Vertical problems on PTK195
 

Occassionally I have PTK195 lightbox come in with coolant slop on the
front most PCB where vertical circuit & micro are. Usually a wash and
check of components fixes these after several rounds.

Except this one is resisting me. BTW this particular is P56830xxyyy

Every components are checked, cleaned if required and replaced: diode,
caps, and 8 pin SIP reistor pack and vertical IC.

Every time the vertical is turned on or replaced, The 26V side
vertical amp stage dies slowly in several seconds but the ground side
of vertical amp stage is working, giving noisy 3" band of raster in
middle. No overheating or blowing craters.

RCA uses TDA8172 IC between 26V supply and ground with 15V feeding
through IC's output via vertical yoke winding. Voltages are there and
15V starts good then unloads to around floating 22V as deflection
slowly collapses. So waveforms looks like a flat waveform with small
pips for retrace and a ramp sloping down from 15V mid-point to ground.

BTW, 26V is there at vertical IC, no noise either.

Cheers, Wizard

Vertical problems on PTK195
 

Missed some spillage or corrosion on the board there Jason. Cleaning and
restoring these after the glycol seeps into the boards can be a real
challenge. I'll bet some of the glue under smd components have become
contiminated as a result. Going to take a bit more inspection and cleaning
to restore the beastie.

"Jason D." wrote in message
...
Occassionally I have PTK195 lightbox come in with coolant slop on the
front most PCB where vertical circuit & micro are. Usually a wash and
check of components fixes these after several rounds.

Except this one is resisting me. BTW this particular is P56830xxyyy

Every components are checked, cleaned if required and replaced: diode,
caps, and 8 pin SIP reistor pack and vertical IC.

Every time the vertical is turned on or replaced, The 26V side
vertical amp stage dies slowly in several seconds but the ground side
of vertical amp stage is working, giving noisy 3" band of raster in
middle. No overheating or blowing craters.

RCA uses TDA8172 IC between 26V supply and ground with 15V feeding
through IC's output via vertical yoke winding. Voltages are there and
15V starts good then unloads to around floating 22V as deflection
slowly collapses. So waveforms looks like a flat waveform with small
pips for retrace and a ramp sloping down from 15V mid-point to ground.

BTW, 26V is there at vertical IC, no noise either.

Cheers, Wizard

Vertical problems on PTK195
 

Sometimes you have to take out the Micro / EPROM and chipper socket
just to be 100 percent sure.
Isn't that vertical IC feed with dual V+ ,one from the fly.
Diode and small resistor I got caught once now I change em when I see em.
Dont even check them just replace them.

kip

"Papa_J" wrote in message
...
Missed some spillage or corrosion on the board there Jason. Cleaning and
restoring these after the glycol seeps into the boards can be a real
challenge. I'll bet some of the glue under smd components have become
contiminated as a result. Going to take a bit more inspection and cleaning
to restore the beastie.

"Jason D." wrote in message
...
Occassionally I have PTK195 lightbox come in with coolant slop on the
front most PCB where vertical circuit & micro are. Usually a wash and
check of components fixes these after several rounds.

Except this one is resisting me. BTW this particular is P56830xxyyy

Every components are checked, cleaned if required and replaced: diode,
caps, and 8 pin SIP reistor pack and vertical IC.

Every time the vertical is turned on or replaced, The 26V side
vertical amp stage dies slowly in several seconds but the ground side
of vertical amp stage is working, giving noisy 3" band of raster in
middle. No overheating or blowing craters.

RCA uses TDA8172 IC between 26V supply and ground with 15V feeding
through IC's output via vertical yoke winding. Voltages are there and
15V starts good then unloads to around floating 22V as deflection
slowly collapses. So waveforms looks like a flat waveform with small
pips for retrace and a ramp sloping down from 15V mid-point to ground.

BTW, 26V is there at vertical IC, no noise either.

Cheers, Wizard

Vertical problems on PTK195
 

On Sat, 13 May 2006 10:47:27 -0400, "kip" wrote:

Sometimes you have to take out the Micro / EPROM and chipper socket
just to be 100 percent sure.
Isn't that vertical IC feed with dual V+ ,one from the fly.
Diode and small resistor I got caught once now I change em when I see em.
Dont even check them just replace them.

kip

26V and 13V comes from fly via two diodes. Does this help?

