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42-761EZ Chassis Restoration - Printable Version

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RE: 42-761EZ Chassis Restoration - Radioroslyn - 01-27-2013

If you wanted to you could use a diode in series with pilot lamp to drop the voltage by half. Then you would just need to loose 60v. Or if you are a math major you could use a paper cap to drop the ac voltage down.
GL
Terry

RE: 42-761EZ Chassis Restoration - Arran - 01-28-2013

What about paralleling the filament of the pilot lamp with part of that dropping resistor you need for the tube heaters, that was what they used to do in AC/DC sets with a plug in ballast. Then you could use an ordinary 6.3 volt pilot bulb of some sort. I'm still not sure about the durability of a mini a stand alone 120V LED, even the Christmas light strings have them connected in a series parallel arrangement. Unfortunately the diode trick doesn't cut the 120 volts in half it comes out closer to 80 volts rather then 60 volts if I remember correctly, they have a calculator posted on a British site for figuring filament droppers out.
Regards
Arran

RE: 42-761EZ Chassis Restoration - Eliot Ness - 01-30-2013

Quote:John, I am planning to try a BA9SF-W-180-120VAC LED from superbrightleds.com:
Ron, a 120 VAC miniature bayonet base LED lamp is well worth the minimal cost to see if it fits your needs. I think these new LED miniature lamp replacements have a lot of potential, but that is the first time I've seen a 120 VAC mini based LED in a bayonet base .. be sure to keep us posted.

RE: 42-761EZ Chassis Restoration - Ron Ramirez - 01-30-2013

I certainly will, John. I expect to be ordering the lamp - and the needed power resistor and electrolytics - by this weekend.

RE: 42-761EZ Chassis Restoration - Ron Ramirez - 01-30-2013

Well, I've ordered the necessary parts - two 120 volt LED lamps from superbrightleds.com , and the resistors and electrolytics from Mouser. I also ordered one extra chassis mount resistor and a few 1813 lamps (14V, 100 mA) in case the LED is not to my liking - this way, I can go back to the original design if need be.

So now it's just a waiting game. Nearly all of the old, rotten rubber-covered wiring has been replaced. I have three more paper caps to replace in the 761, plus I need to figure out what is missing in the coupling between the actual tuning shaft and the shaft inside the chassis which controls the permeability tuning assembly.

RE: 42-761EZ Chassis Restoration - Ron Ramirez - 01-31-2013

Progress report, or lack thereof:

Okay, so I had three rubber-covered wires left. All three went to the front wafer of the band switch assembly.

Knowing there was no access to the terminals of the front wafer with a soldering gun or iron as the space was too tight in there, I decided to try my luck at something I have done previously, and that is to carefully peel off the old rubber insulation from each wire, and then slip on an appropriate length of heat shrink tubing.

All went as it should on the first wire, which leads from the high end of the phono input to the front switch wafer (A5).

Ditto the second wire, which is the antenna lead-in (A1).

You can already guess where this is going...after removing about 3/4 of the old rotten insulation, the third wire broke off at the switch wafer (A4).

There is no way I can see that a soldering iron can get to the terminal.

The third wire carries the phonograph signal from the band switch to the volume control circuit.

As I do not intend to ever use the phono input, I'm tempted to just leave that wire off rather than try to fight with it and and end up damaging something else. After all, these Tropic sets don't exactly grow on trees. It isn't like damaging a part in a Philco 90 as there are plenty of junk parts available for those. Not so with a 42-761.

Your thoughts, please? What would you do in a similar situation?

RE: 42-761EZ Chassis Restoration - Eliot Ness - 02-01-2013

Without looking at it it's hard to say. While it's not a big deal to lose the phono input it would be nice if were there, just because it's supposed to be there. Personally I could live with it, although I might loose a few milliseconds of sleep every other leap year on groundhog day Icon_e_wink

You've seen it up close and personal, think about it, look at it a couple of more times, and if you can't figure out a way to attach the wire and if you can live with it, then as Mr. McCartney sang, Let It Be.

RE: 42-761EZ Chassis Restoration - Chuck Schwark - 02-01-2013

A slim soldering pencil won't get in there far enough?
Ty-wrapped to a dowel rod for extension reach?
I know the "jungle" in this type of construction (sic),
and the collateral damage that can be caused.
I feel for you man...

Number Two

RE: 42-761EZ Chassis Restoration - codefox1 - 02-01-2013

I've resorted to using several hemostats to pull everything else out of the way, and pieces of thin tile or whatever I had laying about to clear a path and minimize chance of collateral damage.

Then deoxit and pre flux switch terminal, and use thinnest pencil you have with a dimmer to get just enough heat to tack on newly tinned wire (if not enough room to wrap properly.)

