Classic Computer Magazine Archive ANTIC VOL. 2, NO. 2 / MAY 1983

Tape Topics

Last of the Schematics

by Carl Evans

This is the last of the five-part series on the inner workings of the ATARI 410 Recorder. Last time I showed you the schematic for the digital playback circuit. This month we will look briefly at the audio playback circuit and I will show you the schematic for it. Next time we will start a new series of cassette file structures. That series will cover many topics, including a description of exactly what makes some commercial tapes "copy protected."

The audio playback circuit of the 410 Recorder is a simple, straightforward audio amplifier. Other than noting that it operates on the second stereo channel, there is nothing special about it. The circuit is more than adequate for the purposes for which it is intended.

The schematic shown here will come in handy if you ever have to troubleshoot and repair the audio portion of your recorder. The parts are common electronic components that you can buy at any local el.ectronics supply store.

I am going to keep the article short this time to allow more room for responses to your letters. If you have any special cassette-related problem, write to me at this magazine and I will try to help you. Join me in the next issue as we explore the nature of cassette file structures.

Tangle Angles

I have heard about loading cassettes at 1200 baud and even 2400 baud. I would appreciate more information.

Bill Creegan
Prescott, AZ

Several of you have asked about increasing the operational baud rate of the Atari cassette 1/0. For reasons enumerated earlier, I recommend against trying to increase the baud rate. Cassette 1/0 at baud rates higher than 600 baud is not reliable. If you stili want to try it yourself, then purchase Programmer's Work Sho p, marketed by Synergistic Software, 830 N. Riverside Dr., Renton, WA 98055 (206-226-3216). This package contains a machine language routine to write cassettes at 900 baud. I purchased the program to test that routine, and it does increase the baud rate to 900. But, l onlygot one good load out of thirty tries, using to p-of-the-line audio tapes. The only way to improve this ratio is to use chrome tape, and that eats recorder heads. Sounds like a no-win proposition to me.

I have a problem. My 410 will CLOAD only a few of my programs. Some were saved to cassette by me and others are third-party tapes such as Crossfire (which does load). Brandnew tapes have no chance.

I have taken good care of my 410. Heads are cleaned and good low-noise tape is used. I have had a technician work on the deck in hopes that this was a head realignment problem.

Bill Cenady

Cassettes can be frustrating at times. The only thing I can really suggest for your immediate problem is for you to try the Hl-REL mod I discussed in ANTIC #7. I hope the new Atari 1010 Recorder will be designed the way the 410 should have been. The FSK decoding could have used phase-locked loops. In a coming issue of ANTIC I will analyse the new recorder.

I am having problems loading some cassette programs that I have purchased. I thought the problem was only with machine language programs but I even have had trouble with some tapes with BASIC programs.

I solved the problem on tapes that are not copyproof by borrowing a friend's new 410 cassette, loading the program into my ATARI 400, then.copying it with my 410. Those cassettes wili then load. However, I can't do this with cassettes that are protected. - Gerald P. Graham,
Associate Professor, Longwood College, VA

Sounds like a misalignment of the recorder heads. First, make sure that they are properly aligned and if that doesn't help, then try the Hl-REL mod I described in ANTIC #7.

Using a friend's recorder is effective, but a hassle. If you need to continue that, you might want a copy of a VER VAN program called CASDUP, marketed byIJG, Inc. (714-946-5805). That program will copy even difficult, multi-file, boot tapes. I haven't found anything that CASDUP 2.0 won't copy.

Atari Customer Service advised me that the 410 should be demagnetized about every six months;. they said to take it to an Atari Service Center.

Could I not use the demagnetizer I have for my regular cassette recorder? It is a cassete with batterypowered demagnetizer built in. You insert the recordet, hit PLAY for one second, and the heads are demagnetized.

What if I insert this in the 410, CLOAD, hit Return, and hit Stop/ Eject after one second? Might this harm my 800?

Larry A. Campbell
St. Louis, MO

Degaussing (demagnetizing) tape heads is controversial in the recording industry. I believe that it does more harm than good, and recommend that you clean the tape heads once every 100 hours per your user's manual, but I recommend against ever using a degausser on your recorder.

I have seen laboratory cases where the residual magneticfield in a record head was actually higher after a socalled degausser was used on it. Also, if a fault should develop in the degausser, it is possible to zap your circuits with several thousand volts (albeit low current). Potentially, this could wipe out your recorder, and your computer as well.

