Hi gang,

I picked up a BX-125 at a thrift shop a couple of weeks ago. I wasn't at all surprised that it didn't work properly when I got it home. I understand that these decks have issues with the idler tire. The deck advanced the tape but the takeup reel didn't turn. It would auto-stop after a couple of seconds.

Fast forward to tonight and I just finished installing a new idler tire. The fix appeared to have worked - the deck was playing normally, or so I thought. I had been testing with a cheap tape of classical music that I had never heard before and it seemed OK when playing through headphones. I popped in a regular tape and that's when I discovered that the machine was playing back way too fast. I tried a couple of tapes that I know like the back of my hand and in each case the vocalist sounded like he was on amphetamines. And no, I wasn't playing old Rush tapes! :D

I followed the idler tire replacement instructions to the letter and there were no surprises along the way. Is there something that I can do to adjust the speed myself? Is this a common thing with Nakamichi decks, like the idler tire problem?

Thanks for any and all suggestions!

There is a small adjustment potentiometer on the back of the motor to set the speed. Without a test tape and a frequency counter you'll have to go by an album you're familiar with and adjust it until the pitch sounds correct.

Be careful not to short the body of the screw driver against the motor case when adjusting or you'll short the regulator and the speed will run away on you. Non-conductive tools are best here.

If the speed does not adjust, then the regulator is bad and the motor will need to be replaced. check to also see that the belt is not riding on the edge of the motor pulley instead of the middle where its supposed to

Two minutes later, an answer. I love you guys! :smlove:

Ahem...

I was thinking about recording a test tone on my rock-steady KX-690 then playing it back on the Nak and the computer at the same time. I'll adjust until the tones match. Does that sound logical? Is 3 KHz a good choice?

Cheers!

Two minutes later, an answer. I love you guys! :smlove:

Ahem...

I was thinking about recording a test tone on my rock-steady KX-690 then playing it back on the Nak and the computer at the same time. I'll adjust until the tones match. Does that sound logical? Is 3 KHz a good choice?

Cheers!

Yes, it is one of the options. Another one is to use a computer program, for instance AudioTester (http://www.audiotester.de/) - that can measure the frequency - so you can adjust the speed accurately.

Cheers

Alex

There is a small adjustment potentiometer on the back of the motor to set the speed. Without a test tape and a frequency counter you'll have to go by an album you're familiar with and adjust it until the pitch sounds correct.

Be careful not to short the body of the screw driver against the motor case when adjusting or you'll short the regulator and the speed will run away on you. Non-conductive tools are best here.

If the speed does not adjust, then the regulator is bad and the motor will need to be replaced. check to also see that the belt is not riding on the edge of the motor pulley instead of the middle where its supposed to

Where in the world is that potentiometer? I see all kinds of voltage regulators sprinkled around the machine but nothing obvious near the motor. The motor is the large metal cylinder, correct? Using the attached photos, can you spot the potentiometer?

Thanks!

It's that black spot on the back of the motor. It's tucked behind the rubber so you kind of have to feel for it with your screwdriver. Might look like someone's already tweaked it.

I think that I might have answered my own question. On the back of the motor is a 1 cm opening. It looks like it has been played with already, which might account for the speed issue. Perhaps the idler tire was losing traction and in an effort to correct the problem, somebody adjusted the speed. There's no clear slot for a screwdriver tip showing. Suggestions?

It's that black spot on the back of the motor. It's tucked behind the rubber so you kind of have to feel for it with your screwdriver. Might look like someone's already tweaked it.

Thanks - I was answering my own question when you posted. :D

flat head screwdriver about 2-3mm wide should do it.

That did it!

I used AudioTester to capture the input from the tape deck. The 3 KHz test tone played back at around 3.2 KHz before I adjusted the motor. After the adjustment my reference tape played back a wee bit slowly on the Nak so I hooked up the Yamaha to the scope and observed where the test tone fell on the graph. Sure enough, I had made the Nak a little too slow so I bumped it up to match the Yamaha. This seemed like a good idea since the Yamaha is my reference deck and will be the one where all my recordings are made. In hindsight, I should have done this first.

The BX-125 sounds great and operates smoothly. I am very pleased with my $9.99 investment! The highs are a little rolled off compared to the Yamaha, when NR is turned off on both decks (my reference tape was recorded with Dolby-S) but this doesn't surprise me in the least given the inherent differences between machines. A little experimentation should lead to a solution that works well in both decks.

A big thank you to all of you who responded to my questions. This was a fun fix and a real confidence builder.

Cheers! :beerchug: