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Author Topic: 2 questions: No RGB signal (HELP) and can I upgrade EP64 to EXOS 2.4 etc. (Read 1082 times)

Online John Fante

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I have been struggeling with a strange display artefact and while trying to fix it I managed to mess up the RGB signal.

In short I messed to much around with C43, R202 (yes I know it was wrong) and a little with L2 and now I can not get Nick to produce a picture and I do not have an oscilloscope etc. to adjust the settings to things going.

Any suggestions to fix this?

I am - as a last resort - considering bying a Egyptian EP64 to use as backup. I am using a Symbiface 3 for RAM so that should not be a problem.

My question is. I have a Exos 2.4 ROM in my present machine? Can I just swap that out with the ROM on the EP64? Or is it better to use Symbiface 3 for that?

Is there any other modifications for a EP64 that I need to do?
« Last Edit: 2020.August.16. 11:52:04 by John Fante »

Online gflorez

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Whoa! You want to kill fleas with cannon balls....

First of all.... calm... calm... calm...

I have never touched these trimmings, so I can't say you a word about their effects, probably you know more now of this than me. Zozo is the guy that can aid you.

But.... When I have suddenly lost the RGB image it has been after touching the cable, so I recommend you to check that all the pins on one end have continuity with the other on the other side. You can use the probe points of a multimeter to test them.  Follow Zozo's page connectors diagrams.

Usually one of the colours, sync or blanking are cut, and that is an easy fix.

------

On the other side... It is always a good idea to have an spare Enterprise...

Just for clarifying, EXOS.ROM is the internal Rom, while EXDOS.Rom is the massive storage Rom(FAT12) for floppies, SD cartridge or IDE devices.

Also, the EXOS stock versions where 2.0(EP64) and 2.1(EP128) both 32KB. The modified EXOS Roms from Zozo have higher versions, and are 64KB Roms.

It is not so easy to swap Roms to have a 64KB Rom in the place of a 32KB one. You need an additional signal from the address bus, that can be took from a near spot on the expansion connector. But better burn a new 64KB EPROM for the purpose and leave your old EP with its own Rom. Or ask who can do it for you....

Yes, SF3 can emulate the EXOS.Rom on the segment range 00-03, but for that you must remove the internal Rom from its socket, because if not it can happen a clash of data and the EP will not boot. Really I think this is a procedure for skilled users when repairing a computer, not very useful for common users.

Offline szipucsu

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You want to kill fleas with cannon balls....
Do you say this? It is interesting. We Hungarian say: to shoot at a sparrow with a cannon.
100 SOUND SOURCE 3,STYLE 16,LEFT 16,RIGHT 64,SYNC 2
110 SOUND SOURCE 2,STYLE 128,PITCH 25.2,SYNC 2
120 SOUND PITCH 25,SYNC 2
Videos

Online gflorez

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Si, decimos "matar moscas a cañonazos......"

Online John Fante

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We also shoot sparrows with cannons here in Denmark :)  .... A very fitting expressions since I right now feel like shooting something :evil:

Back to the problem!

@gflorex: You are of course right that it should have been EXOS not EXDOS. Typing error that has been corrected.

It is - unfortunately - not the cable. I am using a new - and very good - cable that judge supplied and have tried with a couple of others from retrocables. Same result.

The powersupply is also fine and I have also tested the 7805 voltage regulators to be sure that they where giving the correct 5v voltage. They give 4,98 and 4,99 so they are fine and are not causing the artefact.

I therefore turned to trying to adjusting the Nick clock - as advised by Zozo - with C43 and L2. C43 and L2 - as far as I know - starts/adjust the crystal that controls the Nick clock.

I had problems finding L2 so by mistake I at first started messing a bit around with R202. I think I have set that back to the correct value so that it outputs 2,83 voltage. And since R202 only controls the voltage to the RF modulator that should not be the cause here.

At first I adjusted C43 and R202 when the machine was on to see the effect on the picture. I did not see any effect but after doing that I turned the machine off and I lost picture.

Or to be more correct I can not see the picture. I am using an OSSC and it looks like the machine is outputting some kind of signal that at least the OSSC can not use. See examples here and here.

The possibilities are - as I see them - as follows:

1) I have messed to much around with R202 and fried something along the way. Not that likely since it runs to the RF output.

2) C43 (and maybe L2) is either badly out of position so that it/they does not start the crystal/Nick correctly or they are out of order.

