Cromemco JS-1 Joystick Replica

[labomb]

I looked at several datasheets for TO-220 regulators, all seem to specify a max of 6.35mm length for the wide portion of the pins. The holes are currently located at 6.35mm from the bottom of the package. Factoring play with the mounting hole, that should be fine. I also aligned the holes... using a 2mm pad doesn't present an issue doing so. And assuming the new pad sizes are a go for everyone, I adjusted the part positioning in the lower right corner a bit.

Last, I am assuming a double sided board. All tracks, with the exception of the regulator supply, are at the bottom and all pads are through hole.

 

[Hugo Holden]

I looked at several datasheets for TO-220 regulators, all seem to specify a max of 6.35mm length for the wide portion of the pins. The holes are currently located at 6.35mm from the bottom of the package. Factoring play with the mounting hole, that should be fine. I also aligned the holes... using a 2mm pad doesn't present an issue doing so. And assuming the new pad sizes are a go for everyone, I adjusted the part positioning in the lower right corner a bit.

Last, I am assuming a double sided board. All tracks, with the exception of the regulator supply, are at the bottom and all pads are through hole.

View attachment 1278769

Cool !

 

[Hugo Holden]

@nullvalue:

I'm still double checking some things about the placing of the holes on the front panel.

I'm not sure if there is a discrepancy, or not.

One issue is the photos have edge shading and distortions. This is where a flat scan of the panel comes in handy.

Looking at your dimensional diagram (re-attached) it is the distances A & B that I am wondering about on the original panel. The reason is that the front panel photo (although a little angled with a shadow too) suggests those two distances are roughly about the same, but the dimensions on your diagram suggest otherwise. Can you double check the panel measurements to check this feature ?

I have attached another photo from the thread, it also suggests distances A and B are equal, but again it is a tilted image.

And trying to allow for the perspective and photo tilt, projecting the size of the 1" long slot forward, it appears that the the distances A,B and C are all close to 1".

 

[nullvalue]

@nullvalue:
Looking at your dimensional diagram (re-attached) it is the distances A & B that I am wondering about on the original panel.

Hey good question, but yes A≠B≠C.

A=30.00mm
B=26.67mm
C=25.00mm

 

[1944GPW]

When taking photos for later photogrammetry, a round coin of known denomination often works better than a ruler. Rulers are not always held perfectly parallel or perpendicular to item features and owing to their length are also not always held flat against the item's surface. The two benefits of a coin are that a scaling line can always be drawn across the diameter that is parallel to the focal plane of the camera, even when perspective is involved, and that the coin is usually small enough to lie flat on the item surface. I've used this technique numerous times to get reference photos of WWII military vehicle markings when I only had a limited time for access.

I have a question, what is the new enclosure's sheet metal thickness? As a gauge or preferably measured with digital calipers or mic.

 

[Hugo Holden]

I have a question, what is the new enclosure's sheet metal thickness? As a gauge or preferably measured with digital calipers or mic.

The cream painted part, excluding the paint, where I was able to measure it, is close to 1.6mm thick.

On the other hand, the blue painted part is close to 2.2mm including the paint, so it is possibly closer to 2mm without the paint.

 

[Hugo Holden]

I looked at several datasheets for TO-220 regulators, all seem to specify a max of 6.35mm length for the wide portion of the pins. The holes are currently located at 6.35mm from the bottom of the package. Factoring play with the mounting hole, that should be fine. I also aligned the holes... using a 2mm pad doesn't present an issue doing so. And assuming the new pad sizes are a go for everyone, I adjusted the part positioning in the lower right corner a bit.

Last, I am assuming a double sided board. All tracks, with the exception of the regulator supply, are at the bottom and all pads are through hole.

View attachment 1278773

I just noticed something.

I think you should move C2 and R3 back to where I had them on my proto pcb.

The body of the regulator is close to 10.1mm wide and the axial 10uF capacitor 5mm wide.

If they are mounted in the new position you selected, the capacitor body would be just touching the regulator body.

