RUN & WAIT ON All the Time ???

[Walt Perko]

Hi, 

What things would cause both the RUN and WAIT LEDs to be ON all the time on the Don Caprio mini-Front Panel?  

I've tried with different CPU boards and different RAM boards ... same results.  

https://www.youtube.com/watch?v=AZw6mR6sIBw

.

[Patrick Linstruth]

Would need to look at the schematic. It would tell you what could cause that.

It sounds like PRDY is low and RUN is high or the LEDs aren’t displaying correctly. Have you tried scoping out those signals on the MiniFP to verify the LEDs are displaying correctly?

What happens if you press RUN and then STOP?

Additional information might help. Working before and not working now? New board that has never worked before? CPU cards are known to be good? New backplane?

Sent from my iPhone

On Mar 20, 2026, at 4:56 PM, Walt Perko <r4r...@gmail.com> wrote:

Hi, 

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[Walt Perko]

Hi, 

I hate getting old ... I thought I scanned and checked my soldering the mini-Front Panel, but I guess I got distracted and forgot.  Now the computer is much closer to working.  

Currently, I can EXAMINE and EXAMINE NEXT though RAM, but I can only DEPOSIT into 0000 

https://www.youtube.com/watch?v=pSRwRR2j47s

This is all the doc's I have for the Don Caprio mini-Front Panel and I'm not sure which is exactly correct for the version board I have.  

.

[Walt Perko]

Hi, 

C3 is 0.001µF in the schematic ... C4 is 0.01µF in the schematic ... c8 is 0.1µF in the schematic.  

This BOM on the S100Computers website is wrong for C3 and C8 : https://www.s100computers.com/My%20System%20Pages/Mini%20FP%20Board/FP%20Parts%20List.pdf

After looking at the original BOM and high-resolution images of my other boards and the schematic, I've updated my BOM for the Don Caprio mini-Front Panel board, but I'm still not sure it's 100% correct.  

BTW, the BOM shows RR7 as 4.7KΩ Resistor Array, but I don't know how to identify RR7 on the schematic.  It looks like the schematic wants 47KΩ, but I think it was determined that it should be 4.7KΩ ... This needs to be verified by other working Don Caprio mini-Front Panel boards.  

.

[Patrick Linstruth]

RR7 is located on the bottom left of the schematic. It is 47K (47000).

To view this discussion visit https://groups.google.com/d/msgid/Altair-8800/c71c4d61-aaf7-4fef-ba58-5d18741abee1n%40googlegroups.com.
<Don Caprio mini-Front Panel UpDated.xlsx>

[Patrick Linstruth]

Is your Deposit Next switch working?

Examine 0000 and Deposit 05

Change your switches to Deposit Next 50

Examine 0000 again. Did 0000 change from 05 to 50? If not, Deposit Next isn’t depositing anything and your switch is broke, isn’t soldered, or the Deposit Next logic is broke.

On Mar 20, 2026, at 6:58 PM, Walt Perko <r4r...@gmail.com> wrote:

Hi, 

I hate getting old ... I thought I scanned and checked my soldering the mini-Front Panel, but I guess I got distracted and forgot.  Now the computer is much closer to working.  

Currently, I can EXAMINE and EXAMINE NEXT though RAM, but I can only DEPOSIT into 0000 

https://www.youtube.com/watch?v=pSRwRR2j47s

This is all the doc's I have for the Don Caprio mini-Front Panel and I'm not sure which is exactly correct for the version board I have.  

<mini-Front Panel Schematic.jpg>

.

On Friday, March 20, 2026 at 2:36:38 PM UTC-7 pat...@deltecent.com wrote:

Would need to look at the schematic. It would tell you what could cause that.

It sounds like PRDY is low and RUN is high or the LEDs aren’t displaying correctly. Have you tried scoping out those signals on the MiniFP to verify the LEDs are displaying correctly?

What happens if you press RUN and then STOP?

Additional information might help. Working before and not working now? New board that has never worked before? CPU cards are known to be good? New backplane?

Sent from my iPhone

On Mar 20, 2026, at 4:56 PM, Walt Perko <r4r...@gmail.com> wrote:

Hi, 

What things would cause both the RUN and WAIT LEDs to be ON all the time on the Don Caprio mini-Front Panel?  

I've tried with different CPU boards and different RAM boards ... same results.  

https://www.youtube.com/watch?v=AZw6mR6sIBw

.

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<Schematic IMSAI CPA 2014_Josh_wNotes.pdf><mini-Front Panel Schematic.jpg><FP Parts List.pdf><FPMini-Rev-E-Schematic.pdf>

[Walt Perko]

Hi, 

The schematic I have doesn't have the RRs:  

As far as I know, the schematic I have is supposed to be the newest version ... but that maybe incorrect.  

.

[Patrick Linstruth]

I think you should be using Caprio’s schematic, not Josh’s, unless you’re going to use the errata that was posted here earlier.

https://s100computers.com/My%20System%20Pages/Mini%20FP%20Board/FPMini-Rev-E-Schematic[1].pdf

It has what you’re looking for.

On Mar 26, 2026, at 8:49 PM, Walt Perko <r4r...@gmail.com> wrote:

Hi, 

The schematic I have doesn't have the RRs:  

To view this discussion visit https://groups.google.com/d/msgid/Altair-8800/35a94efd-6ba4-405b-a8be-05a1ca644ee4n%40googlegroups.com.
<Don Caprio Schematic U24.jpg>

[Walt Perko]

Hi, 

My understanding is that the schematic on S100Computers is Rev. C and the first board released was Rev. E with a different schematic that never got added to John's website.  

Now we're getting Rev F boards and the BOM is incorrect and there doesn't seem to be a Rev F schematic.  

From past discussions the Josh Bensadon schematic should be the most accurate, but I think that needs verification.  

.