Is anyone having trouble getting your Digital converter box to work with old sets?

[Findm-Keepm]

Originally Posted by Tubejunke

There are no 'over the air' channels, if that's what you mean by "OTA."

Are we talking a ATSC to NTSC converter box or a Digital Cable Converter box?

Here, Cox Communications muddied the Digital Transition with an all-out advertising campaign for "convert to digital - upgrade your cable service" kinda ads. They were referring to upgrading the QAM boxes to their digital (read:HDTV) service. Half the folks on cable thought the ATSC to NTSC boxes WERE the ones Cox was talking about, and bought them in stores. I got one of my Zeniths for cheap from a lady that experienced that very confusion.

The Motorola (Cable) Digital HDTV Boxes are noisy. I get moire/co-channel lines on my RCA roundie (CH3 or 4) unless that sucker is standing on edge (and presumably radiating in the horizontal plane above the set's cabinet).

I'm not assailing the OP's intelligence - just wondering what converter he's referring to, given there are "no 'over the air' channels.

Cheers,

[cbenham]

I just tried to search Radio Shack online for the variable rf attenuater 15-678 mentioned earlier. No such number in their system now so it may have been discontinued. #:^(
Cliff

[jr_tech]

Originally Posted by cbenham

I just tried to search Radio Shack online for the variable rf attenuater 15-678 mentioned earlier. No such number in their system now so it may have been discontinued. #:^(
Cliff

That is too bad! They have really changed their emphasis !....But Solid signal seems to have pretty much the same unit:

http://www.solidsignal.com/pview.asp...u=853748001293

not affiliated,
jr

[Phil Nelson]

What's in those attenutators, exactly, besides a potentiometer? I have a similar looking Radio Shack model. Got it at a garage sale for a nickel or something. Maybe it's defective. I tried it a couple of times, and it seemed to have a range between distorting the signal and really really really distorting the signal.

Back to tubejunke's question. I see no clear statement that any source works well on channels 3 and 4 and I will respectfully renew my advice to clean the blasted tuner already. Quick and easy. I could show a child how to do it. Costs about 3/8 of a cent. Can't hurt, and it just might help

Phil

[Old1625]

Because those whammy-boxes are made in China the quality control is apt to be suspect. I tried several converters, and then DVD recorder/players, then finally bought a digital-ready flat-screen which was finally rock-n-roll.

[Reece]

Phil Nelson wrote: "it seemed to have a range between distorting the signal and really really really distorting the signal."

[jr_tech]

"What's in those attenutators, exactly, besides a potentiometer? "

Mine is soldered shut all around the box, so I have not looked inside... but here is how it acts:

At "min", input to gnd =200 ohms, input to output= 2 ohms, output to ground=200 ohms.

"centered", input to gnd =180 ohms, input to output= 220 ohms, output to ground=380 ohms.

At "max", input to gnd =48ohms, input to output= 510 ohms, output to ground=560ohms.

Any guesses as to whats inside? perhaps 2 pots and a couple of resistors?

A nice switched rf attenuator can be constructed using this guide:

http://www.merseyworld.com/wadarc/Te...Attenuator.htm

The values given are for a 50 ohm environment... for 75 ohm, recalculate the resistor values... 3db r1&r2=440 ohm r3=27 ohm; 6db r1&r2=220 ohm r3=56ohm; 10db r1&r2=140 ohm r3=106ohm; 20db r1&r2=91ohm r3=370ohm.

jr

[Findm-Keepm]

I have two of these variable VHF-only attenuators, one Blonder Tongue and one Channel Master. Both are very similar in construction - the BT has a 220 ohm resistor across both the input and output, with a 1K pot between the input terminal and the output terminal. The writing is worn off the case, so no model or attenuation factor.

The Channel Master has 240 ohm resistors (1/2w film types) and a 1.2K pot between the input/output terminals. It is obviously Asian made - there was an earlier model with a slide pot, but mine has the rotary pot. It's a carbon or cermet element. I had to desolder the shield to get to the guts - not service friendly.

Down East Microwave has the schematic to follow, about half way down this page:

www.downeastmicrowave.com/journal.htm

Just make sure it's in a shielded encosure. Hammond and Pomoma make nice little boxes for this kind of use.

Cheers,

[Phil Nelson]

Thanks, maybe I should try making an attenuator. I have a couple of pieces of equipment, including a pattern generator, that tend to overload some old TVs. This despite a level control on the (cheap) generator.

Phil Nelson

[Zenith26kc20]

The attenuator may or may not help. On my Zenith Color I had to very carefully align the quadrature coil and buzz control to the converter box. It makes it livable except when heavy graphics are on the screen. I have had success with putting the converter box thru a VCR (RF to RF out and using the VCR's tuner/IF and RF modulator to clean the signal. It seems to take away a lot of the overload.
Using the VCR with cable is the only way with cable but a video stabilizer is needed to get the lines out of the top (information sent during retrace).
This works better than anything on my VT-71.
Rebroadcasting may present problems, I haven't tried it but it may be fun!

[jeyurkon]

M Access HD converter box has horrible RF output. It has noisy audio that doesn't align with the video on any set, old or modern. However, if I run it's composite output through a modulator it works great.

John

[Robert Grant]

Yes, I noticed that when I reviewed the AccessHD DTA1030D in November, 2008.

It also had poorer multipath performance than the Zenith/Insignia, Philco or Zinwell CECBs (but still far better than the old RCA HDTV set top boxes from 2003).

To its credit, the DTA1030D has excellent EPG.

Also note that several completely different models of CECB were sold undet the AccessHD brand.

[bandersen]

I get the same results as John with with my Access DTA1010 and vintage sets.

[andy]

...

[Robert Grant]

In the US, at this point, generally nothing. In a few situations, there are digital TV stations on lowband, but the few that are in population centers are on channels 5 or 6.

In Detroit, RF channels 2 and 4 are both clear.

In any summer before 2009, sporadic-E skip to the South would mean WBRZ in Baton Rouge would be fighting it out with local WJBK.

In 2009, I had YNFA302 in Managua, Nicaragua, all alone with a weak signal!