Dead neck HG problem

[ram]

When installing a toaster in my neck position the HG seems to have been damaged. It was working before I took it out. Nothing on the ohm meter after. I had to swap the toaster and HG back-plate as one of the threaded holes on the toaster was stripped. I was careful but maybe not careful enough. I tried soldering the terminals the wires connect to; and when the one on the corner was heated the meter swung up to about 9K ohms as would be expected. When it cooled the reading went back to zero. So looking at the pickup inside the bobbin just above the solder connection there is a tiny hair wire kind of sticking out. If I put the probe on that and to other on the center wire I see the meter swing back to about 9K again.

So do I have any options here other than to send it off to someone to fix? Would that even be worth it? A new HG goes for about $75 at the Ric boutique. This one is from a 1974 4001. Any thoughts or notions?

[johnallg]

Sounds like the coil wire broke. Your seeing and having access to the wire is hopeful. Yes it is worth fixing this - it IS a 70s higain! (My favorites) If you don't feel up to trying to fix this I could take a look at it for you.

[jps]

This could be a MARF IV workshop subject!

[ram]

What would constitute fixing it? I mean do I just lift the wisker wire a little, put a blob of solder on it while attaching the lead wire... then potting it with RTV??? Is there any preferred methodology?

[paologregorio]

Be very careful; I can't remember if the corner wire is the negaive terminal wire, but if it is, overheating the wire leads to it de-soldering internally, or something like that, where the it connects with the windings, and then the pickup would need a rewind.

[analogpackrat]

On the RTV thing--I wouldn't do it. But if you do, you need to avoid any product that outgasses acetic acid as it cures. Most of the stuff you can buy will and acetic acid fumes will not do nice things to electronic parts. The only product I know of that does not and is commonly available at Home Depot, Lowes, etc. is "GE Silicone II." Anything else is probably going to cause problems.

[ram]

RTV was more a figure of speach... that's what we pott connectors with (among other things) where I work. Silicone would be my gook of choice. Anyhow - so my premis of a little blob of solder at the bobin, bridiging the wisker and the lead wire is OK? Then to pott it with Si to take the strain off the little wire? This is a or the way to do it? I can't remember but I think the corner wire (the one I am talking about) isn't the GND but I will need to look when I get home.

[johnallg]

Tom, can you take a clear closeup pic of the trouble area so we can see exactly what you mean?

[ram]

I'll try but it is tough to see in real life - I used an aid.... my wife said I look like Jr Sherlock Holms... I'll see what I can come up with.

[ram]

OK this is the best I could do with the resources at hand. The hair wire is just to the right of the white spec at the lower corner of the lower plate. You can see a little copper color on the upper lip of the lower plate (just above white insulation on the wire in the fore ground) - that's about it. Hope this helps... let me know and I'll attempt some more if not.

[johnallg]

I can't really see the copper, but something like that should be repairable without losing too many windings. Let me know if you want an assist.

[ram]

Yeah the picture stinks - in real life I have to us a magnifying glass to see it real well (it’s a really fine little wire).

So what is the procedure here? I have never done anything like this before but am willing to try. An assist would be appreciated.

[johnallg]

Yeah the picture stinks - in real life I have to us a magnifying glass to see it real well (it’s a really fine little wire).

So what is the procedure here? I have never done anything like this before but am willing to try. An assist would be appreciated.

By assist I meant send it to me and I will try the solution. Price is right.

This looks like an earlier one than the current molded ones. I have not opened up a coil on this type. On the newer ones, you take the black electrical tape off, find the tiny copper wire end hopefully still soldered to the black wire through a hole in the plastic coil form, and start carefully unwinding until you come to the break, hoping it is only a little bit (couple hundred turns or less), then when you get to that tiny (#44) wire you presently see, you solder it back to the black leadout wire removed earlier and then support that wire like it had been and retape the outside of the coil. When your done you hopefully still get a reading above 8k and not an open.

[ram]

Wow John! That is totally nice of you! Thanks! I'll PM shortly.

[johnallg]

Glad to say the repair was an easy one. Odd construction in the way the coil wire was attached - not sure if it was factory or later repair. It is working now, finished off like present higains, and still has a 8.31k reading.