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  #1  
08-31-2023, 05:58 PM
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Having issue narrowing down an issue with a TBC-1000 video board.
Here is what is happening:
https://www.youtube.com/watch?v=GYtZOnkNojA

- TBC amp board is bypassed
- Capacitors replaced on VP 301E board
- All voltages within tolerance
- Max temperature on main chip 117 F after 15-20 minutes
- Audio is directly connected to CRT for reference of what should be appearing screen

Any thoughts are appreciated.

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  #2  
09-01-2023, 01:50 AM
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So the image is
- quickly losing stability (vhold? vsync?), fast recovery
- slowly/violently losing stability + losing a chroma channel, slow recovery
- freezing static for long period

117 F is 47 C. Not excessive, but not as cool as desired. What happens when cooling is applied to the main chip in use? Rig up a heatsink, with fan if needed. Get that temp down. Use removable pads, not paste.

You need to check the temp of each chip. I'd pay particular attention the ADC and DAC here (the CX BT864AKRF and NXP SAA).

Something may have happened to this TBC in prior shipping, perhaps excessive static discharge, or excessive package force that loosened chip contacts. You may have to reseat/reflow some of the chips. Again, my gut feeling is pay attention to the ADC/DAC chips, not as much the microcontroller.

The microcontrolled has to be extracted, then reseated, no solder. Dust may have invaded, so probably good idea to exact, plain-air blow (not compressed/duster; not mouth spittle blow), and reseat. Amazon has some decent chip extractors, and extractor kits, if you don't have one.

If any chips still have labels or glue, clean it off. That junk can contribute heat.

Remember, that board has a lot of capacitors, beyond the few large electrolytic caps. It has dozens of SMDs.

Some of this may trace back to the TBC-1000 design being bad. I've never liked how the board attaches to the base, it can be subjected to warping. Not just from impact, but heat/cold twisting it, especially (for example) being in a hot truck in summer, and then being in a cold house AC, without any slow adjustment time at middling temps. That can unseat chips.

You need to also re-verify that your replace/bypass work so far is actually good. Always check yourself.

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  #3  
09-02-2023, 04:49 PM
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Update:

All testing has been done with other power boards and the amp is bypassed so it's direct feed from the video board.

Checked more temps and did some comparisons to my two other video boards. The DAC is running hotter comparatively. I added a heat sink and got temps down 10-15%, which is what my other two (working) units run at, but the issue remains.

I checked and compared every SMD resistor, cap, and diode(checked these powered on as well in case one was breaking down with live current). All within tolerance and similar to my other boards

Wondering again if it was truly a heat dissipation issue but not on an IC, I cooled the board while running with a stream of contact cleaner, but still the issue continued.

I'm thinking now there is an internal issue with one of the IC's you mentioned, but ordering the DAC/ADC will take a minimum of 4 weeks to ship, if they are even truly available. So that's an option but not ideal.

Any other thoughts from the community?

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  #4  
09-02-2023, 05:15 PM
latreche34 latreche34 is offline
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Keep in mind that not all capacitors can be tested on the PCB, depends on its location in the circuit you may have to desolder one leg if possible or completely in case of SMD ones. Honestly, you will be far better off replacing all those SMD caps, It's an investment for the future, they will fail eventually at some point in time even if they are good now.

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  #5  
09-03-2023, 04:13 AM
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I mentioned DAC/ADC because I've seen where those have gone bad on Cypress and BV units. The units are fine, then one day not. No transition period, just fine to failure overnight. The output is some sort of garbled, and overheating was a tell-tale in at least one case.

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  #6  
09-03-2023, 01:16 PM
latreche34 latreche34 is offline
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No doubt that there is a possibility of bad chips, When a cap shorts out, it bridges an output from the chip, the chip can resist only for so long while overheating before it pops and you get a dead TBC, hence my recommendation to replace them all. Heat dissipation by using heat sinks is a patch solution, it is better to address the root cause of the unusual heat.

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  #7  
09-03-2023, 01:27 PM
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Yep, good call. I often mentioned cascade issues, but did not here.

I've seen irreparably bad DataVideo TBCs, especially the 1000. This isn't that kind of unit. It actually is a minor error, it's just being elusive and a PITA to locate. Replacing all the SMD is not out of line, and the DAC (or ADC) is still high on the troubleshoot list, due to the error presenting.

Anything could have triggered this. Temps/heat as mentioned, or the natural power surge of powering on the unit. Or just making any mistake, no matter how tiny or overlooked (plugging in with power switch on, flipping off too quick, off/on too quick). Some of the most innocuous things that zapped my AG-1980, TBC-3000, green AVT-8710, and others.

My 3000 actually isn't yet repaired, very recent failure. I already have somebody that can analyze it deeply, but I'm tempted to let you look at it, if you want. (But don't screw it up.)

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  #8  
09-03-2023, 01:49 PM
latreche34 latreche34 is offline
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I wish I could but as it stands I have no time to even repair my own stuff, I have a Sony EDV-7300 ED beta that needs alignment but I've been putting it off for over a month. Like they say when you're young you have time but no money, when you get old you have money but no time, very true.

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  #9  
09-03-2023, 02:08 PM
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No, I meant send it to Diopter_Doctor, since he's trying to learn DataVideo repair, and somewhat succeeding at it so far.

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  #10  
09-03-2023, 06:10 PM
latreche34 latreche34 is offline
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Oh, my bad.

