Cassette Deck Maintenance Archives

This cool looking Gizmo is the ‘C64 Tape Pulse Visualizer’ and is the creation of a guy who goes by the handle of @BWACK on the internet and has been manufactured and supplied by the good folks over at Shareware Plus.

Back of the box.

Inside the cartridge sized box you get the visualizer itself along with a card that gives a little info about the device along with a link to @BWACK’s github page.

C64 Tape Pulse Visualizer – What’s included.

The device comprises six 10 segment ‘light bar graph’ LED display modules, each with an accompanying resistor, an Arduino Nano v3 and finally the pass through connectors for your datasette.

C64 Tape Pulse Visualizer Device.

The odd looking 7 pin mini DIN socket on the top left corner is so you can use it with the tape decks that came with the Commodore 16 and/or Plus 4. This is a thoughtful addition if you have one of those systems (sadly I don’t).

Reverse side.

The back of the PCB isn’t very interesting at all with no components on show, just a bunch of solder joints.

Closeup of the Arduino Nano board.

The Arduino nano, pictured above, does all the work here, processing the signals being read off the tape and converting them into a cohesive display on the LED’s.

What does it do?

If you’ve ever had problems loading a game or program off a cassette on your trusty Commodore C2N Datasette then this gizmo could be just what you’ve been waiting for, but before I get into that I need to explain a little bit about *Azimuth adjustment…

Normally my first port of call when I have an issue loading a game is a bottle of Isopropyl Alcohol and some cotton buds to clean the heads, capstans and pinch roller. If that doesn’t work then I will reach for my trusty Azimuth alignment kit from Interceptor Software – a bit of kit I’ve owned since the dawn of time itself**.

* Azimuth is basically the angle of the tape head relative to the tape being run past it.

** Actually about 1984.

My Azimuth Alignment Kit

This essential bit of hardware comprises a small Philips screwdriver, a cardboard arrow with a hole in it and a tape containing a special calibration program. The cardboard arrow is arguably the most important thing in the box – you certainly can’t complete the process without it!

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To use this you first load up and run the program and leave the tape playing. Next you twist the screwdriver in one direction until the program makes a ‘bong’ sound and the counter stops. You then repeat the process in the opposite direction. This will give you two angles, denoted by the cardboard arrow, the centre of which is the correct Azimuth and should give you the strongest signal when loading stuff. I have simplified this somewhat to keep it brief as there are a few more steps involved but that’s the gist of it.

The test tape contains a constant 3000 baud signal and is supposed to have been recorded on a professionally calibrated machine to guarantee the integrity of the signal. This is what makes adjusting the azimuth possible with it.

C64 Tape Pulse Visualizer

However what happens if your tape head is so far out of alignment that you can’t even load the program? You could try blindly tweaking the azimuth a bit and trying to load it again but that’s a very hit and miss approach and a sure-fire recipe for frustration and headaches. This is where the ‘Tape Pulse Visualiser’ can come to the rescue.

How to use it

You don’t really even need to run the program when you have access to the Visualiser as it literally does what it says on the box and lets you see (visualise) the signals being read by the tape head as illuminated segments on the displays.

A well adjusted Azimuth using our test tape is represented by two groups of illuminated segments on the display that are tightly packed together. The more ‘scattered’ they appear, are the weaker the signal, and thus more badly aligned the head is. There are 3 strips of LED’s that represent short, medium and high length pulses. Not all the strips will illuminate – it will depend on the nature of the recording such as whether it uses a turbo-loader etc.

The idea is to adjust the screw and ‘focus’ the LED segments as much as you can as in doing so you are aligning the head. It’s far easier to understand by just watching it in action.

If you watch the video above you can see me adjust the azimuth screw from a correctly set position to an incorrect position in both the clockwise and anti-clockwise directions. Note how the LED’s start flickering across the display as the head is moved further and further out of alignment. It changes from just having 2 or 3 LED’s constantly illuminated to having a bunch of around 10 of them flickering away like mad. The ‘bonging’ noise is coming from the Azimuth alignment program as I still had it running whilst recording the video clip.

In a nutshell, you just need to twist your screwdriver slowly , first in one direction and then the other until you find the sweet spot where just a couple of LED’s are steadily lit up and you should be good to go!

There’s no reason to unplug this when you are done adjusting your azimuth either as it just looks super cool to have the LED’s flickering away whilst you are loading a game. You can see it working whilst I’m loading up my copy of ATF which employs the use of a turbo loader and it loads up just fine.

