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Sky+ power supply: you can rebuild it!

Freesat Freeview euro tv skyThe best kit, The best programmes

2 What Satellite & Digital TV

Last year my Sky+HD box started behaving oddly. Channels began disappearing and reappearing,

pictures became intermittently ‘blocky’ and scheduled recordings failed.

After a long weekend away I found that the box wouldn’t receive anything at all, with a ‘no satellite signal is being received’ warning on screen at all times. If your equipment is working properly the most common cause of this type of thing is very heavy rain or snow that attenuates the incoming signal beyond usability. But this was a sunny summer’s day.

I checked the signal strength meters, which you’ll find by pressing ‘Services’ and selecting ‘Signal Test’ from the ‘System Setup’ option. They showed zero signal strength and quality from both tuners. I then connected the two LNB cables in turn to a free-to-air receiver. The pictures and sound they produced proved that my dish and LNBs were innocent.

the service callTime to call the Sky customer service – it looks like the tuners in my box have failed! After going through various tests

– checking the signal strength, invoking the ‘Installer’ menu (Quickly press: Services, 4, 0, 1, Select) and, from the ‘LNB Setup’ submenu, switching the LNB power supply off and on again – they came to the conclusion that this was a non-serviceable fault.

A technician’s visit would cost me £65 as the system had failed outside of the one-year guarantee period (surely one has every right to expect more than a year of reliable use out of a major-brand consumer electronics product?). No wonder that Sky has been promoting a £5.75-a-month repair plan!

The technician would realign your dish, replace a faulty LNB or receiver, or replace the box itself. To be fair to Sky, a Sky+HD receiver is worth considerably more than £65. You get a reconditioned receiver but you’ll lose all your recordings; they won’t transfer the original box’s hard drive to the replacement. This led me to ponder whether I could do anything to restore my Sky+HD box to working order. Time to sneak inside the Thomson-made box! In doing so, I managed to find out what was wrong and repair it.

Inside Sky+HDThe Sky+HD makes extensive use of custom surface-mounted chips which you can’t repair at home. The switch-mode power supply, however, is of conventional design.

I decided to check this as a last resort. Using an oscilloscope, I discovered the various DC outputs were far noisier than they should have been. If the power supply is out of spec, then the receiver cannot be expected to behave properly.

I removed and examined the power supply. Thomson has used non-branded electrolytic capacitors (so you can’t be sure of their quality), and these have deteriorated over time. Those on the low-voltage side of the power supply had started to physically bulge upwards.

The high-running temperatures inside this noisy-fanned power-guzzler (40W in use, 20W in standby!) don’t help, and neither did the power supply designer’s decision to position some of these vulnerable capacitors slap-bang next to a heatsink!

Unless Thomson has improved these components since my Sky+HD was made, there will be a rash of disgruntled HD subscribers. I alerted Sky to my findings, but never received a response.

The same power supply is used in several Thomson models – the DSI6210 (Sky+), DSI8210CS (Sky+) and DSI8215 (Sky+HD), so this information may also be of interest to owners of misbehaving Sky+ boxes.

If you’re capable, replacing the capacitors is more convenient and cheaper than a service call – they can be bought as kits of parts or individually at component retailers like Maplin.

I kept all of my recordings, too. If your receiver doesn’t turn on at all,

then there’s a fair chance that the power supply might have ‘blown up’ (we’ll describe further symptoms shortly). However, some companies offer power supply exchange or repair services.

Next month we’ll discuss hard-drive upgrades – which you might also want to consider while your box is in pieces n Martin Pipe

Sky+ power supply: you can rebuild it!A blown power supply usually means an expensive replacement Sky+ or Sky+HD – unless you follow our step-by-step guide

Polite disclaimer:IF YOU’RE NOT ENTIRELY SURE WHAT YOU’RE DOING, LEAVE IT TO SOMEONE WHO DOES!

ProjecT

What Satellite & Digital TV 3

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Leave the receiver unplugged from the mains for a few hours (ideally overnight).

This will allow the high-voltage smoothing capacitor in the power supply to safely discharge. Under most circumstances this capacitor should discharge quickly as soon as mains is removed because the receiver is so power-hungry.

Completely disconnect the unit from the outside world (LNBs, TV, mains and so on).

After you have removed a few screws the metal-cased receiver will slide out of the plastic outer enclosure. The metal top panel is ‘tab-hinged’ to the box on one side; a couple of screws secure it to the opposite side. Undo these and carefully remove the top-mounted control panel which is held in place by two countersunk screws – and the lid can be swung open and removed, revealing the complex electronics that makes it all happen.

