Cold solder joint?

[Richard Ellis]

Our VCR/DVD,CD et.al. player started acting up the other day...It would shut down (No power) at times for no apparent reason.
After checking power cords for bad connections & all I extracted it from our system.
Wiggling power cords made for no malfunction.....time to crack-er open.
I went directly to the PS board..sad design lemme tell ya.
Looking over..... a TO-220 device with the SMALLEST heatsink.....and THAT was the source of the radiant heat that this thing puts out??Please!
A power resistor slightly discoloring the board,,OK tweek it away from that MOV its leaning up against.
On to the underside, lo & behold no less than four of those circular solder cracks we mostly stick right up to the nose to see.(Sans magnifying glass). Thought a reheat would clean it up....the joint just up & "collapsed" Is that a cold joint??
Dab of fresh stuff did it up fine. Three more times.
Found a pair of four pin devices...no heatsinks. I was of the opinion any "sand" device with the hole in it was an invitation for an obligatory heatsink..so I had some copper structure that I clipped onto both...........better than nothing I thought.
So far so good its been running all day with no malfunction.
Talk about your designing at the lowest common denominator.
I have a beautiful TO-220 heatsink.............Na,.. wifey probably won't be too keen on my "modification"...to something that works fine.."Don't mess with it". Sorry already did! but I could'nt find said heatsink in time to descreetly mod the thing.


____________________________________________Rick.. ...

[DigitalJunkie]

I just tracked down an issue in a friends LCD TV set. The backlight inverter board had some bad caps,as well as the SMPS board(all next to a hot resistor),no biggie got those replaced-but it was still acting up! I started scoping out the various voltage rails,and found a 1.7V LDO regulator happily oscillating away at a couple Mhz(!)-it didn't have any bypass cap on the input! Design flaw? I tacked 0.1uf//10uf on there,and it was all happy.
The regulator was feeding the 'CPU' chip,and the buttons/OSD were unresponsive/spazzing..Apparently it had a bit of the flakey-menu issue since he bought it.

[nigelwright7557]

Originally posted by DigitalJunkie
I just tracked down an issue in a friends LCD TV set. The backlight inverter board had some bad caps,as well as the SMPS board(all next to a hot resistor),no biggie got those replaced-but it was still acting up! I started scoping out the various voltage rails,and found a 1.7V LDO regulator happily oscillating away at a couple Mhz(!)-it didn't have any bypass cap on the input! Design flaw? I tacked 0.1uf//10uf on there,and it was all happy.
The regulator was feeding the 'CPU' chip,and the buttons/OSD were unresponsive/spazzing..Apparently it had a bit of the flakey-menu issue since he bought it.

Typical high volume scrimping on a capacitor to save a couple of pennies.

2p * 10,000 units is quite a few pennies......

[Matt.B.H.]

Yep, I worked in a TV repair shop for a few years in the early 90s. i would say that it is fair to say that most modern junk is SH*(.

We used to repair all sorts of stuff and some of the suposed "high end" was often the worse. I dont mean to ruin a good make but Phillips was particularly bad with Sony a close second, then JVC (no longer imported to the UK) although they did some very nice stuff and I guess still do.

This can be good for you, I just got a Hann Spree monitor for a tenner with no backlight. Easy fix.

B+O is the best quality (mass produced) kit I have seen, some of their CRT TVs had a diecast ally case and very very good quality boards and design. Wonderfull. You can pick em up on ebay for pennys.

Another good one is old Sun Microsystems stuff. Your talking full HD CRT for nothing.

You can see I am a CRT fan. 100 odd years of development really can not be beat, at least in this half of the century (for the price, OLED)

Cheers Matt.