Repairing a printer: HP DesignJet 110plus

[mockingbird]

http://www.hardwareinsights.com/repa ... psn-130ab/

[ononos]

Hi
First of all i'd like to say that this is a great presentation of repairing the designjet printer.
Secondly i'd like to state that my electronic skills and knowledge are moderate, and so is my English.

I own a designjet 70 printer which is similar (smaller) to the 110plus but has the exact same psu (DPSN-130AB A). I'm having problems with it and i'm assuming that the psu is faulty (not sure yet). When i turned on the printer it would stay on for a few seconds and then would shut down as if you uplugged it. No lights no power. Only a green light blinking at the back of the machine vissible through a small slot next to the parallel conection (i recently discovered after dismantling the machine that the led is located on the main control board). To get the machine working again i had to unplug it, wait for about half an hour or so, then plug it, wait a few seconds for the green led on the control panel to turn on (this is normal), and then push the power on button. And then after a few seconds it would shut down again..
Now the printer won't turn on at all.

Anyway i dismantled the printer, took the psu out, opened it but saw no visible signs of damage. I also took some measurments with a voltometer: When i unhook the psu from the mainboard 3.41 V and 31.8-32.2 V. When i hook the psu to the mainboard 2.6-3.2 V and 23V-29V (not stable). Also when unhooked i hear a very faint wierd sound from it (like crackling) and when hooked the sound dosen't go louder, it just goes periodical. Is there a way to determine if the psu is faulty? Or is the printer mainboard faulty?

Also i'd like to ask if you remember which capacitors besides the 100/450 did you replace? I noticed in one of your photos that a compnent that is attatched with a cooler (don't know what it is transistor or regulator) is missing. Was it faulty? did you replace it?

I would apreciate any help at all
Thanks

[LongRunner]

Those small caps with gold printing (one of which showed as totally dead on the ESR-micro) were from LTEC, right? I can even make out on the one tested that the series is "TK", LTEC's general-purpose 105°C/1k-hour series comparable (in specifications) to Chemi-con KMG or Nichicon VZ. Yet the text clearly says that "Delta used parts from the higher-quality series capacitors that were available back in 2005".

Incidentally, presuming that the Nichicon GU 100/450 was 22mm diameter, then the Chemi-con KXJ of the same value in 18mm diameter would be the same height (not counting any extra space that may be required for lead forming). Another alternative is the LXM in a 22mm diameter snap-in like the original, with 7k-hour endurance (though it's still 5mm taller than the GU).

[Behemot]

IIRC all the caps were japanese. But compared to current series they are just obsolete, rated life, volume capacity etc. all went up. That's what I meant by using the best available - most of the caps there are really best of the time it was made.

ononos: was that you who e-mailed me about the unit on 12th this month? Or it started dying for so many ppl now

[LongRunner]

Well, I can also see in the close-up photo of the GU, what looks like the LTEC logo on a small cap nearby. And if any of the Japanese makers had a "TK" series, I wasn't aware of it…

[Behemot]

I think its that Panasonic 47/25.