Main > Monitor/Video Forum

nt-2701 vs nt-2701n

Pages: (1/1)

merkin:

Does anyone know the difference between neo-tec's nt-2701 and nt-2701n?
The service manual for the nt-270x family does not mention anything..

Am I correct in assuming the nt-2701 is positive sync and nt-2701n is negative sync?

Long story short I have an nt-2701 but having a sync issue with gt4 complete.


If I am reading the schematic in the service manual correctly, it appears the nt-2701 is configured for positive sync, but can easily be converted to negative sync by swapping a couple discrete components. 

I know I could just test it by swapping the parts, but I would also like my suspicions to be confirmed by someone more experienced.

grantspain:

i have only worked on a few 2701 and none have been + sync, + sync was pretty much only used on very early game boards from 70's to early 80's
is the golden tee fore io board set to 25khz or 15khz?

merkin:

@grantspain
The dip switch is set for 25khz.

So here is my confusion..
LA7851 application circuit from Sanyo:


Neotec NT-2701 schematic:


It seems that according to Sanyo in order for the Neotec to be in negative sync, R401 & R402 should be flopped and C403 needs to be swapped out with a 470p cap.

Again Neotec maybe could have designed other parts of the circuit to handle the pulse differently, but I can't read schematics that well enough to confirm.

grantspain:

i would find it hard to believe that neotec ran a production line of positive sync chassis after 1981
the horizontal hold pot gives you no difference? R414

Pages: (1/1)

Go to full version