Hardware Trouble Shooting...
I must preface this section by stating that I am not an Engineer or E-Tech. This info I am presenting is only my experience and is presented in a practical manner. It was gleaned by sweat and determination not intelligence so take it for what it is worth.
Horizon P-Gram cards
The Horizon P-Gram cards is a device that simply emulates a cartridge through the PEB. It's value lies in the fact that carts can be save, modified and used in place of the real cart. For example if you have a RAM Disk and want Extended Basic to look for the "LOAD" file on DSKA instead of DSK1 then you can make that happen. There are a lot of cart dumps available on WHT and other sites for use in these and other GRAM devices. It also can contain a real time clock which can be used for time/date stamping or anything else that needs a chronological record.
I have had two of these cross my bench recently, courtesy of Bill Gaskill, both with similar issues. Aside from the blown logic chip or two the sockets were causing frustratingly unpredictable behavior. Pulled them and replaced with quality dual wipe types and the cards are again solid. One thing to mention about both cards is that they are of very high quality. A good solid board with plated holes and a good, thick solder mask. Made it much easier to work on than some others.
/ START RANT /
I really don't know why the majority of the third party cards insisted on socketing every chip. It only creates another failure point in the circuit. Personally I agree with socketing drivers and transceivers or other IC's that are connected directly to the buss or the odd chip that is prone to failure or very expensive but the interior chips are fairly protected and socketing seems unneeded and prone to failure. That's just my two cents though.
/ END RANT /
I have had two of these cross my bench recently, courtesy of Bill Gaskill, both with similar issues. Aside from the blown logic chip or two the sockets were causing frustratingly unpredictable behavior. Pulled them and replaced with quality dual wipe types and the cards are again solid. One thing to mention about both cards is that they are of very high quality. A good solid board with plated holes and a good, thick solder mask. Made it much easier to work on than some others.
/ START RANT /
I really don't know why the majority of the third party cards insisted on socketing every chip. It only creates another failure point in the circuit. Personally I agree with socketing drivers and transceivers or other IC's that are connected directly to the buss or the odd chip that is prone to failure or very expensive but the interior chips are fairly protected and socketing seems unneeded and prone to failure. That's just my two cents though.
/ END RANT /
Horizon Ram Disks
The Horizon Ram Disk is an extremely useful piece of of hardware. It can also be a frustrating pain in the ass. The cards that only have one level of RAM chips are usually pretty solid. The stacked and/or modified ones can cause you fits. Following are my tips over where to start in trouble shooting these cards.
1) SOCKETS....... About 50 percent of the HRD cards I have seen suffer from shitty IC sockets. Apparently someone got a "good" deal deal on them back in the day. You can tell if your sockets are suspect by OHMing from pin to pin on the 12 SRAM IC positions on the card (U-3 through U-8 and U-12-U17 .) You should see full continuity between all SRAM IC's except for the *CE pin. If for example pin 12 of U-14 does not show a good connection to the corresponding pin on U-8 then Suspect the sockets. If you find bad sockets on the SRAM chips then also suspect every other socket on the card. It's a real PITA to cut them out and replace them with quality sockets but may be the only way to keep this problem from resurfacing. I find it a good policy to examine the sockets and if they are single wipe or show other issues then replace them no questions asked.
2) STACKED SRAM ICs...... Should be self explanatory as to what can go wrong here. Again OHMing between pins of the SRAMs May show a bad connection. OHMing between pins of the same SRAM may show a shorted connection. When checking use a light touch on your probes so as not to force a connection between pins. This problem will usually show up when using one of the HRD memory test programs as a consistently bad IC. You may or may not be able to isolate the pin(s) by watching the bit pattern on the test program but at least you will know what IC is showing the issue.
3) CONTROL WIRES.... By far the most frustrating problem I have run into. On stacked SRAM varieties the *CE pin is not soldered to the IC below but rather it is connected to the expansion jack. If there is a broken wire then it causes a condition known as a floating input. If you have a floating input it will NOT exhibit a consistent problem during any of the memory test programs. Since the chip is NOT being controlled by the card it may pollute the bus causing any variety of failures including the card not being seen by the configuration program. Again if you have a card that acts erratically, shows unbelievable failures of ICs during testing or shows a nonexistent amount of RAM then I would suspect that there is a control wire issue.