If you insist upon using such a device, unplug your recorder from the wall outlet and remove the 1/0 cable that goes to your computer.

After six hours of typing, I think I ruined the ending frequency of the program by rewinding (by mistake), and recording over the top of the last little bit. If I knew the frequency (Hz) of the "CSAVE" ending, I could run that +, POKE the RUN C (as in your column) and salvage the whole mess. What think?

T.S. Tomingas
Pacific Grove, CA

I don't understand exactly what you mean, but I have some general advice.

Whenever you are writing, editing, or simply typing-in a program of any length, you should periodically save what you have done. There are bugs in the BASIC cartridge program that can cause the computer to freeze up, thus destroying everything.

When I am writing a program I create a backup system as follows. I label three tapes 'ONE, 'TWO, and 'THREE' After I have worked for an hour I dump it to tape ONE. About an hour later I dump the current version to tape TWO, and an hour later I dump the latest version to tape THREE. Then I start the sequence all over again with tape ONE. This way I never lose more than an hour's worth of work at any one time.

As soon as I have finished debugging the program I write a copy on both sides of tape ONE and break the write protect tabs on the cassette. I simply erase tapes TWO and THREE for later use.

I teach at the Lelean Memorial School in Fiji, and use an ATARI in class. We have such trouble with the 410 Recorder! I've tried CSAVE and LIST C, and now stick to the latter, since at least I don't lose the memory.

In class cassette loading is so slow. Can the 410 be speeded up? Finally, I've heard that the cassette tape can be used to give verbal instructions controlled by the program. How do you do this?

Rob Pattison
Nausori, Fiji

I am surprised to hear from a reader so far away. I encourage letters from readers outside the US (just to see how far my articles are reaching)!

You have the same problems with the 410 Recorder that we all have. You might try the HI-REL mod I described in ANTIC #7.

Your second question asks how to increase the baud rate of the cassette I/O. You can increase the baud rate to about 900 by installing a machinelanguage program that will replace the OS-resident cassette handler. But don't do it! The only way to obtain any kind of reliability at such a high baud rate, on this computer, is to use chrome tape, and chrome tape requires special heads which the 410 doesn't have. If you use chrome tape with the 410, you will rapidly destroy the heads.

Your third question has a happier answer. Add a voice track to your cassette programs with a standard stereo recorder that has separate record controls for each track. See De Re ATARI (availablefrom Atari, Inc.) and articles in ANTIC #4 and computer magazines. One of these days I will write a column on the subject.

I purchased a 410 Recorder and used it rarely. I acquired a program on a cassette but it would not load. The footage counter would advance to about '9' then an error code would be displayed. I tried an older cassette that had always performed and the result was the same. I tried various places on the tapes and eventually got no tape movement at all. The local Atari service store checked it with a different computer and assured me that the Recorder was defective. The recorder will still advance and rewind, but will not play. I was told to send it to Atari, plus $50, for a new one. This seems like a rip-off to me.

Fred Godar
Florissant, MO

The most likely cause of the problem is a bad switch under the PLAY button. The switch is a simple mechanical one. If the bar is broken, then you should replace it. Look in my last column (ANTIC #6) for a good source for parts.

If you have a high school in the area that offers a computer programming course, you might be able to order blank tapes from the teacher. Schools order in large quantities. I pay $1.00 for blank tape and plastic storage box.

Bonnie Plagge
Hebron, KY

I can't find short audio tapes by a reputable manufacturer. The C-10's I found are garbage. I've turned to Maxwell C-46s (low noise). Would it be better to use U.D. tapes? Is the C-46 too long for short programs, in terms of tape stretch?

Geoff Campbell
Simi, CA

You can obtain good C-10 and C-20 cassettes at most good computer stores. If you don't have one near you, several are advertized in the computer magazines. The source I have been using is:

Joe Duetsch Company
17173 Staedler Street
Fountain Valley, CA 92708
(714) 540-2772

MAXWELL 'UD' are not any better for computers than the 'low noise' tapes.

I know of no 'name brand' manufacturer who sells C-10 or C-20 tapes. The shortest commercial tape I have been able to find is a C-30. Remember, those guys are selling their tapes for 'music' recording, not computer programs.

A C-46 cassette tape should not exhibit any "ape-stretch problem. That kind of problem usually only occurs on C-90 and C-120 cassettes.