Rombo Romboard reverse engineering troubleshooting help required

Started by The Equalizor, 02:02, 03 March 18

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Audronic

Procrastinators Unite,
If it Ain't Broke PLEASE Don't Fix it.
I keep telling you I am Not Pedantic.
As I Live " Down Under " I Take my Gravity Tablets and Wear my Magnetic Boots to Keep me from Falling off.

IanS

Quote from: Bryce on 20:49, 08 March 18
Ok, tell me which device to produce (with modifications if required) and I'll have some PCBs made up. If required I can make up kits with the parts too.

Bryce.
I think the Rombo design is pretty good. Which is where the thread started. As far as I know the circuit in the first post is good.

Bryce

Ok, as soon as the @The Equalizor has confirmed the design I'll make up a layout.

Bryce.

The Equalizor

I'm actually having some PCBs made, should be here in a  week or so. There will be spares if anyone wants to buy one and kits/built available too if that sparks anyone's interest.Obviously I need to make sure it works.


Rob

Bryce


The Equalizor

Although lets be honest, you're a freakin' CPC genius so your take on it would probably be 100 times better than mine. Do you use Altium?


Rob

Bryce

I've used Altium in the past at work, but my main experience is with OrCAD and some (hobby) Eagle.
My take on it probably wouldn't be much different to yours. I like to get the PCB size down to an absolute minimum, so that might be different, and if I was building them myself I'd probably use SMD for the logic and passives and put them underneath, but as it's for kit purposes, I'd stick with all thru-hole this time.
The problem with classic ROMBoards (as you've most likely just found out) is that there's an aweful lot of soldering to be done! :D

Is yours done to be "M4 friendly" ? That's something I would also have done.

Bryce.

||C|-|E||

I strongly support the whole "through hole" notion  :) I much prefer to solder these than the SMD  :D

CPC_Fan

I would definitely be interested in a fully assembled classic ROM board or Rombo Rombox clone if someone was going to make one.

tjohnson

I would be interested in a board and happy for just the raw board which is the difficult bit for me and to buy the components solder myself but not smd!  If you were able to include an idc connector header and make ribbon cables available like talrek does with the mf2 clone that would be welcomed.

Sent from my E5823 using Tapatalk


The Equalizor

Ah now you see I'm the opposite. I hate thru-hole and much prefer to work on SMD. PCBway has a limit on "cheap" PCBs of 100mmx100mm so I'm trying to keep the board size down and SMD also helps with this. They haven't turned up yet, but they're on their way. I'm also working on 2 other projects at the moment, a rework of a 4164 DRAM chip tester that gives a simple go/no-go  and a reverse engineer of the Amstrad 464 Diagnostic board with maybe a rewrite of the ROM to test the extra 64k on a  plus....


Anyone interested in any of that?


Rob

robcfg

The diagnostics board would be nice.


I have the diagnostics board Habi made for the PCW, I have used it several times now and I discovered my main PCW has a faulty ram chip.


So it may save time when diagnosing a CPC.

arnoldemu

Is there a dump of the rom from the diagnostics board?
My games. My Games
My website with coding examples: Unofficial Amstrad WWW Resource

robcfg

You mean the rom of the diagnostics 'cartridge' for the PCW?


Here is the original 9512 test cartridge rom: http://habisoft.com/pcwwiki/doku.php?id=en:hardware:perifericos:pcw_9512_test_pcb
Here is Habi's combined test cartridge for PCW: http://habisoft.com/pcwwiki/doku.php?id=en:hardware:perifericos:pcw_universal_test_pcb


I don't know whether there's a dump of the 8000 series test pcb roms, but I'll take a look around.


The Equalizor

I haven't dumped the ROM ..Yet. But I will do.

Regards

Rob

The Equalizor


robcfg

Coooool!


I cannot read the eprom text. It would be nice if you can take some high res pictures/scans of both sides for the wiki.


My bet is that it's a standard 27xxx eprom, but better safe than sorry before dumping it.

The Equalizor


The Equalizor

Okay guys, initial tests look excellent, the banks are working (0-7 and 8-15) the ROMs can be seen and they disable okay.

I have a couple of fixes to do to the boards that I've done a manual fixup on (nothing to do with the schematic per se, just my lack of understanding of Altium's Bus naming conventions) and then I'm going to get them redone now I know they work.

I have updated the schematic and will repost the new one once I have the final boards in a week.

I reckon if I'm going to sell them it will be as fully assembled units as people don't like soldering SMD as much as me, and they'll sell for about 35/40UKP.

If anyone is interested in that please PM me.

Once its built I'll put a video up on my YouTube channel : https://www.youtube.com/channel/UC0vHFBNVST8_xzUoRqIbz6Q

Rob

CPC_Fan


The Equalizor

Boards now ordered, should be here mid next week.


Rob

Bryce

Layout pictures? How small have you got the board down to?

Bryce.

The Equalizor

Pic attached. Board size is  96.78mm x90.17mm


Regards


Rob

Bryce

Top marks. Really nicely done.

Put me down for a blank PCB if you are selling them like that.

Bryce.

Edit: Just noticed a minor mistake. C30 and C138 should have been physically on opposite sides of the PCB, but I doubt it matters. I'd leave one off completely and use a single 47µf capacitor instead.

Edit 2: Just noticed a bigger mistake. The EPROMs with the capacitors across VCC/VSS don't seem to be connected to the ground plane??

The Equalizor

Thank you for your kind words!


I've actually seen ROMboards that dont use any capacitors at all on them! In fact during testing I didn't even bother soldering any of the caps on and I never once got it to crash. They're really there for just belt and braces.


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.


If I sell the 10 I've ordered then I'll order some new boards and make that change :-)


Regards

Rob

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