Although the regulator only get warm in the application, and some heat is transferred away from its tab by the mounting screw to the enclosure, it would transfer heat into the body of the capacitor which is not ideal.

 

[labomb]

Ah... seeing the actual prototype is quite helpful.

Here is the update. The only other thing I changed was to eliminate the two pads next to Q1 and Q2, which I assume were used to bolster the track junctions (vs. as test points or some such). I added some additional copper at those locations instead. If they need to be pads for whatever reason, I'll change it back.

 

[DougM]

These look great! I'll DM you about shipping.

Actually I took another look at these from my main computer now and I think we decided we wanted to mount the joystick centered (front-to-back) but this looks like it has been placed forward. Spacing on the buttons look good but I think we'd want to center the button array as well.

I'm on it.

 

[labomb]

So after seeing the built up prototype, I was motivated to take another look at the regulator and as suggested, I looked at my Dazzler replica that I did a couple of years ago. As it turns out, Hugo's original layout was spot on.

With that, here's yet another update...

 

[DougM]

I'm on it.

Ok, in this zip is a 0v2 version of the panel DXF. Lmk your thoughts. I think I can cut a test piece today, though weirdly it'll be out of plexi since I have a ton of it in stock.

 

[Hugo Holden]

Ah... seeing the actual prototype is quite helpful.

Here is the update. The only other thing I changed was to eliminate the two pads next to Q1 and Q2, which I assume were used to bolster the track junctions (vs. as test points or some such). I added some additional copper at those locations instead. If they need to be pads for whatever reason, I'll change it back.

View attachment 1278809

I put those extra transistor base connections/pads there for alternate transistors in the prototype.

I was at one point going to use the vintage 2N3053 and 2N4036 in a TO-5 package and their bases point the other way compared other transistors that have reversed collector and emitter connections on the pinouts; say compared to the 2N3904/6 in the versions of those that have preformed leads. Or other common transistor types.

Viewed from the bottom with the flat side pointing down, and from L to R the 2N3904 is cbe , but for many other parts it is ebc, hence that extra pad, but its not needed. I decided better to go with the 2N3904/6 because the unit contained the 2N3904 in the first place and they were up to the job.

 

[Hugo Holden]

I just received my D+7A board from the USA. It is a factory assembled version. Has seen some work. One of the presets has be changed for a superior type (hardly surprising because those non sealed thumbwheel pots are a real nemesis, they always require cleaning and often go intermittent, they are a nightmare in my Tek scopes and I have been replacing them over the years). Also resistor R22 is missing.

There are three modfications on the board solder side, two link wires and one resistor: @nullvalue, does your board have these same mods ?

I will have to go over it fully, cleaning all of the IC pins and checking the socket claws (they appear to be TI sockets). But I think I'm lucky, the board looks like it has seen little use. I have nearly all the spare IC's for it including the 1408. The interesting ones I don't have are the CA3140 OP amps.

It is odd though, the board schematic specified CA3130 OP amps, but this board is fitted with CA3140 Op amps. These have different output stages, the 3130 has a cmos output stage, but the 3140 uses BJT's.

 

[nullvalue]

I also just got a D+7A this week. Haven't had any time to mess with it though. My R22 is also missing. How do you know if it's the factory-assembled version? Mine does not have any solder-side mods. Mine came with a bonus edge connector attached! I can't make out what Rev yours is? Mine is Rev E. Let me know if you've come across any D+7A diagnostics/testing software.

 

[Hugo Holden]

Wow, I like the vintage CA3140 OP amps on your board, with early 70's date codes.

With those round package versions, they formed the lead wires to fit the 8 pin DIL sockets. That was a common thing to do back then.

I have done it myself with those packages; the best way is to pass the lead wires through a standard array of holes in a 2.54mm grid on some proto board, then cut all the wires off the same length, and then you can plug them into a DIL socket.

I probably should not know this, it shows my age. For this application, the ideal sockets are machine pin, because the receive the round lead wires very well, but dual wipe sockets still work ok.

This sort of thing is "classic 1970's engineering" and just as interesting as the kind of graphics that the Dazzler board produces. I just love this vintage computer gear.

