Sunday, December 14, 2008

Boards 08

Photos I have of the random things I put together this year, since we're nearing the end of it.

First up:

This is some level shifter and 3.3v regulator combo, It's intended purpose I don't really remember. Uses Maxim components. I ended up using just the 3.3v reg part of it. PCB was made with PnP Blue, and perma-marker

This is a board for 4 TIL311 displays ics(shown left), it's still sitting in my drawer, with TILs soldered in. Same PCB making method, this is going to be the same for everything else as well.

This is a single cell LiIon charger. Uses a Linear tech. charger ic (on the left) It was left over from the samples I ordered for repairing the Zipit1s

This is a lead acid smart charger board, that I never finished from here.

This is a lead acid battery desulfator from here.

Now this is a SPI (bios) flash programmer. It's based on this one made by Sergey Kiselev It uses a 74HC04 instead of the CD4049. I've only multimeter-tested it sofar. Built it for a mis-flashed motherboard I bought on the cheap. Still waiting for C2D prices to fall, so I've shelved this along with the mobo. (I'm a cheap bastard)

Okay this is.. modern art! Functionalitywise it's a low power step-up transformer. (really)

Thursday, December 4, 2008

PDA repair

I've wanted to post this for quite some time now, but laziness has so far stopped me from doing so, and since this was finished quite a while ago, some of the details are already a bit hazy, so to keep the info from deteriorating further, I've decided to do it now.

A while back I got a broken PDA for a relatively good price. Broken screen and mobo failure. It was some HP model I don't really remember. After opening it up I found that there was one fried component on the mobo, all the SMD fuses were intact, and since the fried part was a Maxim I decided to free-sample it and try a replacement. The part was a MAX1586, a "Power Management IC" for PDAs in TQFN40 (6mm x 6mm). It seemed to handle pretty much everything power related for the PDA. The original part was a bit melted-through and would get real hot, real quick, when power was applied, so it obviously needed a replacement.

Desoldering TQFN40 without any of the usual tools meant for doing so is not easy :)
What I went with was a hot-air blower, that wasn't at all meant for SMD soldering. (I think it was meant for burning away old layers of paint)
The mobo was wrapped in aluminum foil, in an attempt to shield other components from the hot air. This was mostly ineffective.

Below is the mobo after the the extra blown-off components were hastily reattached, before cleaning up the mess.

I free-sampled MAX1587, which is a bit higher power than the 1586 was, no special reason behind this, if I remember correctly it was the only part available for free-sampling.

As for soldering in the replacement that was mostly done with luck, an ordinary soldering iron, and lots of soldering resin ( I didn't have no-clean flux at the time ).
Thankfully TQFN pads have a "shoulder" that allows them to be soldered in with a regular soldering iron. This was not easy, nor would I recommend it to anyone, but it did turn out "good" in the end :)(

Below, the mobo with replacement PMIC in, after cleaning up.

After about an hour of playing around with setting the chip right, the device did power on. I don't remember if by that point I already had a replacement display, or if I ordered it afterward, but after that was installed the device came to life, functioning perfectly, complete with the original owner's data, which I proceeded to wipe. I kept the device around for about a week, then sold it, with very little financial profit, but lots of experience gained.

Notice the broken watch effect :)

Monday, May 26, 2008

Glossy paper toner transfer test

Part of a circuit onto a junk piece of pcb, with glossy paper result:

While it does seem OK at first look, after further testing I would not recommend this method to anyone, as the results are not so spectacular. I'll stick with using satin-matte photo paper and PnP Blue Transfer film, as they both provide superior accuracy.