| Electronics > Repair |
| ADVANTEST R9211B |
| << < (32/39) > >> |
| stfjohn:
Sorry, but I'm out of town for work: as soon as I get back I'll let you know. Thanks. |
| stfjohn:
I disassembled the main board again. Connections checked: 9914 GPIB oin 9 connected HC148 pin 2 71054 U52 pin 19 connected HC 148 pin 16 71054 U86 pin 19 connected HC 148 pin 16 71054 U67 pin 25 connected HC 148 pin 16 No connections LS164 pins 1 , 2 , 8 , 9 LS07 pin 7 connected HC148 pin 10 LS07 pin 10 connected HC148 pin 11 LS07 pin 14 connected HC148 pin 16 |
| m k:
Since it's now available take couple new pictures for unknown chips. Low left corner area and area right from add-on connectors between power connector and GPIB controller. If you like take few pictures from the under side also. Any of your added connectors blocking something is not a problem. These pictures are not for any exact connection stuff, just something that can possibly reveal some designer's thoughts. Areas of interest are HC138 chips between CPU and DMAC, crystal surroundings and logic section of left side. Then recheck. HC148 is 16 pin chip and LS07 has 14 pins. Is HC148 pin 10, one pin away from corner, connected to LS07 corner pin, end of left side of its top side? Are previous timer chips pins 19 and 25 connected also to LS07 top right corner pin of its top side? |
| stfjohn:
Pin 10 HC148 connected to pin 7 LS07 and pin 7 LS164. Pin 19 U52, pin 19 U86 , pin 25 U67 connected to pin 14 LS07. |
| m k:
For sanity check test how other HC148 pins are connected to ground, to pin 7 of LS07 and pin 8 of HC148. HC148 pin 11 function means that pin 9 goes low when pin 11 goes low, but pin 10 operates differently. Means that pins 9 and 10 shorted to ground by the same situation is not very high. So it has been visible since reply #47. Then reply #146 connects it and now this last stint verifies the cause. CPU pin 24 or its signal source seems to be shorted to ground. Means that interrupt is always on, it shouldn't be, HC148 pin 11 going low is never going forward. Next you must find the source of that short. Easy start is to pull PAL chips out, start from left of CPU. Then when chip is off measure CPU pin 24 to ground. If ground connection disappears you've found the cause. If PAL chips are not the cause remove HC148. If short is still there you can try desoldering CPU pins 24 and 25. When pin holes are empty you should be able to position pins so that they are floating. If you succeed you can test floating pins to ground, if connection is still there CPU is the cause. E, you can also cut the CPU leg just above the PCB and bend it up a bit. If it wasn't the cause you just add a stump of wire and connect the leg back. |
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