Set Top Box Combo Looses RF Gain

= this is the stuff make me cry,why try to say I am wrong,?I will never hope less than a planet with massive potential,I forgot how you crfor are so comfortable rap into critical one way,,,your fear will allow this long long way to show and piss off poor country,sorry again I was wrong. gussesseu whio

Oh no Sir, youm gets more than you pays for- these are throwaway(unless higher price & under warranty)- it is worth reading your user manual- most of these stb have self diagnostic regarding antenna input/quality- which could be your prob- try inserting good stb antenna into bad stb at a time etc& vic-ver- in general, stb,s need a better antenna than analogue- I myself had probs when first using my perfectly satisfact analogue setup on stb- dropouts etc as the wind, rain etc acted- the solution was to invent my own antenna - perfect on analogue,perfect on digital- no dropouts, about 12" long with 6 copper elements!. Oh & I use 300 ohm twinlead balanced(as did the 1st uhf tv,s).

Take a pencil eraser and clean all connectors, don't work, get a new one.

If you open the STB you will find a small metal box (approx 10x40x70mm) at the antenna input. That contains the tuner and the demodulator circuits. Everything is integrated into one or two chips. Not repairable. The rest of the STBs internal is irrelevant about the RF signal.

Did you try the other box at the same connector or just on the same network with the same antenna?

Hello Halando,

Thanks for the comment - I have lifted the lid and checked the power supply voltages - all seems to be in order there.

The other set top box works perfectly when plugged into the same antenna cable.

I can refine the symptoms a little - when one changes channel, the picture is perfect for some seconds and then commences to break up - also after abrupt scene changes the picture is ok for the same several seconds before breaking up.

This break up seems to be independent of signal level - I inserted an in line RF amplifier and the breakup was unchanged - also seems to be independent of frequency, since all channels appear to have little difference in the pattern of breakup.

What thoughts?

Cheers,

GC

It seems to me that the error is not in the tuner module. As the picture is good after a new scene I think the problematic part is the chip decoding the MPEG. It is like you receive the 'I' pictures from the GoP but the box cannot process the changes of it. Like it cannot calculate the shifts of the macroblocks.

Other channels are not necessarily in other transport streams (other transponder in case of satellite/other frequencies).

Suggest you check/r/p electros in power supply- look for those up against a heatsink, or with bulgy tops- use ESR meter-check all comp with multimeter- look for bad solder joints- if all else fails, take the stb & throw to the *&()$% house!. The new ones are so cheap that repair is not viable- if you got a year out of this utter crud, you are average!.

Hello Halando,

I have been thinking about your comment about the antenna input box - if this was faulty would it be causing the breakup due to erratic behaviour of one of these chips you mention? Probably the demodulator?

If so, replacing this box would be a fix for the problem, yes?

Then, if so, where does one get a new antenna input box?

thanks

Geoff

I don't think that you can buy the tuner separately nor that it is the problematic part, as I mentioned above.

It is easier to buy a new STB.

Halando Hello,

My local whizz kid Electronics man has suggested maybe "noise", ripple etc on the Power Supply, it is a switched mode type, and is investigating accordingly.

Results to be advised.