[TM-TWIN-OE] Intermittent "Tune Fail" - receiver sometimes selects wrong tuner

[m1maj]

Ever since I've had my Technomate TM-TWIN-OE I have suffered from intermittent "Tune failed" problems. I've always suspected that it was a software bug rather than a hardware problem, and now I am convinced of it. I have not reported it before because I had no real evidence, and I knew I was running rather old firmware. However I recently reflashed with up to date firmware and have the same problem, but also some new evidence. I fear the description of my problem will be rather long, but please bear with me.

First of all, my setup (copied from the OpenWebif screen):

Box
Brand: Technomate
Model: TM-Twin-OE
Chipset: 7335
Frontprocessor Version: 0
Total Memory: 137268 kB
Free Memory: 56164 kB
Box Uptime: 4d 3:06
Software
System OE: OE-Alliance 2.3
Distro: openvix
Firmware version: Apollo.097
Driver date: 20141126
Kernel version: 3.9.7
Gui version: 2014-12-05

Tuner A is connected to a motorised dish with DisEqC 1.2 positioner using USALS, universal LNB.

Tuner B is connected to one port of an octuple LNB on a fixed dish pointing to 28.2E.

Tuner priority is set to B to avoid occupying the motorised dish unnecessarily.

The symptom:

Sometimes, when switching the receiver out of standby, expecting to receive a station on 28.2E, I'd get "Tune failed". Similarly I'd find that recordings on 28.2E unexpectedly failed, recording nothing. In the former case, changing channel within 28.2E made no difference. However, switching to a channel on another satellite, and then back to 28.E fixed the problem instantly. From then on, as long as I left the receiver on, there was never a problem.

The breakthrough came recently, when I observed a different symptom. Under similar circumstances to the "Tune failed", I observed instead a very weak and broken signal from the station I wanted. Again, flipping to another satellite and back fixed the problem. I then realised that I had left the motorised dish pointing 26E. Was it possible that the receiver was in fact using tuner A, and picking up some weak off-focus signal?

Next time it happened, I proved it. When I got the weak signal, I disconnected the tuner A cable, and it stopped. The on-screen display said that tuner B was in use, but the signal I was getting was actually on tuner A. Again, flipping to another satellite (which obviously had no signal) and back brought the signal back at full strength, this time back on tuner B.

That's as far as I've got. I still don't know exactly what triggers the problem. However it seems that sometimes, when selecting a channel on tuner B, the receiver sometimes selects tuner A instead, but does not move the dish. The software reports that it is using B, but the signal is coming from A. Of course one reason that I was only observing the problem intermittently is that quite often the movable dish happens to be left on 28.2E, in which case it can use the wrong tuner and I won't notice.

This must be a bug, surely. Can somebody look into this? Is there anything I can do to get more evidence? I can't yet reproduce it to order, but it happens quite often.

 

[m1maj]

Does nobody have any thoughts on this problem?

I hit another example last night which I assume is the same underlying issue.

I set 2 programmes to record, both on Astra 2, a 90 minute programme starting at 19:30 and a 60 minute programme starting at 20:00. They would have been different transponders, so both tuners would have been needed. Box was left in "standby".

What happened was that the first recording started properly, and then when the second recording started the first one aborted. So I have ended up with the first half hour of the 90 minute programme and the whole of the 60 minute programme (all timings approximate give or take the pre/post-recording margin).

ISTM the first recording was supposed to be using tuner B but was actually listening to A. Then when the second recording starting, intending to use A, it effectively pulled it away from the first recording.

This is really annoying.... It obviously can't be a commonplace problem or everybody would be screaming, so I'm wondering what is unusual about my setup.

 

[Daysleeper]

Hi mate. I have a TM Twin, currently on Vix 100. I have and have not had any such issues. Given that that is the case, I'd suspect a hardware rather than software issue. Have you tried a fresh flash either with Vix or a different image?

 

[Rob van der Does]

"Tune failed" literally means what is says: the box tries to tune, but fails. So for some reason the signal is bad or absent or intermittent. This can be caused by any part in the line, starting by a misaligned dish, a (partly) faulty LNB, a loose connector, water or corrosion in a connector and/or cable etc etc.

