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Author Topic: Broken EP (Read 11553 times)

Offline Saint

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Re: Broken EP
« Reply #45 on: 2014.March.02. 22:26:52 »
Quote from: Zozosoft
Interesting the different oriented texts! Anyway it is look same, just the date code different. But it is sure these are come from different batch of chips.
The first is which have a problem with the slower EXDOS EPROM?

Jltursan! If I remember right you found same problem about EXDOS EPROM speed? Can you post photos of your Dave chips?

I will look around at my spare machines about can I reproduce this problem?
Anyway I always suggested using least 150ns fast EPROMs. But will be interesting if can be found slower Dave chips, it is can be affect the overclocking ability?
Yes, the Issue 5 is the one with the problem with slower EPROMS. It is odd the text is put on at a different angle between the chips... :)

The older Dave will run with 250ns EPROMS in EXDOS. But also, I put the old beep test image onto a 250ns EPROM and this ran ok from the motherboard socket of the Issue 5 board.

Offline jltursan

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Re: Broken EP
« Reply #46 on: 2014.March.02. 22:38:04 »
Yep, along the next week I'll try to open the EPs and take some photos of their Dave ICs.

I suposse its an issue related to the EXDOS card itself or the expansion bus. I'm sure I've also used slower EPROMs in the motherboard socket without flaws.

Offline Zozosoft

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Re: Broken EP
« Reply #47 on: 2014.March.02. 22:44:11 »
Quote from: Saint
 But also, I put the old beep test image onto a 250ns EPROM and this ran ok from the motherboard socket of the Issue 5 board.
It is not a surprise, because the internal ROM (and the cartridge) have a faster enable signal directly from the Dave. On the EXDOS card many additional 74LS logic ICs used for the address decoding, these are many more nanoseconds.

Offline SlashNet

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Re: Broken EP
« Reply #48 on: 2014.March.07. 11:43:51 »
Hello.

One member, from zx.pk.ru forum, trying to repair his EP 128k (he don't speak english).

He made some videos. What can you say about that problem?
Where to look first?

Videos:
https://www.dropbox.com/s/r1i2rjukv35zvaj/break_enterprise.zip

Offline Zozosoft

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Re: Broken EP
« Reply #49 on: 2014.March.07. 11:57:12 »
Quote from: SlashNet
He made some videos. What can you say about that problem?
Where to look first?
It looks the common "no 12V" problem.
Check it at U35 (LM1889) Pin 14,15,16.
If no 12V then replace TR2 (BC337). And probably the C9 capacitor dried out this killed the transistor. It is a good idea to replace it too.

Keyboard membrane tails need some cutting.
« Last Edit: 2014.March.07. 20:57:24 by szipucsu »

Offline SlashNet

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Re: Broken EP
« Reply #50 on: 2014.March.08. 10:20:12 »
On these pins - +6.5В.
Replacement of TR2 (replaced to C945) did not change anything.
Capacitor C9 in good condition.

Offline Zozosoft

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Re: Broken EP
« Reply #51 on: 2014.March.08. 11:42:08 »
Ok the problem was what I thought: no 12V
Are C945 fully compatible with BC337? Can't he get BC337? I use BC337-40 type.
« Last Edit: 2014.March.08. 17:31:06 by szipucsu »

Offline SlashNet

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Re: Broken EP
« Reply #52 on: 2014.March.09. 19:24:42 »
He repaired 12V and all working now. Thanks.

Little bonus: his EP was ordered by advertisement in magazine "Юный техник" (Young Technician) in 1993. Manual on english. SN with additional label "QC passed:"

Offline Zozosoft

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Re: Broken EP
« Reply #53 on: 2014.March.09. 19:49:52 »
Quote from: SlashNet
He repaired 12V and all working now. Thanks.
Great news!

Offline SlashNet

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Re: Broken EP
« Reply #54 on: 2014.March.31. 20:58:39 »
Recently noticed that some time after the power on EP, some demo start behaving buggy.
What could it be?
Comp is mine.

http://youtu.be/Us8QcNU5knk

Offline Zozosoft

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Re: Broken EP
« Reply #55 on: 2014.March.31. 21:32:04 »
Previously you tried to run this demo on this machine?

Offline SlashNet

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Re: Broken EP
« Reply #56 on: 2014.March.31. 21:46:30 »
Only week ago. Same effects.

Offline Zozosoft

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Re: Broken EP
« Reply #57 on: 2014.April.01. 12:30:46 »
Then I'm afraid you have the older 08-04 version of Nick chip :-(

Try to run this little BASIC program:
Code: [Select]
  10 GRAPHICS ATTRIBUTE
   20 SET INK RND(16)
   30 PLOT RND(1280),RND(720)
   40 GOTO 20

It is draw a random color pixels, with the buggy version Nick you see some pixels are flashing as the stars on the sky. After the machine (and Nick) heating up then more flashing pixels.
Also good test view interlaced IVIEW picture (from my Interlace Demo 3 package), see this video. At the start you see many green and purple flashing pixels, then I placed a cold heatsink to the Nick then the most of the buggy pixels are eliminated.
Another good example the Eat-it-up game, see the video. Many yellow buggy pixels, which are removed when the Nick cooled.

These are extreme examples with very bad Nick with removed heatsink. In normal situation you can see something wrong pixels but not as bad in these examples.

Also reported other interesting effects with these Nick chips, for example at the Tape Level signal at the status line, when it is green red vertical line can be remain.

The 08-47 revisions Nick chips are don't do these, also running fine without the heatsink. (I verified the temperature of both revisions and are same!)
Originaly no heatsink developed, when the first machines builded then ordered heatsink to Nick.

If your Nick are 08-04 then you check the Nick heatsink! After the 30 years it is fall in many machines. If this happened when it is glued back then buggy effect are reduced.
If you order memory expansion from Saint then you can put better, bigger heatsink to the Nick :-)

I not tested this specified demo previously but I will run on know 08-04 machines.

Offline SlashNet

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Re: Broken EP
« Reply #58 on: 2014.April.01. 20:55:13 »
No. I can't see any green flashing dots.
Heatsink was glued fine.
Nick (as I see on marking that was left on heatsink) is 08-47.

Offline Zozosoft

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Re: Broken EP
« Reply #59 on: 2014.April.01. 22:21:20 »
Quote from: SlashNet
Nick (as I see on marking that was left on heatsink) is 08-47.
Then very interesting! :shock:

Once someone reported crazy screen bugs what I can't reproduce on my machines.
Try the Jack The Nipper:
White line before the title text.
And Fast Food:
Screen garbage under loading.
And under the game.