Recent content by DrAM19

Hi Everyone, I recently picked up an VIC-20 to repair, and fixed all the minor issues on it. The big issue for it was that the 6560 was bad (the giveaway was no clock out of the VIC-I, but a good clock in to the VIC-I; I verified by swapping in a known good VIC-I from my personal VIC-20). I...

Wonderful news and congratulations! I'm really glad to see that it's working. The screen looks just like mine; so I'd say you're at normal operation. Make sure to also heatsink the TED. If you do look at an ePROM programmer in the future, that nice extra feature is being able to extract ROM...

Very cool. The data lines look like normal activity. The lower address lines seem alright up through A6. A7 and A8 look like they're stuck high but trying to do something (those little dips). So that is where I'd be going first. Looking at the schematic, A7 shares a line with +5 on the MUX...

Just a few excerpts from Bagnall: Not going to type the direct quote here, but on P305 Bob Russell talk about how Commodore almost purchased ZiLOG straight up, because they needed a 16 bit processor for a high-end business computer, wanted vertical integration of production, and MOS had not...

Most Commodore stuff is old news. I just figured its a good video and does answer alank2's question.

Good troubleshooting so far. You'll find the answer before you know it. And no worries about a delayed reply. We all have to attend to life. Good to see the voltage and proper reset behavior. The clocks look fine in those pics. On the topic of that daughterboard bypassing the system RAM, did...

What tests have you done (like voltage, clock, reset), and what did you see? Without more information: The the next thing I would check then is activity on the address and data lines. I'm curious if the system is attempting to execute instructions. Doubtful since this behavior is unchanged with...

Hi DistantStar001. That's not a screen I've ever seen on my TED machines. That this occurs if the CPU is removed means you should look at the basics first. Voltage rails, clock, reset circuit. What diagnostic tools do you have? An oscilloscope would be best. A logic probe is good for checking...

rhyoraptor, this is amazing. You are a lucky person! I tell you, the hand-drawn traces on the Kim-1s are beauty; a real work of art in their own way. Remember if you search eBay, filter and show only sold/completed sales. That will tell you what people actually paid. For recent Kim-1s: one...

Great! You should have all the tools and know-how to get these machines back to working order. Don't be discouraged! You will get them all working, or at least know why they don't. Like you said, I'll ignore the black screen VICs for now so we can focus on the ones semi-working. First thing to...

Hi Cami. So I and others can help recommend the right troubleshooting steps, what tools/capabilities do you have? Multimeter, logic probe, oscilloscope, etc? Are you good at soldering and desoldering components? For all 3 boards, first thing to check is that you have good VCC and VSS on all...

Hi Robert, I had the same concern as you (wanted a dust cover), and hit the same wall as you (couldn't find a vendor or plan online). What I did was make a two piece cover. One section, 3 pieces of thin vinyl connected using two long stitches covers the monitor. Then another 3 pieces with two...

I've used a pink pencil eraser on the PCB for the keyboard with good success where IPA was not sufficient. Very very very fine sandpaper if that doesn't work. You can also get a conductive paint for the key plunger. I've never done that but have seen videos of people doing that.

One time recently, rather than cutting the pin, I desoldered it and then pushed it slightly so it was in the center of the through-hole and not touching anything. Verified no continuity, and then carried on with my testing. Saved me from cutting the leg on a good chip.