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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Lenny
 
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Default Zenith Z25A11S tuner replacement

The original problem with this set was that it would not find any
channels when autoprogram was selected. There was OSD but no raster.
On video mode the external audio came through but the video did not. I
removed the tuner from the set and confirmed proper operation in AV
mode, so it does appear that the tuner was bad, locking up the set,
one or the other, or both. Not sure. I suggested to the customer that
they could just leave it as a video monitor but they want it fully
repaired. Go figure!
Anyway, the original tuner was a 175-2721. I pulled a 175-2701 which
David had mentioned as being a variant, (don't know what he meant by
that,) from a working set and tried it in this one and I found that it
would not work in this set.
Does anyone know if these two tuners are interchangeable? The 2701 out
of the other model working chassis came up in this chassis with
symptoms as a tuner with a bad mixer stage. I got a snowy raster with
a hint of signal information in the background, with no tuning
function and it would not find any channels on autoprogram, but the
set did have working AV inputs with this one.
Thinking perhaps I may have damaged the good tuner in swapping it, I
put the 2701 back into the set it came out of just to be certain it
had not died and noted that that set still works ok. Now, should a
known good 2701 have worked ok in the Z25A11S chassis?
Mat has the original 2721's on special for 17.95 but will I have the
same problem in replacing this tuner with an exact same part? I'm
assuming also that as David had mentioned this same part number would
not be an updated tuner designed to deal with the design flaw in this
set.
In any case, given that the known good 2701 tuner would not work in
this chassis, now I'm wondering if I may have other problems besides.
Can anyone please tell me what the part number is for the updated
tuner for this Z25A11S set? Also I can't seem to find any information
on the 5 volt line modification that needs to be done to correct the
corrupted data problem that David also mentioned. Will I need a
schematic for this?
Many thanks again. Lenny stein, Barlen Electronics.
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David
 
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Default Zenith Z25A11S tuner replacement

The 2721 was the updated tuner, but if the 5v line modification was not
performed it will fail again.

Measure the 5v line going to the tuner with the tuner installed and you will
find it running low.
There is a resistor change for the 2721 tuner on the 5v line.

There is also the chance there is another problem on the board, but I would
bet the 5v line was simply being pulled to low by the older tuner.

David

Lenny wrote in message
om...
The original problem with this set was that it would not find any
channels when autoprogram was selected. There was OSD but no raster.
On video mode the external audio came through but the video did not. I
removed the tuner from the set and confirmed proper operation in AV
mode, so it does appear that the tuner was bad, locking up the set,
one or the other, or both. Not sure. I suggested to the customer that
they could just leave it as a video monitor but they want it fully
repaired. Go figure!
Anyway, the original tuner was a 175-2721. I pulled a 175-2701 which
David had mentioned as being a variant, (don't know what he meant by
that,) from a working set and tried it in this one and I found that it
would not work in this set.
Does anyone know if these two tuners are interchangeable? The 2701 out
of the other model working chassis came up in this chassis with
symptoms as a tuner with a bad mixer stage. I got a snowy raster with
a hint of signal information in the background, with no tuning
function and it would not find any channels on autoprogram, but the
set did have working AV inputs with this one.
Thinking perhaps I may have damaged the good tuner in swapping it, I
put the 2701 back into the set it came out of just to be certain it
had not died and noted that that set still works ok. Now, should a
known good 2701 have worked ok in the Z25A11S chassis?
Mat has the original 2721's on special for 17.95 but will I have the
same problem in replacing this tuner with an exact same part? I'm
assuming also that as David had mentioned this same part number would
not be an updated tuner designed to deal with the design flaw in this
set.
In any case, given that the known good 2701 tuner would not work in
this chassis, now I'm wondering if I may have other problems besides.
Can anyone please tell me what the part number is for the updated
tuner for this Z25A11S set? Also I can't seem to find any information
on the 5 volt line modification that needs to be done to correct the
corrupted data problem that David also mentioned. Will I need a
schematic for this?
Many thanks again. Lenny stein, Barlen Electronics.



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Default Zenith Z25A11S tuner replacement

On Wednesday, 31 December 2003 15:41:19 UTC-8, David wrote:
The 2721 was the updated tuner, but if the 5v line modification was not
performed it will fail again.

Measure the 5v line going to the tuner with the tuner installed and you will
find it running low.
There is a resistor change for the 2721 tuner on the 5v line.

There is also the chance there is another problem on the board, but I would
bet the 5v line was simply being pulled to low by the older tuner.

David

Lenny wrote in message
om...
The original problem with this set was that it would not find any
channels when autoprogram was selected. There was OSD but no raster.
On video mode the external audio came through but the video did not. I
removed the tuner from the set and confirmed proper operation in AV
mode, so it does appear that the tuner was bad, locking up the set,
one or the other, or both. Not sure. I suggested to the customer that
they could just leave it as a video monitor but they want it fully
repaired. Go figure!
Anyway, the original tuner was a 175-2721. I pulled a 175-2701 which
David had mentioned as being a variant, (don't know what he meant by
that,) from a working set and tried it in this one and I found that it
would not work in this set.
Does anyone know if these two tuners are interchangeable? The 2701 out
of the other model working chassis came up in this chassis with
symptoms as a tuner with a bad mixer stage. I got a snowy raster with
a hint of signal information in the background, with no tuning
function and it would not find any channels on autoprogram, but the
set did have working AV inputs with this one.
Thinking perhaps I may have damaged the good tuner in swapping it, I
put the 2701 back into the set it came out of just to be certain it
had not died and noted that that set still works ok. Now, should a
known good 2701 have worked ok in the Z25A11S chassis?
Mat has the original 2721's on special for 17.95 but will I have the
same problem in replacing this tuner with an exact same part? I'm
assuming also that as David had mentioned this same part number would
not be an updated tuner designed to deal with the design flaw in this
set.
In any case, given that the known good 2701 tuner would not work in
this chassis, now I'm wondering if I may have other problems besides.
Can anyone please tell me what the part number is for the updated
tuner for this Z25A11S set? Also I can't seem to find any information
on the 5 volt line modification that needs to be done to correct the
corrupted data problem that David also mentioned. Will I need a
schematic for this?
Many thanks again. Lenny stein, Barlen Electronics.







Hello Sir, I need help. I purchased a replacement tuner for Zenith CRT tv. 175-02721 is the tuner number. I installed tuner but nothing is showing. Can you tell me what modification needs to be made to this set for tuner to work? Thanks much.
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