What do these go with?

[Foster]

I would suggest
Net+VDC to +VB
NetGND to Ground
Those other 3 are inputs at least on the Spectrum. for some reason the machine does not care if spectrum or spectrum II goes out as long as the netplex bus is not brought down with it.
I would try Net TxD to DD0 and Mreset to STB2 or Net RxD to DD0 and MReset to STB2.
I am not sure the S+/S2000 Soectrum can Send info to the S2000 like the Spectrum II can.
That maybe why the machine is not picky about it being there or not. I can play my S2000 without the Spectrum II plugged in with no problem.

[stayouttadabunker]

Nothing would go into the 6th pin "Strobe 3" on the Spectrum?

[Foster]

Takes Apart S2000 and S+ to test spectrum in a S2000

 I have tested and tested every wire combination that was safe to try.
No luck

Then I looked at the PSR for Game 363 neither one of my Spectrums are listed as usable with it
I do not know if one of my older game chips would allow it to work with the 75512000  SD0091 Spectrum or not.
I have like SG 48, SG 85, and 312l, and 362.

[stayouttadabunker]

Tried the first combo with 5 wires...no go.
I'm doubting that this particular Spectrum will communicate with the S2000.
By the way, my Spectrum board version number is: 7550720
The eprom chip occupying socket U35 is: SD0094 (1998)

Powerstroke says his works in his S2000 and it looks like Idesign's first photos.

In Railroads photo, I would love to see exactly which green wires he has going into that plug
but his photo is too grainy when blown up.
Too much green and not enough stripe colors to make out what is what.
It's hard to tell from Railroad's picture even if it's a 5 or 6-pin molex plugged in there.
I'd have to say his molex is a 5-pin from his photo though - not a 6-pin like mine.

Notice, my Spectrum has the LED brightness potentiometer black knob nearby.
I'm suspecting that there may have been various board versions before they went with the SpectrumII.
Railroad's is on top picture, mine on the bottom picture.>>>

[Foster]

Railroads is 5  pin for sure.

what board do you have?
Also unless the spectrum that railroad has is wired backwards the colors match the netplex on the door for the VFD.

SG 363 PSR
Spectrum Display:
SDF100 is required for controller boards with part number 75512602.  
SD0111 or SD0112 is required for controller boards with part number 75512600.
SD0092 is required for controller boards with part number 75508400.

[stayouttadabunker]

Thanks for all your help Foster!
I think after all this, I am in agreement with you that it's pretty much certain
that the plain jane Spectrum I have is really only made for the S+.
The SpectrumII or Spectrum2 is definitely for the S2000.
backwards compatible with an S+?  I don't know...I don't care...lol
It was certainly fun to try but there was no way I could
get the plain Spectrum board to communicate with an S2000.

Let me correct myself...
It may be still possible to get other non-Netplex progressive systems to work with the S2000
and to increment credits on the odometer display.
How? Hook two wires from the Spectrum into the "Bet one Credit", the "Max Bet" buttons,
the handle switch button and also using plain magnetic door sensors along the coin path coming down from the slot.
These are all "normally open" circuits and each will trigger to "close" the circuit to 2 specific pins
that enable the odometer to increment.
This way of course will need a lot more wiring than any joe can handle but I'm sure will work.
To trigger the Jackpot - would have to be a relay morphed with the bell signal for a "Hand-Pay" mode.

And finally, the reset key can also be spliced/leeched upon to send the reset "closed" signal to the Spectrum.
However, that reset may not work if the signal needed is a lowered or raised voltage
signal rather than an "Normally Open" or "Normally Closed" signal.

These ideas may only work with other progressive systems such as regular Chams
along with a simple CON1 or CON2,  using the normally open/closed pins and can be easily programmed with the PSP program.
Using the plain Spectrum or Mini-photon would be a lot more difficult because you wouldn't
be able to set them up as these progressive systems are non-Netplexed.