HOT output from TU-50/51 is it adjustable??? - AVS Forum
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post #1 of 12 Old 08-22-2001, 01:38 PM - Thread Starter
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I did a post a while ago and only came up with expensive solutions so I thought I might try this approach.

Does anyone know if there is a single pot on the boards on these where I might be able to knock down the output of the the component video out on? I would rather not try to knock down the output on individual channels. My eletronics experience consists of putting together a lot of kits and replacing heads on VCRs.

The output simply is too hot for my D-ILA and they both even look hot compared to my 6000 on my LT-150. I tried using a 75 ohm resistor on each line and that was too much. Running back and forth to and from Electronic Supply trying to figure out which will work is a pain. I'd prefer an adjustment on each.

Anyone played with this at all?

My next call is to Panasonic but I have the feeling they won't help me. They seldom will give users info like that.

Larry Vale

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post #2 of 12 Old 08-22-2001, 06:00 PM
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Wow. Mine is way dim compared to my DTC 100 and my Faroudja. I was wondering if their was a way to turn it up. I'm sure their is a service menu which has this adjustment.
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post #3 of 12 Old 08-22-2001, 06:06 PM
 
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Video outputs are usually low impedance so you could try a 50 or 75 ohms in-line attenuator. Either impedance would do. Attenuators with RCA connections are probably unavailable, but they are available with BNC connectors and sometimes F-connectors. If you could find some you could use adapters at each end to get to and from the RCA cables.

For me in the electronics industry they are easily available, sometimes in surplus electronic stores, but it could be hard for you. If you could find some, you could start with 2 dB or 3 dB. They are additive so 2 + 3 does equal five. The attenuators could be in the $10 range each.

Alternatively, Mitsubishi owners are making their own attenuators out of Radio Shack parts (go to HDTV spot and search for fixing red push in Mitsubishi sets.)

If you are looking for really cheap, you said that a 75 ohm parallel resitor was too much. Why not try a larger value, say 150 ohms and keep moving up until you find the right value.


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post #4 of 12 Old 08-22-2001, 07:02 PM
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Larry,

It seems odd that 75 ohms was too much. How long are the cables and which end got the load?

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post #5 of 12 Old 08-22-2001, 08:07 PM - Thread Starter
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George,

Yes I may end up trying that but thats what I was trying to avoid. I was hoping for a pot.

Roger,

I am running about 30 ft presently AFTER the Extron switcher...medium grade simple rca type coax. I put the resistors on just before the switcher on that input. I did call Panasonic and didn't quite get a runaround surprisingly but by the time I got a number of someone in the know...it was past 5 EST so I'll see how far I can get tomorrow. Maybe even order a service manual. :/

Apparently no one has really played with this problem ehh? (a lot of time in Toronto with friends does that)

Larry

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post #6 of 12 Old 08-22-2001, 11:48 PM
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This fooling around with resistors, either in shunt or series is a bad idea for this application. In HDTV you are approaching frequencies of 30mhz in the Y channel. Adding resistors changes the impedance of the cable from it's desired 75 ohms. The end result is ringing or HF roll off.

It is possible to make attenuators that maintain a constant input and output impedance but it takes some university level math.

Another approach is three wideband video distribution amplifiers. The gain can then be adjusted. This is however a bit expensive.

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post #7 of 12 Old 08-23-2001, 07:58 AM - Thread Starter
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I found a friendly Tech at Panasonic who understands I don't want to hear "It's within Spec!" and I want to get access via software..probabaly a "secret" menu and adjust the output. He is going to talk to another tech when he gets in who really knows these toys and we'll see. This has to be controllable. Did anyone buy the sevice manuals for either of these? If the information is in there I will buy 'em.

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post #8 of 12 Old 08-23-2001, 10:36 AM
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There are no pots on the main board, so I don't think it's possible to adjust the output levels that way.

I'm not aware of a real service manual either. There is a service guide, but it's only 20 pages. It explains how to replace circuit boards and enter the service menu, but no mention of output level adjustment.

I assume your using the Extron to convert from component to RGB. Have you tried another converter like the Keytronic?

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post #9 of 12 Old 08-23-2001, 10:47 AM - Thread Starter
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Roger,

No, both the D-ILA and the NEC accept RGsB component.

The Extron is a plain old RGBS but with 300 Mgz bandwidth and fully independent channels so using 3 rather than 4 of them.

I just hope Panasonic doesn't approach service on these like a car dealership. If the A/C system electronics don't seem to work, put in a new one.

Larry

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post #10 of 12 Old 08-23-2001, 12:51 PM
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Which Extron are you using?

Correct me if I'm misunderstanding this, but if it's a passive switcher then you're feeding the component output of the 51 (Y,Pb,Pr) into an RGsB input on the switcher and on to the D-ILA. That puts the luminance (1.0 V p-p) into the R input on the D-ILA which expects only red at 0.7 V p-p. The Extron would have to be active and with a matrix to correct this.

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post #11 of 12 Old 08-23-2001, 03:13 PM - Thread Starter
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Roger,

an SW 4

It's a powered switcher. Should I be sending the Y on the sync line? I understood that it didn't amplify the signal. Correct me if I'm wrong. In any case when I moved the G/Y line over to the synch ins and outs just now the results are the same. The Panasonic output is much hotter than the Dish 6000. Not a WHOLE lot but it needs to be adjusted to make them equal or rejust the D-ILAs pic.

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post #12 of 12 Old 08-23-2001, 05:09 PM
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Larry,

I looked at the specs on the SW4 and I believe it just passes thru component video and doesn't matrix it. That means you are feeding Y,Pb,Pr to the RGB input on the D-ILA.

I had a senior moment in my last post. Y carries the sync so that would have to be connect to G on a RGsB input. But synch is not the problem. Y is R+G+B which is good old black and white or luminance. On the DST50/51 the Y component output is 1.0 volt p-p. The other two are color diffence signals B-Y and R-Y. They only have an output of 0.7 volts. If the SW4 doesn't do the conversion from component to RGB by properly adding Y back to the difference signals to get B and R, and subtacting B and R from Y to get G, then your colors will be screwed up.

Please forgive me for that last sentence... it's a dilly.

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