Dead DM800 - help please.

[Lomax]

Got those 4 caps removed OK. I used solderwick and they came out quite nicely. Just have to get to Jaycar for some replacements now...

[theriddler_1]

Just remember , the 4 caps were just a sugestion that fix my simular problem P
Im curious , have you tried to power up the box now you have removed them , also look for others that sit on the power rail. See if they are slightly bloated or look at the bottoms to see if the rubber gromit has lifted. If you do power up the box , only make if brief now you have removed the caps

[best4less]

Hey theriddler_1 i don't own one of these DM800 but was wondering if they get that hot say like the old DM500S or something ??

[Lomax]

I've just replaced the 4 caps, but still no joy

As previously mentioned, I get a flash of garbage on the OLED for a fraction of a second, but do not get any lights on the network port.

Another piece of info - I notice that the fan is "trying" to spin. This may be unrelated to the issue (the fans are pretty crappy in these units and likely stopped spinning some time ago ) but it may indicate that power is at least getting to the fan.

I'm not sure how to proceed - any advice will be appreciated.

[best4less]

Have you got pics of the circuit board or circuit diagram Lomax ??

[Lomax]

I do not have a circuit diagram or schematic (maybe there are some floating around the web - I couldn't find one), but here are a couple of pics of the power circuit area.

Top:


Underside:


Edit: Found a schematic:

[Lomax]

OK, I'm organised now. I think I shall begin by checking all 12v points as per this diagram:



But can someone tell me where I can find U7 sector? - I'm having trouble locating it. EDIT: found it (straight down from U22 on the underside of the PCB).

[best4less]

Check to see if this reg gets it's 12 volt feed and see if the 5 volt is present if not lift the leg on the diode and see if the volts comes then



Uploaded with

Here is a link to the specs of the IC

[Lomax]

I'm getting 0v on that diode leg.

EDIT: Have lifted the leg by using the iron and jimmy-ing it up gently. I am still getting 0v on the pad where the leg was, and 0v on the leg itself.

Please advise. Learning heaps here best4less ;-)

[Lomax]

More info:

Referring back to this pic of the DM800 12v test points from 2 posts ago:



They all check out OK EXCEPT for the U23 points (I get 0v). Does this give anyone some clues?

[best4less]

Hey Lomax it is so hard without the thing in front of you LOL

But if the 12 volts are missing from some where thats a great place to start
look for things getting hot, things get hot when they have shorts in it,
and also where the 12 volts are missing you need to lift a leg and just see if the 12 volts comes up as there could be a short further down the circuit

happy fishing LOL

If you get a real circuit diagram that would make things way easier to trace

Cheers

[Lomax]

So, should I put that diode leg back down?

[mandc]

Not sure if this is any help:
From another forum:
Dm800 U23-U24-U25
Dreambox death, only two lan leds on.
U6 and U7 outputs are okay.

Other symptom may, Oled display goes very short on/off by power on the box, fan is working, the rest is death only two lan lights on.

Possibly U25 defective.



From

http://www.sat-planet.net/showthread.php?t=29407

[Lomax]

CORRECTION:

All the 12v points check out OK.

[Lomax]

Where should the COM lead from my multimeter be placed? I've been placing that on the main -ve solder pad on the PCB (the one where DC first enters).

Is this the correct way to measure?

[Lomax]

Next test. Check the voltages as per this picture:





My results:

Pin 1 0.55v
Pin 2 2.13v
Pin 3 1.47v
Pin 4 0.56v
Pin 5 1.34v
Pin 6 12.15v
PIN 7 0v
PIN 8 0v

LM2599S 0v
GND 0v


The levels look pretty screwy, and no 5v at all! Any ideas?

Thanks,

Lomax