Resistors between cassette port and video port?

[otherside]

I opened up a VIC-20 (old board, ca. 1982 with the voltage regulator on the board). Someone had added two resistors in series between pin 4 on the cassette port and a pin on the video port. See attached pic.

I don't get what they were trying to do. Pin 4 is "read" and I didn't bother trying to figure out which video pin it was soldered to, just desoldered and cleaned up both sides. Any guesses what they were trying to do?

[cbmeeks]

It's hard to tell unless we knew what video pin it was attached to.

But if it were GND, then maybe they were trying to create a pull-down resistor on the READ pin? Not sure why though.

[srowe]

Looks to be connected to pin 3, the audio out.

[groepaz]

ugly hack so you can hear whats being played on the datasette?

[Radical Brad]

I did something like this back in the day as well!

I had one of the only VICs that could play real music, and do rhythm tracks for my lead guitar practice.

At one point my goal was to create a crude media player that could even catalog and find the songs on the tape based on how long it took to fast forward or rewind.

Mine had a switch though, since hearing actual tapes loading through a 100 watt tube amplifier is not cool.

Brad

[otherside]

Nice, Brad. I think that's the most likely answer. I'll check with my meter to confirm it is indeed pin 3 on the video port.

[Gorf]

I did something like this back in the day as well!

I had one of the only VICs that could play real music, and do rhythm tracks for my lead guitar practice.

At one point my goal was to create a crude media player that could even catalog and find the songs on the tape based on how long it took to fast forward or rewind.

Mine had a switch though, since hearing actual tapes loading through a 100 watt tube amplifier is not cool.

Brad

I've always thought that would be a neat idea, what would you save to the tape to produce sounds usable in music?

[Radical Brad]

I saved actual music!

By simply leaving play pressed, you could control the cassette motor with the VIC.
Imagine the expressions on the faces of your pals when the VIC screen displayed "Playing.. Judas Priest", and The Sentinel rocked on through your monitor speakers! It was mostly a gimmick, but fooled a few people.

Later, I added a TIP-22 transistor H-Bridge to the casette motor, address through IO2, and could even change the speed of playback, play in reverse, or (slowly) rewind to make the tape act like a crude non-sequential music storage system. It was still capable of standard saving and loading of VIC programs.

Ah, the ugly hacks from back in the day!

Brad

I've always thought that would be a neat idea, what would you save to the tape to produce sounds usable in music?

[Gorf]

I saved actual music!

By simply leaving play pressed, you could control the cassette motor with the VIC.
Imagine the expressions on the faces of your pals when the VIC screen displayed "Playing.. Judas Priest", and The Sentinel rocked on through your monitor speakers! It was mostly a gimmick, but fooled a few people.

Later, I added a TIP-22 transistor H-Bridge to the casette motor, address through IO2, and could even change the speed of playback, play in reverse, or (slowly) rewind to make the tape act like a crude non-sequential music storage system. It was still capable of standard saving and loading of VIC programs.

Ah, the ugly hacks from back in the day!

Brad

Nice! That's really a neat idea!
So, how would you get it to display "Playing.. Judas Priest"? Would you save a small program before the song? Or am I completely misunderstanding what you're saying?

[Radical Brad]

Exactly.

I loaded up my 1980's VIC version of "ITunes", which did nothing more than know how long to run the casette motor in order to search or play a song.
After the program was loaded, I swapped out the tape with an actual audio casette, and flipped on the switch that played the audio to the amplifier. Vic could find all the songs on a standard audio casette as long as I initially plugged in the time between them into the crude program.

The VIC was really just acting as a robotic PLAY / FWD / RWD controller!

A few years later when I was more into the band than programming, I took the datasette apart and made a really nice sounding fuzz box out of it. By feeding the guitar input directly to the tape head amp (tape mechanics removed), the extreme amplification was as good or better than many of the distortion pedals I used at the time. I had a really unique sound for the day, with crazy long sustain and massive overdrive thanks to Commodore!

Brad

Nice! That's really a neat idea!
So, how would you get it to display "Playing.. Judas Priest"? Would you save a small program before the song? Or am I completely misunderstanding what you're saying?

[Gorf]

Exactly.

I loaded up my 1980's VIC version of "ITunes", which did nothing more than know how long to run the casette motor in order to search or play a song.
After the program was loaded, I swapped out the tape with an actual audio casette, and flipped on the switch that played the audio to the amplifier. Vic could find all the songs on a standard audio casette as long as I initially plugged in the time between them into the crude program.

The VIC was really just acting as a robotic PLAY / FWD / RWD controller!

A few years later when I was more into the band than programming, I took the datasette apart and made a really nice sounding fuzz box out of it. By feeding the guitar input directly to the tape head amp (tape mechanics removed), the extreme amplification was as good or better than many of the distortion pedals I used at the time. I had a really unique sound for the day, with crazy long sustain and massive overdrive thanks to Commodore!

Brad

That is awesome! Would you mind showing the program you used? I would also love to see a diagram for the datasette fuzz box if you know of a place that can provide those.

Thanks!

[Radical Brad]

Thanks!

Unfortunately, the hacking I did in 1982 using the old man's plumbing solder iron, scotch tape, and twist ties for wiring was never documented. The tapes that once held that code are probably rotting in a landfill, having first been overwritten by pirated copies of Judas Priest or Black Sabbath!

As for the mondo datasette fuzz box, here is how I made it back in 1983...

1) Rip all guts from datasette.
2) Bolt said guts to piece of chipboard.
3) Cut tape head from input wires.
4) Install 1/4 guitar jack to input wires.
5) Solder blob over switch that makes "PLAY" function.
6) Turn on your 50 watt sears silvertone tube amp.
7) Probe around datasette board until you get overdriven signal output.
8) Warm up the old man's plumbing solder gun.
9) attempt to solder 1/4 output jack to the board.
10) Staple down a 9v wall wart for power.
11) Plug in axe, start learning Eruption with your new distortion.

I think there was also a lot of scotch tape and luck used in the project.
Doing this to a working datatsette is not recommended!
Just google for "Big Muff Pi" schematic instead!

Brad

That is awesome! Would you mind showing the program you used? I would also love to see a diagram for the datasette fuzz box if you know of a place that can provide those.
Thanks! :mrgreen:

[Gorf]

Thanks!

Unfortunately, the hacking I did in 1982 using the old man's plumbing solder iron, scotch tape, and twist ties for wiring was never documented. The tapes that once held that code are probably rotting in a landfill, having first been overwritten by pirated copies of Judas Priest or Black Sabbath!

As for the mondo datasette fuzz box, here is how I made it back in 1983...

...

I think there was also a lot of scotch tape and luck used in the project.
Doing this to a working datatsette is not recommended!
Just google for "Big Muff Pi" schematic instead!

Brad

Ok, thanks! Your assistance is appreciated!