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Vintage Honda Prelude radio restoration

A customer contacted us while in the middle of restoring their 1986 Honda Prelude 2.0Si, and wanted to see if we could get the original cassette deck back in working order, along with the original equalizer unit. The cassette deck wasn’t working, and the audio output from the radio was scratchy. Sounded like fun, so they shipped it to us and we got to work.

The radio and EQ were made by Matsushita (aka Panasonic) for Honda.

First things first, we powered it up using a bench power supply, and played the radio through a small speaker used for testing. All the controls were dirty which made a static/pop noise in the output every time they were changed. We used MG Nu-trol to clean them, and it improved quite a bit, but still not perfect. Our customer OK’d the removal of the controls to run them in our ultrasonic cleaner. The ultrasonic action is very effective at removing old, built-up gunk that control cleaner alone cannot remove. After reinstalling, we were delighted to hear perfect audio output with no more scratchiness!

There are four separate PCBs in the radio: main control, tape, volume, and the amplifier. Each one had a good number of electrolytic capacitors which tend to dry out and can cause serious issues when they get old. For older equipment that uses components that have been no longer available basically since they were first made, that can be a dangerous combination. After talking to the customer, we decided to strategically replace the ones where it made sense. We ended up replacing ~20 of them.

We noticed while doing that work there were several mini incandescent bulbs that were burned out. Luckily, replacements were still available, so we got the okay from the customer to replace them. This added light around the cassette door and in a couple of other spots, awesome!

The next item to address was the tape deck. The original belts were stretched and badly needed replacing. The deck would play a tape, but was sometimes very slow, other times would stop, sometimes FF/FR wouldn’t work, etc. It was also dirty (see above), so we cleaned it up and re-lubricated everything with white lithium grease.

The playback issue was almost definitely the old belts. With new ones in hand, we expected the deck to play after replacing them, but we were still running into issues.

That’s when we discovered some additional damage.

There is a worm gear that is pressed onto a shaft with a pulley, and the pulley runs on the main drive belt. There was a lot of vertical play here as there was a gap between the worm gear and where it attached to the chassis (see above). We noticed this gear wouldn’t spin and the belt would slack up causing the speed issues.

Amazingly we were able to locate one that was still new in the box!

The old, damaged pulley on the left compared to the new one on the right.

With this replaced, and a bit more cleaning, we popped in a test cassette that has a 3kHz tone and checked the output:

The speed looked good, so the cassette deck was ready to rock!

This was a long process, but we ultimately ended up with a beautiful restored deck ready to rock for decades to come in our customer’s equally beautiful Honda. Our finishing touch was a 3D-printed volume knob that we designed and printed in-house to replace the original which had cracked.

After carefully packing and shipping the radio and EQ back, our customer got in touch with us after to report that it was playing their old cassette tapes perfectly! We’re grateful we were able to contribute to a project like this. These types of restorations aren’t for everyone. It may not make sense to some to spend money and time on something so old, but for many, nostalgia is priceless and we couldn’t agree more.

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