You should have left sufficient time for the power supply to discharge. If you have a

multimeter set it to one of its DC ranges and – observing correct polarity (see step 7) – measure the voltage across the terminals of C14. This capacitor (100µF, 400 Volts) is the large one located at the mains power connector end of the circuit board. Your meter should not register anything!

Was your Sky+HD ‘dead’? Examine the mains fuse, identified on the board as ‘F10’.

It’s adjacent to the rear-mounted mains power connector. If it is blackened, then it has suffered damage beyond what could be addressed here. A charred resistor (R15, which is next to C14) is another tell-tale sign of serious damage. All of these components are on the primary side of the power supply.

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WARNING: If the mains fuse of a ‘dead’ SkyHD is still intact there’s a strong possibility that C14 might be still charged – allow extra time for it to discharge safely. Fortunately, some companies, including Satcure, sell reconditioned power supplies as well as DIY repair kits. Remove the power supply (following steps 4 and 5), pack it carefully and send it to the company with the relevant payment. You’ll then be sent a working replacement that, when fitted (refer to step 10) should return your unit to full working order. If your power supply has suffered a particularly serious ‘blowout’ (and cannot be easily repaired) you’ll almost certainly have to pay extra.

If your receiver did manage to power up before you disconnected it, then there’s a

good chance you can carry out a much cheaper repair! Examine the low-voltage capacitors – the ones that tend to fail are marked on the board as C20, C21, C33, C41, C42, C43, C51, C52, C60, C61, C70, C71, C80 and C81 (refer to Table 1 for their values). Any that are bulging on top are prime candidates for replacement, but we recommend replacing all 14 in one go – along with the high-voltage capacitor C14. WARNING: Running a SkyHD with failing power supply capacitors could cause serious damage, so if your box is in this state as you’re reading this, unplug it immediately!

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Now it’s time to carefully remove the faulty capacitors using a desolder pump or braid.

Make a rough sketch of the power supply, noting the location of the parts as you remove them (they’re also marked on the board legend). Electrolytic capacitors are ‘polarised’ and it’s important to ensure the correct orientation of every one you replace. The negative terminals of the capacitors are marked with white arrows on their cases, and with diagonal stripes on the circuit board. Ensure that all solder is removed from the pads that secured the capacitors to the circuit board.

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Project: repairing the thomson Sky+ power supply

Now take out the power supply. Remove the power supply cooling fan, held to the

side of case by a series of four rubber ‘bungs’. Use long-nosed pliers and jeweller’s screwdrivers. This is the trickiest part of the job. Next, unplug the wiring loom that links the power supply to the rest of the receiver. Remove the four screws that secure the power supply to the base of the case. The power supply can then be carefully lifted out.

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Hot tipExcess heat can cause the capacitors and other components to degrade faster. A Sky+ or Sky+HD PVR should always be given adequate airflow – don’t block the ventilation slots. We recommend a breathing space of at least 100mm on top and at the sides, and raising a Sky+HD box to provide a 15mm gap underneath is also advantageous. Fail to ensure good ventilation, and you’ll only increase the chance of a breakdown.

Top control panel

Inside the Sky+HD

Bulging capacitors

Braid and desolder pump

Removed power supply

Desolder old capacitor

Capacitor removed

4 What Satellite & Digital TV

Project: repairing the thomson Sky+ power supply

The replacement capacitors can now be fitted. Ensuring correct polarity, poke the

replacement capacitor’s two lead-out wires through the circuit board mounting holes. Pressing the capacitor flush against the component-side of the circuit board, gently bend the lead-out wires to hold it in position. Carefully solder the wires to their pads and then, using a pair of wire-cutters, trim off the excess lead wires on the solder side of the board. Ensure that there no solder ‘bridges’ or whiskers – these could cause short-circuits.

With all faulty capacitors replaced, check your work once again for any solder

bridges, ‘balls’, dry-joints (these look dull in appearance – if you see any, resolder them!) or other anomalies. If you’re satisfied replace the power supply board in the enclosure. Fit the four screws and reconnect the wiring loom.

Don’t yet refit the fan, but move it into a position where nothing can foul its blades.

Ensuring that the detached control panel cannot come into contact with any exposed metalwork, apply power. If the red standby LED, hard disc and/or fan comes on that’s a good sign. Reconnect your display and LNB cables and then turn on. If all is well, then satellite reception (and access to recordings) should be restored.

