My Predicta crapped out

[madlabs]

Originally Posted by Kevin Kuehn

For what it's worth your L22(Philco 32-4754-3) crosses to Thordarson HS-16.

https://www.ebay.com/itm/23403929297...IAAOSwy9pguZCy

Originally Posted by Yamamaya42

oddly enough
that is exactly the same part that they are selling in the link I posted above from Talon!
Item #
COIL152
Other Part Numbers
GE WT36X402 RCA 111380
and they have 3!
not so hard to find after all!

I guess not! And thanks for the link. This really is the place for old TV's.

[Tube TV]

Originally Posted by old_coot88

If you can find the break in that coil, there's a neat method of stripping hair-fine wire without mechanically abrading it, called the 'aspirin trick'. No lie, it really works. Put an aspirin tablet on something like a jar lid. Use a soldering iron (or gun) to heat the aspirin so it forms a puddle. Dip the end of the wire in it, and the hot acetacylic acid strips it clean. The fumes are gawdawful, so use plenty of ventilation.

Never heard of that one before. Thanks for the tip.

Originally Posted by madlabs

Took a break from tile and fired up the set. It looks really good. So I am of a mind to leave it alone. And I have the sub part coming so if it becomes a problem I am ready.

One question I have, is if I am going to run it shorted would it be better to tack a resistor instead of a wire to short out the coil? I just want to make sure that too much current isn't flowing.

Again, thanks. I'm gonna have a beer and watch Honey West later.

Good to hear you found out what the probem was madlabs. I doubt you have much to worry about with overcurrent, but you could put a low ohm small resistor in there and try it.

[old_coot88]

Originally Posted by madlabs

One question I have, is if I am going to run it shorted would it be better to tack a resistor instead of a wire to short out the coil? I just want to make sure that too much current isn't flowing.

There's already that 15K resistor in series with it which limits current (plate load resistor R62). There'd be no advantage in adding another resistor.

[madlabs]

Well, it is indeed working. Instead of beer I had some slivovitz and watched 5 episodes of Honey West. The set is working great. So I will emulate Madman Muntz and just leave the coil shorted.

Duh, of course there is a 15k resistor in series so a low ohm resistor wouldn't change anything. Sorry old_coot, I should have looked at the schematic and engaged my brain before posting.

While I have it out I am going to play around with the sound. I started running it through the stereo because it was buzzy. I will start by redoing the fine tuning/ audio inductor adjustment. I didn't have my plastic diddle sticks with me. I will bring them next week.

[Tom9589]

This reply is slightly OT, but it might explain the repeated failures of this coil. I had to replace over the years all four speakers in my Suburban. Every time it was the same fault. The wire coming from one side of the voice coil broke at the point of connection to a larger wire. The person assembling the speaker obviously didn't know of old_coot88's trick with the aspirin. I suspect that the assembler was using a sharp (dull?) blade to scrape the annealing off of the wire and damaged the fine wire in the process.

I finally gave up on GM speakers and switched brands. No more problems.

[Electronic M]

Originally Posted by Tom9589

This reply is slightly OT, but it might explain the repeated failures of this coil. I had to replace over the years all four speakers in my Suburban. Every time it was the same fault. The wire coming from one side of the voice coil broke at the point of connection to a larger wire. The person assembling the speaker obviously didn't know of old_coot88's trick with the aspirin. I suspect that the assembler was using a sharp (dull?) blade to scrape the annealing off of the wire and damaged the fine wire in the process.

I finally gave up on GM speakers and switched brands. No more problems.

In my suburban the cone suspension foam rotted too...I saw $80 a pop for OEM replacements and indignantly hard passed on OEM.

[old_coot88]

Originally Posted by madlabs

The set is working great. So I will emulate Madman Muntz and just leave the coil shorted.

The coil and its paralleled cap were probably intended to stabilize the circuit against thermal drift. So when the set is warmed up good, you might wanta watch whether the H lock point is drifting off (or not).

[Yamamaya42]

Originally Posted by old_coot88

The coil and its paralleled cap were probably intended to stabilize the circuit against thermal drift. So when the set is warmed up good, you might wanta watch whether the H lock point is drifting off (or not).

exactly, it was put there for a reason, AND you can get one to replace it, so it makes no sense not to put one back in IMOH.

[madlabs]

Well, I watched it for 4 hours and it was rock solid. When the replacement part comes I will look at piggy backing it as old_coot88 suggested. The thing with the Predicta board is 28 wires plus the ground stakes make it difficult to remove. It isn't just the hassle, removing the ground stakes really heats up the board and it is hard to remove it once un-soldered without twisting the board. So it is fairly invasive surgery and all surgery has risks. So unless I cannot get satisfactory performance without the coil or with the coil piggy backed I am reluctant to pull the board.

Next week I am going to try to improve the sound. If it turns out that requires removing the board I will do so. It really isn't laziness, it is risk VS gain.

[Tom9589]

Tom C., I had rotted suspension rings as well. I found a company in the Tampa area which sold replacement rings. Very easy to repair with good results. I even replaced the ring on the big sub-woofer in the very back. It's a 2 ohm speaker with a very high price tag.