Yesterday we continued debugging the RK8F data-break problem revealed when running MAINDEC-08-DHRKA-B RK8E Diskless Control Test. We ran the "B" revision of this diag because it was the newest version that we had both a BIN image and a PDF file. We found "C" and "D" versions of the BIN file but no PDF, and an "E" version of the PDF but no BIN.
Last week's failure showed that we could data-break successfully to address 0000 but not to 7777. We suspected a problem in the 74161 or 8881 chips that make up the CA register and Omnibus drivers. From the prints we found that the IOT decoding is done on the M7104 board and the CA is on the M7105. We pulled the M7106 so we could get to the ICs on the M7105. It would have been easier to put the M7105 on an extender, but we don't have extender cables for the over-the-top connectors. We could see the data on the input pins of the 74161 chips, but no output. The LD signal that comes from the 6RK4 signal (IOT 6744) was active but the CLK signal was always high. The IOT 6744 is ANDed with the IDLE signal and TP3. The IDLE signal was at 2V, so probably a bad 7474 flip-flop. Ah, the IDLE signal comes from the M7106 that we removed. We grounded the signal and could see the Omnibus MA signals go active. Unfortunately the upper four bits of the CA also come from the M7106 that we removed. We put the M7106 back in, put the diag in a scope loop, and looked at the Omnibus on the bottom of the wire-wrap backplane in the DW8E. All 12 bits of the CA were active, so the RK8F is probably OK.
One thing that we noticed on the RK8F is that the MA signals on the 8881 chips are not gated like they are on an RK8E. Since there is on processor in the Omnibus in the DW8E this works OK.
We looked at the MA signals on the Posibus and found that one was inactive. The M7102 boards that drive the Omnibus MA signals onto the Posibus cables were previously tested in Warren's flip-chip tester, and one was repaired. We put the M7102 in slot AB20 on an extender and then all of the MA signals went active. The DHRKA diag also passed, so everything in the RK8F and DW8E is now working. We cleaned the gold contacts on all of the DW8E boards with a white eraser and 91% alcohol, and the DHRKA diag still worked OK.
We bought a new NiCd battery pack and weather strip for the RK05, so that will be next week's project. There seems to be a power supply problem in the RK05 because the relay K2 that activates the blower and voice coil in the RK05 drive chatters after the drive is powered on for about 10 minutes.