3) I have shortcircuted something along the way - I was also planning to remove the internal speaker and therefore removed the glue under it so that it is now moving around freely with the risk of a shortcircut.

At the moment I have some limitations in error finding:

I do not own an oscilloscope. And buying one is almost as expensive as buying a new Egyptian EP :)

My voltagemeter broke last night - I will get a new but it will take a day or two. But for now I can not messaure anything.

I know it is a rather big thing to just buy a new machine but I must admit that the screen artifacts I have really has taken the joy out of using the EP :(

So either I need to be able to fix the machine or someone else - any volunteers? - has to give it a go. I will ofcourse pay for the trouble. Or else it is the Egyptian way. And as glorez states: It is always nice to have an extra EP.

Online gflorez

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Ok, I understand your despair.

But... it is not the first EP that Zozo has repaired remotely... Wait to what he can say about your subject, and maybe you can repair it in your house. These strange frequencies can indicate him something obvious that we can't see.

About the loose speaker... Ok there are a lot of Enterprises working but with the cooper sink unglued from the Nick chip...

You at least know how to manage an oscilloscope. (I have no idea... but want to learn), Then you probably would be able to manage a cheap digital analyser. I have one sitting on a drawer... I need some teaching before I can use it... or some day the necessity will force me to learn...

On the other side, I have opened my EPs a lot of times, and I have made with them a lot of experiments... I think they are well built, with a lot of pull-up or pull-down resistors to protect the components and buses. Your EP will be fixed soon. Sure.
« Last Edit: 2020.August.16. 13:47:53 by gflorez »

Online John Fante

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I have gotten a (small) bit further :)

When I alter the settings on C43 and L2 I get changes in the output signal that the OSSC recieves. It therefore looks like they are working - at least a bit - but are not configures correctly.

Does anybody know how to configure C43 and L2 and what the correct settings are?

Thank you in advance!

Online John Fante

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In the english monarchy you use the expression "An heir and a spare" when you have an extra son if the heir is killed in battle.

I now have an spare. Or to be more precise an Egyptian EP spare :)

I have so far not found a solution to my frequency problem. Hopefully it will show up soon but until then I will use the Ep64 I have just bought in Egypt. If it works that is ... I just could not wait and hopefully the "new" machine does not have the same artifact problem that started all this.

I am considering moving my Exos 2.4 rom from my present nonfunctioning machine to the new one. I understand that I also need to solder a ekstra wire besides moving the ROM. Can anybody direct my to a more precise description?

But first I will use my Symbiface to inject the ROM (and remove the present exos2.0). Does anybody have a link to the latest EXOS2.4 ROM with IS basic etc.?

Thank you in advance!

Online geco

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I thought that ROM's are available on enterprise.iko.hu but i did not find any, but if you install ep128emu it will download ROM's EXOS 2.4 included also.
« Last Edit: 2020.August.19. 23:31:19 by geco »

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please check 4th post on downloads link

Online John Fante

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please check 4th post on downloads link

Thank you! :)

Online gflorez

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Almost all up-to-date Roms are downloaded with the EP128emu emulator from IstvanV.

The best explanation on how to put a 64KB Rom inside the Enterprise is from Zozo here but it lacks a picture of the point on the PCB where to take the A15 signal, so I have prepared this one. On it you can see the point signalled in a red circle. It is pin B9 on the Expansion Connector at the Right side of the computer PCB.


Online gflorez

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And about leaving your "old EP" without the internal ROM, you say that you plan to inject it with the SF3.

Ok, remember to put on the INI file the line

Code: [Select]
ROMEXOS_ENA=ON
and the line

Code: [Select]
ROM[#00]  =SD:EXOS2.4.ROM
Remember that your old EP will only start with the SF3 connected.
« Last Edit: 2020.August.20. 11:37:51 by gflorez »

Offline Judge

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25281-0

25283-1

Be careful! Pin 1 of the chip must be outside the socket! Solder the wire over there. This is my 64k spare motherboard. :)

25285-2

This way... 
« Last Edit: 2020.August.20. 15:09:46 by Judge »
Üdv.Judge

Online John Fante

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Thank you for all the great advise :)

Just one thing. On my present machine the ROM is not wired to the expansion port but to the U6 chip. See here.

The wire to the expansion port is wired like this.

Is this an alternative way of doing it?