CurtPalme.com Home Theater Forum

[JustGreg]

Hey Guys,
A buddy of mine has a VERY old Oscope that I'd like to use to:
1) Get my feet wet with an Oscope
2) See what kind of noise I have on the line(s) feed to my theater

I'm getting noise in the image, very faint but still there. Ramps up (frequency/timing) when C&B is increased. That alone tells me the problem is probably not related to line noise but I also have some telemetry problems with 2.4 and 5.8Ghz equipment in the house.

I'll have to call my buddy to see what this ancient beastie is but in the meantime I wanted to toss this out there. I'm not even sure he has probes; or the right ones. Like I'd know what the 'right' ones are!

Thanks!

[JustGreg]

Talked to the guy tonight and from what he says he's not even sure it's an Oscope...I'm guessing no by the description. It's an HP but he says it has a display that's something like 14"!? He says it's heavvvvvvy. I wouldn't doubt it. His dad got it a long time ago...says it's something like 30-50 years old. I'm thinking it's either not an Oscope or it's so old it runs on DC current.
I'll find out this weekend when I recap his Toshiba 52" RPTV and give it a tuneup (scan sweep board problems) and post at least a pic of it for you EE's to identify and chuckle at.

[VideoGrabber]

Greg,

first off, don't handle an oscilloscope if you've got your feet wet.

Secondly, the places you can use a scope (and what type of scope will be adequate) depend, not surprisingly, on what type of signal you want to look at. For example, looking at line noise on a 60 Hz power line is a whole lot different than trying to see residual noise on a millivolt level 1080p analog signal line.

> I also have some telemetry problems with 2.4 and 5.8Ghz equipment in the house <

Well, if you really want to see signals at those levels, you're talking mucho bucks. The widest bandwidth instrument I have in my lab is a 1 GHz Tektronix, and that wouldn't help. Most scopes you'll find at a semi-reasonable price will be 50 MHz or less. At those high frequencies, if you're worried about the fundamentals, you'd probably be better off with a spectrum analyzer than a scope. Even there, the best SA I have is only 1500 MHz, far below what you're talking about. But if you've got $5-20k to spare...

The other thing to keep in mind is that at those frequencies, you'll probably see NO impact on your PJ directly. I.e., those frequencies are simply too high. They're outside the bandpass of anything that's happening inside your PJ. However, it is possible for them to be rectified and "picked up" by various stages in your PJ, and those "alias components" (much lower difference frequencies, or demodulated carriers) to get coupled in and amplified along with the frequencies you DO want to maintain. Your best friends there are usually capacitors on the supply lines, which shunt those undesired higher frequencies to ground... before they get into your signal chain. In a practical sense, Mike Parker here probably knows more about dealing with that problem than anyone.

Maybe if you provided some more details on the characteristics of the noise you're seeing in your image, someone here could be more specific in helping you sort it out.

What kind of "telemetry problems" are you having, BTW?

[JustGreg]

Note to self.....Keep feet dry.

I'm sure I butchered your trade syntax via my ignorance, for that I apologize.

OK...the noise. It may just be that the green tube is easier to see this noise than the other colors?...but I can only see the noise on that one clearly. With brightness at ~25 and contrast at ~15, with the PS3 dashboard up, lenses off, there are broken moving lines moving from bottom right up diagonally to upper left.

They move fairly rapidly with the B&C set to these numbers but move faster as I increase brightness. I don't know how to describe it better than that; broken, or dotted lines that is brighter than the surrounding image by a small amount. Nothing too drastically bright, just there.

As I increase Contrast they move faster, change direction a little to more upward, and cycle faster. BTW, the red tube and mags are brand new. In another week or so the others will be too so time will tell if the problem is just at the green.

I've routed all the heatsink cables away from the HV and HDM sweep cables the best I can but it persists. I also added the ground strap from the vertical board connector to chassis ground as suggested by MP in another thread.

As far as the telemetry issues, a while back, a year or so, I was trying to send A/V to the bathroom outside the HT where I have a 17" LCD on the wall and of course audio in the form of a PC sub/amp and bookshelf speakers. I was trying X10 to do it and in the past it was more than aqequate for the task when used upstairs to beam out to the deck from the livingroom ~10ft away.

For some reason trying to send a signal out of the HT, through a drywall and 2x4 wall, and into the bathroom results in OK video but the audio was hosed. Alot of noise and drop outs. (or it was the audio that was OK but vid sucked...can't remember exactly as it was a while ago) The xmtr and rcvr point directly at each other and the distance is ~20ft. I've tried pretty much everything I can think of. I gave that up for double runs of CAT5e for baluns with toslink support which works great.

That fact the X10's failed (I even had another set of them RMA'd to me thinking they were the problem) still leaves me thinking something is generating some serious RF down there. That's pretty much all I meant by telemetry issues.

[Nashou66]

Greg remove the Contras Modulation Board above the CLM bay and see if the issue goes away.

Athanasios

[JustGreg]

[Sparky015]

halos are common for AC sets. THat is one of the benefits of going to a LC, I believe. Unless it's really bad haloing. Are you using HD8s?

[VideoGrabber]

Paul,

I think Greg is talking about haloing he's seeing right on the tube face, with the lense removed.

Greg,
> I thought of changing out the glycol but I haven't heard anybody ever talk about doing that on a non LC set. Any merit to doing that? eg, are those small chambers subject to fungus or clouding? <

Yes, they are. Fungus is relatively rare (but seems to have happened to folks here a lot), but the glycol will definitely darken over time. Thus robbing you of some of your precious light output. And it's not clouding (i.e., tending toward milky white)... it actually turns brown!

[JustGreg]

Yeah I was talking about haloing at the tube face. Never having owned an LC set I had nothing to compare it too. The glycol 'looks' clear enough tho. Put it this way, the B&G look the same as the new red tube.

Thank guys. I was just thinking 'out loud'. I found the problem with the green tube and the noise...one of the new caps I just installed (C26) had really high ESR so I replaced it and all is good now. Yay!!
And the new tubes are on the way so..I'm going tubing this weekend!! Thanks Paul!!