Faulty Preamp PSU Caused Humax Reception Problems on Some Muxes

Some interesting results from readings taken with the new meter this morning between 10:30 and 11:30. Weather in Woking: fine, sunny and clear.

In the loft, coming from the aerial (UHF channel - Signal strength in dBuV - C/N in dB - Post-correction BER):
22 - 51.5 - 32.0 - QEF (defined as <1.0E-04 BER or less than one uncorrected error event per hour...
23 - 48.0 - 31.0 - QEF ...but used here to indicate meter read "Post BER:<1.0E-08".)
25 - 49.5 - 30.5 - QEF
26 - 48.0 - 31.0 - QEF
28 - 49.0 - 31.0 - QEF
30 - 49.5 - 30.0 - QEF
35 - 37.0 - 20.0 - QEF

In the lounge, going into the PVR:
22 - 66.5 - 23.0 - poor
23 - 65.0 - 22.0 - poor
25 - 65.5 - 22.5 - poor
26 - 64.5 - 22.0 - poor
28 - 64.0 - 23.0 - poor
30 - 65.0 - 22.5 - QEF
35 - 51.5 - 20.0 - QEF
 
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Repeat at the OUTPUT of the amp in the loft, powering the amp via the meter (section 3.2 of manual says it does provide that).

Or just repeat measurements downstairs with the psu-splitter removed first as a start on diagnosis of this problem. It may be something like AC ripple from the PSU adding noise?
{On analogue PAL one got rolling hum bars with such faults).

As you know, the HDR Fox-T2 has a 5V antenna power option... which may give slightly less gain than 12V.

As for the signal level in loft (direct from antenna):
Wolfbane predicted field is miles out.
Poor antenna gain or cable / connection losses are enormous.
Or there's some other fairly severe path blocking / attenuation going on between CP and your location.
Fairly level readings (3.5 dB max) suggest that my standing waves suspicion is pretty much unfounded though!
 
Rodders53 said:
Repeat at the OUTPUT of the amp in the loft, powering the amp via the meter (section 3.2 of manual says it does provide that).

Or just repeat measurements downstairs with the psu-splitter removed first as a start on diagnosis of this problem. It may be something like AC ripple from the PSU adding noise?

As for the signal level in loft (direct from antenna):
Wolfbane predicted field is miles out.
Poor antenna gain or cable / connection losses are enormous.
Or there's some other fairly severe path blocking / attenuation going on between CP and your location.
Fairly level readings (3.5 dB max) suggest that my standing waves suspicion is pretty much unfounded though!
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That first suggestion is a good one. Re the second one, not sure how I'd interpret the results given that the signal would have passed through an unpowered preamp.

I've already checked at the output of the PSU/splitter to confirm the problem is present there (as it should be with only coax thereafter). I previously measured 11.0V with A DMM at the preamp but will take my 1985-vintage Hameg 'scope up to the loft to see how clean the supply is. Could this be another dried-out electrolytic fault..?

I still have the Fringe 18dB Group A preamp which the Antiference one replaced in Mar 2003 if the preamp proves to be at fault.

Signal strengths from the aerial are broadly similar to those I measured in Mar 2018 (post #13).

More anon.
 
Your expensive brand new meter has an 'antenna power' option :RTFM: Section 3.2 (5V, 12V and 24V options).
THAT powers the masthead. Use it. Simples.

11 V from a 12V nominal 50mA amplifier draw is low (imho) suggesting poor DC conductivity in the cable? A DMM can measure ac ripple - but not on DC V range.
 
Newcoppiceman said:
Pic showing UHF 22, 23, 25, 26, 28 and 30 muxes. The 64-QAM muxes' post-error correction BERs have improved since this morning and are now (15:00) varying between E-03 and E-07; the other two remain at a solid <1.0E-08 so very definitely QEF (Quasi Error Free).
Click to expand...

I suspect you have some trees that have increased in height in the signal path. Now the wind is blowing them around and creating problems.
 
Rodders53 said:
Your expensive brand new meter has an 'antenna power' option :RTFM:

11 V from a 12V nominal 50mA amplifier draw is low (imho) suggesting poor DC conductivity in the cable? A DMM can measure ac ripple - but not on DC V range.
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Yes, yes I know! I RTFMed before the meter had even arrived! I misunderstood your "just repeat measurements downstairs" as meaning the ones I'd made this morning (without antenna power enabled) but you meant with it on I now appreciate.

I was a tad suspicious of that 11.0V reading ...and rightly so. Attached are two pics showing the 12V supply (and 0V ref) measured at the preamp. The PSU (pic with the droop) is obviously knackered; the other pic is the clean 12V supply from the meter - which then measures QEF for all muxes at the preamp output. Pics of PSU/splitter also attached - should find fault quite quickly with 'scope.
 

