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Aiwa radio teardown

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steve30:
How about a temporary departure from the usual subject of test equipment, so we can go and listen to some music?

Here's an Aiwa R22 radio from roughly 1980. It is shown in this photo with the matching A22 integrated amplifier and a nice Keesonic speaker. I also have the matching L22 cassette deck, but that's hidden away in the cupboard as it doesn't work.



It has FM and MW. Sound quality is very good and it is pretty selective. The radio is based around the Hitachi HA11211 IC, which is basically a radio-in-a-chip, but there are tons of passives surrounding it. Tuning is accomplished by an air spaced variable capacitor which is coupled to a multi turn knob by some gears and bits of string.



This photo shows the back of the front panel board which contains the LED displays. As far as I can tell, the big circular thing is just some kind of flywheel on the tuning knob. Also a couple of bodge components.



Here's the front panel. The Toshiba T1400-E chip is some kind of frequency counter. The LED display just shows the measured frequency.

The bar graph display is driven by another IC hidden under the black painted metal thing.



The electronics in this has a slight bodginess in the construction, but overall is generally well built and works fantastically.

SeanB:
The mass on the shaft is to damp out the mechanism, and gives a smooth feel to the tuning. Those pale blue caps are getting past their prime though, and probably are nearing replacement time. Good reliable electronics though, nothing really runs hot in it at all. Only things I have had fail are the 1161 stereo decoder IC, which fails and drops a channel. But it is a cheap IC, and readily available, or at least it is so by me.

steve30:
Ah ha. Makes sense as the tuning mechanism does feel really nice :p.

Nothing in it seems to have died yet. Hopefully it won't die anytime soon.

The HA11211 IC seems to get fairly warm. But not hot.

steve30:
A problem with this radio which I have had for a while...

After you have turned it on, the unit 'warms up', and as it warms up, the frequency drifts a bit, which means I have to dial the tuning knob back slightly as it warms up. Then if I leave it to cool down, then put it back on again, it will be cold, so I have to twiddle the tuning knob forward a little.

Any ideas? Maybe some components are past their best. I did manage to find a service manual, so I will certainly have a fiddle :).

SeanB:
Power supply caps getting warm, and the mechanical parts expanding as they get hot. Normally this is compensated by a few capacitors in the unit, but this is not always perfect.

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