modessitt
Volunteer: Encyclopedia Submission Moderator
Anyone know what the major differences are between a Tempest Rev C and a Tempest Rev D?
I am attempting to repair a bad Tempest CPU. The board was an attempted repair by someone else and it got hacked a bit. Basically, it doesn't display the right half of the screen (it's squished into a vertical line), and the left half might as well be written in Russian, as it's all funky.
Before anyone asks, it is definitely the CPU, as I have a good working boardset that I have put in and gotten good picture (so no bad monitor) and I have swapped aux boards and the good one still works (so no bad aux board).
The good board is a Rev C, and the bad board is a Rev D. I've noticed a couple differences in the two boards. For example, Pin 12 of C12 is tied to ground on the Rev C, but not on Rev D (it goes to a resistor instead).
I tried swapping the A10, D10, E10, B11, E11, N/P3, R3, and C2 from the working board and got no change.
Just for grins (and lacking an o-scope), I did a volt reading on every leg of the X/Y section (where the pots are) of the working board, and compared them to the non-working board.
Most of the readings were similar, but a few were way different. Some of these differences could be explained by the various pots being at different settings, I'm sure.
Others, I'm not so sure.
For example, Pin 4 of A/B 12 reads +0.10vdc on the working board (WB), but +5.69vdc on the non-working board (NWB). Pin 5 of WB is -1.28vdc and +4.21vdc on NWB.
Another example: Pin 9 of C12 of WB reads +0.10vdc, but reads +5.77vdc on NWB.
And another: Pin 1 of A11 reads +0.11vdc on WB and +8.53vdc on NWB. Pin 7 of WB reads -O.10vdc, but reads -9.20vdc on NWB.
Last one: B11 pin 3 reads -0.10vdc on WB and -9.19vdc on NWB, pin 14 reads +0.11 on WB and +8.54vdc on NWB.
Are these discrepancies in readings caused by board design differences? Or is it an indicatio of what the problem is?
In case anyone cares, the chips that gave the same (or close enough) readings in both boards are: A/B13, C13, D/E13, D/E12, D11, E11.
Haven't been able to find good schematics showing this section, for either Rev.
Anyone have an idea?
I am attempting to repair a bad Tempest CPU. The board was an attempted repair by someone else and it got hacked a bit. Basically, it doesn't display the right half of the screen (it's squished into a vertical line), and the left half might as well be written in Russian, as it's all funky.
Before anyone asks, it is definitely the CPU, as I have a good working boardset that I have put in and gotten good picture (so no bad monitor) and I have swapped aux boards and the good one still works (so no bad aux board).
The good board is a Rev C, and the bad board is a Rev D. I've noticed a couple differences in the two boards. For example, Pin 12 of C12 is tied to ground on the Rev C, but not on Rev D (it goes to a resistor instead).
I tried swapping the A10, D10, E10, B11, E11, N/P3, R3, and C2 from the working board and got no change.
Just for grins (and lacking an o-scope), I did a volt reading on every leg of the X/Y section (where the pots are) of the working board, and compared them to the non-working board.
Most of the readings were similar, but a few were way different. Some of these differences could be explained by the various pots being at different settings, I'm sure.
Others, I'm not so sure.
For example, Pin 4 of A/B 12 reads +0.10vdc on the working board (WB), but +5.69vdc on the non-working board (NWB). Pin 5 of WB is -1.28vdc and +4.21vdc on NWB.
Another example: Pin 9 of C12 of WB reads +0.10vdc, but reads +5.77vdc on NWB.
And another: Pin 1 of A11 reads +0.11vdc on WB and +8.53vdc on NWB. Pin 7 of WB reads -O.10vdc, but reads -9.20vdc on NWB.
Last one: B11 pin 3 reads -0.10vdc on WB and -9.19vdc on NWB, pin 14 reads +0.11 on WB and +8.54vdc on NWB.
Are these discrepancies in readings caused by board design differences? Or is it an indicatio of what the problem is?
In case anyone cares, the chips that gave the same (or close enough) readings in both boards are: A/B13, C13, D/E13, D/E12, D11, E11.
Haven't been able to find good schematics showing this section, for either Rev.
Anyone have an idea?
