Pointers to repair info for Sony 68cm TV?

How best to find service info for this Sony J29SZ2 TV? I normally don't look at TVs, but if I can fix this, it's mine :-).

Clifford Heath.

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Clifford Heath
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Probably should've described the symptoms. No picture, no EHT, but screen does flicker when you press the degauss button, so I expect at least one of the guns is emitting :-). Power supply seems to be working, at least the 32V rail is there.

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Clifford Heath

On Sat, 19 Mar 2005 12:52:44 +1100, Clifford Heath put finger to keyboard and composed:

If the screen flickers, then EHT must be present, although it may be low. There should be a HT or B+ rail, around 120V or so, usually filtered by a 160V cap. If your "32V" rail is filtered by a 160V cap, then I suspect that the cap itself is O/C or high ESR, or the small caps on the primary side may have dried out.

- Franc Zabkar

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Franc Zabkar

Thanks Frank, my son must have been mistaken about the flicker. Further investigation shows the HOT is blown, 2SC4927. Collector-emitter is 15 ohms one way, 20 the other. Some repair websites recommend a 2SC5148 as a replacement. Where to get these in Australia? Or alternative? 1500V 8A rated, with hFE min of 3.8 at five amps, 2MHz fT and 110pf Cob.

The power supply parts I've tested seem ok, including the transistors which are often affected by the HOT going. The 32V was filtered by a 50V cap, though there is also a 160V rail and cap. There are also supposed to be one or more fusible 0.1ohm resisters - would those be little yellow tubular items? There are two, and they check out ok, well under 1 ohm anyhow.

I'll check more after I get a replacement HOT.

Clifford Heath.

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Clifford Heath

"Clifford Heath"

** WES sell the 2SC4927.

Have fun destroying it.

........... Phil

Reply to
Phil Allison

Thanks.

A likely outcome, I admit :-). I don't have ESR testers etc, so whatever caused the failure is probably still there...

Reply to
Clifford Heath

On Mon, 28 Mar 2005 15:07:38 +1000, Clifford Heath put finger to keyboard and composed:

WES Components list both in their catalogue.

I don't know, but if these are located on either side of a rectifier diode, then I'd say you were right.

I'm not familiar with your Sony chassis, but as a general rule I'd check/replace any small electros on the primary side of the PSU. I'd also change any electro near the HOT's base drive transformer. Resolder the pins of this transformer and also of the FBT. Before replacing the HOT, attach a 240V 100W lamp load to the B+ rail and make sure the voltage is OK. Also check that the tuning cap (~1.5kV, film) is not O/C, as this often results in the immediate failure of the HOT. Finally, ring the FBT to test for shorted turns. Now install the HOT, run the TV for a minute or so, switch it off, and check whether the HOT and/or heatsink is hot to the touch. If it's very hot, then suspect a horizontal drive problem, or the transistor itself. I've had temperature problems with WES transistors in one particular Panasonic chassis. In that case I had to substitute a 2SC1413A, which then ran cool.

- Franc Zabkar

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Franc Zabkar

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