As you have a twin tuner box best way is to set it up as single tuner (so one tuner not configured), see if the issue is still there. If it is (not), change the coaxes and see again.

 

[m1maj]

Have you tried a fresh flash either with Vix or a different image?

Yes, as I said in the first post, I recently reflashed. I re-entered all settings from scratch, as if it were a new receiver.

I haven't tried anything other than ViX.

Obviously it's possible that it is a hardware fault, but it seems odd that a simple sequence will invariably fix it. When tuner B fails, I just select a channel on tuner A (i.e. any position other than 28.2E) and then go back to B. It always works. But of course recordings don't know to do that.

 

[m1maj]

"Tune failed" literally means what is says: the box tries to tune, but fails.

Yes, I know that. And if you read my first post carefully, you will see that I have some very strong evidence that the reason it fails is that it picks the wrong tuner. Sorry to be anthropomorphic, but it thinks it is using the fixed dish but is actually listening to the movable dish. Whether I get a signal or not depends on where the movable dish happens to be pointing, because it makes no attempt to move it. If I _actually_ go to the movable dish and back again, it sorts itself out.

 

[Daysleeper]

Still sounds suspiciously like a hardware issue. I suspect you'll have to go through a process of elimination. Flash with a different image. If it sorts it, great, if not, you can rule out software

 

[m1maj]

Flash with a different image.

Any suggestions?

Obviously I'd need something with similar functionality, otherwise there's not much point. I get the impression that there is a lot of common code between different images anyway, so even seeing the problem in a different image doesn't actually prove that it's hardware.

I think I can only prove it's hardware by getting another receiver, which is a slightly expensive option! And I'd be really annoyed if it did the same thing.

I might try the experiment of swapping over the functions of the two tuners and seeing what happens.

 

[Daysleeper]

Try the 4d image. Like I say, I have the exact same receiver, with a similar setup, on Vix, and I've not experienced any such issues

 

[hilly]

Have you tried swapping the cables so motor is on B and fixed on A .Try a different set of bouquets. I've also had a dodgy lnb cause all sorts of problems.

 

[Rob van der Does]

Tuner priority is set to B to avoid occupying the motorised dish unnecessarily.

Please explain, as there is no such setting.

There are:
1- "preferred tuner" that sets the general preference to a specific tuner, and
2- "preferred tuner for recordings, which does the same but specially for the tuner used for a recording.

Unless you know exactly what you are doing, and have a special purpose in mind, you'd best leave the to the default values. Then E2 will always first try to use the fixed.

Or, what I have done: Set 'preferred tuner' to the motorised dish and 'preferred tuner for recordings' to the fixed dish. This way I have the motor free for live-TV as much as possible.

I can't see any point in using a different image. There is either a hardware or a setup/usage issue.

 

[abu baniaz]

Can you post a screenshot of your motor tuner configuration please?

 

[m1maj]

Please explain, as there is no such setting.

There are:
1- "preferred tuner" that sets the general preference to a specific tuner, and
2- "preferred tuner for recordings, which does the same but specially for the tuner used for a recording.

Unless you know exactly what you are doing, and have a special purpose in mind, you'd best leave the to the default values. Then E2 will always first try to use the fixed.

Or, what I have done: Set 'preferred tuner' to the motorised dish and 'preferred tuner for recordings' to the fixed dish. This way I have the motor free for live-TV as much as possible.

I can't see any point in using a different image. There is either a hardware or a setup/usage issue.

I meant that I had set both of those options to "Tuner B". Sorry if I used the wrong terminology.

I set these options in the (probably mistaken) belief that they would stop the software from occupying the motorised dish unnecessarily. From what you say, perhaps this isn't necessary. I suppose I assumed that the options wouldn't be there if I wasn't meant to set them.

I will try setting both to "auto" and see if it makes any difference. Does that seem reasonable? I can't actually remember what the defaults were.

 

[abu baniaz]

Reason I asked for a screenshot of your tuner config is that you have two opposing setups mentioned.

Also, if you suspect the dish is misaligned, you would be better off establishing whether this is correct or not. Disable the fixed dish and scan 28.2 on the motorised dish. How many channels do you get?

 

[m1maj]

Reason I asked for a screenshot of your tuner config is that you have two opposing setups mentioned.