ATF Title Screen

I’m a sucker for VU meters and flashing lights on old Hi-Fi decks and my C64 is no different – this will be staying plugged in for the foreseeable future! I’m delighted to be able to confirm that it still works if you have Gideon’s Ultimate II+ cartridge and cassette adapter installed too, although it is a bit tight when attaching the USB cable!

If you’d like to get hold of your own Tape Pulse Visualizer for your C64 head on over to sharewareplus.blogspot.com where you can pick one up for £28 pus P&P.

Addendum / Pro Tip

If you think your Commodore 64’s cassette port might be damaged and you also happen to have a JiffyDOS ROM installed – turn it off! I had totally forgotten about JiffyDOS utilising the space used by the tape routines so it could have more for itself to beef up disk commands! I was getting a ‘Device not present’ error every time I tried to load something off a tape. After wasting an embarrassingly long time faffing around I disabled the JiffyDOS ROM and BOOM it started working again. In my defence it has been over 2 years since I installed JiffyDOS and I haven’t used a tape since…

In addition to regular cleaning another vital part of keeping your cassette deck running smoothly is demagnetising the tape head. This applies to both computer cassette decks and Hi-Fi ones. Over time a residual magnetic field can build up on the head. Not only can this adversely affect playback (more noise and loss of high end response) but it can also degrade the quality of any tape passing over it.

A cassette tape is basically a strip of thin plastic coated with a ferrous material. Music (or data in the case of a computer tape) is recorded onto it by using an electro-magnet to magnetise the tape surface to varying degrees. A tape can be erased by placing a strong magnet near it so even a weakly magnetised head will, over time, slowly erase any recordings passing over it. The more you play a tape on a deck with a magnetised head, the greater the cumulative effect will be.

TDK HD-01 Tape Head Demagnetiser

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So what can you do about it? Well thankfully there are a number of different ways you can demagnetise tape heads. Popular methods include a mains powered electro-magnetic wand and those cheap cleaning cassettes that contain a rotating magnet on a little disc. In the past I relied on an the latter; an old Maxell cleaner/demagnetising cassette. However just recently I stumbled across this TDK one advertised as ‘New Old Stock’. I’ve always trusted TDK as a brand, they make good quality products and know their stuff. It was a little on the expensive side due to me needing to pay shipping and import taxes from the US but I felt it was worth it.

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Although the box it came in was very tatty, the contents were like new. Inside there was a small instruction manual and the demagnetiser itself. The device is powered by a small 1.5V lithium battery which should be good for 500 uses according to the instructions.

Naturally I had to install a new battery before I could get it to work. The rear of the instruction manual is stamped with the year 1978 so this little gadget is now over 40 years old! Thankfully it takes a standard size A76/LR44 button cell battery that is still readily available.

How does it work? – Demagnetising the tape heads

So how do you use it? Well it really couldn’t be any simpler. You basically pop it into your cassette player and press play! There’s a small plastic micro-switch above the play head that is activated by the motion of play head moving upwards when you press the play button. A red LED illuminates at the centre of the cassette to demonstrate that it’s working and that’s it, job done! When activated the circuitry inside the demagnetiser generates a pulse signal which demagnetises the play head in a matter of seconds.

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There’s a little more to the process than that if you are using the device in a cassette deck that doesn’t have a mechanical play button. The device won’t work until the play button is pressed so if you have a deck that won’t allow you to press play whilst powered off then you need to take a few precautions. This is because of the strong signal it outputs which can damage amplifiers and headphones if you don’t make sure to fully turn down any volume controls first. My Hi-Fi has a fully electronic transport mechanism so I have to be careful when using it on that device for example.

Commodore C2N – Demagnetising the tape head in progress!

Thankfully most older devices have fully manual play buttons and need no such precautions. With devices like the Commodore C2N Datasette I can simply pop the cassette in, press play and the get the job done in seconds. I would imagine virtually all Walkmans would be equally simple to work with.

The manual recommends demagnetising your tape head every 30 hours of playing time. Therefore, how often you need to do this will depend on what sort of tapes you are playing and how often you play them. For my Hi-Fi deck regularly playing C60 and C90 tapes this could be as often as once a fortnight. For my computer decks playing relatively short C15 tapes much less frequently, once every 6 months would be more appropriate.

Despite the cost I think the device is totally worth my time and money. Given how precious some of my old cassette tapes and games are to me, anything I can do to help prolong their lifespan is worth doing in my book.

Tag - Cassette Deck Maintenance

C64 Tape Pulse Visualizer

What does it do?

How to use it

Addendum / Pro Tip

Cassette Deck Maintenance: Demagnetising a Tape Head

TDK HD-01 Tape Head Demagnetiser

How does it work? – Demagnetising the tape heads