Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Dave Moore
 
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Default Rewinding pc coil for 9-1270 Zenith boards ?? anyone know inductance? 9-1270-02 9-1270-3 mod# SR3587DT

Ok here's an update,

I did rewind the coil (ref# LX3201) and while I did,
I measured the length of the wire and compared it to
the length of the wire on the older
Zenith coil p/n# 20-4284-01, and determined that
if you add 7-9 turns to it, it should work as a replacement
for the coil on the 9-1270 board.
Sorry I can't say
the part no# for the coil on the 9-1270 board as the top
of the part with the p/n# is missing.

Anyway, interestingly enough, the rewound origional coil
measured .39mh which was darn close to the 20-4284-01
coil which has approximately 8 less turns wich weighed in at
..38mh. Not surprising since I wound it rather imperfectly
by hand.

Ok, so then I added 8 turns to the 20-4284-01 and
measured it. It measured .48 mh which I'm guessing is
probably what a new coil for the 9-1270 board should
read.

Ok, the results? I put the 20-4284 coil with the additional
8 windings @ .48mh, in the set. The set now works better,
but still not quite right. The coil and the pincushion xstr
both run hot, but possibly acceptably hot. I just don't know.
Uncomfortable to the touch, but not boiling water.
Antone know? Is it the norm for these parts to run fairly
hot in these sets?

Before I reworked the coil, the set would work, but
shut down during bright scenes. Seems to be
overcurrent protect.

Now with the coil reworked, it still shuts down on
some really bright scenes, but it has a very much
obvious improvement in tolerance. In fact it might
run for 15 minutes or more.

I guess I'm going to have to get the schematic on this
one.

Oh, one thing I forgot to mention was,
I replaced the Flyback origionally. I ordered the
part from http://www.slelectronics.net/fl.zenith.htm#

I ordered the origional part p/n# 95-4134-28
and they sent me a 95-4134-11 which they claim
is a valid sub. The part had both numbers on it
and appears to be aftermarket.

I ordered a different flyback from them for a
Zenith PTV awhile back, and it worked just fine,
but they didn't give me a sub in that case.

Anyone have any opinions about whether this supposedly
valid sub could be the problem with this set?

Also.FWIW, I checked out the brightness limiter circuit,
best I could without a schema that is, and it seems to be ok.

Don't mean to go on so, basically I'm just speaking to the
archives here, which is why, as you may have noticed,
I put so many model and board numbers in the title.

Ok thanks.
=^^=DM



"Dave Moore" wrote in message
...
Hello folks.
I came across this article by the great Dave D., about
rewinding these coils, ref.# LX3201

http://groups.google.com/groups?hl=e...6C.A54D88A9%40
locl.net

Being faced with this problem, I have decided to rewind rather than wait.
However, I have a few coils from older Zenith boards that I could just add
a few turns to.

Only, to do this, I need to know the inductance value to shoot for.

Anyone know what the value of this coil is supposed to be?

Thanks
=^^= DM




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John Del
 
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Default Rewinding pc coil for 9-1270 Zenith boards ?? anyone know inductance? 9-1270-02 9-1270-3 mod# SR3587

Subject: Rewinding pc coil for 9-1270 Zenith boards ?? anyone know
inductance? 9-1270-02 9-1270-3 mod# SR3587
From: "Dave Moore"


Now with the coil reworked, it still shuts down on
some really bright scenes, but it has a very much
obvious improvement in tolerance. In fact it might
run for 15 minutes or more.
one.


Oh, one thing I forgot to mention was,
I replaced the Flyback origionally. I ordered the
part from http://www.slelectronics.net/fl.zenith.htm#


Dave, the problem is your replacement generic flyback. Every one I tried did
this, sometimes shutting down as soon as the CRT lit. Basically, one of the
secondary sources off the flyback is too high, I don't remember which one. You
need to fudge this voltage with a dropping resistor, or fudge the shutdown
circuit. The board is actually marked and cut for a shutdown pot that was
never used. It's near the front of the board (away from the flyback). You'll
need a schematic to locate this, but it's an easy mod that will allow the
replacement flys to work properly. BTW, those coils run really hot even when
everything is normal.

John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)
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Dave Moore
 
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Default Rewinding pc coil for 9-1270 Zenith boards ?? anyone know inductance? 9-1270-02 9-1270-3 mod# SR3587


"John Del" wrote in message
...
Subject: Rewinding pc coil for 9-1270 Zenith boards ?? anyone know
inductance? 9-1270-02 9-1270-3 mod# SR3587
From: "Dave Moore"


Now with the coil reworked, it still shuts down on
some really bright scenes, but it has a very much
obvious improvement in tolerance. In fact it might
run for 15 minutes or more.
one.


Oh, one thing I forgot to mention was,
I replaced the Flyback origionally. I ordered the
part from http://www.slelectronics.net/fl.zenith.htm#


Dave, the problem is your replacement generic flyback. Every one I tried

did
this, sometimes shutting down as soon as the CRT lit. Basically, one of

the
secondary sources off the flyback is too high, I don't remember which one.

You
need to fudge this voltage with a dropping resistor, or fudge the shutdown
circuit. The board is actually marked and cut for a shutdown pot that was
never used. It's near the front of the board (away from the flyback).

You'll
need a schematic to locate this, but it's an easy mod that will allow the
replacement flys to work properly. BTW, those coils run really hot even

when
everything is normal.

John Del
Wolcott, CT



Ah, thanks John, I really appreciate the info you gave me,
really took a load off my mind,,, this bugger's really been
eatin da' icing off me cake.

I kinda thought that something like that might be
the case, and is the reason I've been trying to get a schematic.
Ron gave me 3 alternative Models that use this board and Zenith
doesn't have a single one of the schematics for any of them!

You just may have saved me $20 as I was about to pay that much
more for a service manual from http://www.servicemanuals.net/service.asp

Now I can probably knock this one out now and just order the
$13 manual from Zenith for myself and suffer the backorder wait.
I'm willing to wait a month,
but my friend with the tv probably wouldn't. Come to think of it,
I guess you saved him $20 since I woulda just passed the charges
on to him anyway.

I'm pretty sure I can find the unused pot and rig something.

Thanks again
=^^=DM





"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)



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John Del
 
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Default Rewinding pc coil for 9-1270 Zenith boards ?? anyone know inductance? 9-1270-02 9-1270-3 mod# SR3587

Subject: Rewinding pc coil for 9-1270 Zenith boards ?? anyone know
inductance? 9-1270-02 9-1270-3 mod# SR3587
From: "Dave Moore"



Now I can probably knock this one out now and just order the
$13 manual from Zenith for myself and suffer the backorder wait.
I'm willing to wait a month,
but my friend with the tv probably wouldn't. Come to think of it,
I guess you saved him $20 since I woulda just passed the charges
on to him anyway.

I'm pretty sure I can find the unused pot and rig something.

Thanks again
=^^=DM


I remember a diode that you can cut out that will prevent the shutdown
entirely. I'll see if I wrote it down at work. If I can give you the board
location, you can fudge some resistor values (you don't need to add the pot).

John Del
Wolcott, CT

"Nothing is so opportune for tyrants as a people tired of its liberty."
Alan Keyes

(remove S for email reply)
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