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Original Imsai Front Panel Repair
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.
I've read the CP-A rev. 4 construction and operation portions in the documentation. I found these threads http://fixunix.com/cp-m/50-imsai-troubleshooting-hints-faqs-etc.html and http://ana-3.lcs.mit.edu/~jnc/cctalk/2001-September/1400.html with some tidbits. Anyone know of other resources I might want to review?
Some help nailing down a parts list would be appreicated.
Thanks! - jeffa
Jameco Shopping List "Imsai Front Panel"
www.Jameco.com
1-800-831-4242
Export Date,02/25/2015
Jameco Part Number, Description, Manufacturer, Manufacturer Number, Quantity, Unit Cost, Link
46404,"IC,74LS10N,DIP-14,TRIPL 3INPUT","MAJOR BRANDS","74LS10","2.0","$0.59","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=46404&langId=-1";
49040,"IC,7404N,DIP-14,HEX INVERTER","MAJOR BRANDS","7404","1.0","$1.59","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=49040&langId=-1";
49074,"IC,7405N,DIP-14,HEX INVERTER","MAJOR BRANDS","7405","1.0","$1.29","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=49074&langId=-1";
49189,"IC,7410N,DIP-14,TRIPLE 3-INPUT","MAJOR BRANDS","7410","1.0","$1.49","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=49189&langId=-1";
49234,"IC,74107N,DIP-14,DUAL J-K","MAJOR BRANDS","74107","1.0","$1.19","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=49234&langId=-1";
49357,"IC,74123N,DIP-16,DUAL MONOSTBL","MAJOR BRANDS","74123","1.0","$3.95","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=49357&langId=-1";
50139,"IC,7427N,DIP-14,TRIPLE 3-INPUT","MAJOR BRANDS","7427","2.0","$0.99","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=50139&langId=-1";
50227,"IC,7430N,DIP-14,8-INPUT","MAJOR BRANDS ","7430 ","2.0","$0.69","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=50227&langId=-1";
52468,"IC,8212 (74S412),I/O PORT","MAJOR BRANDS","8212","1.0","$4.95","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=52468&langId=-1";
283792,"IC,SN74LS04N,DIP-14,","TEXAS INSTRUMENTS","SN74LS04N","1.0","$0.55","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=283792&langId=-1";
830047,"IC,SN7402N,QUAD 2-INPUT NOR GA","TEXAS INSTRUMENTS","SN7402N","1.0","$2.05","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=830047&langId=-1";
910901,"IC,SN7400N,DIP-14,QUAD 2-INPUT","TEXAS INSTRUMENTS","SN7400N","1.0","$1.45","http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&catalogId=10001&productId=910901&langId=-1";