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Просмотр полной версии : Pentagon 128k debugging



Shockwav3
10.02.2013, 01:45
Hi there,
I'm currently in the progress of building a Pentagon 128 (Revision 2011 produced by zorel). Good things first, it already boots, accepts keyboard input and even lists betadisk directories. Now comes the bad part, after a few seconds I get junk characters on the screen, but the machine remains operational for a few more seconds til it crashes (mostly after 30-45 seconds). Sometimes it reboots, but most of the time it just hangs requiring a hard reset. Any ideas what could be wrong?

Further info:
- IC type is all 74lsxxx except for dd02, dd11 & dd12 (used 74hct93 there). I used the translation table from here: http://sblive.narod.ru/ZX-Spectrum/Pentagon128k/Pentagon128k.htm (except for dd100 which is wrong there and should be cd4069).
- RAM chips are 41256 and have decoupling capacitors
- random decoupling capacitors have been placed on the board
- resistor and capacitor values have been used according to pentagon.pdf from here http://zxspectrum.it.omegahg.com/doc/Pentagon.pdf

Here's also a picture:
http://img855.imageshack_.us/img855/9778/pentagon128k.jpg

So any ideas what to try next?

null_device
10.02.2013, 02:38
Are all the errors of the board have been eliminated?

http://zx.pk.ru/showpost.php?p=535392&postcount=371

Is the board AY \ YM, it also is an error.

Shockwav3
10.02.2013, 03:07
Thanks for letting me know about that one - didn't know about that one before, fixed that, didn't help much :(
I've also fixed the missing track on dd31 and added R50 (56kohm)

null_device
10.02.2013, 03:22
Sorry if this mу advice does not help.
In the next branch, discussed the assembly and adjustment of the board, try to ask a question there.

http://zx.pk.ru/showpost.php?p=574471&postcount=983

Shockwav3
04.03.2013, 18:29
Just to let you guys know: both of my Pentagons are up and running :)
Appears the first one was suffering from a flakey PSU (I was using my PC's) and C7 being soldered in the wrong place and the second one must have had a cold solderjoint, as it magically started working once I re-soldered every chip.

So ... what are good measures for testing that everything is working alright?
I've tried loading and running a demo from disk (Alienate by Hooy-Program), loading and saving a program from/to tape, testing the INT and RAM using Test 4.30 (which also confirms the tact at 171680 cycles).
One more thing that comes to my mind would be testing a demo that uses covox sound and that would be pretty much all.

solegstar
05.03.2013, 15:26
testing the INT and RAM using Test 4.30 (which also confirms the tact at 171680 cycles).

How many INT cycles? "Too short", "Too long" or..?


One more thing that comes to my mind would be testing a demo that uses covox sound and that would be pretty much all.

If you connect DAC (R-2R or 8bit chip) on "printer port"... only after that you can hear covox sound.

Shockwav3
08.03.2013, 00:08
Test 4.30 gives me 32-28
TestInt reports 40-36
Hidden part of the Insult Megademo shows just fine.

solegstar
08.03.2013, 00:58
Test 4.30 gives me 32-28
TestInt reports 40-36
Hidden part of the Insult Megademo shows just fine.

there are no more questions) pentagon work properly. my congratulations!!! :)

ZXMAK
10.03.2013, 08:28
there are no more questions) pentagon work properly. my congratulations!!! :)

он жаловался на то что все работает, выводит каталог диска, но через несколько секунд появляются случайные символы и затем через 30 сек крешится..

solegstar
10.03.2013, 12:05
он жаловался на то что все работает, выводит каталог диска, но через несколько секунд появляются случайные символы и затем через 30 сек крешится..

где? этот баг кажись устранен давно. он вроде отписался, что всё работает замечательно и он погонял разные тесты, демы и т.д....:v2_conf2:

Shockwav3
10.03.2013, 14:32
The computer crashing after a few seconds has been fixed indeed (was caused by a faulty connection of C7). But there's still 1 problem remaining.
KJoy does not seem to work at all - #1f reads all 255. I could get that semi-fixed by adjusting R11 to 1MOhm, which allows me to randomly use the joystick (#1f reads 0 or 255), but this also makes the machine a good bit more unstable, since it sometimes would give me a black screen with white border and random disk access when powering up.

Using /IORQ instead of /OIRQ to drive the joystick interface allows me to use the joystick without any issue (#1f all 0 and reacting to input) but eliminates TRDOS (listing a disk gives me a *no disk* error)

Any ideas what could be wrong there?

solegstar
10.03.2013, 15:31
try to replace silicon diodes on germanium diodes or Schottky diodes with small voltage drop on P-N transition. The R11 resistor shall be 10 kOhms. On scheme (http://sblive.narod.ru/ZX-Spectrum/Pentagon128k/Pentagon128VMGPage3.jpg) used /OIRQ signal and germanium diodes Д9.

Shockwav3
10.03.2013, 15:36
try to replace silicon diodes on germanium diodes or Schottky diodes with small voltage drop on P-N transition. The R11 resistor shall be 10 kOhms. On scheme (http://sblive.narod.ru/ZX-Spectrum/Pentagon128k/Pentagon128VMGPage3.jpg) used /OIRQ signal and germanium diodes Д9.I'll try that with adjusting R11 to 10kOhms, in case that alone won't help, I'm going to drive /RD, /OIRQ and A5 through OR-gates as shown here: http://8bit.yarek.pl/hardware/zx.joystick/kjschem.gif

Shockwav3
10.03.2013, 17:56
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 :)

Shockwav3
30.01.2014, 15:36
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
31.01.2014, 03:40
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
04.02.2014, 07:29
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
16.02.2014, 17:26
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?


---


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/v2/355x679q90/31/csbe.jpg
https://imagizer.imageshack_.us/v2/483x517q90/534/n10k.jpg

Roger Wilco
11.03.2014, 14:49
For switch TV to RGB mode, you need connect pin 16 of SCART to 5 V through 180 Ohm resistor.