Pentagon 128k debugging

[Shockwav3]

Good news, disabling the diodes and instead using OR-Gates (74ls32/555ЛЛ1) the kempston interface works reliable. #1f outputs all 0 and reacts to joystick inputs, while floppy access works nicely

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[Shockwav3]

After almost a year it's me again.

I tried to power up my Pentagon once again, sadly the video output seems to be extremely butchered. Otherwise the computer seems to work (keyboard, menu, sound, trdos).
Here's a picture of the output (3MB): http://imageshack.com/a/img11/2371/ojpv.jpg

The problem is as follows: all characters shown on screen are just very delicate shadows of what they're supposed to be, there's no color - except when entering the tape loader which causes the whole screen to flash in red and cyan.

The scart cable is correct (connecting R, G and B - SYNC on Pin20, +5V on Pin16)

Any idea where to start? I've already tried counterswapping most of the Pentagon logic chips and replaced the VT1 & VT2 transistors.

[Shockwav3]

Seems like this was related to the PSU. Using another one I got a proper picture and managed to load half a demo before the machine crashed.

Time to add some more decoupling caps and a properly adjusted PSU

[zorel]

The essence of the question is not very clear. To facilitate the understanding of fault recommend to make a video of what is happening on the screen to make it clearer to others, in what appears a fault.

---------- Post added at 07:58 ---------- Previous post was at 07:57 ----------

Shockwav3 Recommend to continue the discussion here http://zx.pk.ru/showthread.php?t=14277&page=43

---------- Post added at 07:59 ---------- Previous post was at 07:58 ----------

topic is more relevant here.

[Shockwav3]

And another patient, this time a Pentagon 1024SL 2.2

For some reason I can't get the RGB Video working, as I just get a white screen (second photo on the first image). Composite Video seems to work (upper picture). Connecting SYNC via Composite, I get a slight tint of the image as I should. Since I get a fully white picture when using the SCART cable I suppose the mode switching (pin 16) works as it should.
The second image is the pinout I used to connect a SCART connector.
I already doublechecked R42 ... R53 and VT13 ... VT15.

Any ideas what could be wrong?


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И еще один пациент, на этот раз Пентагон 1024SL 2.2

По некоторым причинам я не могу RGB Видео работает, как я только получить белый экран (второе фото на первом изображении). Композитный видео, кажется, работает (верхний рисунок). Подключение SYNC через Composite, я получаю небольшой оттенок изображения, как я должен. Так как я получить полностью белое изображение при использовании SCART кабель Я предполагаю, что переключение режимов (контактный 16) работает как надо.
Второе изображение является распиновка я использовал для подключения разъем SCART.
Я уже перепроверили R42 ... R53 и VT13 ... VT15.

Любые идеи, что может быть не так?

https://imagizer.imageshack_.us/v2/3...90/31/csbe.jpg
https://imagizer.imageshack_.us/v2/4...0/534/n10k.jpg

[Roger Wilco]

For switch TV to RGB mode, you need connect pin 16 of SCART to 5 V through 180 Ohm resistor.