Gridleak: You Da Man!!! My TU-DST50 Unseating/Reseating Story - AVS Forum
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Old 03-10-2002, 04:49 PM - Thread Starter
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In July of last year noted AVS forum member/HDTV recording guru Gridleak (aka Roger) posted this thread outlining how one could repair his own Panny TU-DST50/51 STB. A month or so after Roger's post I purchased a used Panny TU-DST50 off of eBay. Alas this unit had the dreaded "blue sparkly" syndrome, but miraculously Panasonic agreed to replace my blue sparkly model with a refurbished unit that had no such problem and ran a lot cooler to boot. I soon added a Panny PV-HD1000 recorder to complete my setup.

All was well the first month or two I had this equipment. Then I started having video/audio dropout problems on the CBS-HD feed, but noticed no such problems on the DISH demo, HBO, or Showtime feeds. Since no one else was reporting problems with the CBS-HD feed off of 61.5, I began to think that there might be a problem with either my DISH modulator or perhaps the DISH 5000 receiver. I pretty much was resigned to the fact that CBS was going to be a problem for me and that I would just have to be satisfied that I could record HBO/Showtime content. Then, about 2 months ago I started noticing random pixelation on my HBO HD material, both live and watching recorded movies. These symptoms were exactly as Roger described in his thread, so yesterday I managed to work up the courage to pop open my TU-DST50 case and attempt to reseat the eprom chips and main board connectors. I was easily able to unseat and reseat the 4 eprom chips with a chip puller. The main board connectors were a problem though: I was able to unseat/reseat the lower transport stream connector with little difficulty (again using the chip puller-Roger's paper clip suggestion didn't work for me). However I absolutely could NOT budge the remaining 5 main board connectors. I swear those Panny punks in Elgin fused them to the MB! :) For the connectors that I could not unseat I used the chip puller to rock them a little bit and I then pushed them back down very firmly.

The results of my labors? I watched a couple of hours of CBS-HD and HBO last night and did not see one instance of pixelation nor did I experience any video or audio dropouts on the CBS-HD feed! It would seem that Roger's "slapping around" is a good thing!

Roger if you see this a couple of questions:

1) Does the copper tape attached to the back panel have a specific function? In my unit the end of the tape that was supposed to have been attached to the back panel had become dislodged. The techs had used some kind of waxy material to attach it.
I used a piece of electrical tape to reattach it
to the back panel after I had finished the unseating/reseating dance.

2) In your thread from last July, at the end of the thread you mentioned that one more installment
was going to follow...guess you never got around to that. What was that installment going to discuss?

Many thanks again Roger for your incredibly useful and helpful posts! :)

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Old 03-10-2002, 11:05 PM
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It's very encouraging to hear that my posts have helped you. The sharing of skills is what makes this such a great forum. Right now I'm setting up an XP computer to explore the incredible offerings from Leszek. I doubt we'd ever see stuff like this in "Widescreen Review".

Regarding the main board connectors: they are a bitch. The trick is to lever against the circuit board surface with a fairly heavy piece of steel wire acting as a crowbar. I used a large paperclip with 0.045" wire, and that worked ok. I wanted to suggest using 0.050" music wire, but I figured that wouldn't be in everybody's junk box.

In terms of importance, the EPROMS are the first to reseat, and the transport connectors are next. You caught both of those, so I think you'll be good for a long time.

The copper tape is part of the shielding scheme that was needed to meet FCC RFI requirements. I've operated these boxes with the lid and inner cover off and they work just fine. Probably everybody in my neighborhood lost channel 5 while I was doing it, but who cares about people who watch NTSC. (Just joking, of course.) Whether you successfully reconnect the copper tape or not, your STB will work just fine, and I doubt there would be any measurable difference in the RFI, once the lid is on.

