Sharp Carousel microwave LCD repair

The LCD on my Sharp microwave oven recently failed, beginning with a few segments but quickly getting worse. I’ve seen quite a few similar models with the same problem and a quick Google search proves this. Sharp even offered a recall at one stage.

If your microwave oven suffers a similar fate and you could give this a try. Note that it is not actually an LED display as some seem to think; Sharp have simply done a pretty convincing job of making the LCD look like one. Continue reading

Japanese import FM tuner conversion

This post describes how to modify a McIntosh PF-2142I (often but incorrectly referred to as PF-21421) JDM car radio to natively tune from 87.5-108MHz as used in most countries around the world. This model of radio is fitted as standard equipment in many JDM Subaru Legacy and Outback cars manufactured between 1998 and 2003. Continue reading

Brother HL-2150N in Ubuntu Karmic

Normally I try to stick with HP printers when using them in Linux as they seem to have the best support thanks to HP’s efforts with HPLIP.

I recently went against my own advice and purchased a Brother HL-2150N monochrome network laser printer. Brother have at least tried to provide drivers for Linux and even supply Deb packages. Unfortunately installation is a mess involving ugly binary wrappers and packages that don’t appear to conform to Debian policies very well.

Whilst there is no official support for this printer model in Ubuntu 9.10, it can be set up to work via Ethernet fairly easily. Continue reading

Simple Arduino 7 segment display example

It appears that there are many different ways to interface a seven segment LED display to the Arduino; the humble 4511, 74HC595 shift register and a multitude of fancy (and expensive) serial ICs such as the MAX7219.

I decided to use a 4511 driver IC for this purpose as it was the only suitable chip I had lying around. It saves a few pins over driving the display directly from the Arduino and also works from a wider voltage range so can be used for driving large display modules.

LED display in action
Continue reading

McIntosh EF-1080I silent output fix

I recently acquired a McIntosh EF-1080I car amplifier that was almost completely dead. There was a small amount of sound coming from the speakers but it was quite distorted.

With the amp opened up I measured the +/- 26V and +/-15V rails and all were fine. I then concentrated on the muting circuit seeing the problem affected all channels. If you need to open one of these amps, take a note of where each screw goes as replacing them incorrectly can permanently damage the amplifier.

All of the channels in this amplifier model are based around the TDA7295 by ST Microelectronics. This chip features standby mode and muting on pins 9 and 10 respectively. Both must be held high (5v) for the chip to operate.

The power supply section of the amp has a de-thump circuit that pulls these pins low for a small delay at power on and immediately after power off to prevent noises in the speakers. Unfortunately the mute pin was staying tied to ground.

I traced the problem to SMD transistor Q607 that normally switches all of the mute pins. It actually disintegrated while I desoldered it, and replacing it restored the amp to life.

Close-up showing Q607

The transistor bears the marking IY and is  in fact a 2SA1162 general purpose PNP transistor. I replaced it with an identical part, however a friend suggested replacing it with one of a higher current rating such as a FMMT591. The FMMT591 works fine as a direct substitute and has a maximum rating of 500mA so should be a lot more reliable.

Grep for Windows

Ever since using Ubuntu as my primary OS I’ve missed many of the command line tools when using Windows. However I just discovered Windows has it’s own version of the grep command called findstr.

I’m probably a bit behind the eight ball here but despite it’s awful name, mangled switches and  other Microsoftisms findstr seems to behave in quite a similar fashion to good old grep, enough for basic commands at least.