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When I tried this on mine, it complained incessantly about the aerial being short-circuit. It sticks a box up over the picture that cannot be dismissed. It worked to power the amp., but was obviously unusable due to the incredible annoyance of the box.
 
Rodders53 said:
Problem solved? Perhaps.
Click to expand...
No perhaps about it! I still have an old single output Antiference 12V PSU so have deployed this with a splitter to provide the two feeds (temporary arrangement until I fix the original PSU - probably the reservoir electrolytic).

Thank you for your interest, insight, suggestions, etc. Nice to get to the end of this saga - full green bars on all muxes again and SWMBO very happy.
 
Black Hole said:
Why not keep it as-is? Don't fix what ain't broke.
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The simple satisfaction of fixing a faulty device?

I fixed an old 2-way saddle-clamp wired amp - replacing the psu faulty electrolytic that gave the hum bars mentioned earlier, way back in the late 80s/early 90s... that same amp was left in the loft of my last home in 2016 when we moved.

prpr said:
When I tried this on mine, it complained incessantly about the aerial being short-circuit. It sticks a box up over the picture that cannot be dismissed. It worked to power the amp., but was obviously unusable due to the incredible annoyance of the box.
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Hmmm. Sounds like the masthead amp was pulling excessive current - hence the (overload) s/c type warning. I'd have expected the volts to be collapsed to 0 by the protection circuit, though. Strange Humax design (as is quite typical of the brand).

I powered a Vision Gold masthead from my -T2 in a touring caravan OK a few times (I rarely needed it). That amp was 5-12V input by design though if it makes any difference.
 
Black Hole said:
I suppose if you like an "exciting" life (eg SWMBO wanting to watch Strictly in 10 minutes)...
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Sure do.
Our Foxsat decided to lock up on a decoder and produce no sound (but perfect pictures) the other night and needed a mains reset, with less than 10 minutes before a 'vital' recording was about to happen (discovered by going to standby and back on in an attempt to fix the sound).

That first boot while it acquired the time from the home transponder and back to standby took, seemingly, f_o_r_e__v__e___r r r r
 
Rodders53 said:
The simple satisfaction of fixing a faulty device?
Click to expand...
Quite so, plus the fact it would be easier to replace the likely duff reservoir cap than to sanitise the temporary setup; also would need a working spare. The unusual splitter design is because I ripped the original inductive one apart trying to remove it from the Antiference PSU (very tight fit) so had to repair this then populate the chassis with a resistive one instead (3 x 75R in delta).

The ESR meter read between 4 and 7uF with ESR >20R for the 470uF/35V faulty reservoir; its replacement read 480uF/0.1R.
 

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As previously discussed, this thread needs to be retitled to be more helpful to others. How about "Faulty Preamp PSU Caused Humax Reception Problems on Some Muxes"? How do I go about this?
 
Newcoppiceman said:
As previously discussed, this thread needs to be retitled to be more helpful to others. How about "Faulty Preamp PSU Caused Humax Reception Problems on Some Muxes"? How do I go about this?
Click to expand...
As the OP, you have the "power" to do that yourself (assuming you have edit privilege at all) – just open Post 1 for editing, and the title is available to edit too.
 
Tidying up some loose ends on this one...

On Saturday I swapped the two PVRs over so that the original PVR was back in the TV cabinet as our in-service PVR and the spare connected up to a second HDMI input of the TV until we'd watched the two or three recordings left on it after its stint as the in-service one.

While out of service I installed the 1.03.12 modified firmware (the spare still has the unmodified 1.03.12) and briefly familiarised myself with its features. I didn't install any packages.

After powering-up the original PVR I noted it did a couple of freezes/auto-reboots. All was well until Tuesday evening when, while recording two programmes at the same time, at around 20:20 it again froze/auto-rebooted. The recordings were manually restarted but after a short while the same thing happened again. This happened a few times, resulting in several one-minute recordings, even after I'd done a mains power-off. We bailed-out to the other PVR for the 21:00 programme we both wanted to watch. After 22:00 I reverted to the original PVR to watch some recordings while it also recorded a programme at 22:45. At around 23:30 it again froze/rebooted, losing the last 15 minutes of the recording it was making.

As this is unusual behaviour for our PVR (although, as noted on another thread, when moving recordings between folders, about 1 in 20 times, it does the same) I assume this is due to the modified firmware. I planned to revert to 1.03.12 and read https://wiki.hummy.tv/wiki/Remove_Modified_Firmware - is this still the best/only way to get back to manufacturer's firmware?

Also, I'd feel happier reverting to 1.03.12 but this doesn't seem to be available from Humax - only 1.03.13. Yes, I know it should be the same, other than the iPlayer fix.
 
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