4) BATTERIES..... There is plenty of info available from WHT telling you the how's and what's of the battery configuration so I'll skip that but rather relay an issue I have seen. On large cards that have 2-3 layers of chips I have seen memory loss and subsequent problems cause by using a 3.6V lithium battery or 3-1.2V rechargables. This problem was solved by changing over to normal 1.5V alkalines (3 in series.) The 4.5V provided by the latter setup solved the problem. If you change from rechargeable cells to "dry cells" then you MUST change some other components. See the HRD 3000 construction manual on WHT for information.
1) SOCKETS....... About 50 percent of the HRD cards I have seen suffer from shitty IC sockets. Apparently someone got a "good" deal deal on them back in the day. You can tell if your sockets are suspect by OHMing from pin to pin on the 12 SRAM IC positions on the card (U-3 through U-8 and U-12-U17 .) You should see full continuity between all SRAM IC's except for the *CE pin. If for example pin 12 of U-14 does not show a good connection to the corresponding pin on U-8 then Suspect the sockets. If you find bad sockets on the SRAM chips then also suspect every other socket on the card. It's a real PITA to cut them out and replace them with quality sockets but may be the only way to keep this problem from resurfacing. I find it a good policy to examine the sockets and if they are single wipe or show other issues then replace them no questions asked.
2) STACKED SRAM ICs...... Should be self explanatory as to what can go wrong here. Again OHMing between pins of the SRAMs May show a bad connection. OHMing between pins of the same SRAM may show a shorted connection. When checking use a light touch on your probes so as not to force a connection between pins. This problem will usually show up when using one of the HRD memory test programs as a consistently bad IC. You may or may not be able to isolate the pin(s) by watching the bit pattern on the test program but at least you will know what IC is showing the issue.
3) CONTROL WIRES.... By far the most frustrating problem I have run into. On stacked SRAM varieties the *CE pin is not soldered to the IC below but rather it is connected to the expansion jack. If there is a broken wire then it causes a condition known as a floating input. If you have a floating input it will NOT exhibit a consistent problem during any of the memory test programs. Since the chip is NOT being controlled by the card it may pollute the bus causing any variety of failures including the card not being seen by the configuration program. Again if you have a card that acts erratically, shows unbelievable failures of ICs during testing or shows a nonexistent amount of RAM then I would suspect that there is a control wire issue.
4) BATTERIES..... There is plenty of info available from WHT telling you the how's and what's of the battery configuration so I'll skip that but rather relay an issue I have seen. On large cards that have 2-3 layers of chips I have seen memory loss and subsequent problems cause by using a 3.6V lithium battery or 3-1.2V rechargables. This problem was solved by changing over to normal 1.5V alkalines (3 in series.) The 4.5V provided by the latter setup solved the problem. If you change from rechargeable cells to "dry cells" then you MUST change some other components. See the HRD 3000 construction manual on WHT for information.
WHT SCSI Cards
The Scuzzy card from WHT is another neat device. Will give you more storage space than you could possible use. I have seen two issues with the card that can cause failures.
1) THE CARD IS NOT MODIFIED FOR USE.... The card out of the box WILL NOT work on a TI (at least both of mine didn't.) They must be modified by the addition of a daughter board created by Michael Becker and installed by Richard Bell. Richard can be found on one or both of the Yahoo list servers.
2) I HAVE BEEN USING MY CARD FOR A WHILE BUT IT JUST STOPPED WORKING... My cards both exhibit the same issue. They will work for about a year then die on power up one day refusing to work or locking up the system. The cure is always the same. Replace the 7805 regulator. Don't know why my cards eat them but they do. It's a simple fix.
1) THE CARD IS NOT MODIFIED FOR USE.... The card out of the box WILL NOT work on a TI (at least both of mine didn't.) They must be modified by the addition of a daughter board created by Michael Becker and installed by Richard Bell. Richard can be found on one or both of the Yahoo list servers.
2) I HAVE BEEN USING MY CARD FOR A WHILE BUT IT JUST STOPPED WORKING... My cards both exhibit the same issue. They will work for about a year then die on power up one day refusing to work or locking up the system. The cure is always the same. Replace the 7805 regulator. Don't know why my cards eat them but they do. It's a simple fix.
