RCA ColorTrak 2000 (CTC 158B) won't power on.

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

no your alphabet marks don't matter if you can locate C4120 33uf @180 volt positive side that cap is same point as TP4008

looking at top of your chassis right bottom corner you should see SCR4101 or might say SCR101 on board it's 3 leg transistor mounted on heat sink in front of that you see T4101 and to left of that in that area you should see TP4008

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Okay found SCR4101. I think I found T4101. TP4008 is eluding me due to wires and dust. However there is a 33uf@200 volt capacitor right next to the flyback. I'm thinking that's C4120 as there's no other 33uf caps of that voltage rating anywhere else that I know of.

So I'm thinking solder a jumper wire to the positive lead of that cap, connect my multimeter with the negative lead on the HOT heatsink, and it'll tell me something when I plug it in.

No wait, looking under the board it's C120k. I'm confused again. C4120 has got to be pretty big.

Wait wait wait, C120k/C4120. They have to be the same cap, right?

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

C4120 should be to right of your ihvt on edge of board and going by your alphabet markings @ 2LL on board c120/k not same

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Yeah at 2LL is that big 33uf cap.

That cap has to be it. It's labeled weirdly but that has to be the one.

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

yes

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Okay testing at that point, positive lead connected to the positive lead of that 33uf capacitor, and negative lead connected to the HOT heatsink, and plugged in I get 0.00 volts.

Hit the power button and it briefly jumped to 0.05 volts, then dropped back to dead zero.

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

ok need know voltage @ anode of SCR4101 3 leg transistor heat sink mounted or @ pin 1
of T4401 reference to HOT gnd should have 150volts dc

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Okay, looking at it from the back, which pin on SCR4101 should I connect the multimeter to, left, middle, or right?

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

middle pin of SCR that's the anode

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Yep, just saw that, They were nice enough to label it, and I didn't see that the first time. Okay gonna connect that up and see what I get.

Okay multimeter connected positive lead to the anode of SCR4101, and negative lead to the HOT heatsink, and, again 0.00 volts. Multimeter goes to dead zero when I plug the TV in.

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

ok @ bottom right corner looking from top see big capacitor C4007 or could also be label C7
need voltage with Hot gnd positive side should be 150volts dc

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Okay that's got to be the 680uf 200 volt filter cap. (I replaced that cap with a newer one when I last worked on the set)

Hot gnd positive side? Okay, so I should connect my positive multimeter lead to the HOT heatsink? Which lead of the cap to I connect the other lead to?

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

no connect your pos probe to C4007 positive side and your negative probe to HOT gnd

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

This is getting really bizarre. Did as you said. Still 0 volts, not even a blip when I hit the power button.

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

ok now remove resistor R4001 from chassis it also could be referred to as R1 it's the big 2.7 ohm resistor 15 watt @ bottom right corner near your C4007 cap once you have out circuit put your meter on ohms setting about 200 ohm scale and read the resistor,make sure all power removed from set before desolder

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

That's gotta be the big white block resistor.

Hey I think we found the problem! That resister is open.

Question is why?

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

ok now make sure the bridge diode network CR4001-CR4004 none are shorted also make sure no pins of the SCR4101 are not shorted to each other, i have seen from age these big older wire round resistors just open up or possible little power surge trickle

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Okay I see 4 diodes in the area, but they're labeled CR1 CR2 and so forth. I'm guessing those are the ones I want.

Okay just tested them, and all 4 diodes check out just fine. Knowing this, do I really need to test the SCR? I ask because getting it out would be a PITA that I'd much rather avoid if possible.

[RON_CET]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

yes CR1-CR4 correct and you can read SCR in circuit your just making sure no direct shorts between the three pins

[Mrx3750]

Re: RCA ColorTrak 2000 (CTC 158B) won't power on.

Hmmm, well not exactly shorted, but testing the SCR in circuit, I'm getting readings of roughly 0.05 ohms