Magnavox RH8524 dead

[Kirk S.]

Got an older projection TV that quit working. Power switch turns set on
however that is it. No sound or picture. It is a NAP PTV300 chassis. I
checked the HOT on the deflection board and it is ok. At this point, I'm
thinking something on the power board is probably gone; perhaps the flyback.
The plastic looks a bit melted and it smelled like burning plastic when the
set quit. There are a number of areas that the manual describes as
*non-servicable*. Since replacement boards aren't readily available nor
cost effective, how can I determine the flyback number and once it is
replaced, adequately set the HV?

The crt coupling/cooling fluid also will probably require changing. How
difficult is it to realign the set? Any "tricks of the trade". The
deflection board is a later model and not covered in the service manual. It
is a B10326 and the service manual indicates that this version of the board
was used in the larger (56" vs 41") sets.

Thanks for any and all help offered...

Kirk S.

 

[Bill S.]

There are a number of areas that the manual describes as
*non-servicable*.

Translation: we're not going to tell you what it is because
we want to control the repair/replacement market.

Since replacement boards aren't readily available nor
cost effective, how can I determine the flyback number and once
it is replaced, adequately set the HV?

I pulled the number 362140-1 off a junk board, which crosses to
new number 483514067162. If memory serves, this is the later
version transformer, so hopefully will be the same one you have.
The early version transformers had a screw-on HV lead that came
off at an angle, were all junk, and are not available, thank God.

I've had good luck adjusting RP2 (remove the can to get at it) for
about 180~190 Volts at TP14. I've never seen any sets, even new,
go as high as the 210 the schematic shows. Expect about 110 Volts
on the emitter of Q14 regulator (the big power resistor is a
convenient test point).

The crt coupling/cooling fluid also will probably require changing.
How difficult is it to realign the set? Any "tricks of the trade".

Some folks like to suck the fluid out and clean without pulling
the tubes from the frame, others get all huffy about this idea,
but there are no boards under the tubes to drip on in these old
sets, so it's a significant labor saver.

Fluid change doesn't usually affect convergence beyond what the
user (static) controls can compensate, but of course these sets
were a bit drifty anyway, so may need a bit of touch-up.
Fortunately, the controls mostly do what they say. The problem
is that you can't see the screen very well when you are close
enough to turn the pots. Unless you have a 10 foot screwdriver,
there's nothing for it but to go back and forth as long as it takes.

Reasonable color balance can often be restored by only tweaking
the blue screen control, since the blue tube is driven hardest,
burns out fastest, and grows the most crud. I've found that if
you have to start from scratch, the procedure in the manual almost
works, except that if you do things their way you always end up too
dark. So after doing the jumper thing and setting the screen controls,
give them all an equal sizable nudge upward. Then set the cutoffs
and drives.

The deflection board is a later model and not covered in the
service manual. It is a B10326 and the service manual indicates
that this version of the board was used in the larger (56" vs 41")
sets.

That number doesn't come up at all in Philips part seeker, but
A10326 does. Yours may be some kind of universal replacement(?)

 

[Kirk S.]

Bill...

Thanks for the advice and the humor...

Kirk S.

 

[Emilio]

Kirk,

Try this link, it will provide much information on chaning the coolant.

http://www.tv-forums.com/forum/TV_Equipment_C4/Projection_TV_Forum_F24/Chang
ing_CRT_Coolant_P15302/

Emilio