DVB-S2 MPEG4 tuner issues

gtg60

I recentley purchased a Mvision HD200 combo but am having some issues with channels that are MPEG4 and on DVB-S2 transponders.

As I bought this item to replace a Sky HD box with FTV card one of the primary channels I wanted was Channel 4 HD, I use a T-Rex (Dragon) CAM and a genuine FTV card.
When watching the channels the sound and picture break up constantly making it totally unwatchable, on further investigation (and with help from fat-tony) I have discovered that virtually all DVB-S2 transponders on 28.2 are suffering the same problem, the problem manifests itself as follows, Signal strength remains constant at ~80% but signal Quality drops from 98% to 0% and the colour dissappears from the scale meaning it has lost it's lock, this happens continously in a cycle of anything from 1-~30 seconds.

I have noticed, however, that if I switch the receiver on from cold that it does not happen for up to ~5 mins, the DVB-S2 transponders are as follows:

I have 12363V with no problems,
12344H cycles between 86~98% and occasionaly drops out completely.
12324V, 11798H, 11720H loose the Signal Quality and lock constantly.

Does this sound familiar to anybody? It would appear to me that once the tuner(?) heats up that perhaps a component becomes out of spec and causes it to loose lock?? I have heard that if you cool the receiver with a fan the problem goes away (I cannot confirm this at the moment but will try this evening).

Any and all thoughts appreciated, at the moment the only correlation we have found between the failing channels is that they are DVB-S2 and HD using MPEG4 but there is at least one transponder that this doesn't happen on and BBC HD / Luxe HD via DVB-S are fine also.

Apogee

Are these dropouts occurring only when the CAM is inserted or all the time?

gtg60

Apogee wrote: »

Are these dropouts occurring only when the CAM is inserted or all the time?

The CAM has nothing to do with it, it happens whether I have the CAM inserted in the CI slot or not.

Apogee

More than likely a flaw in the tuner then. Move the dish to Astra 1 and tune in the FTA DVB-S2 TPs to confirm.

11362, H, 22000 (Arte) or 11914, H, 27500 (Astra/Anixe).

gtg60

Apogee wrote: »

More than likely a flaw in the tuner then. Move the dish to Astra 1 and tune in the FTA DVB-S2 TPs to confirm.

11362, H, 22000 (Arte) or 11914, H, 27500 (Astra/Anixe).

My dish is stationary, fat-tony kindly did some tests for me, he stated:

The DVB-S2 channels in the clear on 5W (11139V 26707 2/3) were fine. The encrypted channels here on 11471 29950 2/3 were rock solid also.

All DVB-S2 channels on 19.2E were fine also.

Apogee

Does fat-tony experience the same dropouts on those particular DVB-S2 TPs (12344H etc) on Astra 2?

Do you own a DECT phone?

gtg60

Just confirmed that it is an overheating issue, held a hairdryer (on cold) at the tuner, after a minute the drop-outs stopped and continued to stay perfect not only until I stopped the hairdryer 5 mins later but for a further 3 mins after that (until it heated back up again I assume).

fat-tony

Interesting - I'll check that out also - funny it's only happening on the Astra S2 transponders (and then not on every one)! Wonder is the heat causing some clock reference to go out of step? As I said in an earlier post the maximum symbol rate capability of the tuner is 30,000 on an S2 transponder (but 45,000 on S), so it may be that it's just up against the very edge of the ability of the tuner which is affected by the temperature. It might be possible that a firmware fix may be able to take this into account, but it may be a physical limitation. You may have to install a CPU cooling fan over the affected area.....It's a pity that this spoils what is otherwise a pretty good little box. Though I have issues with the user interface as regards the motor handling - but a new release of firmware would sort that.

gtg60

fat-tony wrote: »

Interesting - I'll check that out also - funny it's only happening on the Astra S2 transponders (and then not on every one)!

Baffling is the expression I'd use!

fat-tony wrote: »

Wonder is the heat causing some clock reference to go out of step?

I was thinking along the same lines, if this didn't have a 24 month warranty (and a warranty sticker!) I'd have taken it apart and started fitting heatsinks to suspect components in a bit to sort it out!! I'd really like to stay away from fans.

Bottom line here is that the receiver isn't performing as it should and it is looking like I may have to return it as I don't think this can be fixed with a bit of firmware.

fat-tony

Ok I tried your hairdryer trick. It took a good 5 mins of cold air to affect the problem at all. The hottest part of my STB is over the power supply, so that's where I aimed the airstream. The signal quality (which had been varying between 50% and 0%) then started varying between 50% and 98%. Within a minute of switching off the air, the SQ dropped back to 50% - 0%. It was only when I re-read your posting that I noticed that you aimed the airstream at the tuner module. This is over the other side of the box from the PSU and it doesn't seem to get warm. I'm stumped as to why it's not happening on each transponder, although I noticed that the SKY Sports HD transponder was varying between 50% and 98% quality at all times (though never dropped to 0%). This would mean that you mightn't notice an issue while viewing this transponder. It's puzzling all right - may be a faulty batch of tuners....:eek: (just like the crap USB extenders!).

gtg60

So, did you actually try it on the tuner module? The problem disappears within a minute and takes a few minutes to return after you remove the hairdryer.

Oh yeah, the USB extender I got with mine was faulty too, what's that all about?