Sharp Image SI-134 / KTM-F 33 Vertical Collapse++

check positive side of the cap
Roger Wilco.
#1: cold solder joint on the "right" side of C606.
#2: These chassis have un"protected" traces in between capacitors as you see here.
#3: R901 from pin 7 on the flyback.
#4: Bend back and make sure there is no continuity there.
#5: top 2 legs on the left
#6: (Just below D605) Oh that's T601. Did you #7 R904, is it supposed to be on the bottom?
#1 Can do. The pad is burned from a previous owner's attempt to fix it, but I can probably clean it up better.
#2 I saw that too, checked it, it doesn't have continuity to the adjacent pads.
#3 Had the same thought, it's good.
#4 Will do.
#5 That's IC201. Also burned up by previous owner. The right of the two, pin 11, isn't used. The left, pin 13, I have soldered to an exposed part of the trace right above it. Continuity is good.
#6 Also was concerned by that, but the image of the reference board you posted has a similar setup. I think they came that way.
#7 Had to move it to the bottom for the new flyback to fit. I could probably do a better job soldering it, though. Will do.

Won't be able to get to my shop tomorrow. Will report on Sunday!
 
What I would do to solve the R903 issue is run the power supply with a dummy load (the usual 60W light bulb). This can be done by removing L602 and attaching the bulb to the cathode of the B+ rectifier D605 (and secondary ground). Attach the meter with croc clip (not hand held) to the cathode of the 25V rectifier D607 (and secondary ground). R903 good and in circuit. Pin 14 of vertical IC201 desoldered from its pad (no continuity from the pin to R903. One side of J8 lifted from the chassis (yes, this will be difficult due to that big blob of silicone on top side) or solder sucked from either pad if that's easier. Turn on the chassis (in fact only the power supply) and see if you have 25V (or something in that range) on the cathode of D607 and R903 doesn't burn. If it doesn't, reconnect J8 and check voltage again. This would prove that the problem is in the vertical circuit and not in the east-west circuit.

Just to be clear, R903 is in series with the 25V line that supplies the vertical circuit and through J8 also the east-west circuit (pincushion/H size).

I see that the filter caps on the 25V line C906 and C210 have the correct polarity. The most likely culprit then would be the IC which has already been replaced or so I've read in some post above. Clean up the flux around its pins with alcohol or solvent and help yourself with a toothpick or a brush and make sure there are no bridges across any pins.z0.jpg
 
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Caps haave a short to ground
Checked each cap. Three... anomalies:
C119 pos leg = 0.5ohm
C902 pos leg = 3.0ohm
C903 pos leg = 0.5ohm

Everything else was completely open.
What I would do to solve the R903.
Lightbulb test complete. 29v read at D607 with L602, IC201 (pin14) and J8 removed from circuit. R901 did not burn up!

Edit: Oops, I didn't try again with J8 reattached. D'oh! Doing that next. Retested with J8 in place, still 29V, no burning R901
 
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Now you know that the problem is in the vertical circuit. With pin 14 desoldered from it's pad, measure its resistance to ground (e.g. middle pin of the same row or negative of C906 or one of the screws of the heat sink). If it's low or significantly lower than on a new IC, I would say that it's the IC itself that is bad and causing the burning of R903. But first clean it up as per my previous post.

I hope R901 is a typo as it's R903 we were talking about.

R903: SMSP-derived 25V supply for vertical deflection.

R901: flyback-derived 12V supply for video/sync circuits.
 
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Ok, I MAY have found the culprit. I asked earlier about this mysterious unlabled diode. I believe it is the elusive D410 (listed on the schematic as an IN4742). Seems shorted? 0.5ohm one way, 0.003ohm the other. Is that supposed to be so low? Ordered a new one anyway.
 

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Lightbulb test complete. 29v read at D607 with L602, IC201 (pin14) and J8 removed from circuit. R901 did not burn up!

Edit: Oops, I didn't try again with J8 reattached. D'oh! Doing that next. Retested with J8 in place, still 29V, no burning R901

L602 is way far back in the circuit, and with it out of circuit, yes you won't have a burning up resistor because the flyback isn't getting any voltage.
D605 Cathode is a more interesting measurement spot to me, as that is how you test the B+.
D410 you should use diode check on your meter. Black lead on cathode (white stripe) and read lead on other, should be .4-.7 voltage drop, other way should be open. (Test this again please, as I am excited that this may be the culprit. LOL )
L602 needs to be in circuit, but you can test leaving the others out and see if it smokes it. (that is IC201 pin 14, J8, maybe even c906)

So, if you are measuring that low of a resistance on all 3 caps (C119-0.5ohm,C902-3.0ohm,and C903-.5 ohm) that is a problem. I would assume they would be in the thousands at least. And that would definitely wreak havoc on poor R901.

I have marked a schematic with all the probable components in the circuit that could be causing the problem, as an attachment if the above doesn't solve it. Pink boxes in the circuit. Red boxes are items that are connected directly to ground. Caps should never have that low of a resistance. Also make sure the measurements taken to GND you are using chassis ground which is the heatsink by the flyback and the one the H.O.T. is connected too.

