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Discussion Starter · #1 ·
My Samsung RPTV Model: SP62T6HCX/XSG Chassis: J54A

The Set emitted a high pitched whine and would not power up

Noticed a coolant leak from all three tanks

Fixed the coolant leak

The set still emitted a high pitched whine and would not power up

Noticed some coolant leaked on the convergence board

I had an older convergence board which had a green bow from top to bottom

TV turned on with older board and green bow

Decided to replace STK's on older board

The service manual says the rails for the Convergence Board should read +20V / -20V

My set reads +24V / -24V

When I set my meter to AC voltage mode the +24V rail reads 54V
-24 V rail reads 0V

My convergence board does not have any pico fuses

No sign of any burned resistors

I reset all convergence data and have convergence data all under +/- 100 mV

Despite all of this put the new ICs in and they heated up and failed

Also IC's were heating up without the yokes or convergence data being connected.

I tried changing all electrolytic capacitors on the power supply board

Now the +24V rail reads 54V in AC mode
-24V rail reads 54V in AC mode

Now the STK 392-040 ICs are rated +/- 50V max could this be the reason they are blowing?

Any help would be appreciated?
 

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Supplies to the convergence ICs are d.c., not a.c., and are measured relative to chassis ground.

Was the convergence board the same part from the same model?
 

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Discussion Starter · #4 ·
I had a green horizontal bow 2 years ago

Replaced the convergence board with an original Samsung convergence board model BP94-00392A

TV ran fine for two years

The squeal problem (and coolant leak) started a few months ago

No more spares(boards) for these TV's with Samsung so had to go for aftermarket ICs

Replacement IC's were heating up even without connecting deflection yokes or CG data

Similar problem to another thread a build up of charge which discharges when connecting the CG Amp board power connector i.e., +20V/-20V i.e., after powering down the set

The discharge takes place at the +20V terminal ((Hence was curious and measured in AC mode))

TV starts up and runs without CG board or CG board without STKs

When the STKs fail the squeal comes back set shuts down

BP94-00392A seems to have jumpers where the pico fuses should have been

Set is 6 years old
 

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The STKs are not supposed to be run with the yokes disconnected. They normally get hot and will usually fail before long in any set when you do this.

I am not understanding what this discharge is and what terminal you are referring to. There will be residual charges in the set after power down.

The squeal is probably due to a load on the PS.

At this point I am quite confused by your posts and it seems that you are chasing a couple of wild geese. Without more clear descriptions about your observations I cannot make any good suggestions other than to refer the problem to a professional.
 

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Discussion Starter · #6 ·
The discharge is the +20V / -20V power supply connector on the SUB board

When you try to plug in the power supply cable that goes to the CG Amp board you get a discharge on the + 20 V pin which is on the connector on the SUB board. (TV is on standby mode).

Don't wan't to waste more STK IC's if there is another problem related to the SUB board.

Yes the load on the PS is probably the shorted STK ICs but what is causing them to short?

My only reason in posting is if you had an experience that was similar
 

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This discharge is completely normal. The caps in the power supply hold a charge. It will typically dissipate in the circuit over time but if the connector is not in place it may hold a charge longer. The caps should be discharged before making such a connection, as it can cause damage.
 

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Discussion Starter · #8 ·
Thanks!

I went over the Convergence Amp Board BP94-00392A yesterday and found that the low value resistors
RZ123 and RZ 124 and RZ142 and RZ143 (all 3.9 ohms) were open (infinity)

Could this be because the replacement STK ICs were defective?

Strangely all the fusible resistors on the board which suffered the coolant leakage are fine.

Could I try to replace the resistors and try with STK ICs sourced from a better vendor?

I'll attach the Convergence Board Schematic.
 

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The resistors burned because you ran the set with the yokes disconnected. You likely blew the chips as well. I suggest using the vendors recommended in the parts post in the convergence repair sticky.

Posting schematics takes up lots of space. While it is not prohibited, and someone may review them for you, I will not. I cannot give specific troubleshooting advice and review circuits in the forum, only give general information and general advice on common problems. If you wish to post schematics so that others may make use of them, I suggest you put the model number of your set in the subject line.
 
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