Godbout Interfacer 1 stops Imsai´s front panel...

[Dwight Elvey]

Removing pin 20 was OK ( my error ).
Follow the following, remove these and leave them out, in sequence. Test after removing each chip.

I assume when you said that you remove the buffer, you meant U25 and U26
I remove jumper on J11
U21
U23
U22
U9
U19
U20
U25
U26
U24

These are all the chips that can effect the main bus, in any form. If the front panel starts working stop and let us know which chip was offending things. Most of them are inputs. If it still causes trouble with all of these chips removed ( do keep track of which came from were ) we'll need a picture of the card edge connectors, front and rear.
Dwight

[glitch]

If the only thing you can do is STOP/RUN and RESET/EXT CLEAR with a board in, it's almost always an issue of pins 70/20 being grounded on the board. Grounding pin 20 disables all of the one-shot circuits on the front panel, which disables most of the front panel functionality. I usually just cut pins 20 and 70 on the front panel card itself, since there is no known use for these signals on an IMSAI.

[Jan1980]

So, i removed all ICs. No changes. Then, i made tape on Pin 20 and Pin 70, now it works. I don´t understand, i cutted the trace to Pin 20 and 70, this did not work.. mmmhhh.. But, i can use the front panel again. I found some broken legs on IC 10. I removed the socket, soldered new socked and i soldered ic to another socket to repair the connections. I made the serial setup to 00h. I connected RXD and TXD on connector a. Then, i wrote the following routine:

org 000h
in FFh
out 00h
in 00h
out FFh
jmp 0000h

This should make an echo and i should see the switche setting on the LEDs. But it does not work. Then, i connected ground and TXD to oscilloscope. I have got -10,5 V. I wrote:

org 0000h
in FFh
out 00h
jmp 0000h

I should see a signal on oscilloscope, but nothing. I found the 5.0688 MHZ oscillator. The frequency jumps between some hz and 7 MHZ. I have to check for cold solder points or damaged capacitators.

THX

Jan

[Jan1980]

Ok. I checked BR2941 baud rate generator. It does not work correctly. Voltage and ground is correct, frequency from oscillator is also correctly now. I have to swap this IC first..


Jan

[Jan1980]

YES YES YES !!! It works !!!!!!!!! ))) I have to learn better to clean this old stuff before soldering. I soldered again th baud rate generator. Now, it has signal on clock output to the uarts. I wrote my echo program again and everything is fine...

THX

Jan

[Dwight Elvey]

YES YES YES !!! It works !!!!!!!!! ))) I have to learn better to clean this old stuff before soldering. I soldered again th baud rate generator. Now, it has signal on clock output to the uarts. I wrote my echo program again and everything is fine...

THX

Jan

20 and 17 has a feed through, connecting them together. For the IMSAI, they shouldn't be connected together.
Dwight