Pin 1 on the Pi (3.3 volts) is not used on the PCB, other than going to a pad that can be used for user modifications/additions.
Pins 2 & 4 are used on the PCB and should have 5 volts to ground (which is available on pin 6) - that is what is being fed to the IC. So measure from pin 4 to pin 6 and you should have 5 volts.
There is a diode in the path to the IC to drop the voltage slightly. It would be good to check to make sure the diode isn't installed backwards. Also, if you check the voltage on both sides of the diode (relative to ground on pin 6), you should see roughly 5 volts. The side of the diode with the black stripe will have slightly lower voltage than the other side of the diode.
Steve
On 2/15/25 01:47 PM, Flavio Villanustre wrote:
> Yes, it could be the setup of the pi. Did you make sure that the pidp process is running? When you login to the pi over ssh, do you see it? "Ps -ax" will tell you if it runs. You can try to run it again, just in case.
>
> On Sat, Feb 15, 2025, 13:42 John Durgan <
durgan...@gmail.com <mailto:
durgan...@gmail.com>> wrote:
>
> I checked the IC for folded pins, no problem there. I can't see why there is no power getting to the PCB. Pin one on the pi has voltage. I am not sure how to check the voltage on the PCB. Could there be something wrong with the setup on the PI itself. It seems to be working fine.
>
> John
>
> On Saturday, February 15, 2025 at 12:35:38 PM UTC-6
fvilla...@gmail.com <mailto:
fvilla...@gmail.com> wrote:
>
> Check the circuit schematic that I included with my first response to you. Also check that the IC legs are not folded (sometimes it happens when you are pushing it in if not extremely careful).
>
> Best,
>
> Flavio
>
> On Sat, Feb 15, 2025, 12:04 John Durgan <
durgan...@gmail.com> wrote:
>
> I have checked the 3.3vdc output of pin one on the pi. It is reading 3.28vdc. How is the best way to check if the PCB is getting that power? On the PCB if I want to check voltage coming into the PCB where can I touch the ground probe of my meter?
>
> On Saturday, February 15, 2025 at 10:23:33 AM UTC-6
fvilla...@gmail.com wrote:
>
> Not that I remember. But all the lights should come up once the pi boots because switches are not there yet. Test #1 in the build instructions is quite clear.
>
> It seems to me that there is no power to the main board, so something wrong with the connection of Pin 1 in the GPIO would be my first guess.
>
> Best,
>
> Flavio
>
>
> On Sat, Feb 15, 2025 at 11:12 AM
timr...@gmail.com <
timr...@gmail.com> wrote:
>
> I built my pidp-11 long ago so don't remember all about it. Is there a "lights test" script like there is with other kits? Have you tried to boot one of the provided OS's?
> What have you done since power on? I have no spare Pi right now to try my pidp-11. One is on order. I stole the one I had in the 11 for my 8. :)
>
> On Saturday, February 15, 2025 at 10:01:39 AM UTC-6
fvilla...@gmail.com wrote:
>
> John,
>
> This is where the fun begins! There could be a million reasons for the LEDs to not come up (well, maybe not a million, but at least a dozen :) ). First of all, do you have a multimeter? If no LED comes up at all, check the traces that provide Vcc and ground (3v3 should be on pin 1 of the raspberry pi connector). Secondly, there is a wonderful schematic at:
https://obsolescence.wixsite.com/obsolescence/pidp-11-technical-details <
https://obsolescence.wixsite.com/obsolescence/pidp-11-technical-details>. Using that one, you can see where things are connected (if you need help interpreting it, just ping me). Third, make sure that the raspberry pi is plugged correctly on the GPIO connector and not shifted up, down or to a side. Fourth, double check that the insulation that you put on between the metal on the raspberry pi connectors and your board is properly placed and the pi is not creating a short circuit.
>
> And, I think I ran out of ideas. If you need help, just ping me and we can run a live video session to see where you are at and give you some ideas.
>
> Best,
>
> Flavio
>
>
> On Sat, Feb 15, 2025 at 10:50 AM John Durgan <
durgan...@gmail.com> wrote:
>
> I just finished the initial soldering of part and did the initial test. The pi Powered up with no problem, and I got a prompt on my monitor. I was very meticulous about the polarity of the both the diodes and the leds. This is my fourth kit, so I know the solder is good. I have gone over all the solder joints a second time just to be sure. I re seated the IC, and am quite sure about its orientation. Any Suggestions. It doesn't seem like the PCB is getting any power.
>
> I will be very grateful for any help on this.
>
> p.s. This is my second PDP-11. The first one works perfectly.
>
> John Durgan
>
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