RCA 32V434T chassis ATC010A

[cmj21973]

Going to need help with this one.

My mom's tv quit will watching it. She heard a sound similiar to a fart. Which made my 4 yr old nephew laugh, untill he realized he couldn't watch Disney anymore.

Thought it was caps, but visual inspection turned up nothing. Searched web and found possible problem and solution.

TV symptoms:
When turned on, power led blinks 25 times and then is steady. No picture and no sound. Have to unplug set to turn off.
Same symptoms after being unpluged for 24+ hours.

Web search indicates flyback transfomer.
Took back off set and powered it up. Sure enough, the picture tube not glowing. Only spot on PCB, that i have a little concern about, is some color disfiguration around some resistors located next to FBT.

I have "rca_32v434tyx1_ch_atc010a_[ET]",but I can't upload it.

Were to beging testing?
I have DMM, anolog MM, BlueESR, & RING test.

[cmj21973]

Re: RCA 32V434T chassis ATC010A

Maybe some nude photos to get response!

[retiredcaps]

Re: RCA 32V434T chassis ATC010A

I can't help with your problem. Never worked on a CRT and hope I never will.

I don't know about where you live, but where I live, there are free TVs given away everyday. TVs like the back breaking 160+ pound Sony Trinitrons anywhere from 32 to 36 inches (with the TV stand).

People are also giving away free 50+ inch RPTVs, some work and some need repairs.

[cmj21973]

Re: RCA 32V434T chassis ATC010A

Tech manual

[cmj21973]

Re: RCA 32V434T chassis ATC010A

I have narrowed the problem down to the SMPS.
While the front panel keyboard On/Off button has 5VDC, the 5VDC STBY on the main board is about 42VDC.

Using the attached placement chart, I measured the voltage (VTP-8A) between D861 and L861 and it was about 42VDC.

Using the attached SMPS schematic, I plan to test the components from L861 back towards D861.

The attachments are pages from

Any help or suggestion welcomed.

[cmj21973]

Re: RCA 32V434T chassis ATC010A

While test voltages, probe slipped and I blown the fuse.
It's F800, mfr. part# 273739, 5A, 250V, glass 5x20mm

I replaced it with a 5A 250V slow-blow fuse from RadioShack, and it blew again when I plug the cord into outlet.

[marius.moise]

Re: RCA 32V434T chassis ATC010A

Hello,
As i see in your description 5V stan-by is 42!! i think you d'ont have feedback from secondary part of psu
I suggest to recap 100% PSU(small one-5vdc st-by and bigger one), after that check and replace if necessary: ic 804,d 869, q 860, and resistors, capacitors around ic 804.
After that i suggest to check regulators (5v ,3.3v,1.8v..etc),and maybe your main ic from tv is broken.
Check bigger power supply and do the same like a say(check optocupler, ic 803, etc).

[cmj21973]

Re: RCA 32V434T chassis ATC010A

Found RT860 PTC blown.
It's a thermistor marked 5, 5D210, D V
It has a 4.5 ohms reading.

Will this one from Digikey be an equivalent?
http://search.digikey.com/scripts/Dk...63658373885660

Could this be causing the fuse to blow when power is applied?
Could this also be the cause of the 5VDC STBY to measure about 42VDC if it was begining to fail?

[PlainBill]

Re: RCA 32V434T chassis ATC010A

Found RT860 PTC blown.
It's a thermistor marked 5, 5D210, D V
It has a 4.5 ohms reading.

Will this one from Digikey be an equivalent?
http://search.digikey.com/scripts/Dk...63658373885660

Could this be causing the fuse to blow when power is applied?
Could this also be the cause of the 5VDC STBY to measure about 42VDC if it was begining to fail?

It is good. A 5D210 is a power thermistor, the 5 is the resistance at 25°C (room temperature). If it were bad, it might cause the fuse to blow, it has nothing to do with a high standby voltage.

marius.moise explains the likely cause of the high standby voltage.

RT860 provides an excellent means of troubleshooting the problem. First, don't just keep replacing fuses. Instead wire a 40 watt light bulb across the fuse position. If there is a short, the light bulb will glow brightly when power is applied. If there is no short it should flash on momentarily, then glow dimly.

