Power Supply capacitors??

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Snowy

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#1
Hello all,

I have a thread elswhere on this board about a loss of signal that I had with my receiver, (on multi-lnb set-up via DiSeqc switch. Eventually I checked the LNB voltage at the receiver end and found that I only get a range of 4volts to 7 volts. I'm now told by several sat suppliers that it will be the power supply board in the receiver that is goosed, and will more than likely be a capacitor problem.

Can anyone please confirm this and perhaps give me a clue how to identify which capacitor need replacing?

The receiver isa GbSat 2CIP, (the P means it also has a 36volt locator).

I understand that this is the same as a EMTECH 200 receiver.

Many thanks.
 
Channel Hopper

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#2
First stop should be the dealer you got it from, they should have a chart of troubleshooting for any machine supplied

A low LNB voltage from the tuner when everything else if functioning points to a switching or driver transistor fault rather than a power supply
 
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spiney

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#3
Channel Hopper's right, it's very unlikely to involve the power supply at all. LNB volts come from a separate circuit, under software control, then go into the tuner. There's some "typical" examples in Newnes satellite tv guide, available public libraries.
 
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#4
Spiney and Channel Hopper,

Thanks for your advice, and sorry I'm slow getting back to you but I've been away.

The 'dealer' I got it from goes by the name of eBay! I have heard though from Hisat, (main GBsat distributor), that it could need a new tuner, so looks like you may be right. This does not sound quite the repair option that the power supply did.

If anyone out there has a spare tuner, or wants to purchase a spare box .. ;)
 
Llew

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#5
The LNB voltage takes a direct path through the tuner - it's isolated from the tuner circuitry itself, so I would guess that the tuner won't be the cause of the problem.

Llew
 
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#6
I'll 2nd that, the lnb 14/18v is generated elsewhere on circuit board, it only goes through the tuner cos it has to appear at antenna socket. So, you shouldn't need to replace the tuner.

Sat tuners are fairly standard items, if you can discover which tuner pin the 14/18v usually feeds in on, it should also be that one in your receiver, then you can "work backwards" to find where the lnb volts come from.

Short circuiting the lnb socket causes damage, on some sat receivers, that's probably what happened, usually a transistor needs replacing (some makes have fuses you can just replace, eg Pace, but not this one it seems!).
 
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#7
I can see that you people know your stuff. Unlike myself, who is handy with a screwdriver and soldering iron but analytically lacking. I think I would need a diagram with arrows pointing to the hot spots!!!
 
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#8
GB sat, wasn't that a brand sold by Spectrum, Croyden?

The repair should be fairly easy, almost certainly it's a transistor (shorting the lnb ouptut just blows it!), the best strategy is as above.
 
Llew

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#9
The LNB supply invariably goes in on one of the tuner pins at the front of the tuner (nearest the LNB socket).

You should be able to use an ohmmeter to trace it from the socket to the pin and work back as spiney says.

Llew
 
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#10
i've just looked this up, apparently it should be pin 1, that's nearest to the lnb input socket (from Newnes digital tv guide). You might be able to follow the circuit board track by eye, otherwise it's an ohmmeter as Llew says!
 
Llew

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#11
The transistor in question will (probably) look something like one of these -
 

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spiney

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#12
and you'll need one of these .......
 

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Snowy

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#13
Spiney, Llew, many thanks again for the advice. This may stretch my skills a bit, but I'll take a look as you suggest. Might be a while before I get round to it though; the wife wants some painting done outside :-doh!

Cheers.
 
Channel Hopper

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#14
GBSat have a main repair system in Europe. Youve asked HiSat, and theyve told you 'its most likely the tuner'

Why would Hisat tell you its a tuner problem when its most likely not ? How would they pinpoint this issue to the tuner, unless they have specific repair guides from GBSat pinpointing a weakness in the metal can ?
(Why ask here when the UK distributor has given a difinitive answer)?

Have you asked GBSat directly ?
 
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#15
A very good point, Channel Hopper (hello again!).

I assume the receiver otherwise "appears" to work normally, eg, it responds to software commands, etc. In which case, the main power supply is ok, and it must be lnb control volts only (since that's been measured).

Many problems are due to a failing power supply, fair enough. But, from these symptoms, it must be the lnb volts control circuitry. I don't see how it could be anything else. This is a known sat receiver problem, usually (but not necessarily!) caused by short-circuiting the lnb socket, which just blows the transistor (some receivers have a protection fuse, apparently GBSat doesn't!).

As to why the distributors said "power supply capacitors", I've no idea.
 
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#16
Thanks for keeping on the case gents. And that's why I've posted the thread, to get some valuble input and learning.

One good point; no I haven't yet asked GbSat directly. Don't know why not??? I will.

And my reasons for going to so much trouble? Well, I'm still smarting from only having the box a few weeks before it failed, (or I broke it!), and having to spend good money on a replacement. I've phoned/emailed a number of sat people and got various answers, so don't want to send away my power supply for repair if it's not broken; (more money wasted). Hope you understand.
 
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#17
I'm not guaranteeing this is the problem (obviously !!!!), just going by the described symptoms. What you should really do is find the transistor, and test it with multimeter, that'll soon tell you. Remember to avoid the mains power supply section, 350V there, dangerous when switched on!
 
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