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I have attached the info required to make these boards. Since the audio output with the 8 Ohm speaker has about x3 the power of the 45 Ohm speaker system, it possibly could be a tad loud. So I added a link on the pcb where a resistor could be placed at the input, in series with the audio input...

I built a home made proto pcb . (In lieu of plated through holes on a proper pcb where wires pass into a pcb on these home made ones I use 1.5mm brass eyelets) I will test it out today. I want to run it up with an actual OP amp driving the the audio system, rather than a signal generator, just...

Yes, I agree, it is the next project to be targeted for replication. I suspect it would be a rare item to find either built or un-built. But if somebody has one and could provide the details, I think we (the Cromemco replica team) could do a good job on it.

That Monkey.mov reminds me of a Bruno Mars music clip.

I'll post just the track image and artwork. Probably this could be converted into a Gerber in little time ( by Gary maybe) in Kicad. I'll make a couple of boards by hand as well. I cannot see any issues, never hurts to double check everything.

How do you know the opto-couplers are dying ? there is no scientific evidence presented. Just because they are getting hot doesn't mean that they are dying or dead. If anything, one with an open circuit LED would be as cold as a cucumber as it would be if the LED were shorted out. If the...

@nullvalue wanted a pcb for this project. After looking at this for a while, I tend to agree, it is the way to go. It is all about keeping everything as orderly and tidy as possible. The original design was a little messy and it had the pull up resistors for the switches wired in a messy...

Multiple appliances (not just the PET) had filter cap units applied across the incoming line voltage. Many were three wire types which had a capacitor from phase & neutral to ground called Y capacitors, of the X type are connected across phase and neutral, though if they are placed before the...

Yes it is all over the place on ebay, have a look at this German cable, the label in the photos, they called it a D sub 9: https://www.ebay.com/itm/233540296789? In any case, there is no confusion about the connectors & cables I am referring to now, even if the terminology is all over the place.

Can you lift up the lid of the PET to move the VDU further away from the power transformer and see if that is the cause. After that, if it wasn't, the next thing to do would be to check the power supply voltages for ripple with the scope.

Yes it is kind of charming. What I will do for mine is get one 5m long or similar F:F or M;M RS232 cable (and cut it in half) since they are cheap enough and the cable good quality and wire the cut ends directly into the edge connector for the D+7A board, this way the two control units can be...

There was a phase shift error in the horizontal timing of the text signals with respect to the H drive pulse timing, but not the cursor which was interesting. It might not mean much, unless you had the real CRT VDU connected and saw it there. If it does in on the actual PET CRT VDU, can you...

I was surprised what good value it was. The software disk installed effortlessly (on my HP computer running Windows XP), And it has worked without a hitch ever since. No problem with either 21 or 25V parts. When I was using it initially, I found that if it was set to a DS1225 Dallas NVram, it...

I cannot agree: The DC signals from the Joysticks are derived from a Thevenin resistance of 2.5K and not prone to interference, nor are those signals from the switches. From what I can tell the connection between the shells of the typical DE(or DB) or D9 connector, is via the shield of the...

Unfortunately, this is what started the You-Tube urban myths by latter day repairers of vintage TV's and VDU's who where completely clueless about the physics of CRT's and started scare mongering by showing big sparks when a CRT's charged anode got shorted out. By the way, the energy stored in...

"Equally Bulky" ?? a 25 pin plug is about 2 1/4" wide ! All of the 9 pin cables I have , the metal shell is connected to the metal shell at each and the 9 pins are isolated from that, Do you have commercial 9 pin cables that are different from that ? Can you check ? The 9 pin connector is...

DB9 bulky ? Not compared to the size of this box. Well as least the changes only requires a 10 conductor cable, likely thinner than a 12.

There is one thing about this unit that I'm not fond of, the cable hanging out of it. For some reason this bugs me, the dangling cable dilemma. It might just be an OCD I have, all of my lab equipment that had line power cords hanging out, I fitted IEC line panel connectors ! I think ideally it...

This basically confirms that the Cromemco document is correct and it is close to +/- 2V. Therefore, since out Kraft units ,at least the ones I have (check yours) appear to have a tad more output voltage deflection, we should power them from +/- 10V. To help confirm this can you repeat the the...

I'm doing more work on this. According to this document the output voltage from the Joystick (in the original Cromemco unit) should sit on zero volts and defect each way 2V. Or a 4V swing. Not 4.5v.... see Page 5 under Joystick operation...