The final segment of the thread was about remounting the circuit boards to the case. It got very complicated, and I decided I needed to reconsider how to present the information. The problem is centered around the ATSC tuner, which is astoundingly sensitive to mechanical shock and vibration. I did post a little about this in the "War on Pixels" thread, but I still haven't figured a way to explain this in understandable terms.

-Roger
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Old 03-11-2002, 08:33 AM - Thread Starter
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Roger:

I watched and taped the CBS-HD 9/11 special last night. While watching the show live I again saw absolutely no pixelation or dropout events the entire two hours. However I watched the first 30 minutes of the tape and noticed a few random pixelation events (I say random because I rewound the tape and played the same segment again and did not see the pixelation at the same spot again). Is it surprising to you that I see pixelation on the tape but not the live broadcast? I'm using Fuji ST-160 tapes which I know are not among your favorites.

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Old 03-11-2002, 03:31 PM
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Nothing about the Panny combo surprises me anymore. I've even seen the opposite situation where there were visible pixels while recording and none during playback.

The problem you describe would indicate that the signal is being compromised in the loop starting at the MPEG2 decoder and including the 1394 system in the STB, the firewire cable and connections, and the recorder.

I'd start by looking carefully at the iLink jacks on both the STB and the recorder. I keep bringing this up because problems with these connectors are so common. Although the information being sent is digital, the actual signal in the firewire is analog. Noise, and bad connections, and poor quality cable can have an effect. This is what a really bad iLink jack looks like. You'll need a good magnifier and good light to see this. http://home.earthlink.net/~rogercc/_...Linkjacktn.jpg Enlarge
Try different cables too.

The next place I'd look would be the recorder. All the usual suspects should be checked and cleaned (heads and pinch roller), but unless you're seeing green blotches I'll be surprised if any of that helps. If I were working on it I'd pull and reinsert the Digital CBA. Two screws and 4 connectors have to be removed to do that. I'd also look closely at the iLink harness that runs from the iLink jack to the Digital CBA, making sure the wires were tightly bundled.

Besides trying different brands of tape, there's one remaining thing you can do in the recorder that doesn't require instruments or disassembly. It's called the Bit Error Rate adjustment, and Dylan nicely described the process here. I have yet to run into a situation where the BER adjustment made a difference, but it certainly helped Dylan.

Beyond that, it's full disassembly -- a hair-raising experience to say the least. I'll do a photo shoot of that when I think it's time for everybody to replace their capstan bearings.:rolleyes:

One last possibility is back in the STB on the ATSC tuner board where there are a series of pots that control the AGC and local oscillator. Some of them affect tape playback, and all of them affect tuner performance. There's no documentation on setting them, so you're on your own if you decide to walk that gangplank. Take a photo before you start, so you can restore the settings precisely.

-Roger
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Old 03-11-2002, 06:55 PM
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Why don't we use RJ-45 connectors for everything instead of fire-wire?

AT&T and Bell labs did a tremendous amount of work testing and developing these connectors way back when. Overall, they have a excellent success rate and they are dirt cheap.

-Mr. Wigggles

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Old 03-12-2002, 01:56 AM
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RickD_99, I forgot to mention another likely suspect: the record current adjustment. It has been mentioned here before, but I don't remember the name of the thread. It requires a scope of only moderate capablities. If you have such a device I'll post the details of the adjustment.

MrWigggles, it is a shame they can't be used. The RJ connectors are truly well designed and reliable. Unfortunately, firewire connectors need to be of the shielded variety.

-Roger
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Old 03-12-2002, 08:57 AM - Thread Starter
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Quote:
Originally posted by gridleak
RickD_99, I forgot to mention another likely suspect: the record current adjustment. It has been mentioned here before, but I don't remember the name of the thread. It requires a scope of only moderate capablities. If you have such a device I'll post the details of the adjustment.
Thanks for the info. I just ordered a service manual for the PV-HD1000 from Panasonic. I think it's time to start educating myself on the proper maintenance of this unit. I would much rather work on the Panny combo myself and get the pieces working properly together than screwing around with the JVC units.

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