7z35fqauyt....jpg?raw=1]

Terry, back in post #22  you mentioned making sure I check the voltage on the 200 uF cap that supplies the filament voltage for all the tubes except the rectifier.  Is my thinking for the following correct?  The tubes are 1.4 volt filaments each and there are 7 of them so I should make sure not to exceed 7 x 1.4 or 9.8 volts between the 200 uF cap and B-  .

[klondike98]

Schematic Link

Brought the set up to voltage slowly with variac and the voltage on the 200uF cap went to 8.1 v so all OK there I think.  I got a bit of static on the speaker but nothing tunes in and I get no tone when I put the signal generator on 455kc with modulation to pin 1 of 1LC6 (converter) and the radio tuned to 600kc (step 1 o the alignment procedure).

Voltage measurements around the tubes were:
[Image: https://www.dropbox.com/s/wdp1vnfd6cck7y....jpg?raw=1]

The tubes should all be good, I just got them from Bob Dobrush (and I find my tube tester has the same disease that sam's does in that it seem to fry the filaments for these when I test them    )  .  The "unstable" label means I'm seeing the voltage jump around on the digital meter, never getting a stable reading.  I do get an increase in static when I put the meter probe on the plate of the det. amp 1LD5 to get that unstable reading.

I'm not quite sure what to look for next.  Any thoughts???

[edit-this post was updated to revise the voltage chart after Terry helped me sort out the ILD5 Det. Amp voltage problem.  so voltage are reasonable but still no tone]

[Radioroslyn]

I'd crank up the variac a bit till I got close to 10v on the filament string (at the 200mfd cap). I trust the audio stages are working ok? If so then try injecting a 455kc signal though a small cap (200mmfd-.01mfd not critical) at pin 2 of the 1LN5 if ok then pin 6 if ok when pin 2 of the 1LC6 then pin 6. With the generator on pin 6 you can align the IF transformers.

Do your self a favor and only use the digital meter for ohms measures.Get a VOM or if you are going to be measuring hi impedance circuits a VTVM. Digital meters can't deal well with any sort of voltage with signal on them.I think what happens is some of the semiconductors act as diodes and rectify the signal portion of the voltage and it comes up with a goofy reading. There ok if it's just voltage  like right out of the power supply or cathode and screen grid circuit but plate and control grid circuits I don't trust them. Once I was working on the TV set, measured some voltages and they where no where near what they should be. Was thinking this set is all kinda screwed up. The next few days I was scratching my head tiring to unlock this puzzle. Left my Beckman 310 meter somewhere so I grab the Simpson 610 ('50s analog meter)and the reading were much closer to what they should be.

GL
Terry

[klondike98]

Thanks Terry, I will try those suggestions!!

[klondike98]

hmmmm.... I did use the VTVM to get a 0.2 v reading where I had an unstable reading with the DVM. Unfortunately I do not get tone with 455 kc on the generator + audio modulation and tuning the radio to 600kc (and I tuned above and below that to see if I could hear tone) at any of the pins you indicated in the post above so something else is going on. I'm going to reclean the pins and sockets to see if its something simply like that.

You asked if the audio stages are OK... can I check that?

I did recheck my generator with another radio and the generator as if it were a transmitter and I do pick up tone.

[Radioroslyn]

You can check the audio stages by touching pin 6 of the 1LD5 with the tip of a screwdriver that you are touching the screwdriver's shaft. If all is well you'll hear a loud buzz. Bare in mind that the buzz you'll be hearing is going to be as loud as the set will ever get is it should be rather robust. Portables generally aren't a loud a a 10 tube console with having the two 1LB4's in the output should be able to make about 1/2 watt of audio.

Terry

[klondike98]

Thanks to Terry's help we sorted out the ILD5 Det-Amp voltage issue on pin 2 (plate). I thought I had checked all resistors but I must have missed one and it was causing a problem. Still don't have signal generator tone coming through but that's another day....Thank you Terry!

[klondike98]

Back to the Zenith…
The voltages on all the tubes are now in line with what they should be but still no audio tone.  I do get a buzzing sound when touching pin 6 of 1LD5 as Terry suggested, indicating audio stage is working.    1st step in alignment is feed pin 6 of 1LC6 with modulated 455kc with radio tuned to 600kc.  Nada.
Plate of 1LC6 goes to the 1st IF transformer so I checked and found about 18 ohms on both sides of it (blue-red leads and green-black leads).  On the 2nd IF transformer I get 17 ohms on the Blue-Red side and 450K ohms on the brown-green side.  Looking at the schematic I think I should see something more like 47k for that brown-green side of the transformer.   Does that sound right?
[Image: https://www.dropbox.com/s/iwp813pdl6txno....jpg?raw=1]

[Radioroslyn]

Well YES and no. The actual coil is 15 ohms but it has a 47K resistor in series with it in side the can. So what you a measuring is 47k+15 ohms. If the coil was bad you would see infinity ohms. Since the 15 ohms is so much lower than the 47K it's hard measure it but we know it's ok cause it's not open.
I bet I know what the next question is!!

Terry

[Radioroslyn]

Sorry miss read your post. If transformer secondary is open at 450K. So what to do? Well just for grins connect a small cap (like 100mmfd) to the two plate connections. Plate of the IF amp to the diode plate. This will couple the IF signal to the detector. It should pass an IF and rf signal now.
Don't get old it sucks!

Terry

[klondike98]

Terry...so if I understand you correctly, I should try putting a 100pF cap between the plate of the 1L5N IF tube and the diode plate (DP on the schematic) of the 1LD5 Det.-Amp tube (essentially by-passing the 2nd IF transformer).  Then try the signal generator again...right?  see...chemists can learn this stuff too...

...and not getting any older does have its down side as well.... 

[Radioroslyn]

Terry...so if I understand you correctly, I should try putting a 100pF cap betwee the plate of the 1L5N IF tube and the 1LD5 Det.-Amp tube (essentially by-passing the 2nd IF transformer).  Then try the signal generator again...right?

...and not getting any older does have its down side as well.... 

Yup that's it. Pin 2 of the 1LN5 to the diode plate pin 4 of the 1LD5. It's not quite as effective as having a tuned circuit. The audio portion is being coupled though the small resonating cap inside the IF transformer. It too is about 100mmfd so it's not going to couple a bunch of audio.
>Then try the signal generator again...right?
Yup.


Terry