How do I fix a Durabrand PSTB1 freeview box?

Another receiver using this Power Supply design is the SEG Model CDST900. Failure of the chopper chip is caused by the failure of the 4.7uF 400v caps and it's usually only one!This is because they are not rated for 130kHz ripple current and only one sees the full ripple -the other is decoupled by a filter coil. The new caps will also have a short life regardless of temperature rating as their effective series resistance rises with frequency and hence the heating effect of the ripple current will dry it out- the answer is to ease the passage of the high frequency ripple via a parallel small value ceramic say 10nF 500v mounted on the underside of the board (watch the insulation gap to the case). Why isn't this done at manufacture you may ask? 1) Cost and 2) Modern design whizzkids tend not to want to learn from us old stagers!

Trevor TV Retired!
November 2012

My Digilogic DSTB1000 has the same board and also blew the TNY256. Two rectifiers diodes next to the power connector had also gone s/c and one of the 4.7uF caps was bulging. The 4.7nF clamp capacitor was a little discoloured on its side so that was replaced with a 3.3nF I had.
Diodes replaced with 1n4006s and caps and a TNY266.
Powers up fine.

Rich270
January 2012

Wharfedale DV832B looks to have the same board.

Worked well for around 3 years, then ~1 year ago woke up one morning to find it dead. Quite a lot of smoke damage on the inside which is not the best thing to find after sleeping in the same room :/

Was looking at it again to finally repair it as preferred it to the replacement I bought and currently use.

The power supply had gone. C668 (4.7uF, 400V) had vented, and the fuse has gone. Sadly, it may not be worth the cost/time to go any further if it turns out there's more damaged. Very useful post David.

bm
January 2011

Just got one of these in, it has blown everything mentioned here hardly worth repairing now.

Arnie
November 2009

Sorry I'll get that right in a min (I guess I cant edit the post??)

Those resistors are 3 x 510K and 1 x 470K to give 4 in total.

Got there in the end!!!

superstardeejay
September 2009

PS that should be 3 x 410K and 1 x 470K to make 4 in total.

superstardeejay
September 2009

Also available in UK as SEG and AMSTRAD brands and fail in a similar way. I agree with the inductor replacement. The capacitors can leak/weep and make the pcb conductive so go bang. Can also take out smt resistors, there are 4 in series to the right of the Tinyswitch IC, for 240V supplies they are 4 x 510K and 1 x 470K.

Superstardeejay
September 2009

Mine is called Techwood TWVFD2. The smoke alarmed the user, and so much is fried I wouldn't want to risk a repair with same-rated components. Tempting to go in with a low-volt supply conversion as RF looks OK, but I can't see where to get in and maybe the opto-link would frustrate. Replacement unit tomorrow - so much for 'CE' certification.

Steve
April 2009

Most probably TNY265PN- available from mouser or digikey or many chinese sources.

Venkataramanan
June 2008

Further to my previous article. I’ve now used a HCPL-817-060E opto-coupler as a replacement for the Cosmo 1010 817 and it works OK.
I’ve also found a received with the choke L614 short circuit in addition to the other failures. It should have a resistance of 2.9 ohms. I haven’t yet tried it yet but a possible substitute might be the Toko: 822LY-102K, 1000UH, Farnell order code: 1193637

The following receivers use the same basic power supply:
Strong 5116, with RF output.
Panasonic TU-CT41, no RF output.
Durabrand PSTB1, no RF output.
Digihome DV940B2, no RF output.

I hope this information is a help.
David.

David
January 2008

I have one of these PCB's to repair. on this one D614 & D615 have also failed & inductor L614 has melted. The inductor was a HYT 30027512 - can any one advise me on a near or equivalent replacement?

DJL
January 2008

There must be several receivers using this board, the Strong SRT5116 being one. They are worth repairing as they have RF output which many receivers don’t have. IC 601 blows up because C667 and C668 (both 4.7 mfd. 400 volt) have dropped in value. I’ve repaired a few of these receivers. If you’re lucky all that needs replacing are IC601, C667 and C668.
Other items that can require replacing are diodes D614 to D617 & fuse F600. I’ve even know the primary tails on T600 to be damaged when IC601 blew up. This was quite easily repaired.
The mains side of the transformer is very similar to the circuit given for the TNY263-268 IC page 7. (http://pdf1.alldatasheet.com/datasheet-pdf/view/139784/POWERINT/TNY263G.html)
The output voltages at the secondary side measured at the diodes are:
D605 34.1, D606 13.7, D607 5.1 and D608 3.1.

Spares are available from Farnell (http://uk.farnell.com/jsp/home/homepage.jsp) as follows:
D614 to D617 original RS1M available replacement RS1J order code: 408-5043.
C667 & C668 original 4.7 mfd. 400 volt 85ºC replacement 105ºC, order code: 969-3343.
IC601 original TNY265PN suitable replacement TNY266PN, order code 992-1346.
F600, Wickmann T3.15 amp fuse, order code: 951-6182.
The original opto-coupler is a Cosmo 1010 817. I’ve not known this to fail but a HCPL-817-060E is a possible replacement, order code: 124-4550.

The components can be tested in situ with a volt meter once IC601, C667 & C668 have been removed. The opto-coupler can be tested with two ohm meters. Connect one across the output so that it gives a reading and apply voltage with the other at the input. When connected one way round if the output reading changes the opto-coupler is probably OK.

Before re-assembly make sure the through hole connectors for the pins show zero ohms when tested, if not solder the pins on both sides of the PCB.

David
January 2008

Sorry Mips 4 taking so long getting back 2u!

The optocoupler is beside the tiny diode @ the edge of the board towards the main AC power connector. It has 4 legs coming from it. It look's like an IC, but with only 4 legs.

I do agree with Mike G. I would replace everything that has blown. Although the small PCB mounting diode is going 2be fun 2 remove and replace, it's so tiny. You would need to have a very steady hand and a small tipped low wattage soldering iron.

Remember to put the diode in the correct way round. You would need to have at least some knowledge of electronics and a digital mulimeter (to check polarity) in order to do this.

Good luck, and I hope you get it fixed! :-)

hookie
January 2008

The Panasonic Freeview box TU-CT41, which I have, has also blown its IC601; I guess this is the same board as you've got in your machine. The IC is a TNY265PN made by Power Integrations.
Should be available for a pound or so. However, the nearby capacitors, 4.7uF @ 400 volt working, may also have popped, the pulse transformer may have overheated and the tiny diode mentioned above may have failed. Good luck!!

Mike G
January 2008

I cannot remember my unlock code, can anyone help

Paul Gill
December 2007

Hookie, Where is the optocoupler??

MIPS
November 2007

Mips, Same problem here! You can optain the IC from Farnell. However they don't stock the TNY265PN. They have a TNY266PN in stock, priced @ £0.89. This IC should do the job.
Although you need to check that the optocoupler hasn't blown also. There is also a small suface mounted diode beside that IC, you need to check that it hasn't gone s/c. Good luck!
Let me know if you got it fixed.

PS: One more thing I forgot to mention, check the internal fuse as well (T3.15a 250v). It may have blown too. It's beside the mains power connector. You can also get this fron Farnell

Hookie
October 2007

I'm interested in fixing the power supply in one of these too if anyone has a circuit,or can provide a list of voltages on D605 - D610 cathodes from a working box.

Nick
October 2007

Budget STBs are not worth repairing even if you could get the parts which is unlikely because Durabrand is a Wallmart/ASDA Own Brand and so could have been made by anyone. Boxes are so cheap now I suggest that you buy a new box.

BTW Freeview boxers are not Satellite Receivers.

t
October 2007