Questions about my PiDP-8 Build
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Ken Hansen
Mar 23, 2024, 12:07:34 AMMar 23
to PiDP-8
Hello all,
A couple years ago I built a PiDP-11 and put the switches in upside-down... it wasn't pretty. Luckily a friend helped me remove the switches, clean up the PCB, and it now works fine. I explain this to explain my over-abundance of caution over the switches in my PiDp-8 kit (circa 2016).
The toggle switches *can't* be installed upside down, so I'm good there.
The momentary switches LOOK like I can't put them in upside-down, since they are center-off, momentary up AND down. Is that correct?
I've had very good luck with this build, and I don't want to make a mistake.
Also, I spent *way* too much time on the 'quick checks' because I didn't pick up on the "Check #3" lighting the LEDs at the VERY top row of the PCB, I was thinking the LEDs directly above the first 12 switches were supposed to light up.
Thanks,
Ken
A couple years ago I built a PiDP-11 and put the switches in upside-down... it wasn't pretty. Luckily a friend helped me remove the switches, clean up the PCB, and it now works fine. I explain this to explain my over-abundance of caution over the switches in my PiDp-8 kit (circa 2016).
The toggle switches *can't* be installed upside down, so I'm good there.
The momentary switches LOOK like I can't put them in upside-down, since they are center-off, momentary up AND down. Is that correct?
I've had very good luck with this build, and I don't want to make a mistake.
Also, I spent *way* too much time on the 'quick checks' because I didn't pick up on the "Check #3" lighting the LEDs at the VERY top row of the PCB, I was thinking the LEDs directly above the first 12 switches were supposed to light up.
Thanks,
Ken
Charles Ess
Mar 23, 2024, 2:30:53 AMMar 23
to PiDP-8
Hi Ken,
Taping sort-of works for the switches: but despite being very careful and everything looking as it should as I went along (I checked many, many times ...), I wasn't as satisfied with the outcome on my 8 as I had expected given the constant checks. Despite it all, an occasional switch is not sitting quite as perfectly flush on the board as I would like. It's certainly more than "good enough" - good enough that I don't feel compelled to go back and de/re-solder the minor offenders - but not quite as fully in line as I would like and think should be possible with still more care.
I'm ordering another when they're available - and hoping to try this approach to the switches instead.
Rather than placing all the switches in at once and then having a go at them as Oscar suggests (first just one pin at a time - excellent advice per se) - I'm wondering if it would work better to try, e.g., three of the far right and far left switches first. After making sure these are in good order, then work in in sets of 3-6 at a time. My thought is that the switches at both ends will provide something of a stabiliser when placing and soldering in the next set - and it will certainly be easier to make corrections along the way as needed rather than wait until the end, only to discover, as I did, that a few went slightly amiss.
I don't know if this sort of approach would work any better or appeal to you - but thought I'd suggest it. And maybe others have tried similar sorts of alternatives to good effect?
In any case - enjoy! Despite my perfectionist issues with an occasional switch - the overall results are more than satisfying aesthetically and certainly technically.
sounds like we've had similar experiences. I put the Pi header on the wrong side of the PiDP-11 board: desoldering that was a nightmare - but I eventually succeeded, in no small measure thanks to Oscar's encouragement and a good number of suggestions from others in the PiDP11 group.
I've also recently completed my PiDP-8 without any significant issues - the only real problem was that a small bit of solder from one point fell into one of the holes for the header. But especially with all the experience of desoldering from the 11, fixing that was easy-peasy.
I was also a bit uncertain about the LED patterns resulting from the self-test - but several folk here were helpful in calming my nerves and assuring me that what I was seeing was correct, even though it didn't fully line up with what I was expecting from the "column" / "row" numbers in the test.
But no, the momentary switches only toggle one direction: here's a reminder:
Momentary switches are all operated by temporarily depressing the lower part of the switch. So mount them such that you momentarily press on the bottom half of the switch to actuate a signal. People get this wrong regularly. The 6 momentary switches have their lower half sticking out to the front unless you depress them momentarily.
Taping sort-of works for the switches: but despite being very careful and everything looking as it should as I went along (I checked many, many times ...), I wasn't as satisfied with the outcome on my 8 as I had expected given the constant checks. Despite it all, an occasional switch is not sitting quite as perfectly flush on the board as I would like. It's certainly more than "good enough" - good enough that I don't feel compelled to go back and de/re-solder the minor offenders - but not quite as fully in line as I would like and think should be possible with still more care.
I'm ordering another when they're available - and hoping to try this approach to the switches instead.