 

[Hugo Holden]

I also just got a D+7A this week. Haven't had any time to mess with it though. My R22 is also missing. How do you know if it's the factory-assembled version? Mine does not have any solder-side mods. Mine came with a bonus edge connector attached! I can't make out what Rev yours is? Mine is Rev E. Let me know if you've come across any D+7A diagnostics/testing software.

View attachment 1278846
View attachment 1278847

It had a stamp on saying factory assembled & tested, you can see the black writing on the solder side in the top area on the photo I posted, albeit upside down.

Hmmm........... I might undo the mods on my board, but first I will have to figure out what they were for. My board is also REV E.

A question; does the switch hole cutout geometry we found suit the actual switches ? What were the exact size of the square holes on the Cromemco unit ?

 

[hmb]

I just received my D+7A board from the USA. It is a factory assembled version. Has seen some work. One of the presets has be changed for a superior type (hardly surprising because those non sealed thumbwheel pots are a real nemesis, they always require cleaning and often go intermittent, they are a nightmare in my Tek scopes and I have been replacing them over the years). Also resistor R22 is missing.

There are three modfications on the board solder side, two link wires and one resistor: @nullvalue, does your board have these same mods ?

I will have to go over it fully, cleaning all of the IC pins and checking the socket claws (they appear to be TI sockets). But I think I'm lucky, the board looks like it has seen little use. I have nearly all the spare IC's for it including the 1408. The interesting ones I don't have are the CA3140 OP amps.

It is odd though, the board schematic specified CA3130 OP amps, but this board is fitted with CA3140 Op amps. These have different output stages, the 3130 has a cmos output stage, but the 3140 uses BJT's.

Cromemco's manual for the D+7A (rev E) specifies both the 3130 and 3140 in the parts list, and 3140 in the schematic. Of course it doesn't matter which part is installed in our case since these 3130/3140s are used to drive the analog outputs of this board, and we are using the board only for its analog inputs.

With regard to R22 - the manual provides a table showing the board mods that need to be made to support different input voltage ranges (bipolar, unipolar positive, or unipolar negative). The joysticks require the D+7A to be set up for bipolar input (-2.56V to +2.56V) which requires the following components and values:
R22 - omitted
R5 and R12 - 500 ohm
R7 and R20 - 2.7K ohm
R14 - 5.1K
R23 - 1.2K

 

[nullvalue]

A question; does the switch hole cutout geometry we found suit the actual switches ? What were the exact size of the square holes on the Cromemco unit ?

On the Cromemco unit unfortunately I wasn't able to get an exact measurement because they switches are already installed in the enclosure and I didn't want to risk anything by trying to remove them.

 

[DougM]

need to make a couple of minor adjustments, if you look at the big joystick hole you can see that there's a bit of a bump out just to the right of the top mount hole. That's a lash problem, I hadn't yet dialed in the lash correctly. Next thing on the agenda.

Also if you look at the right-most joystick mount hole you can see that the cutter loaded up. That's the biggest problem with cutting plexi, it tends to melt. Aluminum does the same thing, not melt, but load up slag on the cutter, which is why I'm afraid to go below 0.125.

There are some vids if you're interested, but I can't load them directly here I don't think.

 

[nullvalue]

need to make a couple of minor adjustments, if you look at the big joystick hole you can see that there's a bit of a bump out just to the right of the top mount hole. That's a lash problem, I hadn't yet dialed in the lash correctly. Next thing on the agenda.

Also if you look at the right-most joystick mount hole you can see that the cutter loaded up. That's the biggest problem with cutting plexi, it tends to melt. Aluminum does the same thing, not melt, but load up slag on the cutter, which is why I'm afraid to go below 0.125.

There are some vids if you're interested, but I can't load them directly here I don't think.

This look pretty good to me! I know plexi can be a real pain. I can't tell by the photo, did the little notches get added to the key switch cutouts? it may just be too fine of a detail to show up on plexi.

Also if you measure and look at Hugo's question above about A/B/C, what did A end up at with your cut?