Another Commodore 64 Black Screen Repair

(This was originally a Twitter thread on September 23, 2018)

September 23, 2018

On the bench today is a Commodore 64 picked up from @Recta_Pete at Atari Party East 2018. This revision is the cost reduced long board because of the sparse components around the VIC-II. I already spot several problems.

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Commodore 64 Black Screen Repair

(This was originally a Twitter thread from September 26, 2018)

September 26, 2018

Next on the bench is an early #c64, 1982 original motherboard with 5 pin video out and a lovely ceramic VIC-II. These tend to be tricky in my experience.

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Recapping an Epson HX-20 Slabtop

(This was originally a Twitter thread from March 24, 2020)

March 24, 2020

The Epson HX-20 is on the bench for some TLC like a new battery, new capacitors, cassette tape belt, and possibly more. Maybe I’ll eventually dial a BBS with it.

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Recapping the Apple PowerBook 160 LCD Display

(This was originally a Twitter thread from May 26, 2022)

May 26, 2022

Today I’m going to recap the LCD display on this PowerBook 160. It has a passive matrix LCD display capable of displaying 4-bit grayscale (16 shades of gray). The display was dim before with some severe artifacts (after adjusting the contrast slider) but now it will only show a black screen.

@mac84tv has an excellent page that lists the capacitors needed for this recap along with the links to Mouser to purchase.

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Getting Programs For The C64 CP/M Cartridge

Picture of Commodore 64 CP/M Cart and Boot Disc


The Commodore 64 CP/M cartridge was released sometime in the early 1980’s, shortly after the introduction of the C64 itself. The cartridge contained the necessary Z80 chip inside to run CP/M software natively. While a novel idea, it was a bit too late with the popularity of CP/M waning which itself had been released almost a decade earlier. To make matters worse, it seems to only work on very early revisions of the Commodore 64. I personally am only able to get it to work reliably on a Rev A motherboard (1982, with no s-video output).

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The Jameco JE520 Voice Synthesizer

Jameco JE520 Voice Synthesizer for C64The latest acquisition is the JE520 by Jameco. This external voice synthesizer came in two variants: the JE520-CM for Commodore and JE520-AP for Apple II. The only difference was the interface connection to the computer. The Commodore version, the one I have, connects to the user port while the Apple II version connects via an interface slot card. Otherwise, I believe the rest of the hardware to be the same. I found an advertisement for it in RUN issue 7 1984— it retailed for $115-$150.

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Commodore 1520 Plots .SVG Images

Commodore 1520 Plots SVG Files
NOTE! Split gears causing causing or plot errors? New replacement Alps gears for the Commodore 1520, Atari 1020, etc are now available! Click here to order your set.

I’ve put together a quick program that can convert an .SVG file into data statements that can be used to plot it on a Commodore 1520 Printer/Plotter. The program doesn’t run on the Commodore 64 (yet) but instead runs in the browser. It’s not ready to release yet as it’s fair picky about the types of .SVG files you feed it.

To whet your appetite, I’ve prepared a .D64 disk image that has four BASIC programs that will plot four different Commodore logos.

Download the disk image here.

And if you need plotter pens for your Commodore 1520 printer, you can get new old-stock pens from @futurewas8bit!

Reddit/r/RetroBattlestations BASIC Week 3– C64 port

Under The Sea: BASIC Week 3 C64It’s BASIC Week on Reddit/r/RetroBattlestations and I ported the BASIC Week program “Under the Sea” to the Commodore 64. The original code was written by FozzTexx for the IBM PC which allows for variable names longer than two characters. The Commodore 64 BASIC version 2 would probably still work using the longer names, it would just ignore everything after the first two characters. Doing this though would run the risk of overwriting variables so it was best to convert them. You can find a list of the variable name conversions at the end of the post.

If you’re keen to type the program in yourself, you can do so here. There’s a few special characters used the code. “CBM-” means hold the Commodore key (lower left) and hit the character after.

If you want to simply run the program from a disc image or to make a floppy, you can download a D64 disk image of Under The Sea here.

The BASIC version is quite slow and there’s room for optimization of the display code. Instead, I ran the code through the BLITZ! BASIC compiler and it runs much faster. This version is on the disc as “c/underthesea”

There’s three keys used the game. ‘A’ makes the turtle (you) go up, ‘Z’ goes down and ‘Q’ will quit the game.

Variable name conversion

Turtle$ = t$
TurtleWidth = tw
TurtleHeight = th
TurtleErase$ = te$
TrutleDead$ = td$
Enemy$() = nm$()
EnemyErase$ = ee$
EnemyW = ew
GameOver$ = go$
GOWidth = gw
GOHeight = gh
AirMax = am
Sea$ = se$
TurtleY = ty
Surface = sf
Score = sc
LastY = ly
TurtleX = tx
NumEnemies = ne
BubbleX = bx
BubbleY = by
Enemy X = ex
Enemy Y = ey
EnemyHit = eh
Food$ = f$
FoodX = fx
FoodY = fy
NewX = nx
NewY = ny
EnemyC = ec
NumBubbles = nb
NumFood = nf
exV = xv
eyV = yv
rows = rw
cols = cl