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How to improve belt quality

Belt is critical component of every cassette player. That’s why choosing correct belt for your cassette device is very important.

Belts can be used on various places of your cassette decks, for example main belt, inter-capstan belt, mode belt, counter belt… Some are square, some are flat. The most discussed belts are those that affect audio quality. Old good belt producers are gone forever and current belt producers cannot make belts of quality required by sensitive cassette deck mechanics.

These are three parameters that have to be taken into consideration, when choosing right belt:

  • belt quality
  • belt dimensions – circumference, width and thickness
  • belt material

Using incorrect belt will have negative effect to tape stability, wow/flutter, mechanics noise and parts wear. Each cassette transport is designed to use belt of specific parameters. It is always good to find balance between belt length, belt thickness and belt material. Some mechanics require elastic , some require harder belts. Some are more sensitive to correct belt, some less. It is given by design.

There is wide choice of generic belts of various lengths and types on today’s market. There are suppliers of generic belts, like ASWO here in Europe, or turntableneedles in US. They are very cheap, optically they look very good. The only problem is that their surface quality is not sufficient enough to meet specs given by manufacturers of cassette decks. Some transports, like Aiwa dual capstan transport, are very sensitive to belt quality.

Fortunately, quality of flat belts can be significantly improved using method of sanding, presented in the following video. It is possible to use this DIY method using very cheap tools, at home environment. The only tools that you need is 600 grit sanding bands rotary tool. As a result, surface of such  belt will be smooth, uniform and flat.

By using this method, I could reduce wow/flutter from 0.07% (10 sec peaks) WRMS to 0.03%, by just adjusting belt A of Aiwa XK-009 cassette deck. This method was tested in various cassette decks with similar results.

Belt improvement procedure
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WM-D6C DC-DC converter fixed

For many of us it is very famous problem. Reversed DC polarity and … 
There were many discussions on this topic. Here I would like to discuss two possible solutions, with simple TO-DO for everyone

1st. possibilty

Replace whole converter by modern type, sold here and there on eBay. You can find various 5V to 12V converters, or even anything to 12V converters. They’re small, much smaller than the original one. They’re more efficient. They can deliver more power. So why not to use them easily?
The answer is simple – they inerfere with internal circuits of D6C. You need to build ground shielding around it. More, their output voltage isn’t “clean” enough and it requires another filtering. Impossible? No, it just requires some time spent. Does anyone have experiences?

2nd. posibility

Repair the old one. Is it easy? Yes and no. The most difficult part is to remove the converter from PCB and open the original shield. It is difficult but everyone will know how to do it as soon as he tries.
I will rather describe how to troubleshoot the circuit that is inside.

Here is crop from service manual. It is just symbolic circuit and it has some basic mistakes. But it is very good start point.

Transformer and transistor on the left side create oscillator. Diode on the top is rectifier. Transistor and diodes on the right create stabilizer. When you reverse polarity, three parts can be burned – the ones marked with red letters and transformer. However, the wire on the transformer is much thicker than on the 33uH coil, that’s why it will survive. In most cases, it is necessary to replace both red parts:

1. Inductor: in blue circle (33uH, bigger version)

2. Transistor: in blue circle.

Instead of hard to get 2SD1048 you can use BC817 as 1:1 replacement. Well, the older one is little stronger (700mA vs 500mA) but in this application it doesn’t matter that much.

It is good to have right soldering station to be able to solder SMD parts. Or ask someone who can.

I hope you find this article useful. Any comments are welcome.


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Wow and Flutter – my know-how


I would like to post my experiences regarding typical problems with tape speed variations. I have fixed about 200 walkmans from Sony, Panasonic and Aiwa. However, I collect and repair only full-metal body autoreverse models made cca. after 1989. But most of my observations are valid for any model.

Many people think that these problems are related mostly to wrong belt used, but my experiences are little different. So here is my knowledge listed in the lowest to the highest probability order.

Continue reading Wow and Flutter – my know-how
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Sony DD series step-by-step repair guide for dummies

Sony DD series (direct drive) walkmans are very popular among portable cassette players because of their high quality construction, excellent fully analog sound quality – and great timeless design.

Although they’re well built, they will not work within specs without proper service. Because they’re 30+ years old, most of them will have some common issues by now.

In this manual I will give very detailed step-by-step instructions on how to fix all common problems – and recommendations on maintenance tasks to do, to avoid future problems. With the help of this manual you should be able to do proper service on any DD unit. I’ve fixed more than 200 DD units and will present my know-how and best practices, discovered through the years. I will try to make it as complete as possible.

This manual is suitable for everyone with at least basic technical skills. Experienced technicians will also find useful information here.

Continue reading Sony DD series step-by-step repair guide for dummies
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Panasonic RQ-S series walkmans – complete step-by-step repair guide

Dear all walkman fans,

from time to time I read here in various posts, how difficult it is to fix those small ultra narrow walkmans and bring them back to the specs. I must say it is not true. Most of them were designed to be serviced easily. Yes, they’re small, sometimes just little bigger than the cassette itself. But after you open them, you will see that there all is perfectly organized and parts are not that small as one could expect. From my experience, they’re much easier to fix than most bigger devices, such as boomboxes. Why? Boomboxes are made of plastics, their construction is cheap, with mix of wires, etc.

Continue reading Panasonic RQ-S series walkmans – complete step-by-step repair guide