With the light bulb across the fuse and RTC860 removed apply power. If the lamp glows brightly, one or more of the diodes in the bridge (D861, D862, D863, D864) are shorted. Replace them all. If the lamp does not glow, IC860 is bad, replace it.

Providing a schematic is very helpful. Thank you.

PlainBill

[randtek]

Re: RCA 32V434T chassis ATC010A

I have narrowed the problem down to the SMPS.
While the front panel keyboard On/Off button has 5VDC, the 5VDC STBY on the main board is about 42VDC.

Using the attached placement chart, I measured the voltage (VTP-8A) between D861 and L861 and it was about 42VDC.

Using the attached SMPS schematic, I plan to test the components from L861 back towards D861.

The attachments are pages from

Any help or suggestion welcomed.

Are you sure you are measuring the 5v Stby in relation to the proper ground? If it were truly running at 42v, you would have caps exploding/venting all over that line.

[marius.moise]

Re: RCA 32V434T chassis ATC010A

Are you sure you are measuring the 5v Stby in relation to the proper ground? If it were truly running at 42v, you would have caps exploding/venting all over that line.

I think that too.
There are 2 grounds!!!! One for primary circuit, and the other for secondary circuits
When you measure 5vdc for example, you must connect your voltmeter to the secondary ground point!

Be carreful DO NOT TOUCH primary ground(live ground) and secondary circuits ground with your hand in the same time!

[cmj21973]

Re: RCA 32V434T chassis ATC010A

It is good. A 5D210 is a power thermistor, the 5 is the resistance at 25°C (room temperature). If it were bad, it might cause the fuse to blow, it has nothing to do with a high standby voltage.

marius.moise explains the likely cause of the high standby voltage.

RT860 provides an excellent means of troubleshooting the problem. First, don't just keep replacing fuses. Instead wire a 40 watt light bulb across the fuse position. If there is a short, the light bulb will glow brightly when power is applied. If there is no short it should flash on momentarily, then glow dimly.

With the light bulb across the fuse and RTC860 removed apply power. If the lamp glows brightly, one or more of the diodes in the bridge (D861, D862, D863, D864) are shorted. Replace them all. If the lamp does not glow, IC860 is bad, replace it.

Providing a schematic is very helpful. Thank you.

PlainBill

Usefull info, thanks. Will test as soon as I replace the thermistor.
I pulled C806 & C861 and tested them, BlueESR meter, and they checkout as OK.

Forgot to add photos of blown RT860 PTC, I still need to replace it.

[cmj21973]

Re: RCA 32V434T chassis ATC010A

I think that too.
There are 2 grounds!!!! One for primary circuit, and the other for secondary circuits
When you measure 5vdc for example, you must connect your voltmeter to the secondary ground point!

Be carreful DO NOT TOUCH primary ground(live ground) and secondary circuits ground with your hand in the same time!

This is were I took the voltage readings from.

After some sleep, looking at the power supply schematic I'm wonder how I got 42VDC on the main board and 5VDC on the control board also!

[Village Electronics]

Re: RCA 32V434T chassis ATC010A

This is were I took the voltage readings from.

After some sleep, looking at the power supply schematic I'm wonder how I got 42VDC on the main board and 5VDC on the control board also!

This a hard set to work on so don't feel too bad.

I think your 5 volt source is coming from D865 which is connected to a cold ground. The pulse that is being rectified comes from pin 5 of T850.

Designers would never put a hot ground anywhere near a place that a consumer could touch. The drawings clearly show hot and cold grounds.
All readings should reference one or the other.

Divide the problem down. Take the H. output transistor out of the circuit.
While it's out make sure it is not shorted collector to emitter. It will have a very low resistance from E to B.

If the power supply starts to run the problem is downstream of the flyback.
That could be any one of the scan diodes or any circuit that they might feed.
The most likely culprit will be the flyback (read: Horizontal output transformer) itself that is if the transistor is shorted.

You have to get that power supply first though.

[PlainBill]

Re: RCA 32V434T chassis ATC010A

Usefull info, thanks. Will test as soon as I replace the thermistor.
I pulled C806 & C861 and tested them, BlueESR meter, and they checkout as OK.

Forgot to add photos of blown RT860 PTC, I still need to replace it.

Yes, that's bad.

PlainBill

[cmj21973]

Re: RCA 32V434T chassis ATC010A

RT860 provides an excellent means of troubleshooting the problem. First, don't just keep replacing fuses. Instead wire a 40 watt light bulb across the fuse position. If there is a short, the light bulb will glow brightly when power is applied. If there is no short it should flash on momentarily, then glow dimly.

With the light bulb across the fuse and RTC860 removed apply power. If the lamp glows brightly, one or more of the diodes in the bridge (D861, D862, D863, D864) are shorted. Replace them all. If the lamp does not glow, IC860 is bad, replace it.

Providing a schematic is very helpful. Thank you.

PlainBill

Tested with 40watt light across fuse hold: bright light
Replaced all (4) diodes D861; D862; D863; & D864

Retested with 40watt light: nothing

Need to replace IC860 and TR860 PCT
http://search.digikey.com/scripts/Dk...66952994897708
http://search.digikey.com/scripts/Dk...66952994897708

Will order upon conformation of correct choices.
TIA

[cmj21973]

Re: RCA 32V434T chassis ATC010A

Replacement IC860 and TR860 arrived today.

Soldered IC860 and ran 40watt light bulb test. While the light didn't glow it did make a slight buzzing sound.

Soldered TR860 and repeated test, Results were the same.

Replace fuse (F800) and applied power. I'm back were I first start, before blowing fuse.

Following the guide on page 22 of RCA ATC010 Training Manual.pdf

1) IC860 pin(8) DC voltage measurement fluxuates from 166.2 to 166.6 OK
2) IC860 pin(1) DC voltage measures 9.0 steady OK
4) IC860 pin(4) DC voltage measures 2.7 steady OK

Control Board has 5.1 Vdc

Will preform "Run Power Supplly Troubleshooting", page 23, tomorrow and post results.

P.S. Readings were gathered while set was in standby mode. Should I preform 40watt light bulb test & measure voltages again, after pressing the ON button?

[PlainBill]

Re: RCA 32V434T chassis ATC010A

Replacement IC860 and TR860 arrived today.

Soldered IC860 and ran 40watt light bulb test. While the light didn't glow it did make a slight buzzing sound.

Soldered TR860 and repeated test, Results were the same.

Replace fuse (F800) and applied power. I'm back were I first start, before blowing fuse.

Following the guide on page 22 of RCA ATC010 Training Manual.pdf

1) IC860 pin(8) DC voltage measurement fluxuates from 166.2 to 166.6 OK
2) IC860 pin(1) DC voltage measures 9.0 steady OK
4) IC860 pin(4) DC voltage measures 2.7 steady OK

Control Board has 5.1 Vdc

Will preform "Run Power Supplly Troubleshooting", page 23, tomorrow and post results.

P.S. Readings were gathered while set was in standby mode. Should I preform 40watt light bulb test & measure voltages again, after pressing the ON button?

Yes, I would. It may also be necessary to move up to a higher wattage light bulb.

PlainBill

[cmj21973]

Re: RCA 32V434T chassis ATC010A

Using a 100watt bulb, across fuse holder, it lit up bright then slowly went off (stanby mode).

Pressed the ON button and the bulb filament glowed red for a little bit and then went off.

Replaced fuse, pressed ON button (out of standby).

1) IC860 pin(8) DC voltage fluxuates around 164
2) IC860 pin(1) DC voltage 10 steady
4) IC860 pin(4) DC volatage 2.6 steady

Will test "Run Power Supply Troubleshooting" next.

[cmj21973]

Re: RCA 32V434T chassis ATC010A

Pulled the Horizontal output transistor Q405 out of circuit.

D3402
701II

DMM diode test:
B(+) C(-) .472
B(-) C(+) .OL
C(+) E(-) .OL
C(-) E(+) .493
B(+) E(-) .044
B(-) E(+) .044

Is the HOT good or bad?