Rather than placing all the switches in at once and then having a go at them as Oscar suggests (first just one pin at a time - excellent advice per se) - I'm wondering if it would work better to try, e.g., three of the far right and far left switches first. After making sure these are in good order, then work in in sets of 3-6 at a time. My thought is that the switches at both ends will provide something of a stabiliser when placing and soldering in the next set - and it will certainly be easier to make corrections along the way as needed rather than wait until the end, only to discover, as I did, that a few went slightly amiss.
I don't know if this sort of approach would work any better or appeal to you - but thought I'd suggest it. And maybe others have tried similar sorts of alternatives to good effect?
In any case - enjoy! Despite my perfectionist issues with an occasional switch - the overall results are more than satisfying aesthetically and certainly technically.
Steven Hirsch
Mar 23, 2024, 9:03:05 AMMar 23
to Charles Ess, PiDP-8
On Fri, 22 Mar 2024, Charles Ess wrote:
> I'm ordering another when they're available - and hoping to try this
> approach to the switches instead. Rather than placing all the switches
> in at once and then having a go at them as Oscar suggests (first just
> one pin at a time - excellent advice per se) - I'm wondering if it would
> work better to try, e.g., three of the far right and far left switches
> first. After making sure these are in good order, then work in in sets
> of 3-6 at a time. My thought is that the switches at both ends will
> provide something of a stabiliser when placing and soldering in the next
> set - and it will certainly be easier to make corrections along the way
> as needed rather than wait until the end, only to discover, as I did,
> that a few went slightly amiss. I don't know if this sort of approach
> would work any better or appeal to you - but thought I'd suggest it. And
> maybe others have tried similar sorts of alternatives to good effect?
That's precisely the way I approached my PiDP-8 build last week and it
> I'm ordering another when they're available - and hoping to try this
> approach to the switches instead. Rather than placing all the switches
> in at once and then having a go at them as Oscar suggests (first just
> one pin at a time - excellent advice per se) - I'm wondering if it would
> work better to try, e.g., three of the far right and far left switches
> first. After making sure these are in good order, then work in in sets
> of 3-6 at a time. My thought is that the switches at both ends will
> provide something of a stabiliser when placing and soldering in the next
> set - and it will certainly be easier to make corrections along the way
> as needed rather than wait until the end, only to discover, as I did,
> that a few went slightly amiss. I don't know if this sort of approach
> would work any better or appeal to you - but thought I'd suggest it. And
> maybe others have tried similar sorts of alternatives to good effect?
worked out well. For me, the trick was to push down lightly when soldering
a new switch. This ensures all switch rockers are seated flat against the
worktable. Easier to do than describe. As always, YMMV, but it resulted
in a good looking unit.
Charles Ess
Mar 23, 2024, 9:15:38 AMMar 23
to PiDP-8
Great - thanks for confirming that I wasn't heading down an unproductive / counterproductive trail, along with the additional good tip. All the more eager to try my hand at it when the next kits are available.
Ken Hansen
Mar 26, 2024, 9:41:48 AMMar 26
to PiDP-8
Charles,
Thanks for the quick reply - my PiDP-8 kit is the 2016 version, it shipped with a spacer board that yours apparently didn't (was it a first version kit?).
I decided that since these machines were hand built back in the day, 'small' imperfections can be explained as 'prototypical.' ;^)
My momentary switches are SPDT momentary on-off-momentary on, in other words, the switch rests in the center position and can be pushed in either direction. They are not like the toggle switches with two distinct settings, these 'rest' in between either of the two 'on' positions.
The switch on the left is a toggle switch with two positions, the switch on the right is my 'momentary' switch, which has three positions.
I don't think the momentary switches can go in wrong, but I'd like confirmation of that before I solder them (I'm 99.99% sure I'm right).
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Obsolescence
Mar 26, 2024, 10:34:32 AMMar 26
to PiDP-8
Ken,
On Tuesday, March 26, 2024 at 1:41:48 PM UTC n2...@w5fc.org wrote:
My momentary switches are SPDT momentary on-off-momentary on, in other words, the switch rests in the center position and can be pushed in either direction. They are not like the toggle switches with two distinct settings, these 'rest' in between either of the two 'on' positions.The switch on the left is a toggle switch with two positions, the switch on the right is my 'momentary' switch, which has three positions.I don't think the momentary switches can go in wrong, but I'd like confirmation of that before I solder them (I'm 99.99% sure I'm right).
You are correct - your PiDP-8 is of the 2nd generation, which had two-way momentary switches. There's no right or wrong way to solder them in.
In later kits, 3rd and 4th generation (gosh) the momentary switches are two-way, and those *do* have a right and wrong way to solder them in.
Other than the switches, and the positioning of the Raspberry Pi, there's no difference in the kit versions.
Kind regards,
Oscar.
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