Vertical only get one feed, 26V, the 13V is fed through yoke winding
to the vertical IC output as midpoint between 26V and ground. Been
this way since CTC17x even eariler through ATC113.

To others, The only one SMD is capacitor for vertical circuit itself,
already replaced with another and through cleaning. The other SMD
items is only for feedback pulses back to the chassis.

I'm very certain that coolant did not leak onto component side because
the holes were shut with original solder and did careful check just in
case. Previous one had few open holes and got some on solder side.

Washing goes like this: HOT tap water (nearly 70C) TSP then rinse then
hot water & oxiclean, rinse throughly, then alochol drenching for
assisting drying. Then dried carefully with heat gun. Yes did both
sides. Done two before with success. That's for only 4" band along
front area where coolant tend to hit anywhere; audio amp, micro,
pincushion and vertical circuits.

Cheers, Wizard

Vertical problems on PTK195
 

Just for the heck of it pull out the chipper socket
the last one that got me puzzled had corrosion only
visible when removed.
kip

"Jason D." wrote in message
...
On Sat, 13 May 2006 10:47:27 -0400, "kip" wrote:

Sometimes you have to take out the Micro / EPROM and chipper socket
just to be 100 percent sure.
Isn't that vertical IC feed with dual V+ ,one from the fly.
Diode and small resistor I got caught once now I change em when I see em.
Dont even check them just replace them.

kip

26V and 13V comes from fly via two diodes. Does this help?

Vertical only get one feed, 26V, the 13V is fed through yoke winding
to the vertical IC output as midpoint between 26V and ground. Been
this way since CTC17x even eariler through ATC113.

To others, The only one SMD is capacitor for vertical circuit itself,
already replaced with another and through cleaning. The other SMD
items is only for feedback pulses back to the chassis.

I'm very certain that coolant did not leak onto component side because
the holes were shut with original solder and did careful check just in
case. Previous one had few open holes and got some on solder side.

Washing goes like this: HOT tap water (nearly 70C) TSP then rinse then
hot water & oxiclean, rinse throughly, then alochol drenching for
assisting drying. Then dried carefully with heat gun. Yes did both
sides. Done two before with success. That's for only 4" band along
front area where coolant tend to hit anywhere; audio amp, micro,
pincushion and vertical circuits.

Cheers, Wizard

Vertical problems on PTK195
 

Washing goes like this: HOT tap water (nearly 70C) TSP then rinse then
hot water & oxiclean, rinse throughly, then alochol drenching for
assisting drying. Then dried carefully with heat gun. Yes did both
sides. Done two before with success. That's for only 4" band along
front area where coolant tend to hit anywhere; audio amp, micro,
pincushion and vertical circuits.

Cheers, Wizard

I was told by the RCA rep to use an ammonia based cleaner like Windex for
the first wash as ammonia breaks up the glycol coolant. Have done many that
way, windex, followed by water/tsp, then distilled water rinse and alcohol
to aid drying. I reccomend some compressed air, make sure to blow out from
under connectors /components. If the fluid has been on there a while be sure
to check for corrosion underneath components, had that problem before on a
Samsung with fluid problems. Cleaned it and the HOT kept failing, the drive
transformer had conductive goo underneath it.

Jammy

Vertical problems on PTK195
 

I was told by the RCA rep to use an ammonia based cleaner like Windex for
the first wash as ammonia breaks up the glycol coolant. Have done many that
way, windex, followed by water/tsp, then distilled water rinse and alcohol
to aid drying. I reccomend some compressed air, make sure to blow out from
under connectors /components. If the fluid has been on there a while be sure
to check for corrosion underneath components, had that problem before on a
Samsung with fluid problems. Cleaned it and the HOT kept failing, the drive
transformer had conductive goo underneath it.

Jammy

Been there many times I have seen coolant corrode components leads in
two. Got this fixed too. This latest 195 got me really stumped!!

Cheers, Wizard