Checking 15V to RL11
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by Bill Degnan - 12/24/2016 09:37 |
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Checked the inbound 15V for the DD11-C. I have the distribution panel connector for PDP 11/40's with serial numbers 6000 and higher. The 15V line is a grey wire in hole 2 of the 15-pin (larger) connector on the panel. The exact reading is 15.5, which is within the range the manual requires.
So...is 15V getting to the controller through the backplane wirewrap, or was this wire removed or altered? Where is this measured? Checking manuals to locate the correct pin, so far not found. FROM THE END OF THE RL02 MANUAL: The early SPCs did not utilize Direct Memory Access (DMA) data transfers to/from memory and therefore those signals were not part of the original SPC pin assignments. Some of the newer options, such as the RLII, do utilize DMA transfers. There is a new pin assignment called SPC PRIME that includes these signals. If the RLII is to be used in an older (non SPC-PRIME) slot, then it is necessary to ensure that the following signals are wired on the backplane. • Pin CAl - NPG In • Pin CBI - NPG Out • Pin FJI - NPR • Pin CVI - AC LO • Pin CUI - +15v If the slot has SPC PRIME pinning, then another precaution must be taken. NPG continuity is maintained across an empty SPC PRIME slot by a backplane jumper from pin CAI to pin CB1. This jumper must be removed whenever a DMA-type option is installed, such as an RLll, and the jumper must be added if the module is removed. This consideration is in addition to the normal Bus Grant Continuity card used in row D of all empty SPC slots I put in a riser card and installed a NPGrant card. I measured for 15V and found the pin where 15V was being fed into the controller. I installed the M7762 on a riser card and located the spot where the 15V feeds the first resistor/regulator on the board. Dead. Nothing coming in. Removed the card. Still dead. Somehow this shorted out the h745 killing both 15v and -15V. Now to find a fuse... Bill Reply |
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