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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.

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

resistor,

same

is

Reply to
Chris F.

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

Reply to
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?

--
Joustman
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Reply to
Joustman

I cannot make out the

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.

Reply to
dharrisfc

yep

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

-- Joustman

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