Alinco DJ-193 no sound from internal speaker.

An Alinco DJ-193 where the built in speaker no longer worked, headphones worked fine.

Opnening was fairly straigtforward, (after finding nothing on the web).

Remove the antenna and pull of the rotary knob.

Then just flex the sides at the points shown to disengage the metal tabs from slots in the case and tilt the whole metal lump out.

A nice straightforward one, the fault was clear to see immediately, the speaker wire had at some point been pinched between the case and the metal assembly and been cut clean off. It had never been opened before so presumable from assembly at manufacture or the wire had moved through use ?

The wire was re attached and the speaker worked again.

LG 32LX2R Faulty power supply.

A LG 32" LCD TV that would not power on, the fault occurred following a mains power outage.

The PSU board looked fine, no bulging or stained capacitors. Aquick google went straight to the point, somebody with identical experiences who recommended changing the output stage capacitors (circled) anyway.

http://forums.moneysavingexpert.com/showthread.php?p=27092505

post number #31

The capacitors were sourced, 14 in all. The board was of reasonable quality, no problems removing the old ones.

Here is a close up, all the old capacitors looking ok

So in went the caps. I measured all the old capacitors and they were all in spec for capacity on a basic Fluke multimeter....

However the TV now worked. I would be interested to know the failure mechanism of the capacitors but a good result and Google delivered as the capacitors really dint look suspicious.

Update:

Here is the capacitor list:

2200uf 10v x 1
1000uf 35v x 4
1000uf 25v x 2
1000uf 10v x 3
680uf   25v  x 2
100uf   50v  x 2

Update:

The likely failure for the capacitors is poor ESR, (equivelant series resistance) at given frequencies. I have access to a proper LCR bridge. A quick measure shows ESR varies with physical size on new capacitors, I will need to look into specs for given values and see if there is a large deviation from spec.

Update:

Ok, I had kept the capacitors and measured them all. Here is a table of typical ESR values. This is from a manual of an ESR meter made by Peak electronics. I hope they dont mind me using it, here is a link to there meter http://www.peakelec.co.uk/acatalog/jz_esr60.html

There are three 10v 1000uf capacitors in the TV PSU, two measured just under 0.2ohms but one measured 2.1 ohms, so it looks like this was the likely culprit.

The esr meter above can be used in circuit, I hope to try one out soon !

Dell 1708fp ultrasharp backlight fault

A dell 1708 monitor, the monitor would power on, screen would display for two seconds then the backlight would go off. You could faintly still see the graphics in the background.

This was exactly the same as the Samsung 540n I fixed in an earlier post, that was bad PSU caps so I was expecting to see similar inside.

Disassembly was straightforward. Four screws in the middle of the back,( behind the stand bracket), then unclip the bezel all the way around (this was tight !). Pull the back off, remove two screws from each side to release the electronics assembly from the panel, remove back-light wiring covers then cables, remove main screen cable. Finally to get to the component side of the board, remove output connector locking screw posts then screws from the back of the PCB.

I wasn't disappointed, more bulging brown stained caps than you could shake a stick at, six in all, all clearly failed.

They should be 35v 330uf, removed they were measuring about 150uf.

Here they are in all their glory.

New caps in, I have circled the six affected capacitors that were replaced.

Back together with the new caps, all working ok !

Hauppauge HD PVR wrong power supply.

A Hauppauge HD PVR that had been powered up using the wrong PSU.

With the correct PSU used again the unit would not work.

Unfortunately I didnt take any pics so I used one off the web to describe what I found, I hope the owner of this picture doesn't mind, it was from a blog post about modifying a unit by fitting a fan.

http://blog.arogan.com/2008/06/hauppauge-hd-pvr-model-1212.html

The picture does however raise an interesting question as it differs slightly, voltage regulator 4 was not present in this faulty unit ??

A good chunk of the circuit runs off 3.3v as you would expect, this seemed to be handled by the regulator #3 derived from the incoming 5v.

However some of the circuit runs off the 5v input straight frsom the wall adaptor, no circuit mount regulation or fuse.

Plug in the wrong supply and....

Pooof, at the very least IC's #1 and #2 were toast, #1 was long gone, nothing at all left of it. #2 was still present (a FMS6403 component video driver) but there was a hole in it.

I didnt spend any longer on the unit and told the owner the bad news, mostly as I could see no easy way to procure a FMS6403 and not knowing what chip #1 was. Chip #1 looked like it was a 3 terminal chip (Vin ground, Vout), there may have been some way to hack arround this.

Im sure some circuit protection would not be too expensive to design in. Hauppauge's idea of protection is a sticker on the back saying 'only use the supplied PSU' well, obvious but accidents do happen, searching the web showed that plugging the wrong PSU in was not an uncommon occurrence.