Hi to all,
the Jaycar QP-5585 " 3.5 Digit Jumbo LED Panel Meter" module seems to be somewhat unreliable - same goes for its smaller brother the QP-5580. After some period of use or storage, a segment in the LED display becomes intermittent or goes completely dead - rendering the unit useless.
In the two cases seen, the red LED displays were not to blame but rather the surface mounted panel meter chip ( ICL7107 type ) was the culprit - probably its attachment to the PCB was poorly executed in China.
In the case of the larger unit, this chip can be fairly easily removed allowing you to fit a standard 40 pin DIL version in place - the PCB has the holes all there already, waiting for this !!
ICL7107 chips ( by Intersil or Microchip) can be bought from Farnell for around $5 each, plus gst and delivery.
To remove the old chip, you will need a hot (450C) soldering iron with a chisel shaped tip at least 3mm wide. The black plastic blob on top of the old chip will soften and begin to crumble when you apply the hot tip anywhere on its outer edge - so just keep working away around the circumference of the blob until the chip loosened & removed.
Clean up any mess and rub the area with some metho on a rag - check with a magnifier that all the fine tracks that previously disappeared under the blob are no longer connected nor shorted together. Drop the new 40 pin 7107 into the holes provided and using a fine tip set to 370C, solder all the pins in place.
No such easy fix is possible with the smaller version.
..... Phil