Pointers to repair info for Sony 68cm TV?

[Clifford Heath]

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.

 

[Clifford Heath]

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.

 

[Franc Zabkar]

On Sat, 19 Mar 2005 12:52:44 +1100, Clifford Heath
<no@spam.please.net> put finger to keyboard and composed:

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.

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
--
Please remove one 's' from my address when replying by email.

 

[Clifford Heath]

Franc Zabkar wrote:

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.

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.

 

[Phil Allison]

"Clifford Heath"

Thanks Frank, my son must have been mistaken about the flicker.
Further investigation shows the HOT is blown, 2SC4927.

** WES sell the 2SC4927.

Have fun destroying it.



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

 

[Clifford Heath]

Phil Allison wrote:

** WES sell the 2SC4927.

Thanks.

Have fun destroying it.

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

 

[Franc Zabkar]

On Mon, 28 Mar 2005 15:07:38 +1000, Clifford Heath
<no@spam.please.net> put finger to keyboard and composed:

Franc Zabkar wrote:
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.

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?

WES Components list both in their catalogue.

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?

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

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.

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
--
Please remove one 's' from my address when replying by email.