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

I have a 1956 Philco that played GREAT for longer than I have been alive, and up to the last day of over the air television broadcast. When I hooked up two different boxes I got more or less the same depressing effect. I get a picture and sound with noise in it; some type of distortion.

NO, it is not pixilating from lack of signal.:D I can go into the menu and there is unwanted distortion or noise. I tried channel 3 AND 4 and get a slightly different effect, but neither one is acceptable. Even my VCR didn't act exactly right, but it performed much better, but with low volume.

I am just curious what others here have experienced with the changeover, and what they have done about compatibility issues. I KNOW that this can work. My 1950 RCA TC-127 does fine but has a low volume issue, but it had that before the changeover, so I know it's the set in that case.

With the Philco I am wondering if the trouble is happening because channels 3 and 4 have NEVER been used around this area. Perhaps there are capacitors in the tuner that haven't seen voltage in many years other than for a few seconds as the selector rolled past 3 and 4.

Any input and ideas are appreciated and will make this a useful thread for now and for future TV buffs. :thmbsp:

I watch RTV and the sound is often messed up, is it doing it on all the OTA channels?

There are no 'over the air' channels, if that's what you mean by "OTA." I'm not sure what you mean by "RTV" either. My problem is there regardless of what DIGITAL channel I am viewing. Again, even the converter's menu has audio and video noise, so I'm thinking that there is an issue with the tuner using channels 3-4, that it has never used. I really don't know, so I hope this thread attracts some folks who have tackled converter issues.

I will add that I did swap out the matching transformer, so that's not causing it, unless they both were bad. :scratch2: I doubt it...

Some have got better results by putting the converter box and antenna away from the set. Something about interference from the box itself was causing noise and distortion in the picture. Make sure the cable from the box isnt leaky also. I've been lucky so far in that I hadnt had any troubles with my boxes and old tv's except for an old Bendix where the signal was too strong and overloading the picture. An attenuator fixed that.

RTV is the retro TV channel I watch, digital over the air, I have a digital receiver that converts to analog out on channel 3. I have not had any problems except for some programming that seems to have lousy audio, mostly been on the RTV network (mostly some of the really old programming they broadcast).

I have yet to put my converter on a truly "old' tv--but right now--I am "kinda", watching RTV on that 1985 sony KV-1371, and it works nice. I know the Sony is not really an "old tv" having digital controlled tuning and remote and such...but to most people--it is an "antique".

Perhaps I will try the converter on my 29JC20 Zenith--and see how it does. It was always pretty good on OTA signals--when analog was still around....and a Laserdisc on ch3 did OK too.

My 53 Philco was overloaded by the output of either the Channel Master or Zenith converter boxes... perhaps I need to work on the AGC, but for now, I just put an adjustable attenuator (R/S 15-678) in the antenna line and adjusted for best sound/pix.

jr

I had an issue with this on a set. I was getting dots across the screen till one day when I moved the coax to get a vacuum hose behind there to get at dust bunnies. After realizing the dots went away, I played with the coax for a bit and discovered that's all it was... just a certain way the wire leaned against the set.

My VCR/DVD recorder has the new style tuner in it, so can I use that as a "converter box" on my sets. I haven't really noticed any difference, but then it's rare that I watch tv thru that tuner. I'm usually watching thru satellite being that I only get one channel OTA and it's only 50% of the time. Sure miss analog... I got that 100% of the time!

I had a similar issue with a cable digital-to-analog setup on one TV a couple of weeks ago. Some of the channels were missing, others would pixelate. I took off one very old piece of coax and replaced it with new: problem gone. Digital likes perfect, non-lossy connections.

I've had the cheap RCA converter hooked up to several vintage sets, including my '52 Kaye-Halbert, and '65 Zenith roundie color set. No problems.

I wonder if your set is having AGC issues? I've seen early sets with keyed AGC do weird things on VCRs and DVD players. How about if you disconnect the matching transformer from the TV, and attach a piece of 300-ohm wire to the matching transformer, and let it lie around behind the TV? If the TV doesn't like the "closed circuit" connection from the box, it might be OK with the wire you laid out, just acting like a transmitting antenna. Most of my pocket TVs will pick up a fair signal that way if up close.

Charles

I used my Zenith converter on a few of my restored sets and didn't notice any real problems. Switching the audio from stereo to mono boosted the volume.

If channels 3 and 4 haven't been used in 54 years, it's possible that those contacts in your tuner are simply oxidized and/or dirty. I have enjoyed a huge improvement after cleaning the tuner on some of my old TVs.

Cleaning isn't difficult. I use Q-tips dipped in DeOxit. Do not "brighten up" the contacts with sandpaper or a file, or you will be a very unhappy man. The plating on contacts may be thin and delicate.

Phil Nelson

I'm not sure exactly what kind of "noise" or "distortion" you may be experiencing, so I'll make a couple of guesses about what the problem may be.

If your local analog signals had been weak, and your picture with the converter box is prone to very high contrast or "tears up", you may be able to fix this by backing up on the AGC control on your set (presuming it has one). When only weak analog stations were feeding the set, signal overload was never a problem. With your converter box, a strong analog signal (capable of overload) is fed to your tuner, whether the DTV signal the box is receiving is across the street or from the deep fringe.

As far as audio noise, this is very common, if your box is not delivering fully-modulated audio to the set. Most CECB's have a volume control inside the box (allowing the user to change volume by remote control, even if the set does not have remote). If the volume setting (inside the CECB) is not at maximum, you are turning up the volume on the set to compensate, which reveals the noise your set's audio chain always had. A problem that is just as serious, and not as well known, is that many CECB's have two "audio modes", one for when the user is using RF input (ch3/ch4), another for when the user is using audio inputs (red/whi RCA cables). When set on "A/V out", the volume level (even on ch3/ch4 FM carrier) is far below what it would be using the "RF out" audio mode, so make sure the audio mode is set to "RF out".

