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HEQ5 (not) dead!


quantumpanda
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Dear SGL Community,

A couple of years back my HEQ5 Syntrek mount stopped working. It was stored in incredibly damp conditions which most likely contributed to its demise. I no longer have this damp issue so I want to fix it. I had a similar problem before this which was intermittent (took the mount apart, did nothing, replaced and it worked).

I am using the original PSU which I have tested (and used an alternative). There is no movement in the motors, no polarscope LED and no power LED when connected. I've taken the mount apart and the motherboard looks very health (to a non electrician), paying close attention to the capacitors. I am happy to pay for a replacement motherboard, but I am keen to identify this really is the issue. Should the front power LED light even if the main motherboard doesn't work? The small power controller board doesn't appear to be replaceable if this is the problem part! I think I have concern for the PSU connector as the original PSU was so short it swung freely when connected placing real strain on it. I also read in an older post about the polarscope led wires being exposed and causing a problem (shorting?). There is black insulation running down to it, but there is about 1-2 cm of bare wire running to it - is that normal?

Many thanks for your help suggestions.

Edited by quantumpanda
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Buy a basic Digital Volt Meter (DVM) from Maplins or the Bay.

With the DVM on a DC voltage range that will measure 12 volts, check for correct volts on the power supply plug (unplugged from the mount).

With the DVM on a 2000 Ohm range, check the resistance across the power socket pins on the mount (no power applied).

If it's not zero ohms, power up the mount and follow the motherboard tracks with the DVM on volts again, until you find where the volts are disappearing.

With luck it may be the PSU lead.

Michael

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20 hours ago, michael8554 said:

Buy a basic Digital Volt Meter (DVM) from Maplins or the Bay.

With the DVM on a DC voltage range that will measure 12 volts, check for correct volts on the power supply plug (unplugged from the mount).

With the DVM on a 2000 Ohm range, check the resistance across the power socket pins on the mount (no power applied).

If it's not zero ohms, power up the mount and follow the motherboard tracks with the DVM on volts again, until you find where the volts are disappearing.

With luck it may be the PSU lead.

Michael

Hi Michael.

Many thanks for your advice. I've purchased a DVM on your suggestion and should be able to begin testing tomorrow.

Unfortunately the simple fix of a faulty PSU is not the case as it has already been tested with a borrowed DVM (and to be sure, swapped with another PSU). It sounds like it's very easy for me to test the mount socket pins, which I have concern for.

When you say 'follow the motherboard tracks' how exactly is this done? Is this continuity testing, such that you select two places on the board, or do you simply test the voltage across specific components on the board? 

Stefan.

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32 minutes ago, quantumpanda said:

When you say 'follow the motherboard tracks' how exactly is this done? Is this continuity testing, such that you select two places on the board, or do you simply test the voltage across specific components on the board?

Keep the black negative probe on a negative/earth point and then check for volts on the tracks and components connected to the positive input to the board.

Michael

 

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On 30/07/2017 at 21:48, michael8554 said:

Keep the black negative probe on a negative/earth point and then check for volts on the tracks and components connected to the positive input to the board.

Michael

 

Hi Michael,

I tested the resistance between the centre pin and outer connector of the mount power socket and it reads a zero. The soldering and component looks fine, although there was some white residue which I cleaned off.

Stefan.

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Hi Stefan

That's unlikely, I wouldn't expect there to be any components in circuit, unless you had the power switch in the ON position.

If the switch was ON, and you were on the lowest resistance range (200 ohms maybe), then this probably indicates a short circuit on the board :-<

And I don't suppose there is a fuse on your HEQ5, or in the power lead - this sort of situation is why there should be.........

Well nothing lost, I would go on to look for +12V from the power socket onwards.

The centre pin shoud be +12v, the outer is where you keep the negative DVM lead on.

Michael

 

 

 

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14 hours ago, michael8554 said:

Hi Stefan

That's unlikely, I wouldn't expect there to be any components in circuit, unless you had the power switch in the ON position.

If the switch was ON, and you were on the lowest resistance range (200 ohms maybe), then this probably indicates a short circuit on the board :-<

And I don't suppose there is a fuse on your HEQ5, or in the power lead - this sort of situation is why there should be.........

Well nothing lost, I would go on to look for +12V from the power socket onwards.

The centre pin shoud be +12v, the outer is where you keep the negative DVM lead on.

Michael

 

 

 

Hi Michael,

I am delighted to report that thanks to your help I have solved the problem! I wouldn't have even known about DMM continuity function if you hadn't posted. Can you believe, the problem was the switch? There was no continuity when in the on position so I stripped it off, isolated the wires and joined them together... working! 

If I can pick your electrical brain one last time - the switch says 3A 250v - does that mean it has a fuse? As in, should I aim to replace it or can I just simply bypass it with a simple wire and switch off at the wall/battery instead?

Thank goodness I didn't pay the £110 for a new motherboard!

Edit: I've just shelled out a hefty £1.20 for a replacement switch, but I guess the question now is, am I safe in the meantime to bypass it with a direct wire?

Double Edit: I popped the switch rocker out and removed the plate corrosion. All sorted! Thank you!

Stefan.

Edited by quantumpanda
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