A guide to hacking Japanese car radios

Do you have a Japanese import car that won’t tune to local FM radio stations? It’s a well known fact that Japan uses a different public FM broadcast band to the rest of the world; 76 to 90 MHz instead of the usual 87.5 to 108 MHz CCIR band. Sure you can use a band expander but these suffer from a number of drawbacks, not to mention that the radio does not display the correct frequency of the station you are tuned to.

Here’s a guide on hacking your radio to convert it to natively tune across the CCIR band. This post is still a work in progress so I may update it from time to time and add more photos as I get the chance. Continue reading

McIntosh PF-2520I-A

I recently acquired this lovely McIntosh PF-2510I-A 6-disc in-dash CD changer. This model was available as an option in the North American market Subaru Legacy and Outback. It is often but incorrectly referred to as the PF-25201 or PF-25201-A.

 

McIntosh PF-2520I-A. Yes those are solid aluminium knobs!

 

Fortunately it shares the same connectors and pinout as the Japanese and Austrailasian market Legacys so can be fitted in cars destined for other markets with very little effort. Having said that there are a couple of gotchas. Read on… Continue reading

Subaru Legacy McIntosh subwoofer hack

Here’s a quickie on adjusting the gain of the OEM-supplied McIntosh subwoofer in many BE and BH series (MY 1998-2003) Subaru Legacy’s. The subwoofer gain and crossover frequency is non-adjustable, at least until now. : ) If you have such a car and want to get a little more punch from the sub, read on!

The amplifier is bolted to the floor under the drivers seat and has two connectors on the end closest to the door. Disconnect and unbolt the amplifier and take it apart. Make a careful note of where each screw goes as they are not interchangeable; you can permanently damage the amp by shorting things out of you replace the screws incorrectly.

Find R519 on the underside of the PCB near the power and speaker connector. In station wagons this is rated at 10k  and in sedans 4.7k, labeled as either 103 or 472 respectively. This resistor sets the negative feedback in the final stage of the subwoofer crossover.

Identifying R519

Replace this resistor with a higher value to increase the gain. Don’t leave it out of the circuit or it may overdrive the sub and do damage. If you short it you will mute the sub entirely.

R519 replaced

After some experimenting I feel 33k delivers quite a nice bit of punch in a station wagon, which should boost the sub by about 5.2dB. Feel free to choose any value you want between 10-100k. Be careful using high values as it becomes quite easy to inadvertently overdrive the sub.

You might want to use a potentiometer instead so you can adjust the sub gain as you please. If you do this, I suggest a 50k linear (type B) pot in series with a 10k resistor. Make sure you use shielded cable and keep the cable very short to help prevent any instability in the amp. Connect the cable shield to a suitable ground point in the amp and (ideally) a 100nF or similar capacitor between the cable shield and the pot casing to prevent possible ground loops.

Enjoy!

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

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.