That being said, I still notice that video intercarrier buzz (which, IMO, seems to have plagued all old sets, even when I was little and those sets were new) seems to be worse with CECB's than it had been with analog OTA signals, and worse with some CECB's than with others (I wonder if CECBs have a whiter max white than analog signals did?). It was a problem with my Emerson 1224, but recently replacing the 5AN8 and 5T8 tubes (in the audio IF, discriminator, first audio circuits) has made the situation much better.

My grandmother was having this issue with her old set in the living room. It's an old GE floor model from the 80's. She was complaining about how strange the audio seemed to her. Once I turned up the audio on the converter box, then turned down the TV audio, everything sounded normal again.

...

This does not make sense at all. The converter box should put out more than enough RF. Check the internal cabling of the set.

For the original poster - if the picture is really bad (sounds like it) and is not an AGC problem, could it be that fine tuning of channel 3 (or 4) is way off and you are attempting to receive the lower sideband? Hook up a VCR with channel 3 output and see if you get the same bad result. RF output of a converter box is essentially the same as RF from a VCR.

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,

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

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

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.

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

:lmao:

"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?:scratch2:

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

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,

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

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!

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

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.

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

...

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!

When we had analog signals, the stations varied in strength but the set was always amazing in the fact that it would pull in the stronger channels with no antenna at all, and it would do the rest with only the built in antenna. Perhaps I will hook it up again tomorrow to give a better description of the noise and distortion that I have mentioned. In short, I was very disappointed that my set that always seemed invincible and strong suddenly became unviewable with all of this digital CRAP! I will say that I am not referring to digital reception. That is why I mentioned in my original post that I use the digital converters MENU as my signal source so I don't even have to think about reception. Again, even when I am in the menu there seemed to be a streaking or tearing in the video with a buzz in the sound which is generated somehow by this box or its associated connections. All symptoms go away when the box is removed. I tried two different converters and RF modulators, but not cabling. Again, tomorrow I will try it again for better description and I will swap the co-ax cable.

Thanks Robert and everyone else who has helped out here! :thmbsp:

Instead of trying to decipher all of the abbreviations, I will describe the "converter" as one of the 'boxes' they are pushing for those of us left who have no, or choose not to participate in, cable or satellite service and were watching over the air ANALOG signal TV. My abbreviation is A.B.O.F.S.! LOL! Go figure....

Also, I see now that I made a mistake in stating that there are no 'over the air' channels. It is STILL 'over the air', what has changed is the TYPE of signal from analog to digital. Sorry for the misinterpretation.

@Tubejunke

Just a thought, have you tried unplugging the TV and plugging it back in the other way?

Perhaps you have a hot-chassis set, a cap has shorted somewhere, and you're putting 120VAC into the tuner when you hook the CECB up to it?

Just a thought.

Good thinking, but my Philco is a transformer set....

If it is properly designed, a "T-pad". This is similar to the "L-pad" used for speaker-level volume controls but it has three ganged potentiometers instead of two.

The stem of the T is a potentiometer to ground and the arms go to source and load.

An L-pad presents a constant impedance to the source and variable to the load (assuming that the source and load impedance are correct).

A T-pad presents a constant impedance to both the source and load (with the same underlying assumption).

Switched attenuators are really stepped T-pads.

Thanks JR for the pointer to the rf attenuator sold by solid signal.

As to the Philco set, some of the early 1950 Philcos had several versions for urban or fringe reception. There were different parts in the AGC circuit for higher gain in fringe areas. If this is the case with your set it is being waaay overloaded by the signal from the converter box. Also it's video amp is narrowbanded to help hide snow in the pictures. If you can give me a model number and code number (something like 50T 1400 code 121), I may have the original Philco bulletin that details the resistors and caps you would change to lower the set's gain for urban use.

Cliff

well I am a believer now that indeed the converter boxes can cause issues. I was fighting a bad sync buzz on my motorola T-14, until I tried a transmission based on a blonder tongue modulator. NO BUZZ, I could not believe the difference, so to the OP yes indeed I was havving trouble with my digital converter box on my old set. It just seems to be certain old sets that can't deal with it. My 59 predicta and up have no problems.

I would be interested to know if these sets that have trouble with the converter boxes also have trouble with VCRs. Also, what does the BT modulator have in it for audio? Separate audio oscillator and modulator, or 4.5 Mhz added to the video like VCRs and converter boxes do?

The 1956 Philco that started this thread has trouble with both digital converter and VCR. The VCR is way better than the digital converter. If I remember right the converter seemed to have some sort of interference, while the VCR signal seemed a little weak with low volume. I haven't checked the tuner and I.F strip tubes yet. Again, the set played fine when I had an analog signal. It seems like years ago I used a VCR with this set with no trouble. Channels 3 and 4 have seen little or no use for many years. Perhaps a good cleaning is in order. I just don't feel like dirt would be the whole problem here....

My 1949 RCA uses a digital converter, VCR/DVD combo with no trouble. Interesting......

Cleaning the tuner would be easier than realigning the RF/IF or rebuilding your AGC section to change its behavior. If that doesn't improve the situation, cross it off your list of possible causes and try something else. Sitting around and theorizing for weeks isn't getting you anywhere.

It's not surprising that one old TV will respond differently to a given source than another old TV. They have many differences, not only in original design but also in the degree to which they have been restored.

Phil