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  #11  
09-04-2023, 01:27 PM
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I doubt anyone happens to have access to an SMD cap list of the video board. The owner and I decided to replace the DAC and see if that solves the issue first. It will take awhile to get it in, but I'll update with the results.

LS,
If you want to send it for me to look it over, I don't mind. I've never worked on a 3000, but I can't imagine it's that different. PM me your thoughts.

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  #12  
11-02-2023, 05:17 PM
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Update:

After replacing the DAC and the SMD caps the problem remains. Our last attempt will be to replace the SMD resistors and hope for the best

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  #13  
11-03-2023, 02:24 AM
latreche34 latreche34 is offline
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Should have started with the caps first, A lot easier and potentially the culprit, If the chip goes dead you don't get any video.

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  #14  
11-05-2023, 11:47 AM
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And the ADC?

Unfortunately, a new DAC may be bad as well, given how these will almost all be recovered chips sold from China. Remember, until 2020, China loved to take our e-waste. And removing and reselling components is often what they did. There is no QC over there, nothing is tested. You seriously haveto source several chips, from several places.

In theory, a RAM chip could be bad, but I don't think it's the situation here, given the errors. I've never seen it.

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  #15  
11-06-2023, 11:21 AM
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I couldn't source any ADCs. The DAC came in a manufactured package and showed no previous signs of solder or bent pins so it's safe to say it was new old stock.

I considered the frame buffer since there was video pausing but haven't dived into looking at them that closely or if they're even available anywhere.

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  #16  
11-07-2023, 06:49 AM
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This is a situation were frankensteining TBCs may be easier, at least to troubleshoot. I wonder if ehbowen still has his failed unit? I've received a few inquiries to repair fully failed 1000s over the years, and I've turned down maybe 4 of those. Most of those contacts were off-forum, but ehbowen was on-forum.

Do you want to play with my failed Pixie? It's not a recommended model (most are truly awful), but this one wasn't a total boat anchor. It has a very similar issue, especially seen in PAL with PAL sources. NTSC just shows black snow, PAL shows fubar image. Perhaps troubleshooting it could help here?

That brings up another good point. Did you test the TBC-1000 in composite, and in PAL s-video/composite? Very often, you'll get different results, which can help trace issues. Though this is a reason the auto-sensing of the TBC-1000 sucks, you don't control it.

In fact, that could (maybe?) itself be the issue. The instability is causing NTSC/PAL flipping (flip-flopping), and bad PAL over NTSC can turn green/purple (a common problem with bad PAL conversions, I ran across many in my VHS collecting days in the 90s; thankfully all of it was eventually released on DVD). PAL/NTSC could also cause violent tearing, putting 625 PAL lines in 525 line NTSC temporal space. That may also help trace.

It's too bad we can't both be in the same room to solve this one.

Do you have PAL VCRs, PAL tapes?

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  #17  
11-07-2023, 09:41 AM
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Quote:
Originally Posted by lordsmurf View Post
This is a situation were frankensteining TBCs may be easier, at least to troubleshoot.
I switched out the microprocessor, replaced all electrolytic caps, replaced the SMD caps other than the I/O ones, replaced the DAC, and I'm replacing the resistors next. All that's left that are single-point failures for both composite and Y/C are the two ADCs, two Crystals, certain diodes, the four Ram chips, and the voltage regulator. Which of these would most likely malfunction after heating up for 30 minutes? I've compared temps to two other working units and after replacing the DAC nothing is significantly different.


Quote:
Originally Posted by lordsmurf View Post
That brings up another good point. Did you test the TBC-1000 in composite, and in PAL s-video/composite? Very often, you'll get different results, which can help trace issues.
What part of the TBC-1000 does the auto sensing?

Quote:
Originally Posted by lordsmurf View Post
It's too bad we can't both be in the same room to solve this one.

Do you have PAL VCRs, PAL tapes?
No kidding, the only other project that has ever stumped me is a CRT projector. 20+ daughter boards with 40+ electrolytic caps a piece. I did get it partially working, though!

I don't have any PAL equipment or tapes. I have PVMs that accept it, but no experience messing with anything but NTSC.

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  #18  
11-07-2023, 09:59 AM
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Quote:
Originally Posted by Diopter_Doctor View Post
Which of these would most likely malfunction after heating up for 30 minutes?
ADC.

Having you considered removing it, then reseating it?

Quote:
What part of the TBC-1000 does the auto sensing?
Likely the main chip, but it probably does not matter. It's taking cues from the input data chips, if that's the issue, meaning ADC.

Quote:
I don't have any PAL equipment or tapes. I have PVMs that accept it, but no experience messing with anything but NTSC.
It helps with some gear, especially many TBCs.

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  #19  
11-07-2023, 02:54 PM
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Quote:
Originally Posted by lordsmurf View Post
ADC.

Having you considered removing it, then reseating it?
Considering it if the resistors don't do the trick.

Is there one for composite and one for Y/C? I'm wondering why there are two.

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  #20  
12-03-2023, 02:19 PM
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Here is a link to the SMD cap values I recorded from this project. These numbers are either an average what my multimeters read or my best guess at what they originally were. All 0805 package size.

We have decided to use this unit for parts after all. After replacing the SMD caps and resistors, the color glitching resolved but the occasional freezing did not. Video here.

After checking the amp board it came with, the voltage regulator that is suppose to output 8V from the 12V DC PSU only put out slightly above 4V. The owner mentioned that the unit didn't always turn on. This is what likely messed up the video board to begin with.

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