I'm attempting to restore an Imsai front panel (FP)
handed down to me by my Father. I've used the chassis back in
the day with a reset switch wired to a proto board with mostly
CompuPro hardware. I believe Dad had the FP working with a
Tarbell controller. Now I've dug out the front panel and would
like to restore it and the entire Imsai 8080 to functionality. I
believe I have the original Imsai boards. I've already
rebuilt
the power supply. And have one of Josh's 8080 cpu boards
running in it. So reset and run work! I also have an Imsai
front
panel simulator running in a VM to remind me of front
panel operation.
I have the original Imsai documentation. I scanned the FP
parts list and OCRed it into a spread sheet.
| 8T97 |
1 |
Hex
Tri-State Buffer/N8T97B |
| 7400 |
2 |
Quad 2 Input NAND/SN7400N |
| 7402 |
2 |
Quad 2 Input NOR/SN7402N |
| 7404 |
1 |
Hex Inverter/SN7404N |
| 74LS04 |
2 |
Hex Inverter (Low Power
Schottky)/SN74LS04N |
| 7405 |
5 |
Hex Inverter Open Collector/SN7405N |
| 7410 |
1 |
Triple 3 Input NAND/SN7410N |
| 74LSI0 |
1 |
Triple 3 Input NAND (LPS}/SN74LSION |
| 7427 |
1 |
Triple .3 Input NOR/SN7427N |
| 7430 |
1 |
8 Input NAND/SN7430N |
| 74LS30 |
1 |
8 Input NAND (LPS)/SN74LS30N |
| 7805 |
1 |
SV Positive Volt Regulator/MC7805CP |
| 8212 |
1 |
I/O Port/P8212/S1002 |
| 74107 |
3 |
Dual J-K Flip Flop With Clear/SN74l07N |
| 74123 |
3 |
Dual
Monostable Multivibrator, Retriggerable with
Clear/SN74123N |
|
|
|
I thought I would lay in a set of spare parts before I
begin. I can get most of the parts at Jameco less expensively
than DigiKey, however DigiKey has specific versions of parts
that Jameco does not. The N8T97B I found at
Wholesale
Electronics, Inc. crossing to a
NTE6887
Didn't see it at JameCo or DigiKey. FWIW I've attached a
Jameco cart as jamecoImsaiFpList.csv
I'm inclined to repair the board with available parts but
am thinking a bit about whether I should restore it with all
original parts. Would that be better for a donation to a
university or museum or just preservation of historically
significant hardware?
What substitutions can be made for 7404/74LS04. Will the LS
version be suitable for both parts? The parts list also calls
for separate 7410 and 74LS10, as well as separate 7430 and
74LS30.
Although reset and run work, it looks like examine and
deposit circuits are having difficulty. With all switches down
I don't appear to be able to deposit to zero, nor examine. the
[deposit | examine] next seem a bit flaky but may be due to
the [examine|deposit] not working correctly. So far I've
tested all the switches. I had to open one up and clean the
contacts. It appears to be working now. I replaced a couple
LEDs, bummer that they are a bit more clear and consequently
brighter but not extremely noticeable with plastic FP
installed.
Some help nailing down a parts list would be appreicated.
Thanks! - jeffa