Aiwa A22 Micro Series Integrated Amplifier

[fordiebianco]

This is amazing. Thanks for sharing. I had the preamp/poweramp pair of the later generation, and it was such a cool little thing.

 

[naviivan]

I had this Aiwa Stack- Amp, Tape deck and tuner all in a wooden rack mount case. it also had the matching speakers.
I gave it to a friend to use but in the end he threw it out when he moved. I was outraged. I still have all the paper work for it somewhere.
The speakers were pretty average sounding though.

 

[capslock]

Distortion rising after 80 mW into 8 R and 40 mW into 4R is a clear sign of the class AB output stage leaving its class A range and the amp not having enought loop gain to correct for crossover distortion.

Aiwa was already owned by Sony back then, and Sony bought Wega, a traditional German radio manufacturer based in Fellbach near Stuttgart, even before the mini modules came out, in 1975. After that, WEGA TVs and Hifi Components were essentially rebadged stuff from Sony and subsidiaries with some kit assembly taking place in Fellbach.

Hence, the Aiwa mini combo series all had corresponding siblings from WEGA:

Klassiker-Service – MM 205A

www.klassiker-service.com

hifimuseum.de - Sie sind im Bereich : Wega 205TD und 205A - das Ende

Elektrotanya for electronics experts

Electronics forum for electronics experts to repair defective appliance.

elektrotanya.com

Eines Tages überflüssig

Der jepanische Sony-Konzern kommt mit seiner deutschen Tochterfirma Wega nicht klar. Die schwäbische Filiale arbeitet seit fünf Jahren mit Verlust.

www.spiegel.de

The Wega 205A sibling to the Aiwa A22 contains an integrated tone control and power stage from Hitachi, the HA1370 (or is it HAI370?). I have not yet found its data sheet.

 

[Mazzeroph]

You're pronouncing Aiwa wrong

 

[AnalogSteph]

The Wega 205A sibling to the Aiwa A22 contains an integrated tone control and power stage from Hitachi, the HA1370 (or is it HAI370?). I have not yet found its data sheet.

Good find. HA1370 may be a misprint, since the level diagram says HA1350, and you can very much get a datasheet for that one (it is, unsurprisingly, a 20 W power amplifier). At the very least, if the HA1370 is real, I'd expect them to be closely related.

This still doesn't solve our headphone mystery, as the 205A has plain 220 ohm (1 W) series resistors much like I would expect. Unless, of course, @MAB had modified his unit while repairing it and forgotten all about it. It would not be hard to add another 220 ohm 1 W in parallel to the headphone output. Then I would still expect about twice the maximum output voltage into 300 ohms though, and less output than observed into the 32 ohm load.

 

[MAB]

You're pronouncing Aiwa wrong.

You're writing AIWA wrong.

 

[MAB]

Good find. HA1370 may be a misprint, since the level diagram says HA1350, and you can very much get a datasheet for that one (it is, unsurprisingly, a 20 W power amplifier). At the very least, if the HA1370 is real, I'd expect them to be closely related.

I found the schematic for the WEGA V210. Here is the parts list:

The amp chip is a Hitachi HA1397. I attached the datasheet below.

Which brings me to the headphone mystery...

This still doesn't solve our headphone mystery, as the 205A has plain 220 ohm (1 W) series resistors much like I would expect. Unless, of course, @MAB had modified his unit while repairing it and forgotten all about it. It would not be hard to add another 220 ohm 1 W in parallel to the headphone output. Then I would still expect about twice the maximum output voltage into 300 ohms though, and less output than observed into the 32 ohm load.

Here is the schematic with headphone output of the WEGA V210:

It's a 270 Ohm resistor. I think I know the mistake I made, I hacked the power calculation and may have made a dumb error. I will recheck tonight, and make sure nobody changed resistors. And get the headphone power right.

Probably a wiring issue (magnetic or electrostatic coupling from transformer wiring into some other loop / high-impedance node). I don't really like the spaghetti wiring in there, though at this point it's hard to tell how much it still looks like it did when it left the factory. The banana-shaped PCBs aren't exactly inspiring confidence either, must be an age thing.

This was during disassembly to clean the connector contacts, switches, and replace three caps. No resistors were changed! And wires got reharnessed, routed between transformer and heat sink just like original, except I did try to bind them more closely. There is no way to adequately route the wires in a way that avoids the danger zone around the transformer.

