After the success in bringing an Aiwa AD-F220 back to life, and the subsequent enjoyment of getting back into playing tapes again, I decided to take a look at my other Aiwa deck, an Aiwa AD-F640, in some markets it is called the AD-S40U. This was my original cassette deck, and the second "decent" deck that I bought myself, the AD-F220 was my first. I bought it a long long time ago, it came with me when I moved from the UK to the USA almost 25 years ago. I bought a parts deck, and robbed the transformer out of it, I wish I had kept the rest of it.
About two years ago, the original belts bit the dust, and it was sitting in my equipment rack gathering dust. Last week, I ordered a belt and idler tire kit from an eBay seller that ships out of Spain. I had heard some good reviews of them. There are two belts, one that goes from the capstan motor to the first flywheel, the second that goes from the first to the second flywheel, this being a dual capstan design.
However, after fitting the belts and idler tire, I noticed something strange. The deck will play for about 30 seconds to a minute, then then gradually lose speed. It doesn't lose it, insofar as slowing to a stop, it just slows down slightly and then maintains this slower speed. Prior to this, the deck has always working fine for me. Observing the belts, I can't see anything obvious going on. With the deck playing, I was expecting to see maybe a belt riding off on the motor pulley, but it stays tracking right in the center of the pulley.
With this in mind, I wondered about the electronics. I measured the voltage across the motor, expecting to see around 12V as it's a 12V motor. What I actually measured was 9.54-9.56V. Looking at the service manual, it appears the motors and the two solenoids run off a separate 10.5V supply, which I measured at 10.43V. When the deck is in play, pins 1 and 2 of connector 8 measure 10.43V and 0.83V, which kind of makes sense of the 9.54-9.56V measured at the motor. I also held my meter across the terminals of the motor as it plays, and it doesn't lose any voltage when the speed drops.
It does not appear to be over tensioning the tape. Indeed, this Aiwa has an auto tape slack cancel feature, which spins both reels briefly to take up any slack when you first insert the tape. I have tried ejecting the tape and closing the door again, and also doing a brief FF/RWD when the deck is running "slow", but it doesn't take away the problem. If you leave the deck for a couple of minutes, it will start up at normal speed again.
Any ideas on this?
About two years ago, the original belts bit the dust, and it was sitting in my equipment rack gathering dust. Last week, I ordered a belt and idler tire kit from an eBay seller that ships out of Spain. I had heard some good reviews of them. There are two belts, one that goes from the capstan motor to the first flywheel, the second that goes from the first to the second flywheel, this being a dual capstan design.
However, after fitting the belts and idler tire, I noticed something strange. The deck will play for about 30 seconds to a minute, then then gradually lose speed. It doesn't lose it, insofar as slowing to a stop, it just slows down slightly and then maintains this slower speed. Prior to this, the deck has always working fine for me. Observing the belts, I can't see anything obvious going on. With the deck playing, I was expecting to see maybe a belt riding off on the motor pulley, but it stays tracking right in the center of the pulley.
With this in mind, I wondered about the electronics. I measured the voltage across the motor, expecting to see around 12V as it's a 12V motor. What I actually measured was 9.54-9.56V. Looking at the service manual, it appears the motors and the two solenoids run off a separate 10.5V supply, which I measured at 10.43V. When the deck is in play, pins 1 and 2 of connector 8 measure 10.43V and 0.83V, which kind of makes sense of the 9.54-9.56V measured at the motor. I also held my meter across the terminals of the motor as it plays, and it doesn't lose any voltage when the speed drops.
It does not appear to be over tensioning the tape. Indeed, this Aiwa has an auto tape slack cancel feature, which spins both reels briefly to take up any slack when you first insert the tape. I have tried ejecting the tape and closing the door again, and also doing a brief FF/RWD when the deck is running "slow", but it doesn't take away the problem. If you leave the deck for a couple of minutes, it will start up at normal speed again.
Any ideas on this?
