On 02/20/2016 11:31 AM, John Robertson wrote:
This is now working!
I have a couple of Gottlieb sound boards with two 6502s on each that are soldered to the PCB. The only 'easy' way to do tests is to socket the 6502s, isn't it? The 6502 does not support floating the Data/Address bus (except for the 6512), does it?
Well, no, there is an easier way - it seems you can float the 6502 Address and Data lines using the following technique:
1) Clip off (leave a bit remaining) of the Vcc pin 8.
2) Find a 40 pin glomper clip and ribbon wire to a 40 pin header.
3) solder 2 40 pin IC sockets back to back after first removing pin 32 from the inner socket (this will contact the cut off pin 8 via the glomper otherwise and power the 6502 CPU) and bend out pin 8 of the other (outer) socket.
4) solder a short jumper wire on the bent out pin and connect it to a jumper that you will hook to Vcc.
5) plug the double 40 pin socket on your 40 pin header and move the connectors on the glomper so pin 1 & 40 move to the correct pins on the outer 40 pin socket.
6) Hook glomper on 6502, connect jumper to Vcc
7) run your 9010 tests! OK, it isn't perfect...need to work on the loading because if I get inconsistent reads from the Eproms on a known-to-be-good board. And the RAM test craps out if the Eproms are installed - sometimes. Need to play with some pullup resistors next...but the RAM short and long tests pass on 6116s.
John :-#)# Ah, all I needed was a 2K2 pullup resistor bank on the Data pins. Now I get clean ROM and RAM tests.
I've included photos of the setup for those who are interested... John :-#)# -- How to subscribe or unsubscribe from TTL http://seven.pairlist.net/mailman/listinfo/techtoolslist _______________________________________________ Techtoolslist mailing list Techtoolslist@flippers.com https://pairlist7.pair.net/mailman/listinfo/techtoolslist FTP site is: ftp://ttl.arcadetech.org/TTL/Test_Equipment Archive site: http://seven.pairlist.net/pipermail/techtoolslist/
