Azimuth head alignment software for the vic ?

Arma · Post by **Arma** » Mon Oct 25, 2004 1:07 am

does software exist to assist in setting the heads up properly for the vic 20 as i have a few datasettes that wll not load stuff very reliably. I have one "golden" datasette that does everything with all tapes but i am a bit concerned that if that it goes wrong i have nothing reliable enough, i would like to make sure i have at least two good ones

can anyone help or anyone have any pratical advice ?

Arma

aneurysm · Post by **aneurysm** » Mon Oct 25, 2004 11:18 am

have tried using a head demagnatizer of a head cleaner on the other decks?

Mayhem · Post by **Mayhem** » Mon Oct 25, 2004 11:25 am

I have a C64 and the Azimuth alignment program for it which is basically what I use (as I can use the same datasettes with the Vic20). There's nothing dedicated for the Vic20 as far as I know to do the same thing.

Arma · Post by **Arma** » Mon Oct 25, 2004 12:53 pm

looks as though i am gonna have to get hold of a C64

carlsson · Post by **carlsson** » Mon Oct 25, 2004 12:57 pm

I wonder how it is decided when or for what to flash the screen. The tape turbos on the C64 also flash the border and to some extent you can use a turbo tape you know is recorded on a virgin recorder to adjust the azimuth. Probably it would be possible to write a VIC-20 loader hook which would do something similar, unless it breaks timing issues. There were a few VIC turbo tape solutions, but I'm not sure if either is or can be compatible with the Turbo Tape 64.

KilrPilr · Post by **KilrPilr** » Wed Oct 27, 2004 12:43 pm

Hey Arma,

If you have the flat style datasette, you will notice a little hole
in the top of it,above the rewind key. That hole is where you stick
in a small phillips screwdriver to adjust the head on the tape drive.
First though remove the see through tape holder/cover by opening it up and gently squeezing the sides of it so that it pops out. This way you can get a good look at the screw.

Then connect the cassette drive to your commodore and turn it on.Enter poke54296,15 so you can hear the output of the tape deck. Put your favourite non-rare vic tape in the drive and push play.Turn up your monitor so you can hear the noise.

Then stick the screwdriver in the hole mentioned earlier and turn the screw gently until you hear the noise get louder.when you find the peak level, its all done.Put the drive back together and away you go.

If you have some isopropyl alcohol (99%) you might as well dab some on a q-tip and clean the head while your at it.Would prolly be a good idea to clean the head first before you adjust it.

Also I found changing the connector on the end of the datasette to a db9 connector and then putting the matching cconnector on the computer helped to sure up the connection 100 fold. I find that the stock hookup of the datasette can be flaky at times. here are some pics of the mod and the hole im talking about. http://www.members.shaw.ca/c64/vic

Hope this helps you!

Leo

carlsson · Post by **carlsson** » Thu Oct 28, 2004 12:31 am

Hm, very interesting. I never thought about the angle of the r/w head will affect how much of the signal the recorder picks up. Does this mean that a tape recorded with a head at a skewed angle but loaded on an unmodified datassette will return "too strong" signals and thus is the cause of load error. Must try some day.

BTW: the volume register on the VIC is POKE 36878,15 but I'm sure most of us did that mental substitution.

I'm not sure if the data in is wired differently on the C64 than on the VIC?

Mayhem · Post by **Mayhem** » Thu Oct 28, 2004 5:14 am

carlsson wrote:Hm, very interesting. I never thought about the angle of the r/w head will affect how much of the signal the recorder picks up. Does this mean that a tape recorded with a head at a skewed angle but loaded on an unmodified datassette will return "too strong" signals and thus is the cause of load error. Must try some day.

Yes. I've got several C64 tapes that suffer from that possible symptom.

Leeeeee · Post by **Leeeeee** » Thu Oct 28, 2004 10:00 pm

Ok people, before you go tweaking your C2Ns to death a few words about azimuth.

Without an alignment tape you can't set up your datassette correctly, not ever, nada.

The level you hear from the tape is not really relevant, if you don't have an allignment tape then the best way is to do as follows ... Do as KilrPilr said to be able to hear your tape as it plays (preferably a pre recorded tape from a software house but even these can be wrong) and turning the screw slowly one way continue until the sound starts to become muffled. Mark this point. Now turn the screw back the other way, through the loud point, and continue until it starts to get muffled again. The point you want is halfway between these two points, it may not be the loudest point but it will be the harshest sounding.

How azimuth works ...

Imagine running along a street with a cast iron fence on the wall beside you. It looks a bit like this...
|||||||||||||||||||||||||||||||||||||||||||||||||||||
... as you run past you see light through the gap and then the dark fence then light and so on.
Now imaging your view is restricted to a slot about as wide as the bars and gaps, as you run you just see dark light dark light, this is with the azimuth correctly set.

This time the fence is still upright .. |||||||| .. like that but your slot view of the world is at an angle like this / . Now as you run past the fence you will see the bottom of one bar, the middle of one gap and the top of the next bar, this is not as light as it would be if you were just looking through the gap. Now you move a little forward and you see the bottom of one gap, the middle of one bar and the top of the next gap, this will be not quite as dark as just the bar would be.

The further away from the recorded azimuth you get the more signal you lose and it doesn't take many degrees of error to remove most of the high frequency components of the signal.

The reason you can only really do this with an alignment tape is that you can't be sure that any other tape was recorded correctly. If the tape you use to set up the azimuth is like this .. /////////////// .. then setting your head like that .. / ..will work but a correctly alligned tape like this .. |||||||||| .. will now fail.

Azimuth rarely goes out of adjustment by itself, the usual cause of faliure is dirt on the head (clean gently with isopropanol and a cotton bud) or head wear. Another thing that can cause problems is the idler wheel going hard and no longer holding the tape against the spindle and print through on tapes that havent been played for a while and have been thermally cycled.

Just my £0.02 worth.

Lee.