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Miami
akira^8GB wrote:

This is my idiot-proof schematic, for people that have no idea of electronics (like me) and want to build two pots with disable switch for port 2 potentiometers:

I have to say I built this and really didn't think it was necessary to bother. I think different rate potentiometers might yield similar results.

Thanks for posting the schematic! The perfectionist side of me was considering re-doing my pots InactiveX style, but I'm too lazy, and now you say it's not worth it. I don't think I'll use the pots much anyway. Expect I'll spend most of my time checking out SID Wizard once I get my uIEC/SD connected internally.

akira^8GB wrote:

The way I do the switch is by connecting the power lines of the pots of the same port together then onto the +5 lne, so all I have is to connect that line to a single switch. You don't need a DPDT switch. No power, no pot. Mouse works fine. I wouldn't like to power the mouse and the pots at the same time on the same pot, sounds prone to disaster.

Wouldn't cutting X and Y disconnect the pots as effectively as cutting GND or 5V? What could go wrong if you leave the pots powered but with their data output disconnected like nitro said?

akira^8GB wrote:

As a side note, I wouldn't do almost ANYTHING that Alpha recommends.

Hm. Why, what else did he do that seems silly?

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New York City
Awol wrote:

Thanks for posting the schematic! The perfectionist side of me was considering re-doing my pots InactiveX style, but I'm too lazy, and now you say it's not worth it. I don't think I'll use the pots much anyway. Expect I'll spend most of my time checking out SID Wizard once I get my uIEC/SD connected internally.

One of the pots still had tapering and even though the other one seemed to be working fine, it was still imprecise to get to a sweet spot for the range. Personally, I didn't think it was that necessary specially if you have MSSIAH and can connect a proper MIDI controller to it. Then you don't have to deal with finicky, flickery C64 pots. I mean, the computer looks bad ass, and it's convenient to have them in-built without depending on an external control surface, but although having them go full range by mid-turn of a pot is annoying, building this circuit was a lot more effort for me and the end result was only marginally better. I still got to try using diffrently rated potentiometers. Haven't been able to bag a C64 I can restore and sell.

Awol wrote:

Wouldn't cutting X and Y disconnect the pots as effectively as cutting GND or 5V? What could go wrong if you leave the pots powered but with their data output disconnected like nitro said?

As I said I know nothing about electronics, but I am also quite cautious when dealing with it. The potentiometers connect to the SID and you don't want to screw up your SID.

So if you disable the data lines and connect a mouse, you are still giving voltage to the mouse AND the pots. Although no data is sent, I rather NOT have two devices plugged in to one port's voltage bits at the same time as the ports were not designed for that.
What I say may not make any sense if you know electronics, but I rather be safe. The effect is the same after all.
The main difference I see here is that if you cut the data lines instead of the power, you may be able to switch it on or off while the machine is on, while my switch is only to be operated with the machine off to be totally safe. My switch is also easier, less cables to mess with.

Awol wrote:

Hm. Why, what else did he do that seems silly?

Well the silliest thing he has done is the case shrinking mod big_smile but for example his "noise reduction" mod just doesn't work. Doing it properly requires a lot more work. If you are interested in a full bad-ass noise reduction mod, check out Vandalism News #58's Hardware Corner section where Lemming explains a proper one, but it's not for the faint of heart. I didn't dare make it: http://csdb.dk/release/?id=102732

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Miami

Well I tried the switch method suggested by nitro and now my mouse works but the pots don't anymore! I'll have to double check all the connections and see if there's a short circuit somewhere or something.

At least the JiffyDOS and uIEC/SD that I just put in work fine. I even managed to desolder the original kernel without damaging it... Ok, I broke one leg.

akira^8GB wrote:

Well the silliest thing he has done is the case shrinking mod big_smile but for example his "noise reduction" mod just doesn't work.

I do get significantly less noise with Alpha's noise reduction mod. Perhaps it's less effective on certain motherboard or SID revisions? I've got a C64C with 8580 SIDs.

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Miami

I fixed it! I had ground and 5v swapped by mistake. I feel stupid.

In the end I went with a 4PDT switch that reroutes the data lines for both ports (1X/1Y/2X/2Y), and I connected the power and ground lines for all 4 potentiometers straight to port 1's pins on the underside of the motherboard. When the ports are switched on, my mouse works in port 2. I haven't tried using an external controller in port 1 yet.

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Sorry to bump an old post...

Is this the diagram in the OP's post?

Does anyone have a clear image of the diagram and a correct list of components (including values)?

Thank you

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Sea of Souls
akira^8GB wrote:

Well it's me again.
I am trying to get the parts and I am having problems sourcing electrolytic 4700pF capacitors. Can I use ceramic ones, the ones shaped as little discs? I read somewhere they might introduce noise to analog signals so they might not be the best thing to use...

I try not use ceramic within the audio signal on boards I sell, but if its an analog envelope or lfo, or decoupling then its fair game. The "noise" it introduces is actually quite trivial.
I would recommend film caps for smaller values.
https://www.taydaelectronics.com/4-7nf- … citor.html

Also note that 4700 pico = 4.7 nano = 0.0047 micro.

EDIT: nice, I thought the new post wa on page 1. tongue Nevermind me...

Last edited by Orgia Mode (Dec 8, 2019 8:28 pm)

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Sea of Souls
neonlike wrote:

Sorry to bump an old post...

Is this the diagram in the OP's post?

Does anyone have a clear image of the diagram and a correct list of components (including values)?

Thank you

Check page 2 of the thread. Several people made different visualization of the schematic.

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Thanks. I have read through but the values are not present and seem to conflict with what I can make out from the best version of this image I can find.

There’s one in google images but the values aren’t clear.

The maplin codes don’t exist anymore and they replied to me saying they no longer stock those parts.

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As far as I can see it's:

VR1, VR2 220K
VR3, VR4 (trimmers) 250K Sub-mini
R1, R2 ?K2
C1, C2 4700pF

What are R1 and R2?

and have I got the others correct? The image is tiny!

This is the clearest I can find:

diagram

Thanks

Last edited by neonlike (Dec 10, 2019 8:21 pm)

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Sea of Souls

R1 and R2 are 8k2.

Theres a tiny bit more info to pick thru here:
http://www.mssiah-forum.com/viewtopic.php?id=1935

http://www.mssiah-forum.com/viewtopic.php?pid=15146#p15146 wrote:

You have a certain lee-way with the values of the pots and caps. The important one to get right on is R1 and R2 (8k2). This affects the taper of the pots, and 8k2 is the ideal fit, regardless of what the other components are rated at.

The 100k pots are a little on the low side though. If you get some higher R ones that might be better (you may find that the trims' sweet spot is near the edge of the dial the way you have it now).

This was in response to someone asking if 2200pF caps were ok to use. The caps reduce jitter, but too high and you'll have delayed response of the knobs.

Last edited by Orgia Mode (Dec 10, 2019 8:35 pm)