ScuzzBlog: Diaries January 2022

Entry 12th January 2022: Post 1: Commodore Datassette - Rogue wire.

Commodore Datassette - Rogue wire.
OK I was reading this query on one of the Commodore forums about
a rogue black wire that had been cut adrift with no idea where
it connected to. I decided it was time to crack open one of these
units and have a good old look.

Not wanting to bust open one of my treasured units I dug out
this old broken unit which has never worked. The clear flap on
the top of the Datassette was broken when it arrived. Kinda has
the feel of someone smashing the thing when it wouldn't play ball.

To open the unit there are four screws on the base. The unit
splits open quite easily to reveal the inner workings. There is
a small PCB mounted under a shield cover. First though I needed
to disconnect the connector running from the main feed, together
with a metal latch holding two wires. The PCB seems to vary in
a number of these units I have seen. The one in the forum query
did not have the plug in connector.

I didn't find anything that looked like the wire in question. The
best I could work out is that the rogue wire was from the main
feed and probably had come away from the connector as it passed
out of the unit. Looking within the body of the machine beyond
the dust and spiders webs I found a larger grey wire but could
only find a red and white running from it. So I gave up looking
for the black wire.

The belts on the Datassette were a little slack though no worse
than I had encountered previously. I did test the unit whilst
open and found nothing wrong with the mechanisms, albeit a little
noisy. All motor and belt actions responded to the buttons and
so I then set too cleaning the heads. To do this I manually did
a clean with cotton buds and then used the tape head cleaner.

Using the Datassette both open and closed resulted in the same
problem. The unit found the program but then threw up an error
message regarding memory. I tested the C64C with another Datassette
and it functioned without fault. My guess is there is something
wrong with say a misaligned tape head. It is possible to fix with
a flat head screwdriver to get the azimuth aligned. Beyond my 
abilities to resolve. Fortunately I have so many Datassettes I am 
hardly ever going to need another. So a taped the broken plastic 
to the inside of the unit and called it a day. Was good to have 
a record of the inner workings, even though I didn't find the 
missing wire.

One point worth noting is that there is a metal tang that has to
locate in a ring slot below the PCB to make a connection. It is very
easy to bend that tang over so be very careful. It is quite tricky
holding the shield, PCB over the locating ring while trying to
screw the very small screws to the PCB. Took me a while that.

PS You can write your own alignment program

0 data 32,23,248,120,169,23,133,1
1 data 32,252,230,169,4,133,212,169
2 data 139,141,17,208,173,17,208,16
3 data 251,162,30,160,0,169,16,200
4 data 44,13,220,240,250,173,32,208
5 data 73,14,141,32,208,152,74,168
6 data 202,224,25,176,230,169,81,145
7 data 211,224,0,208,222,142,33,208
8 data 165,211,24,105,40,133,211,144
9 data 2,230,212,165,212,201,8,208
10 data 190,169,155,141,17,208,186,32
11 data 179,238,202,208,250,32,68,229
12 data 80,166
13 for a=0 to 97:read b:poke 256+a,b
14 c=c+b:next:if c=13420 then sys 256
15 print c:rem micro align 0.1 /enthusi

Use at your own risk. Not my program.

To adjust you use a small flat head screwdriver through the hole
in the front of the case and turn till the three bars align. If
you get a number and not a 'press tape' you have coded incorrectly.

Commodore Datassette - Rogue wire.

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Last updated 12th January 2022

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