IR Receiver sensitivity problem with Scientific Atlanta Box

Capn Trips · Post by **Capn Trips** » Tue Apr 05, 2005 6:14 am

Not a JP1 question by any stretch, nor even a remote question, apparently, but I wonder if anybody here can help me sort this out.

I have a Scientific Atlanta Satellite decoder box, that is VERY erratic in responding to remote signals. It does not matter whether the signal is generated by its native OEM remote or by my HTPro that I've programmed to operate it. It's just extremely hit-or-miss.

When I send a command to the unit, it will respond about 10% of the time. I have tried putting the IR blaster directly in front of the IR window on the SA Box, and it gets no improvement. I know the base station and blaster are working, since I can see the pulses through my camcorder.

Sort of by chance, I noticed yesterday that the Power toggle signal works almost every time IF NO OTHER COMPONENT IN MY RACK IS ON!

As soon as some of the other components are on (VCR, Amp, ..) the SA Box will not receive any signal (or at least ignores 95% of them).

Now I can certainly arrange my macros to power this box on first, and off last, but while it's operating, I still need to access other functions (like channel-changing

) and no matter what I do - with RF/IR base or without, using the IR blaster or not, using the OEM remote, the unit is extremely reluctant to act on any comand sent by a remote.

Short of physically rearranging my entire system to get THIS unit as far away from other A-V components as possible in the hopes that it will help, does anybody (1) have any experience with this kind of phenomenon; (2) have any ideas how I can "shield" the box from whatever interference these other components may be causing; (2a) have any info how to increase the SA Box IR sensitivity?; (3) have any other ideas?

crust · Post by **crust** » Tue Apr 05, 2005 1:51 pm

Some systems are very sensitive to power line noise. I suggest leaving your other components on and dragging an extension cord to another part of your home and plugging kust the converter in there. See if the noise is coming in through the power line.

Capn Trips · Post by **Capn Trips** » Wed Apr 06, 2005 4:11 am

Thanks for the suggestion, but I really don't have a lot of options for power supplies, as half of my gear is US-only, and I'm operating it in the UK, so I'm running through a transformer that supplies three components and a light.

In this case, however, I deduced that the culprit was my Sharp DVD-VCR combo unit, that was immediately below the SA Box. When the DVD-VCR was on, the SA Box IR reception was horrible. With the DVD-VCR off, it was - not perfect, but MUCH improved.

So I have simply rearranged the physical location of my components in my cabinet to have the DVD-VCR as far away (3 shelves) from the SA Box as possible. I still have a small (<5%) IR signal rejection rate by the SA Box, but this is tremendously improved.

Why might/would a VCR or DVD player being on, affect the IR receiver sensitivity on an adjacent PARTICULAR component? I see no other anomalous behaviour in any of the components that are NOW near the VCR-DVD.

zaphod7501 · Post by **zaphod7501** » Wed Apr 06, 2005 6:49 am

The combo DVD-VCR units are what is called in the electronics repair business as "bad neighbor" products since the circuits (power supply especially) generate so much RF noise that they can even interfere with their own operation. (herringbone patterns on weaker stations, interference playing DVD's, etc) Newer designs have moved the power supply away from the tuner inside the unit but did not improve them at all. They are an "open frame" design with no shielding whatsoever.

The DVD-VCR is probably producing a signal that is close to the operating frequency that the original remote runs at. Good power supplies run at 100-200Khz, cheap ones run at 35-50 Khz. Guess what frequency ranges IR remotes run at?

In my jaundiced opinion the best place for a DVD-VCR is in the dustbin (sorry, I don't mean to offend but the combo products are the worst designed, worst engineered, worst built, worst featured electronic products that I have seen in the 33 years that I have been repairing consumer electronics)

Capn Trips · Post by **Capn Trips** » Wed Apr 06, 2005 7:50 am

zaphod7501 wrote:
The DVD-VCR is probably producing a signal that is close to the operating frequency that the original remote runs at. Good power supplies run at 100-200Khz, cheap ones run at 35-50 Khz. Guess what frequency ranges IR remotes run at?

That certainly explains it. I would imagine that the DVD-VCR's current proximity to a pretty high-end (Sky+ box) component - presumably well/better shielded - would explain why it's NOT interfering with its NEW "neighbor", whereas it did interfere with the previous one.

zaphod7501 wrote:
In my jaundiced opinion the best place for a DVD-VCR is in the dustbin (sorry, I don't mean to offend but the combo products are the worst designed, worst engineered, worst built, worst featured electronic products that I have seen in the 33 years that I have been repairing consumer electronics)

No offence taken, I acknowledge that I went for an inexpensive solution to a diemma I was facing. But I still probably wouldn't give QUITE the condemnation that you have. It fills a need for space-efficiency in my setup. I don't use the tuner, but I get VHS tapes and DVDs of all region and color system combinations here, and having separate PAL/NTSC VCR's and PAL/NTSC/multi-region DVD players would have been too painful. As it is, my rat's nest of wires is difficult to keep under control.

This unit that plays back prerecorded tapes and DVD's just fine, thank you, and fills a niche requirement for me.

(Although I have no doubt that ten weeks from now, when it fails due to shoddy workmanship 1 day after the warranty period expires, I will rue the day I bought it and be telling myself "Why did I not heed Zaphod's advice?")

P.S. Are you looking forward to the destruction of Earth to make way for a hyperspace bypass this summer?

Post by **The Robman** » Wed Apr 06, 2005 11:21 am

Maybe it would have been best to get a good multi-system "converter" VCR and a multi-format DVD player. I have a Samsung SV5000 "world wide" VCR that will play tapes of any format and it will convert the output to whatever format I want, so I can easily play tapes from the UK and have the output shown on my standard NTSC TV, and I can record tapes in PAL to be sent back to the UK. I paid about $500 for this VCR quite a few years ago, but I have no idea what the going rate for such a player is now (and as always, the UK prices will be about double what the rest of the world has to pay).

As for a DVD player, there are lots of options there.

zaphod7501 · Post by **zaphod7501** » Wed Apr 06, 2005 9:35 pm

Obviously there is a market for the product but it occurred after all the major manufacturers quit building the needed pieces leaving construction to some really poor companies. Outside the USA they might not have the nasty limitation the US versions have - VCR output on composite and RF only while the DVD will output on S-Video and component. This means you need 2 sets of cables from the single box to connect it correctly.

Actually I think the Earth may have already been destroyed and our thoughts are living on in an intergalactic reality show controlled by a movie studio.