[Eric T]

My next door neighbor just gave me this:

[Image: http://i145.photobucket.com/albums/r233/...113744.jpg]


I guess this will be my next project, which looks like fun. 

He also gave me this:

[Image: http://i145.photobucket.com/albums/r233/...114644.jpg]


It's in like new condition with just a few notes on the back page.
I may find a museum to donate it to.

[David]

[attachment=7132][attachment=7132]

S-120service manual.pdf Size: 641.82 KB  Downloads: 268

Eric-T   Fun set to play with 4 tubes plus a diode rect. Bascially the same thing as a S-38E but no 35W4 tube. I used a IN4007 during the rebuild this was in 1985-86. Had a friend in Germany who was sent to the Middle East during Desert Shield. Packed it up and sent it to his APO he has the radio to this day. The set will be a little weak on the top half of Band 4. Will try and attached some info. David

[Eric T]

Eric-T   Fun set to play with 4 tubes plus a diode rect. Bascially the same thing as a S-38E but no 35W4 tube. I used a IN4007 during the rebuild this was in 1985-86. Had a friend in Germany who was sent to the Middle East during Desert Shield. Packed it up and sent it to his APO he has the radio to this day. The set will be a little weak on the top half of Band 4. Will try and attached some info. David

Thanks a bunch, David. 
Did you have to add a resistor to the diode?
I saw on one website where this guy put in a solid state BFO circuit. I'm not sure if it's worth the trouble. We'll see.

[David]

Doing this without notes!!! C31A,B,C 47uf at 220-250 volts, R21 33ohms to 50ohms. R14 470k change to one watt or use 2 one half watt 1megs this is something I do with every radio using a 35C5 or 50C5. Consider adding a 50ohm to the filament string something I do most of the time. C31D 22uf 50 volt to 250 volt most of the time use 250 just what I have on hand most of the time. 12BE6 try different ones will make a difference on Band 4 forget the tube tester on this one. Simple long wire ant. 10-15 feet.   David 

[Eric T]

Doing this without notes!!! C31A,B,C 47uf at 220-250 volts, R21 33ohms to 50ohms. R14 470k change to one watt or use 2 one half watt 1megs this is something I do with every radio using a 35C5 or 50C5. Consider adding a 50ohm to the filament string something I do most of the time. C31D 22uf 50 volt to 250 volt most of the time use 250 just what I have on hand most of the time. 12BE6 try different ones will make a difference on Band 4 forget the tube tester on this one. Simple long wire ant. 10-15 feet.   David 

What wattage rating should I use for that additional 50 ohm resistor on the filament string?

[David]

I like to use a 10 watt resistor if you are having a problem making it fit or don't have one try 2 100 ohm at 5 watts each in parrell(sp).  If you are reducing line voltage to around 110 volts just skip the resistor. I was in Tampa several week ago my old Junior high was 100 years old. I was pleased with the way Wilson middle school looked a great place for a child to get a education.

[Eric T]

I just happen to have a 50 ohm 10 watt resistor. I'll install it tomorrow.
I just finished replacing old/bad parts and fired this thing up today, but it's not working. Then one of the dial lights blew. They seemed overly bright.
Then again, I have 128 volts at the outlets in my house.

[Eric T]

Found the culprit: a bad 50C5 output tube. I had an extra and it works OK.
AM aligned just fine. All the SW bands are a bit fussy. I can get the upper end of the scale aligned, but then the lower end won't adjust low enough.

[David]

Using the 50  ohm resistor you are dropping the  string voltage only 7 volts. Eric please make up a bucking transformer very easy to do project. Desired voltage drop divided by amps equals ohms.  7 divided by .150 = 46.6 ohms. David

[Eric T]

7 volts puts it safely inside the 125VAC max voltage.

I'm more concerned with the dial tracking. Getting the high end of each band aligned is doable with the trimmers. When I go to the low end of each band, the the coil slugs can't be adjusted enough to align with the dial. 

Ex: Band 2 adjusting trimmers at 4.3 MC OK. When I try to adjust with the dial at 1.9MC, I can't get L2 and T2 to adjust below 2.3MC.

 I'm thinking about changing the cap values in these tank circuits.

[David]

Eric replacing the mica caps will help, Halli caps do not age well. Just remember this is a basic AA5 with a few extra coils and a band spreader. To me I just like them for doing what they do with so few parts.  My SX-130 will blow the S-120,S38-A,B,C,D,E out the window. Please replace the couplate if you move it just a little it will start to fail. David

[Eric T]

I ended up making a dummy antenna as shown in the alignment instructions and using it. I had to wind my own coil, which I found instructions for on the internet.
Every band adjusted well enough. I had some weird intermittent issues with filament voltage on the output tube grid and bad connections in the converter tube socket. Those seem to have passed...

Right now I'm listening to somebody saying a bunch of numbers in Spanish and modem sounds at around 10.7 MC, which is something called "Cuban Spy Numbers."

I also tuned in Riyadh and Bahrain tonight.

[David]

My S-38Ee takes about 10-15 minutes to warm up then good to go. Like I said fun sets to play with If you happen to be up between 3AM-5AM tune between 9.0-11.0 for radio OZ  David

[Eric T]

I had a bunch of weird intermittent problems when I first got this thing going.
I'm going with the theory that my neighbor had this stored in his garage for years and there was moisture in the tube sockets. I had it going for a few hours and all the big problems have been baked out.

[David]

-centralabcouplates.pdf Size: 1.39 MB  Downloads: 300

Bump sorry folks could not figure out how to attach a pdf to a private mail on the Phorum. David