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464 Resurrection - with only mainboard!

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WacKEDmaN:
so ive got the original 464 board completely populated now...
i only have the board.. no monitor, no keyboard, no tapedeck.. im gonna add my own digital versions with overpowered arduino and/or esp32
i will use this thread to document my progress and ask a few questions (so i dont blow it up!)


i need some clarification on the power jack... i cant find the correct information, is it "centre negative" or "centre positive"...
ive done a continuity test...between the side pin of the barrel jack socket (onboard)... and both the AY-3 (pin 3) and Z80As (pin 11) 5v pins... and they seem connected...
but everything ive read is saying the 5v jack is centre positive.. even tho im seeing different on the board...
can anyone clarify it for me please?... (or should i just give up now! LOL)


next no so much a question but my next steps...... i have a SCART to RF modulator.. with female scart in...
i found this... http://www.cpcwiki.eu/imgs/c/c1/Cpc_to_scart.png
i will be wiring the 464 board directly to the scart pins on the RF board (in reverse! female din to female scart)...

heres the current look....


TotO:

Center is positive for 5V and GND is outside... Just check the ground continuity with other connectors.
You can test the 74LSxx IC where the bottom left pin = GND and the top right pin = VCC. (not the RAM)

WacKEDmaN:
thanks ToTO, ill wire up the scart and kick it in the guts...
hopefully theres not other issues on the board...i hope i dont have to break out the sillyscope!


it does seem a bit strange the side pin on the barrel jack socket is connected to 5v positive on the main chips.. and the one coming from the centre is neg... yet it seems swapped from the actual 5v plug... all the other barrel jack sockets ive played with are outside to side pin, and then centre to centre... this seems swapped :/
i guess theres some inverse logic going on here...

tested side pin on the barrel jack socket to bottom RIGHT pin of the 74LS132p and they are indeed ground... (i looked up the datasheet!)



im confuse! ..but ill work it out! (ahh im workin from the top of the board!.. flip it..and yes bottom left is gnd ..top right is pos!)

gerald:

--- Quote from: WacKEDmaN on 19:54, 09 December 20 ---thanks ToTO, ill wire up the scart and kick it in the guts...
hopefully theres not other issues on the board...i hope i dont have to break out the sillyscope!


it does seem a bit strange the side pin on the barrel jack socket is connected to 5v positive on the main chips.. and the one coming from the centre is neg... yet it seems swapped from the actual 5v plug... all the other barrel jack sockets ive played with are outside to side pin, and then centre to centre... this seems swapped :/
i guess theres some inverse logic going on here...

tested side pin on the barrel jack socket to bottom RIGHT pin of the 74LS132p and they are indeed ground... (i looked up the datasheet!)



im confuse! ..but ill work it out! (ahh im workin from the top of the board!.. flip it..and yes bottom left is gnd ..top right is pos!)

--- End quote ---
As far as I know, the plug is positive on centre pole unless you have a very rare version of a 464. :D
How do you check continuity from jack center to the IC pins ?
5V should no go straight from the plug to the ICs. You have to do a short on the tape connector, where the power switch is connected.

WacKEDmaN:
oh yeah! that probably explains why im having issues!... ive got the board sitting on the bloody silver side of the cardboard shield!


now im not getting continuity on the centre to the 5v in on the 74LS chips even with the switch connector bridged :/
(i was forgetting the switch! thanks for the heads up Gerald!)


...it looks like i know enough...just to be dangerous! LOL

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