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American Bosch 670C Dial - Printable Version

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American Bosch 670C Dial - Greg - 11-02-2017

In addition to the usual dust a couple of tiny bugs decided to pupate on the back of the dial scale of my American Bosch 670C. I'd like to clean it. The problem is that the outer tuning pointer shaft has a gear on the back and a "second hand" pointer on the front that prevent me from separating the scale from the metal back panel.

Does anybody know how to safely remove the "second hand" from the shaft? It looks like it's just a friction fit. I assume the notches on either side of the hole allow it to bend a tad.

Is it safe to clean the back of the dial glass, the side the scale is painted on? If so with what? I hope they didn't buy their ink/paint from the same place Philco did. Icon_biggrin

Thanks,
Greg

   

RE: American Bosch 670C Dial - Arran - 11-03-2017

Be careful in cleaning the dial on your American Bosch, it may have "washaway" in or paint on the back. I don't know what to suggest to safely clean it, on the beige coloured plastic Philco dials mineral spirits are the safe thing to use, but those are made out of a phenolic or celluloid based plastic, not glass. I have a Canadian cousin to your Bosch called a Northern Electric, and it has a very similar dial, so I will have a look at it, and report back later about the dial scale and the pointer/s it has. If you can look around the rear of the pointer shaft see if it has a set screw or something holding it in at the back.
Regards
Arran

RE: American Bosch 670C Dial - OldRestorer - 11-03-2017

I believe it is a split shaft press on pointer. There should be 2 slits in the pointer shaft. Wrap it in a thin piece of t-stirt or similar and pull strait up. I would not wash it unless you test it on a corner first as Arran said. I did just clean my AB dial and it did not have an issue but that was not on glass..

Icon_smile

RE: American Bosch 670C Dial - Art Hoch - 11-03-2017

Hopefully your's will turn out looking like mine.
Art

RE: American Bosch 670C Dial - Arran - 11-03-2017

I had a look at the dial and chassis of that Northern Electric, and the pointers are identical to your set and Art Hoch's, the dial is a bit different. Part of one of the dial scales on mine is rubbed away somewhat, it's that light blue colour like the police band on yours, so that makes me think it may be a "washaway" dial, so ask Art what he used to clean his with. However it does not not seem to have as many bands, maybe the longwave band was omitted on my model? Anyhow I think that the vernier scale pointer is just pressed on, I could not see a set screw from the back side, you may have to wraps some string around the hub to gain some purchase to pull it off, the center pointed seems to be held on in the center of it's shaft with a screw.
Regards
Arran

RE: American Bosch 670C Dial - Greg - 11-06-2017

The pointer came off embarrassingly easily. I think I needed to flex it a tiny bit which I didn't do initially. I really did pull on it pretty hard the first time Icon_redface .

The dial cleaned up nicely. I dabbed Q-Tip in some water/ammonia and cleaned around the printing in a small area. Then I gently wiped with a microfiber cloth (soft and no lint). That didn't seem to do any damage.

Now to finish putting it back together.

RE: American Bosch 670C Dial - Foose - 12-30-2017

i just restored one of these...its quickly becoming my favorite of the collection. but im new to this, so a couple questions, if i could....

i cant get anything on my other bands....can you guys? are those bands just retired, or is it because of something i did/didnt do? 

whats the "second hand" for, anyhow? just fine tuning, or does it actually refer to something im not aware of?

what sort of drive belt do you have on your tuner mechanism? mine had a broken rubber band when i got it, and there was this spring loaded arm, but no pulley on it, which i figured ought to have one. so i lathed out a nice little brass belt tensioner wheel for that little arm, and now ive got another rubber band in there, but its basically terrible. i was just curious what the actual drive belt consisted of, i cant seem to find anything on it.

beauty dial, by the way! nice work. i hope im not too far off topic.

Brian

RE: American Bosch 670C Dial - KCMike - 12-30-2017

Take a look here. I think they have a belt you need. Look under Bosch.
http://adamsradio.com/

RE: American Bosch 670C Dial - Arran - 12-31-2017

There isn't much on some of the shortwave bands, especially the old police band from the 1930s, but there should still be some noise coming through. If the set hasn't had the old paper caps and drifted resistors replaced that may be why nothing is happening, alternatively it could be some bad mica caps in the oscillator section. Hopefully it wasn't sabotaged during the war, that could range from simply shorting out the short wave coils, to clipping a few leads, to messing with the band switch.
Regards
Arran

RE: American Bosch 670C Dial - Foose - 12-31-2017

ive replaced all the old paper caps and the electrolytics of course....most of the resistors i tested were actually well within specs, so i didnt test all of them, and i didnt replace any of them either. on my philco 118x i replaced everything (caps and resistors...i kept the big wirewound resistors because they tested in spec) and it DOES seem to pick things up a little better, but i also havent aligned either of these radios yet, so its probably an act of god theyre working at all. ill keep fiddling i suppose, and i just ordered a drive belt, thanks for the link to that one!

cheers!

Brian