1965 Sony TFM-850W issues
 

Hello everyone a couple of weeks ago I picked up a Sony TFM-850W AM/FM Transistor Pocket Radio that when it came and I tried it out it wasn't working and I figured that I'd try to recap the radio to see if that would fix it.

Well I got the radio recapped and there was a yellow wire that I had to remove to get to one of the capacitors and I can't remember where the wire went (I thought I could figure it out by looking at the color of the solder), but I couldn't find the solder spot like I thought I could, and I can't seem to find any service data for this radio.

I know Shango worked on one of these radios once, but I can't remember how long ago it was he worked on it.

Anyways does anyone have any service data for this radio or one like it that is functional that they have some pictures of showing where all of the wire leads went to that they could post?

Thanks for your help.

Photo of radio & chassis may help. You can also contact shango &
see if he will give you the link. He has a crap load.
Nothing on my end as far as a SM is concerned:tears:

73 Zeno:smoke:
LFOD !

Ok, I'll get a picture posted when I get a chance, and see if you or anyone else recognizes anything. :thmbsp:

Here's a picture of the radio "chassis" (PC Board):

That's an excellent radio. I have a Sony AM-FM portable, model TFM-7720W (a trash find years ago) which still works very well; the only thing wrong with it (if you can say this is a problem) is the volume control knob is temporarily missing. I used it as a temporary replacement for another radio I have around here somewhere, so if I find that radio (I know it must be someplace, I don't recall where at the moment) I can take the Sony knob off and put it back on the TFM-7720W, where it belongs.

BTW, one interesting thing I found out about the Sony TFM-7720W (this is probably true of other Sony radios as well) is that it takes just three C-size flashlight batteries, for a total of 4.5 volts DC. This is an unusual voltage for a transistor portable radio, IIRC, as most portables I've seen use either 4 C or D batteries (for 6 volts total) or a 9-volt transistor battery.

What, if anything, was the significance of designing the TFM-7720W Sony (your Sony radio may use the same number and size of batteries) for 4.5 volts, rather than the industry-standard 6- or 9-volt power supply voltage? I personally cannot see how this would make any difference, unless this was done to deliberately limit the maximum volume when the radio was tuned to a strong station, and/or the volume control was set almost to maximum (as a kid might do if he/she were listening to a rock and roll station playing a favorite song). Of course, the set's audio stages, particularly the output transistor(s), would take the heck of a beating from that, but kids don't care about that as long as the radio can belt out the local station as loudly as possible.

Edit: I just looked at the photo you posted of your radio's PC board, and saw a short 2-conductor cable with a 9-volt battery connector at the end of it. This leads me to believe your radio operates with a 9-volt transistor battery, not several C or D cells as some larger radios (such as my TFM-7720W) used. The chassis looks extremely small as well, not unlike the slightly larger than a postage-stamp-size (!) chassis used in the last CRT televisions, before flat screens. I have seen chassis this small even in consoles with 21-inch CRTs; I believe one of Zenith's last CRT TVs had a main chassis that small. How it worked as well as it probably did I will never know, but the TVs which used that chassis may still be in use today (using a cable-TV digital converter box, of course) and are or may be working almost every bit as well as when they were new, in the NTSC era. This would speak well of the quality of Zenith's radios and TVs; it is a crying shame, IMO, that Zenith went out of business in Chicago and went to Korea, never to be heard from on our shores again.

Yes, it's a 9V Transistor Radio, and like I said the only thing I'm having trouble with is figuring out where that yellow wire that's hanging loose on the PC Board in the picture, is supposed to go.

I actually have a 1962 vintage Zenith Royal 2000-1 AM/FM transistor Radio that runs off 8 D Batteries, for a total of 12V DC or a 12V Wallwort.

Difficult to tell from the picture, can’t see an unattended wire end.

jr

In the picture its the yellow wire running over the speaker magnet opening in the PC Board, that wire (even though it don't look like it in the picture) is detached from the top of the board somewhere, but like I said, without the proper service information I can't tell where that wire is supposed to go.