Also, if you suspect the dish is misaligned, you would be better off establishing whether this is correct or not. Disable the fixed dish and scan 28.2 on the motorised dish. How many channels do you get?

Can you explain what you mean by "opposing setups"?

I don't suspect dish misalignment. The motorised dish receives everything from 30W to 53E in the expected positions - no problem at all. The fixed dish is OK too; it actually has an octuple LNB with other ports connected to other receivers. Most of the time my receiver is fine; in particular I can normally receive two different transponders on 28.2E at the same time. I only see the problem I am reporting when the box comes out of standby, either to watch a channel or make a recording.

 

[abu baniaz]

Diseqc 1.2 vs USALS.

I hope your PSU issue is not the cause of this. Some people are known to use a PC PSU with adaptation for testing purposes.

 

[m1maj]

Diseqc 1.2 vs USALS.

I hope your PSU issue is not the cause of this.

I don't think so. The problem which is the subject of this thread is very long standing. The PSU issue which I raised elsewhere was a very sudden and recent failure with a very obvious symptom. With an auxiliary supply providing the power rail that failed, the receiver behaves exactly as it did before the PSU problem, so I don't think they are related in any way.

Latest news is that with the tuner preferences set back to "auto", I did some test recordings overnight and they worked fine. It is far too early to know whether the problem is really fixed though. More tests running while I'm at work today.

I should perhaps add that throughout all of this I am keeping up with updates, so I'm now on build Apollo.108.

 

[m1maj]

I have done various tests and have to report that the configuration change I made to the "preferred tuner" settings have not fixed the problem.

I can only think of 4 general areas in which the problem might lie:

1. Hardware problem external to the receiver (cabling, LNB etc)
2. Hardware problem internal to the receiver
3. Configuration error
4. Software bug

Number 1 seems most unlikely to me. I cannot see how an external fault could cause the symptoms I observe. Each LNB works perfectly once it's got going, and the two dishes are not connected to each other in any way. How could switching briefly to one suddenly make the other work? I just can't see a mechanism.

Obviously it could be 2, a fault inside the receiver. If so, it has been there since new. Unfortunately it is out of warranty now, but if I did try to report the problem to the supplier, I can't help feeling that they would point the finger at the software! If I could prove it was hardware I'd probably cut my losses and buy a new receiver, but I'm really not convinced.

It might be a configuration problem, but if it is, it has happened twice, since I started again after reflashing. It seems that I did misunderstand the purpose of the tuner preference options (and still don't really know how they are intended to be used), but I have set them both back to "auto" now and it has not helped. I would contend in any case that the behaviour I observe is so bizarre that no combination of user accessible settings should cause it.

To me, the problem bears all the hallmarks of a software bug. It is for all the world as if something is not being initialised properly when tuner B is needed starting from "standby" state. The main argument against it being a bug seems to be that nobody else has seen the problem, and this is indeed a strong argument. But every problem has to be seen for the first time sometime, and I've been in software long enough to know that some bugs can be very subtle indeed and only show up in some very specific circumstances. Things that are inadvertently relying on uninitialised variables can easily fall into this category.

I presume that people familiar with the code are absolutely convinced that it cannot possibly be a software bug. Where would I find information on viewing the source code so that I can convince myself of this? I've no desire to change anything, but understanding a bit more about how it all works might in any case give me some insights.

 

[Rob van der Does]

Still could be 1.
The 'briefly' switching to another LNB can be enough. If the first LNB/switch/coax isn't 100% resending the commands might just do the trick.

 

[m1maj]

Still could be 1.
The 'briefly' switching to another LNB can be enough. If the first LNB/switch/coax isn't 100% resending the commands might just do the trick.

Maybe, but it is the use of tuner B that always goes wrong. This is connected directly to a universal LNB. There are no switches or motors to send commands to. The signals to select band and polarisation are, I believe, static signals, so there can be no concept of repeating them.

Remember that I reported earlier in the thread that I have seen a case in which the on screen display said it was using tuner B, but the picture on the screen went away when I physically disconnected tuner A. This is a specific "bad state" and is not how it behaves when operating normally. I do not see how this can possibly be an external problem, when there is no connection at all between the two dishes.