This is my first post and I hope I didn’t put it in the wrong area of the site. My background is woodworking not electronics as you will be able to tell from my questions. Hopefully I can get some needed assistance.
I am a rookie at restoring vintage radios and unfortunately not versed in reading schematics yet but I was given a GE S-22 that needs a lot of work.
I do have both the schematic and a wiring diagram and it may be heresy but I can follow the basics of the wiring diagram, not the schematic at this time. I am continually reading about schematics but it doesn’t come naturally to me.
I have rebuilt the capacitor block, replaced resistors but have come to a dead end with the two electrolytics C17 and C18. I have nothing but two holes where these two caps once were. They may have been Mershon caps and someone removed them. I don’t know. My problem is I don’t know how to install my new caps and get the polarity correct. There is a existing unconnected red wire from the 1st Det coil that I assume went to C17 as well as another unconnected red wire from the resister terminal board that I assume went to C18. I’m assuming the + connections for C17 and C18 are these two red wires.
When reading other posts about the GE S-22 and the RCA 7A, which is supposed to be the same, I saw that restorers would clean out the old electrolytic, put a new cap inside it and solder the negative to the top of cap. In another post, it was mentioned that one of the electrolytics on the RCA 7-A was isolated from the chassis. Unfortunately again I don’t know how to determine if that is the case with my GE S-22 and if so what to do to correct the issue.
I don’t have the option of putting new caps in since I have no cap there at all. Also on the diagram, C17 has a lug on the bottom that has a red wire leading to the reproducer unit terminal board that is gone as well.
I would appreciate any assistance whatsoever in helping me wire in the new electrolytic caps and hope you can be patient with me as far as my inability to read schematics.
I've moved you over to the "Other Radios" section. You should be able to get your questions answered. Just continue that thread with any additional questions.
That is one of GE's "deep" chassis. They can be a little hard to work on. The same basic chassis layout was used for many models. The most easily identifiable difference is the tube count. There are other differences too.
Here is a deep chassis radio that I worked on. There are some pictures of the chassis disassembly.
I advise you take pictures of the chassis underside and top side, and post them in this thread, so that we can see what things look like in relation to the pictures and diagrams in the GE documents. These can be found here: http://www.nucow.com/GE%20S-22-X%20ca%20...manual.htm
I see four condensers in the power supply circuits, a 4 MFD, a 10 MFD, and two .5 MFD. The 4 MFD and the 10 MFD were originally mounted on the top of the chassis with their terminals below, sticking into the chassis. I cannot tell from the pictures in the GE docs if these were mounted with a bracket or with a screw thread base and a nut. This is where pictures of exactly what you have would help. If you have brackets, it is simple enough to make fake substitutes which look good. See my thread on restoring a Philco 38-10: https://philcoradio.com/phorum/showthread.php?tid=22318
Also, a hint about posting pictures here. The easiest way is to post them to a picture posting site like tumbler, and then use the URL of the picture itself from there to post them here using the little icon above the text box.
These two above photos show what should be there and how the Mershons did have a screw threaded base with a nut. The last photo shows my radio. There is nothing there. I could put a terminal strip underneath but as I said I’m unsure of how to wire it correctly.
At a later time I could glue some empty caps to cover the holes to make it look better but my concern now is how to install the new caps.
If you are not greatly concerned about appearances a terminal strip may serve very well. You can use a 3 terminal strip with radial electrolytics of 450 volt rating, and 10 MFD for C17 and 5 MFD for C18. The positive terminals from both C17 and C18 are tied together on an isolated terminal of the strip, and connected to the red wire from L4 on the 1st detector coil, and the red wire from the corner terminal on the resistor terminal board on the opposite side of the chassis. The negative side of C18 goes to chassis ground. For that you can use the grounded terminal of the strip. The negative side of C17 goes to the other isolated terminal of the strip and then to the second terminal in from the catty corner on the terminal board, where R10, a red (or blue?), and a black and brown wire attach. The black and brown wire goes to the center tap of the high voltage secondary of the power transformer, which is the most negative point in the circuit. I suggest you look carefully at each part and locate it on the schematic. This will begin to give you a better understanding of how to read a schematic in relation to the various parts. Another question, did you replace the bypass condensers in the block on the TOP of the chassis? The connections are shown in a little schematic on the right hand side of the wiring diagram. They are in a box on the TOP of the chassis labeled in figure 3 as part 15, Capacitor Pack, R F bypass capacitor pack. You will need to replace these also.
(This post was last modified: 04-29-2021, 03:06 AM by mikethedruid.
Edit Reason: clarify something
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Yes I took the tar and old caps out of the block and put the new caps into the block and reinstalled it onto the chassis.
Thanks Mike for the assistance on how to hook up the electrolytics.
(This post was last modified: 04-29-2021, 10:29 AM by Phil27.)
I do have a question regarding; “the negative side of C17 goes to the other isolated terminal of the strip and then to the second terminal in from the catty corner on the terminal board, where R10, a red (or blue?), and a black and brown wire attach.”
I can see that but I’m attaching a link to a photo of what is supposed to be the same radio (RCA 7A) that has a red wire from the base of C17 going to the speaker. Should I run a red from the - C17 connection to the speaker and then back to center tap of the high voltage secondary of the power transformer.
Just asking because my wiring diagram does show that the GE 22 does have a lug at the base of C17.
Look at the schematic. one side of the field coil of the speaker, labeled as a blue wire on the SCHEMATIC, goes to the negative terminal of C17 and the center tap of the high voltage secondary of the power transformer, as well as one side of R10. That wire labeled "blue" on the schematic seems to be the red one shown on the wiring DIAGRAM, which goes to the "reproducer terminal board" and from there to the negative side of C17. Trace these wires on the wiring DIAGRAM, and then carefully compare them to the SCHEMATIC, and you will see what I mean. It should become clear then that all these points, the second in terminal on the resistor board with R10, and the black and brown wire and the red (or blue) wire, and the negative side of C17 all are directly connected, and should have virtually no resistance between them. I think part of the confusion comes from the discrepancy between the DIAGRAM which shows a RED wire, and the labeling on the SCHEMATIC which says BLUE. I really never bother worrying about colors much since they are mostly so faded on the wires these days that they all look brown. Instead I just trace where they are going.
I have the updated version of one of these, it's an S-42A, the difference being that it uses push pull #47s rather then #45s. The two copper cans are/were wet electrolytic filter caps, inside the two square cans, one is for the audio interstage (I think) and the other contains and assortment of paper bypass capacitors. For the filter caps you can use 10 uf 450, radial lead, electrolytics on a terminal strip if you have to, for the bypass caps I would recommend using plastic film caps of the appropriate values, and voltages, so you don't have to mess with that can again. When I get to my S-42 in the restoration docket I will probably put poly film, or motor run caps inside the copper cans, speaking of which some of the larger motor run caps come in metal cans with threaded bases like the old electrolytic cans, Mouser sells them. Like many pre war radios one of the filter caps has it's negative side connected to the H.V center tap of the power transformer, whilst the negative side of the other can is connected to the chassis, but I would double check the schematic.
Regards
Arran
(This post was last modified: 04-29-2021, 06:23 PM by Arran.)
I followed Mike’s plan as far as the hookups for the terminal strip as well I did run a wire from the same isolated terminal up to the speaker. All good! The radios working. The only thing I need now is a tuner roller since the one that’s there doesn’t work. Not sure who sells them. I’m not even sure what its called.
Thanks all for the help and advice.
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