Rombo Romboard reverse engineering troubleshooting help required

[The Equalizor]

Hi Bryce,


They're definitely connected, double checked on board I've got here, attached a close up of the caps on the board....


Regards

Rob

[Bryce]

I'm going to say this again : I'm not an electronics genius like you, I'm just a hobbyist with an interest in fixing stuff although I do appreciate your comments.

I'd give you a job. I've seen worse from people who get paid to do it!

Good to hear that the GND is connected. I was just suspicious because the trace from the VSS pin goes seperately through the ground plane.

Bryce.

[The Equalizor]

Yeah Altium does some stuff in strange ways. I use the Autorouter a lot and then correct the insanity that ensues  as much as I can.


I'll let you know when the blank boards turn up and I've built one and tested it. If they work correctly I'd actually like to donate one to you in recognition of the hard work you do on this board, I'd be very happy to do that.


Regards

Rob

[Bryce]

That's very kind of you.

Regarding the Altium strangeness (of which there's lots). As far as I can remember, you need to rename the NET between the capacitor and VSS to whatever the ground plane is called and it will integrate it into the plane automatically. (or I may be thinking of a completely different routing program )

Bryce.

[LambdaMikel]

Great job with the Romboard, I'd like to order one, too! 

[The Equalizor]

Mmmm PCB Goodness :-) just in from China!


I'll be building the test one tonight, I'll see how that goes and let you guys know.


Regards


Rob

[CPC_Fan]

That looks really good Rob.

[The Equalizor]

Well, as long as it works as good as it looks I'll be happy!
But thank you :-)


Rob

[Bryce]

Mmmm PCB Goodness :-) just in from China!


I'll be building the test one tonight, I'll see how that goes and let you guys know.


Regards


Rob

Some of the capacitor footprints look to be very small, what package size have you gone for?

Bryce.

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[The Equalizor]

0805 ceramic multilayer. I didn't get too excited about them as some romboards don't even have them, but I wanted *something* on there. The original Rombo had 10nf caps on 4 of the IC sockets


Regards

Rob

[The Equalizor]

And it was all going so well...


The new board [updated schematic attached] has a very odd issue. If I select Bank 1 [8-15] all ROM slots work great and can be switched on and off. If however I select Bank 0 [0-7] ROM slot 2 doesn't work, unless I turn on DIP switch 3 as well as 2.


The only thing I changed before generating the PCB was change around the Bank Selector pins as the way it was before pins 1 & 2 selected bank 1 and pins 2 & 3 selected bank 0.


Any ideas guys?


Rob

[IanS]

Maybe it needs more decoupling caps.

Are the power traces really as thin as they look on the picture earlier in the thread?. The rombo board may not have had many caps, but it had decent sized power rails.

[The Equalizor]

It did, but why would that only affect bank 0 and not bank 1. Also why would it work when DIP2&3 are both on in Bank 0 but not need DIP3 on when its set to Bank 1?


What do you think?


Also the schematic for the previous one before I swapped those bank pins around doesn't exhibit the same issue...


Weird huh


Rob

[IanS]

Ooops, did I forget the sarcasm tag?

I think it's a miracle the board works at all. Can you get your PCB package to highlight the VCC (+5) power rail, and post a picture of the board. Can you measure the vlotage on the ROM furthest from the connector with the board fully populated.

Do you have any test equipment, probably need a scope, to see how dirty all the power rails and signals are with it fully populated with ROMS.

If you shuffle roms around or only fit one at a time, does the fault change?

[The Equalizor]

Im pretty sure its not a power thing - it does it with only 1 rom in the ROMboard in slot 2, and only does it when in the bank 0 position. Thats what I mean when I say it doesn't make sense.


Maybe I'm wasting my time and should hand it over to someone with more knowledge than me.


regards


Rob

[IanS]

Have you done a thorough visual inspection of the soldering around the dil switch and the link, the relevant traces do go very close to each other around there.

[The Equalizor]

Had a look under the Amscope and it looks okay to me.


Thank you for the suggestions though.


Rob

[The Equalizor]

Thats weird. I works great on a  standard CPC6128, All slot, both banks. I'm gonna etst it on another plus in case my "modified" one isn't happy for some reason.


Regards


Rob

[The Equalizor]

I think I'm going to take Ian's advice and shore up the power traces s between the components and see if that helps it behave a little better. No point in having an unreliable ROM board...


Rob

[Bryce]

0805 ceramic multilayer. I didn't get too excited about them as some romboards don't even have them, but I wanted *something* on there. The original Rombo had 10nf caps on 4 of the IC sockets


Regards

Rob

I meant the electrolytic capacitors. They seem to have 0805 footprints too?? What are you using there?

Bryce.

Gesendet von meinem Motorola DynaTAC 8000x mit Tapatalk

[The Equalizor]

There is only one electrolytic cap on the Rombo and my one came off years ago and worked fine without it but for the new board I'll be adding one in.However IanS's expert advice was pretty much correct here. After shoring up the traces between thr 8 rom sockets, the 5 logic ICs and the 4 decoupling caps its working great. Also once again, Altium has screwed me by not connecting the 2 VCC nets together on the ICs with hidden nets. Connecting all those up has fixed the issue completely.


Just gotta work out now how to tell Altium to do thicker traces for VCC in the PCB layout.


Cheers all for your help, especially IanS and you Bryce,

PS Excuse the um inventive bank select jumper....
Rob

[IanS]

After shoring up the traces between thr 8 rom sockets, the 5 logic ICs and the 4 decoupling caps its working great.

Good to see it's now working, thanks for the update.

[Johnny Olsen]

It was possible to connect two original Rombo ROMboard's, one over the other, so that you had 16 rom's in one box,
but if you did, it was impossible to operate the bottom rom switch, so I had to move the switche's to the lid.
It would have been nice if it had been easy to move them.

It was also possible to connect a RAM-ROM, useful if you were to develop a rom without having to burn one each time
you wanted to test it, but not very usefull today.

Equalizor please keep that in mind while developing your romboard.

[The Equalizor]

Okay guys, they're finished, pics attached. Can anyone who's interested in one please PM me again.

Edit : I should point out that the ROMs aren't included and that the cost will be £40.00UKP including shipping to the EU and £45.00 UKP for areas outside.

If anyone also wants ROMs supplied with it, I can do that too. I would charge £3.00 per ROM and that is obviously  for supplying the ROM and programming the Image.

Cheers

Rob

[Chinnery]

Slightly off topic, but which Rom is it that gives the |help extension? I've just built a version of bryce"s megaflash and would like to get the most of it with my 464 with 664 firmware/basic.