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Digicrystal SDT-9000PVR

Hi All,

I have a Digicrystal SDT-9000PVR (Personal Video Recorder) and I rather like the menu structure it has. It has a built-in WD 80G hard drive for record/playback.

So, I was less than pleased when this unit went belly up and refused to detect it's hard drive any more. There seemed to be some strange stuff going on with the hard drive as to whether it was running or not as I switched the unit on and off.

PVR's are so cheap these days it is hardly worth bothering with them, but I decided to pull the top off this unit.

The hard drive 5V supply was fine, but the 12V was reading 17V and it seemed the WD hard drive wouldn't spin up with 17V applied, though if it had started up the voltage would have soon fallen to something more reasonable on my tests.

Anyway, I plugged an external hard drive supply into the WD hard drive and started up the PVR. Immediately everything started working as normal. The HDD detected, and recording and replay was possible.

Of course, now it worked there was no reason to do anything much more so it stayed like that for a long time. :)

You know how it is, I'm sure....... :)

Anyway, just looking at the power supply board I guessed one of the voltage regulators had blown short circuit. Since I couldn't obtain a cheap replacement I thought I'd bodgy up a repair using an LM series linear regulator. There was a bit of spare space in the box where I could put the add-on and all. :)

When I finally got to doing this I discovered the nominal 12V supply wasn't regulated at all, hence explaning why under no load it went up to 17V.

Right.

So, there is apparently nothing wrong with the unit.

Except it won't work.

Anyway, there is a limit to how long you can ponder over these things, and these days I have no shame about anything much.

So, I put my add-on linear regulator between the unregulated 12V supply and the HDD, and regulated the HDD supply to 12V.

The unit now works fine. The add-on regulator card and heat sink is screwed down with one of HDD retaining screws.

And all is right with my world.

However, does anyone know whether hard drives won't start with excess voltage applied to the 12V input?

Anyone else had the same trouble with one of these units?

Ross

Reply to
RMD
Loading thread data ...

Well, it is a pity the facts get in the way of some of my proposed theories.

Unfortunately it seems the HDD start-up problem is deriving from the

5V supply to the HDD.

Even with the HDD 12V supply regulated the unit operates erratically sometimes. One can hear the HDD start repeatedly, but not make it to run speed.

As soon as I put my external 5V and 12V supply onto the HDD then the unit works perfectly again. The unit has worked fine for weeks and weeks with an external HDD supply.

It would seem the load of the HDD is too much for the internal 5V supply for some reason, and it is possibly cycling on and off.

The day is almost gone, and almost totally wasted.....

Sigh. :(

Still, a few more facts determined. :)

Ross

Reply to
RMD

Are any of the electrolytic caps in the power supply looking bulged or leaking? They tend to be the prime suspects when switching supplies start acting ornery.

Bob

Reply to
Bob Parker

Bob,

Believe it or not, last night I noticed two 2200uF 10V electrolytics which are in the twin 5V supplies were looking bulged on the top, and were also running hot. The rest of the units capacitors seem fine.

I was out shopping today and after quite a bit of driving about got some more end mount 2200uF caps. I've changed out the bulged ones just now, but the fault remains.

i.e. The unit runs fine with the HDD externally powered, but as soon as I power it internally I've got start-up problems.

I guess I have to keep looking. :(

Ross

Reply to
RMD

Hmm. The fact that you've found some dubious caps implies that there might be more which still look OK. If you're feeling adventurous and have an oscilloscope, you could try building the 99 cent ESR adaptor at

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and checking the rest of them. Or maybe even take the unit to a repair shop? I hope you can get it working the way it did when it was new, without too many problems. Good luck. :-)

Bob

Reply to
Bob Parker

Hi Bob and others,

I finally got some time to look at this unit again.

Btw replacing the two dud 2200uF capacitors had rectified an erratic front panel display. I had the feeling it was nearly working.

Checking the voltages again, the previous 17V HDD supply had reverted to about 12.5V (much more reasonable), so I figured my silly out-rigger 12V regulator might be the cause of the problem now.

So, I removed the add-on and re-soldered the unit as originally.

I plugged in the HDD to the internal plug, and gingerly powered on.

Eureka! All systems go. I've tested the unit since and the problem is now finally resolved. (I hope. :) )

I haven't encountered the bulging capacitor problem before, being just a consumer these days. It must be fairly rare, since I have a lot of stuff about and nearly all of it works fine for many years.

Anyway, I'll know better next time. :)

Ross

Reply to
RMD

Good one, Ross! Actually failing electrolytics are a very common problem. Have a look at

formatting link
for example.

Cheers Bob

Reply to
Bob Parker

Well done, I have the exact same unit and replaced all the electros a few months ago. If 50% are buggered, all are close to buggered I figured.

Then my DVD player stopped working a couple of days later, another bulging electro replaced and it too works 100% again.

#1 faultfinding rule is test your power supply first. And the first step of that is to eyeball the electros as invariably they are the weakest link.

Ray

Reply to
Ray

Ray,

I figured I was maybe on a roll, so I pulled apart a non-functioning DVD player too.

Unfortunately all the capacitors were fine. :( The trouble was the DVD spin motor wasn't spinning the DVD up.

Very likely if I had the spare parts this unit would also be really easy to fix, but in a home environment and with the price of DVD players currently, the player is really only useful for spare parts.

Oh well, I'm still very chuffed my PVR is a goer. :) Made my week! :)

Ross

Reply to
RMD

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