Thomson DTR6000AU (Comstar FGS8800) bad TREC causing HDD destruction

[japlytic]

At a local junkshop, I bought a Thomson DTR6000AU PVR (it was later found to be a rebadge of a Comstar FGS8800) for a song.

Upon opening, C7 (feedback monitored +5V rail) was bulging, along with CP1 (+12V), C107 (feedback monitored +5V rail), C121, C108, C121, C120 (unmonitored +5V rail) and C3V1 (unmonitored +3.3V rail) being bad.

All of the electrolytics in question were TREC units, with the 450V unit being a "ST" unit.

When C7 loaded down the monitored +5V rail, it caused the +12V rail to rise dangerously high to the point it destroyed the HDD (probably explains why there was no HDD in it when I bought it, with CP1 on the logic board bulging).

The MOV at the mains input was blown (rated at 250VAC, too close for comfort at 240VAC, especially in Western Australia, where it is 254VAC) and replaced with a 275VAC unit. The 400V zener diode after the AC bridge rectifier would have provided additional protection against surges.

All of the electrolytic capacitors were replaced with Nippon Chemi-Con KY Series (the 450V unit being replaced with a 150uF Nippon Chemi-Con KMH Series unit - I recommend that capacitance rating as a minimum), with C111 and C5 being 2200uF units (which I recommend for a PVR unit on the +12V rail)

RV1 was carefully adjusted (initially with the supply disconnected from the logic board) to make sure the output was a safe voltage (it was initially a little bit high).

Rebuilding the remote and placing a hard drive inside (no special preparation required - you will lose all existing data without a prompt! ) made the recorder work again.

[stj]

Re: Thomson DTR6000AU (Comstar FGS8800) bad TREC causing HDD destruction

your lucky with the hd,
some of the boxes i'v seen wont take a used drive.
you have to put them in Linux & use "DD" to write 0's across all the sectors for the box to accept & format them.

[jonesy63]

Re: Thomson DTR6000AU (Comstar FGS8800) bad TREC causing HDD destruction

...All of the electrolytic capacitors were replaced with Nippon Chemi-Con KY Series ... and Chemi-Con KMH Series

Hi Japlytic!

Where did you get these electrolytics from? I looked at the usual sources (Farnell/RS/etc) and had no luck.

The DTR6000AU I'm about to repair looks like the 1000uF TRECs on the supply board were replaced with STs and some point. C101 is still a 100uF 450V ST though - and has a very minor bulge. The only cap which definitely has a bulge is CP1 on the logic board.

One last question: did you also change the voltage rating of the C5/C111 1000uF caps - when you changed them to 2200uF? The original rating of 16V on a 12V rail is pretty close... I was thinking 25V might get them a better chance of surviving.

Thanks in advance,
Rob
(from Sydney, Australia)
P.S. First post here!

[japlytic]

Re: Thomson DTR6000AU (Comstar FGS8800) bad TREC causing HDD destruction

Where did you get these electrolytics from? I looked at the usual sources (Farnell/RS/etc) and had no luck.

Honestly, I pulled them (they were still good) out of power supplies.
The capacitors you are looking for are low-ESR units (except for the 400/450V unit) are from Nippon/United Chemi-Con, Rubycon, Panasonic (previously Matsushita), Nichicon, and Elna.

C101 is still a 100uF 450V ST though - and has a very minor bulge.

Most snap-in (and a few high-voltage radial) units have a plastic top which covers the vent perforations. This plastic top may become warped (which may appear as the capacitor is bulging); so to confirm such a unit is bulging, carefully cut the top of the capacitor sleeve off to reveal if the unit is bulging.

One last question: did you also change the voltage rating of the C5/C111 1000uF caps - when you changed them to 2200uF? The original rating of 16V on a 12V rail is pretty close... I was thinking 25V might get them a better chance of surviving.

Many power supplies for the +12V rail use 16V electrolytics, which is 75% of their maximum rated voltage. As I said earlier, I used quality units.

I am glad that you have found this repair information useful

[jonesy63]

Re: Thomson DTR6000AU (Comstar FGS8800) bad TREC causing HDD destruction

Thanks Japlytic!

Looks like I have a job for the weekend.

Cheers,
Rob

P.S. I also found two bulging 1000uF 10V TRECs on the display/control board.

[Shocker]

Re: Thomson DTR6000AU (Comstar FGS8800) bad TREC causing HDD destruction

I call them Terrible Rubbish Electrolytic Capacitors.

[Th3_uN1Qu3]

Re: Thomson DTR6000AU (Comstar FGS8800) bad TREC causing HDD destruction

Eh, they aren't that bad in their intended use, seen them in audio stuff mostly and they've been fine for years. What i think we have here is yet another use of general purpose caps in applications which required Low ESR, hence the early failure.