Edit: (check these values)
C119- 470uf @ 16v (may have a higher voltage)
C902- 1000uf @ 16v (may have a higher voltage)
C903- 220uf @ 35v (may have a higher voltage)
 

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D410 you should use diode check on your meter.

Reads 0.003v both directions. I have a feeling this is a significant source of issues. Got a replacement coming.

With D410 out of circuit, C119 no longer shows short to ground on positive leg.

C119 = 2.2kohm
C902 = 2.1kohm
C903 = 2.1kohm

The ųf/V values of the caps are correct. The ohm readings I posted before were from positive leg to chassis ground, not across the cap itself.

So, things are looking up! Just more waiting. 💤
 
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Reads 0.003v both directions. I have a feeling this is a significant source of issues. Got a replacement coming.

With D410 out of circuit, C119 no longer shows short to ground on positive leg.

C119 = 2.2kohm
C902 = 2.1kohm
C903 = 2.1kohm

The ųf/V values of the caps are correct. The ohm readings I posted before were from positive leg to chassis ground, not across the cap itself.

So, things are looking up! Just more waiting. 💤
Place your bets people I'm betting that diode is the problem with R901
 
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Success! D410 has solved the burning R901 issue!

Unfortunately, still have complete vertical collapse. I'll take what I can get!

Edit: the intensity is also not so bad anymore. I can see striations in the line, and there are animations playing. It's just 1 pixel tall. Oh, and the high pitched squeel is gone. So that's some progress.
 

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Alright, now we're getting somewhere.

Check your supply voltage to the vertical IC (pin 14). You have to do this with the power on. I will sometimes solder a piece of wire to that pin on the underside of the board, to make it easier to test.

This is a typical troubleshooting method. If the vertical IC goes bad, check for supply voltage first. If there isn't supply voltage there, guess what resistor is probably the problem. (yeah it's R903 lol). So MKL's previous post is exactly what we need for this issue. You should get 25v on that input pin. I would follow his instructions there.
 
27.6V at pin 14. No bridges or continuity between pins. The line of light is returning to an indistinct blob continous across the screen. No more individual pixels implying animation.

As a separate experiment, I've tried bridging the sync inputs, sending the sync to just H, and sending to just V. No changes.
 
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I just wanted to make sure of a particular timeline you mentioned at the beginning.
  • You came to the monitor and it had vertical collapse.
  • You checked R903 out of circuit and it was reading 1k (bad). Replaced with 15ohm (correct).
  • Then did you replace the vertical IC or was it replaced before with that 1k bad resistor at R903?

Okay, some other thoughts:

You need to have the remote adjustment board plugged in, when you're checking this out. Not having it plugged in could show vertical collapse.
Make sure you have your VDY (Vertical Deflection Yoke) header is plugged in (usually green yellow, but who knows with this LOL) but it's the pins that are closer together. Also, check for solder connections on those 2 pins just to make sure it has a good connection. There are 2 connectors you can reflow both, or to verify just plug the yoke in the other one.

MKL asked what the resistance was on pin 14 to ground, it should be in the several thousands. If it's less than 200ish there is a problem there. That would be a decent test to see if the "newer" vertical IC has failed.

You can do all of this with the power off.

Edit: Oh and sorry about not answering the other thread. I am not 100% about this one, I'd guess 95-99% that the A and B yoke connectors are a way of flipping the image so you don't need to break your yoke connector in half to do it. So it really doesn't matter, I don't believe.
 
I just wanted to make sure of a particular timeline
Yes, collapse was present to begin with. Changed IC201, then R901 started blowing up, then we fixed D410, now we're back to vertical collapse.

I have no way to test if IC201 is damaged, other than looking for shorts between legs (there are none). Guess I'll get another and test that?

remote adjustment board
Present, plugged in, continuity is good all the way from vertical pots to IC201.
MKL asked what the resistance was on pin 14 to ground
Oops, thought mentioned it when we did the lighbulb test. It fluctuates, but asymptotically drifts towards 7K ohm.
 
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Sounds like the vertical IC is ok, but it could be failing under load. If you have another that you know is good you can compare measurements, or replace it. It's a guess though.

Pin 1 is the output, it literally goes to R206 (2.2ohm), and R207 (910ohm) then to the yoke connector. Maybe also check those 2 resistors. If everything tests ok, and you're sure the yoke connector is good making connection, I'd say the IC is bad (IC 201 TDA1675).

I don't know if it's an AFC issue (pin 2), I am not that familiar with them, and I think they may only deal with linearity but you don't have full deflection.

Edit: Is the horizontal line going all the way to the side of the screen, or if you adjust the Horizontal Position or Width, does it move or get bigger/smaller?
 

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R206 = 2.1ohm
R207 = 908ohm

I went ahead and tested every R2##. The only anomaly is:

R203 = 3.3k ohm, schematic says 3.3k, your parts list says 2.4k and no change for the 33" model. Leaving it as is.

Yes, horizontal line stretches the entire width, and is effected by the remote board.
 
I am pleased to report it's aliiiiiiive! It was indeed the IC201. It appears the replacement I initially purchased was the culprit.

Thank you so much to everyone who diligently helped me get through this ordeal! @PinFixin @M K L in particular.

I guess eBay is my new supplier of choice.20250725_191758.jpg
 
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