 

[MAB]

This still doesn't solve our headphone mystery, as the 205A has plain 220 ohm (1 W) series resistors much like I would expect. Unless, of course, @MAB had modified his unit while repairing it and forgotten all about it. It would not be hard to add another 220 ohm 1 W in parallel to the headphone output. Then I would still expect about twice the maximum output voltage into 300 ohms though, and less output than observed into the 32 ohm load.

OK. I messed up the original measurements.

I believe I swapped the loads, didn't check my work.

I remeasured, here are the THD into loads ranging from 32Ω to 500Ω. And no-load to see what the voltage limit of the amp is.

Going off of the WEGA V210 schematic, the load resistors are claimed to be 270Ω, which doesn't quite align with my new measurements. I took the cover off again, and sure enough the resistors are 220Ω, as you said may be the case. Which happen to perfectly align with the new measurements!

Apologies, my first attempt at measuring the headphone output was incorrect. Thanks for pointing it out!

 

[capslock]

The V210 belongs to a different series, though.

Wega V 210 | Hifi-Wiki

www.hifi-wiki.de

 

[mhardy6647]

... The rack handles give me a nostalgic buzz.

Only if there is leakage of AC to the faceplate of the amp.

 

[MAB]

The V210 belongs to a different series, though.

Wega V 210 | Hifi-Wiki

www.hifi-wiki.de

Thanks. At some point I will get all of the model numbers right.

I did (finally) find the schematic for the WEGA 205 A, aka AIWA A22:

The headphone resistor is 220Ω, as I saw and consistent with measurements.
The tone/power amp chip is indeed a HA1370, which I was able to confirm is the IC in the AIWA A22.

 

[capslock]

Thanks. At some point I will get all of the model numbers right.

I did (finally) find the schematic for the WEGA 205 A, aka AIWA A22:
View attachment 476520

The headphone resistor is 220Ω, as I saw and consistent with measurements.
The tone/power amp chip is indeed a HA1370, which I was able to confirm is the IC in the AIWA A22.

I had already provided the link to the service manual from Elektrotanya in post #43

The HA1370 seems to exist and can still be purchased:

HA 1370

Power audio amplifier 20W, Supply Voltage Min: ±22V Max: 25V Icc 0: 50mA, Iout max.: - ; out max: 20W, Load Resistance: 8Ohm Bandwidth: 20Hz-20KHz, input Resistance: - THD: 0,15%, Gain: 52dB

elw-elektronik.com

Yes, the model numbers are confusing. The 205 and 210 series have the same width and are very similar, and both of them were made from 1980 to 1982, so that could have been one of the many reasons why Sony were loosing money on their Wega subsidiary.

There is also a 400 series that was also made from 1980 to 1982. Those are a few cm wider and more powerful:

Wega PV 400 | Hifi-Wiki

www.hifi-wiki.de

The PV400 was an OEM Aiwa SA-P 50 and had a Sony sibling that was not sold in Germany.

There is also an SA-P 80 that is the same width as the SA-P 50 but more powerful. It seems to have no Wega sibling:

Aiwa SA-P 80 | Hifi-Wiki

www.hifi-wiki.de

Last not least, the Aiwa 22 / Wega 205 series had Uher and BASF OEM siblings:

Uher LG 105 | Hifi-Wiki

www.hifi-wiki.de

BASF D 6630 | Hifi-Wiki

www.hifi-wiki.de

Quite the zoo!

 

[MAB]

I had already provided the link to the service manual from Elektrotanya in post #43

Yep, I missed that. Among other things...

 

[AdrianusG]

I wonder how below "mini system" would measure, i was kinda in love with it back in the days, but sadly could not afford it, not even close

https://pin.it/4cqHOetLU

 

[Dialectic]

Similar form factor as a Naim Nait, except more features and better performance and aesthetics!

I'm sure the Aiwa's PRAT is inferior, though.

 

[TheFinisher]

I had the series 22 up until last year but sold it and immediately regretted that decision and then last week another came along at an irresistible price.
Fitted new belts yesterday
Replaced a few caps whilst changing the belts and now it’s all singing and dancing once again .
These are excellent bits of kit , I have mine hooked up to some vintage Harbeth speakers in a second system.