Zenith Z35X21D Power Supply
 

This set came in with a blown fuse and a badly burned RX3406. QX3401 was
also shorted, but nothing else appeared out of order. I replaced the
transistors with an NTE type, and took a guess on the value of the resistor,
using a 4.7 ohm fusible. Got nothing but a puff of smoke when I plugged it
in. Redid the power supply but used a 47 ohm resistor instead, with the same
results. It appears that the power supply simply will not oscillate, and is
instead trying to feed pure DC into the switching transformer resulting in
the shorted condition. I also tried replacing the switching regulator
STR53041, with no luck. There are no shorts on the secondary side of the
power supply (HOT and everything is good) so I know the trouble has to be
the power supply itself.
Can anyone provide me with the correct value of RX3406? Also, is it
critical that QX3401 be replaced with an exact part # (2N4923)?
I should also point out that the two small 'lytics in the supply were
checked, one was replaced.
Any help would be much appreciated.

Does anyone have a service manual for this thing? The power supply area is
all I need.

"Chris F." wrote in message
...
This set came in with a blown fuse and a badly burned RX3406. QX3401 was
also shorted, but nothing else appeared out of order. I replaced the
transistors with an NTE type, and took a guess on the value of the
resistor,
using a 4.7 ohm fusible. Got nothing but a puff of smoke when I plugged it
in. Redid the power supply but used a 47 ohm resistor instead, with the
same
results. It appears that the power supply simply will not oscillate, and
is
instead trying to feed pure DC into the switching transformer resulting in
the shorted condition. I also tried replacing the switching regulator
STR53041, with no luck. There are no shorts on the secondary side of the
power supply (HOT and everything is good) so I know the trouble has to be
the power supply itself.
Can anyone provide me with the correct value of RX3406? Also, is it
critical that QX3401 be replaced with an exact part # (2N4923)?
I should also point out that the two small 'lytics in the supply were
checked, one was replaced.
Any help would be much appreciated.

Chris...

Change these
STR53041
CX3413 22mfd/63v
CX3416 100mfd/63V
RX3404 180K ohm
RX3407 47ohm
RX3408 22ohm
QX3401 NTE184
RX3406 47ohm

I carry these as a kit on the truck change em all..

kip

"Chris F." wrote in message
...
Does anyone have a service manual for this thing? The power supply area is
all I need.

"Chris F." wrote in message
...
This set came in with a blown fuse and a badly burned RX3406. QX3401
was
also shorted, but nothing else appeared out of order. I replaced the
transistors with an NTE type, and took a guess on the value of the
resistor,
using a 4.7 ohm fusible. Got nothing but a puff of smoke when I plugged
it
in. Redid the power supply but used a 47 ohm resistor instead, with the
same
results. It appears that the power supply simply will not oscillate, and
is
instead trying to feed pure DC into the switching transformer resulting
in
the shorted condition. I also tried replacing the switching regulator
STR53041, with no luck. There are no shorts on the secondary side of the
power supply (HOT and everything is good) so I know the trouble has to be
the power supply itself.
Can anyone provide me with the correct value of RX3406? Also, is it
critical that QX3401 be replaced with an exact part # (2N4923)?
I should also point out that the two small 'lytics in the supply were
checked, one was replaced.
Any help would be much appreciated.

Zenith Z35X21D Power Supply
 

kip;1297139 Wrote:
Chris...

Change these
STR53041
CX3413 22mfd/63v
CX3416 100mfd/63V
RX3404 180K ohm
RX3407 47ohm
RX3408 22ohm
QX3401 NTE184
RX3406 47ohm

I carry these as a kit on the truck change em all..

kip
Kip
I have this exact same set with this problem. I cannot make out the
original transistor qx3401 and it is shorted. It appears to me thoguht
that the board is silkscreened backwards. BEC is wrong if this
transistor has the same pinout as the NTE184.
can you verify orientation of the transistor?


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Zenith Z35X21D Power Supply
 

I cannot make out the
original transistor qx3401 and it is shorted. It appears to me thoguht
that the board is silkscreened backwards.

Most of these boards are screened wrong.

Here's the way it should be from the front of the chassis to the rear:

E-C-B

The OEM number is: 121-01348, which is probably NLA from LG.

Hope this helps.

David, on the Illinois prairie.

Zenith Z35X21D Power Supply
 

yep
thanks. replaced the parts on KIPs list
It works now.
Thanks for the advice


--
Joustman
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