ÒÅÍÏÎÔ Pentagon128k

Please tell me what could be the matter.

At first the Pent worked, it just kept crashing, all sorts of nonsense popped up on the screen,
but if you click on the board, then everything became OK.

I started looking for a glitch. It seemed like I found it, but then the spec stopped responding to the reset.
There is a stretched chessboard on the screen. Sometimes, when you press reset, all sorts of
attributes come up...

I checked, the data bus reaches the ROM, the reset line also reaches the Z80.
No shorts anywhere in the data... I didn’t check the memory, it seems to be working (after all
it worked before).

I don’t have any equipment at hand except a soldering iron and a multimeter, otherwise I would
check oscillograms from a book on tree stump repair. :(

That’s all for me. Bye, Everybody.

On Thu, 03 Jun 04 22:11:24 +0400, Roman Timofeev wrote:

RT> but if you click on the board, then everything became OK.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Broken track or bad soldering. It is looked for, first of all, by
visual inspection, using a magnifying glass.

RT> I started looking for a glitch. It seemed like I found it, but then the spec stopped responding to the reset
RT> There is a stretched chessboard on the screen. Sometimes when you press reset, all sorts of
RT> attributes appear...

And if without ROM, do you have a mattress? There should be.

RT> There is no equipment at hand except a soldering iron and a multimeter,

If the multimeter has a mode for measuring resistance in ohm units,
breaks and poor soldering in this mode are immediately clearly visible.

On Saturday, June 05, 2004, Kirill Frolov and Roman Timofeev discussed "Re:
repair of Pentagon128k". Let's continue the conversation.

KF> And if without ROM, do you have a mattress? There should be.

Without ROM there are thick (2 or more pixels) color stripes on the screen. One column
of attributes is stripes, the other column is all black. Etc. whole screen. The columns with stripes are the same everywhere.

But when I put the ROM in place, the computer behaved differently. I reacted to the reset with several “resets” in a row (thin red stripes appeared and went down several times - as if you were falling into the 48th BASIC). The border
changed and on the screen there was a black square. Sometimes the computer went to 48 BASIC. Less often - to
the main menu (but it was immediately reset again).

Maybe the memory is acting up? Or is it leaking somewhere?

That’s all for me. Bye, Kirill.

RT> Without ROM, there are thick (2 or more pixels) color stripes on the screen. One
RT> column
RT> attributes are stripes, the other column is all black. Etc. the entire screen.
RT> Columns with
RT> stripes are the same everywhere.

This is called a mattress.

RT> But when I put the ROM in place, the computer behaved differently. On
RT> reset
RT> reacted with several “resets” in a row (thin red stripes appeared and went down
RT> several times - as if you were falling into the 48th BASIC). The
RT> border
RT> was changing and there was a black square on the screen. Sometimes the computer went to 48 BASIC. Less often - in
RT> the main menu (but it was immediately reset again).
RT> Maybe the memory is acting up? Or is it connecting somewhere?

If the effects change when bending the board, as you wrote, the problem
is in the board and installation.