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toolkitThe full ‘Do-It-Yourself’ option for the braven Set of Pozidriv screwdriversn Good-quality soldering iron and soldern Desolder pump or braidn Hot-melt glue gunn Multimeter (analogue or digital)n Replacement capacitors (see above): Maplin (www.maplin.co.uk). Google for alternative sourcesn Kit of replacement capacitors: RELKIT33J, £10.95 from Satcure (www.satcure.co.uk). Additional kit of parts for ‘blown up’ power supply: SATKIT33J, £19.95 from Satcuren Plastic nut/bolt kit for fan: 50p from Satcure

Tookit – if you’re scared...n Set of Pozidriv screwdriversn Exchange power supply service – Satcure (www.satcure.co.uk), usually £32.95 (‘rebuilt’ unit supplied)n Power supply repair service – Digifix, usually £32.95 (www.digifixltd.co.uk, 01298 73989). Send them your old power supply – they will fix and return it. Satcure list other independent repairers at www.satcure.co.uk/psu_fix.htmn General repair service including power supply and hard discs – Digi Repairs (UK & Ireland) Ltd, from £56.65 (www.digirepairs.co.uk). Six month warranty on all work.n Plastic nut/bolt kit for fan: 50p, from Satcure

Turn it off and leave it to discharge before you reassemble the box (step 1).

Disconnect everything once again. The fan should push into position; you may need the long-nosed pliers (or a loop of fishing line) to gently pull the ends of the rubber bungs through the mounting holes. If you run into trouble here you might need bolts to attach the fan to the side of the case – Satcure sells a set of these, too.

Refit the top plate, and screw on the control panel. Finally, insert the unit into its plastic

jacket and fit the remaining screws. Reconnect your Sky+HD to the rest of your system – it should be good for a few more years of trouble-free viewing. My unit, repaired with Maplin capacitors, has been in service for over six months at the time of writing.

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Capacitors from Maplin

Insert capacitor

Solder capacitors

Trim leadout wires

New capacitors fitted

It’s working again!

Refitting the fan

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Fan controlOne of the most annoying problems with Sky+ and Sky+HD PVRs is fan noise. The fan turns on and stays on.

A solution would be to install a fan controller that only turns on the fan when the temperature exceeds a certain level. You can buy one from skyplusfancontroller.com, where the kit shown looks very well-made, with a decent fibreglass circuit board and high-grade components (we asked for a review sample but didn’t get one).

It has adjustments for fan speed and the cut-in temperature. This is ‘preset’ to suit your particular model, but can be tweaked if the fan comes on too often or the box gets too warm. The price varies from £20 to £27, depending on the specific model of PVR.

Table 1 lists the original capacitors, and their Maplin replacements. Some of the Maplin capacitors have a higher working voltage than the originals – no problem there.

However, Maplin doesn’t have the all-encompassing product range it once boasted, and won’t sell suitable replacements for three of the original capacitors: C41 and C51 (1,200µF/16V) and C14 (100µF/400V).

Fortunately, they can easily be found online (Search tip: ‘U’ or ‘UF’ if ‘µF’ doesn’t work, and leave out the comma in ‘1,200’). Be sure to specify low-ESR switch-mode power-supply grade components with a 105°C rating.

The Satcure repair kit contains 100µF/450V and 1,200µF/16V parts, which are direct replacements. There’s no need to accommodate additional capacitors, and so you’ll have an easier job. You should obtain this kit of parts unless there’s no alternative. Satcure sells two different repair kits. The cheaper one (RELKIT33j) contains all of the necessary capacitors (including C14), and is the one to buy if your receiver manages to power up like mine did.

The more expensive kit (SATKIT33j) should be bought (with RELKIT33j) if the power supply has suffered more serious damage and won’t even power up (as detailed in Step 3). It contains replacement primary-side components, some of which are difficult to obtain anywhere else.

Considering the expense and hassle involved, a guaranteed power supply exchange or repair service like Digi Repairs or Digifix is probably an easier option for most people, although it is more expensive.

original and replacement capacitors for thomson Sky+HD

Final disclaimer: Neither the author nor Future Publishing can be held responsible if you blow up your box – or yourself. Only the competent (e.g. electronics enthusiasts and dealer repair workshops) should carry out this work.

reference original replacement Maplin code

C20 47µF/50V 47µF/100V DT60Q

C21 10µF/50V 10µF/50V DT55K

C33 100µF/16V 100µF/25V DT61R

C41 1,200µF/16V 1,000µF/16V n/a

C42 470µF/25V 470µF/25V DT66W

C43 470µF/25V 470µF/25V DT66W

C51 1,200µF/16V 1,200µF/16V n/a

C52 470µF/25V 470µF/25V DT66W

C60 470µF/35V 470µF/50V DT67X

C61 470µF/25V 470µF/25V DT66W

C70 100µF/50V 100µF/50V DT62S

C71 47µF/50V 47µF/100V DT60Q

C80 470µF/16V 470µF/50V DT67X

C81 47µF/50V 47µF/100V DT60Q

C14 100µF/400V 100µF/400V n/a