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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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RCA PTK195 Random Operation
Got a RCA PTK195 (projection). Set has random behavior, turns itself on/off,
changes channels, etc. as long as front keyboard is plugged in. With keyboard unplugged, set functions OK (remote operation). I've read about some problems with conductive glue under SMD parts on this chassis, is this one of the circuits affected? TIA TVFixer1 |
#2
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RCA PTK195 Random Operation
Check those Tac switches one by one pull them out if you have to.
Maybe dirt or liquid got behind them causing trouble. kip -- "Watch the return E-Mail addy its false" "TV Fixer1" wrote in message ... Got a RCA PTK195 (projection). Set has random behavior, turns itself on/off, changes channels, etc. as long as front keyboard is plugged in. With keyboard unplugged, set functions OK (remote operation). I've read about some problems with conductive glue under SMD parts on this chassis, is this one of the circuits affected? TIA TVFixer1 |
#3
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RCA PTK195 Random Operation
On Tue, 26 Aug 2003 18:36:02 -0400, "john"
wrote: Check those Tac switches one by one pull them out if you have to. Maybe dirt or liquid got behind them causing trouble. kip -- "Watch the return E-Mail addy its false" Alteratively, pull the button circuit board assembly out and clean both sides off (especially if that area is heavy smokers), and replace all six switches, they're inexpensive to buy new switches. These switch panels in RCA is still through hole technology. If other problems, unplug all wires to the Gemstar module and run this way. Otherwise do the mods on the tuner and replace both 22pf SMD on that SCA/SDA I2C lines just inside the tuner and one resistor (marked R6) changed from whatever to 100ohms. Cheers, Wizard |
#4
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RCA PTK195 Random Operation
Wizard !
Is the new resistor 100 ohms or is that the bad value of R6 if so what is the correct value of R6. kip -- "Watch the return E-Mail addy its false" "Jason D." wrote in message ... On Tue, 26 Aug 2003 18:36:02 -0400, "john" wrote: Check those Tac switches one by one pull them out if you have to. Maybe dirt or liquid got behind them causing trouble. kip -- "Watch the return E-Mail addy its false" Alteratively, pull the button circuit board assembly out and clean both sides off (especially if that area is heavy smokers), and replace all six switches, they're inexpensive to buy new switches. These switch panels in RCA is still through hole technology. If other problems, unplug all wires to the Gemstar module and run this way. Otherwise do the mods on the tuner and replace both 22pf SMD on that SCA/SDA I2C lines just inside the tuner and one resistor (marked R6) changed from whatever to 100ohms. Cheers, Wizard |
#5
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RCA PTK195 Random Operation
On Tue, 26 Aug 2003 19:44:02 -0400, "john"
wrote: Wizard ! Is the new resistor 100 ohms or is that the bad value of R6 if so what is the correct value of R6. kip 100 is correct, simply do both 22pF SMD capacitors to keep things easier, both are side to side right by tuner shield, both resistors is connected to this capacitors, then via 2 jumpers then on to the PLL IC. Everything are hidden under the tuner bottom covers. This is for the I2C bus to the tuner PLL. This mostly affects the tuner intermittent snowy w/ loud static noise from speakers because PLL IC get confused by intermittent corrupt I2C and get switched around for a instant. Also there is another resistor, near a ground post, this posts is in a row nearest rear edge, one of them has one end of on that ground island.) that should be 39 ohms not 10. If tuner has one solder point on bottom tin, they has to go. Discard both bottom tin and zinc liner, install both new I-bar and 2 point solder bottom tin. Old style covers was a big pain in butt to work with and liner get damaged every time. Warps & cracks easily from that soldering heat and mechanical stress during removal & installation. The new design is easier to work with. Bulletin says to realign 5 specified channels with tuner covers installed and soldered after that 39 ohm & cover (if required) modification, I simply do whole realignment thing (29 of them). That completes tuner's 3 bulletins. This what I just did just that today spread over two days, I did not want to spend too much time on it there was several things to do that day, alignment was done following day without incident. :-) Oh yes, that was paid for everything by owner and that set was out of warrenty. This stuff applies only to xxx195 and CTC197 I'll post more details with notes next day. Very tired tonight and been eyeing to take a shower then bed. Cheers, Wizard PS: Today fixed an older 1990 vintage Mitsubishi, big two piece chassis with high end stuff (relabeled as Electrochrome). Pix looked like ringing (vertical edges had bands (nasty case of ringing) and comets (like sparklers) and found nine lousy caps, except one was totally dried up (that was in cool location, go figure. With electrolyte leaking. Coworker thought tube had it. I saw that tube had good life left so I didn't beat it up with CRT rejuvenator. Cheers, Wizard |
#6
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RCA PTK195 Random Operation
This is a very common problem,usually caused by leaky tact switches on
the keyboard assembly itself.I usually replace the keyboard assy.The most common one used is part# 239125.Yours could be a different number.I would need the exact model # to be sure. 6 Aug 2003 21:00:50 GMT, (TV Fixer1) wrote: Got a RCA PTK195 (projection). Set has random behavior, turns itself on/off, changes channels, etc. as long as front keyboard is plugged in. With keyboard unplugged, set functions OK (remote operation). I've read about some problems with conductive glue under SMD parts on this chassis, is this one of the circuits affected? TIA TVFixer1 |
#7
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RCA PTK195 Random Operation
Many thanks Wizard for the information.
kip |
#8
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RCA PTK195 Random Operation
Thanks for the advice.
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