PDP-11/34a hung bus problem.

Hi. After being sitting dormant for 5 years in pieces, it was time to reassemble my 11/34, but hit a problem (hung bus). What has been done so far : - removed all the cards from the backplane. - vacuum the backplane. - power up the BA11 and check the voltages. -> LTC is ok. -> ACLO & DCLO were 0V, replaced board in switch unit, ACLO & DCLO now ok. - measure voltage at back-plane with no cards, voltage reads 5.35 Volt, trimmed them down to 5.15 Volt (no load). - insert both CPU cards, KY11-LB card & bootstrap card, 5 full grant cards, DL11-W and bus terminator card. - power up the machine, voltages are 5.10 Volt, measured at the backplane. - run light is off - cntrl + boot shows register dump at printer. - sending a character to the console via 777566 does print it. All looks ok. - power down machine, add memory (M7981, 128KW) in slot 4, replacing a full grant card. - power up machine -> run light is on, does not get cleared by cntrl + halt. - power down & replace memory with grand card -> run light is off. - moving the memory card to slot 5 , 6, or 7 and fill the other slots with full grant cards, -> run light does stay on. - tried the same without the bus end termination card (as is suggested in the processor manual), no effect :( - tried a 2nd memory card (M8722, 128KW) in slot 4, 5, 6 or 7, no change. - visual checking the backplane wiring did not reveal any oddity. So what could be the problem here? The bus works without the memory, but with it, it gets a hung bus, arghhh... Any suggestion is welcome! Ed -- Ik email, dus ik besta. BTC : 1J5fajt8ptyZ2V1YURj3YJZhe5j3fJVSHN LTC : LP2WuEmYPbpWUBqMFGJfdm7pdHEW7fKvDz