Your hands and eyes are younger than mine, so you should not have a problem.

RE: 42-761EZ Chassis Restoration - Ron Ramirez - 02-01-2013

The following four photos will hopefully illustrate what I am up against if I even wanted to replace the wire - which I have decided not to bother with.

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-01_00001_zps42e6a854.jpg]
This photo shows part of the band switch assembly. The yellow arrow labeled "A4" is pointing to terminal A4 on the front wafer, which is difficult to see not only in this photo, but the others to follow. This is the terminal from which the wire came off.

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-01_00002_zps80af04e3.jpg]
Another view of the same area. Here, I am holding a small flat-blade screwdriver; the end of this screwdriver is resting upon terminal A4 which is barely visible. You will notice a coil to the right with a slug in it - this is part of the set's permeability tuning assembly. I removed the clip holding it in place last night only to discover that the slug will not allow the coil to be removed. Therefore I am not going to force the issue. If the coil could be removed and moved out of the way, I *might* be able to reach A4 with a soldering iron.

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-01_00003_zps1ea3f3ab.jpg]
Another view with the end of the small screwdriver resting on A4, which can't even be seen here.

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-01_00004_zps9e12e569.jpg]
I have a dual 15/40 watt Radio Shack pencil soldering iron. It is off and cool here, but you can see that it is too big to fit down in there where it would need to go. It would burn up coil (6), the "band spread" antenna coil, before it ever reached A4 - and, besides, the tip is too short to reach A4 anyway due to the cramped quarters here.

Eliot Ness Wrote:Personally I could live with it, although I might loose a few milliseconds of sleep every other leap year on groundhog day Icon_e_wink

I agree 100% with John's (Eliot's) assessment of the situation, and I have made an executive decision to let it be.

Let it be, let it be, let it be, yeah, let it be,
Whisper words of wisdom, let it be.

RE: 42-761EZ Chassis Restoration - codefox1 - 02-01-2013

Aye, does anyone remember the model where by you had to drill a hole into the fender to change a spark plug, or something like that? Probably a Ford, but just can't recall.

RE: 42-761EZ Chassis Restoration - brownie45 - 02-01-2013

My bro. had to cut a 6 inch hole in the inner fender to replace a
heater motor on his '74 Ford sta. wagon. An '84 olds which I had
was a 305---had to take the right wheel off to get the front 2
spark plugs changed. At least it didn't have a tuning coil to
avoid getting hot.
I believe my Weller "hot rod" would be small enough to get in there.
It has a 1/4 inch dia. "nose" about 5 inches long. Jim

RE: 42-761EZ Chassis Restoration - Arran - 02-01-2013

How hard would it be to remove the long screw and the rod running through the band switch on that side? I was just thinking if you could remove that rod nearest to A4 it would give a lot more leeway to get at A4 with an iron and tools.
Regards
Arran

RE: 42-761EZ Chassis Restoration - Ron Ramirez - 02-02-2013

Thanks for the idea, Arran - but it doesn't look possible.

Meanwhile, my LED bulbs were scheduled to arrive on Monday (4th) - they arrived today! Icon_biggrin

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-02_00002_zpsbd120eaf.jpg]

I quickly rebuilt the dial lamp and attached a power cord. Installed one of the two 120 volt LED lamps, and tried the radio out with most of the tubes removed since I am still waiting on the new electrolytics:

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-02_00004_zps49e85509.jpg]

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-02_00003_zps4c681522.jpg]

It isn't real bright. The previous two photos, as well as the next three, were taken with the lights out in the room and only a little bit of light coming in from the window off to the right of the photos. The camera automatically compensated for the low light, so it looks like more light is in the room than there is. (Edit: The camera's compensating for low light also makes the LED lamp look much brighter than it really is.)

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-02_00005_zpsfb29937d.jpg]
AM or "broadcast" band (band 1)

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-02_00007_zpsc6ba79b0.jpg]
2.3 to 7 mc SW (band 2)

[Image: http://www.philcoradio.com/images/phorum/42-761/2013-02-02_00006_zps704153e6.jpg]
25 meters (band 5)

You can just see that each band is illuminated, but barely.

I might just leave it in place and try it inside the cabinet once the electrolytics arrive and I install them and (hopefully) get this set going. If I don't like how the LED light looks with the set in the cabinet, I'll convert it back to use the 14 volt lamp.

RE: 42-761EZ Chassis Restoration - Ron Ramirez - 02-02-2013

Tonight I attached new wires to the 2nd IF transformer, cleaned and polished its aluminum housing, and reinstalled it. I still have to take care of the 1st IF as well.

Hopefully, once the electrolytics and power resistors arrive, I'll be hearing some sound from this set.

I still need to figure out the tuning mechanism. I'll post a photo of it tomorrow.