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Author Topic: EP64 will not boot. (Read 6204 times)

Offline Bagpuss22

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EP64 will not boot.
« on: 2012.September.04. 23:53:25 »
OK my EP64 has finally stopped working, I replaced some memory about a year ago
but have not used it since then, as I normally use my EP128.

Today I am getting random things happening  :cry:

Most of the time it will boot with a display of white and black vertical lines:



sometimes with mixed colours:



sometimes random:






On the odd occasion it will show the EXOS 2.0 test and twice it displayed the
"Enterprise" logo and allowed me in.  As soon as i started pressing keys it
locked up and beeped with a constant tone.

Any thoughts or help in getting this one up and running would help.

I was using an Enterprise PSU which powers my 128 ok,  I was also
using normal TV via the modulator.


Thanks

Russ
 :cry: :cry: :cry:

Online Zozosoft

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Re: EP64 will not boot.
« Reply #1 on: 2012.September.05. 08:06:36 »
Try out the standalone memory test from EXOS 2.4 beta! (twp8ukc.rom)

It is a big bug in the original EXOS test, it is use a CALL instructions to test the system segment. But if the onboard memory is bad then the return address corrupted, the system is frozen, no picture, no sound, no life sign... only see a random picture, because the Nick is running uninitialized and using the poweron random filled bytes from the video memory.

In this test version included my "BEEP test" routine, it is start testing the system segment, writing 00h,FFh,55h,AAh to each bytes and reading back, and say with beeping sounds the readed bits, low sound for 0 high sound for 1.
With this method you get confirmed the machine is least partialy working. And if you detected which bit is bad then know which memory IC is needed to replaced.
This test not use CALL instructions, only run in the ROM.

The BEEP test is started immediately if you put the EPROM to the motherboard ROM socket, using as test EPROM.
If you use on the normal place (the full EXOS 2.4 or the standalone version in the cartridge at the 04h segment), the BEEP test can be forced by pressing down the B key at power up.
And normaly before testing start the system segment (using CALL instructions), test the first byte with all 00-FFh values, if error detected then the BEEP test started.

One additional experience: I found few defective Z80 cpus in dead EPs which is cannot write memory correctly.

Offline Bagpuss22

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Re: EP64 will not boot.
« Reply #2 on: 2012.September.05. 09:52:40 »
Zozo,

Thanks for the reply.

I am sure we changed the memory on this board some time ago, so not sure what
is going on.

What size PROM does this EXOS 2.4 require? Not done this before, think we have a
programmer here at work.  :???:

Going to order a new keyboard membrane and maybe pick up a new Z80 this week.

Russ

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Re: EP64 will not boot.
« Reply #3 on: 2012.September.05. 09:58:55 »
What size PROM does this EXOS 2.4 require?
It is a 64K (27C512). For using this need a connect new address line, A15, from the expansion port B9 pin.
(The BASIC is included, then no cartridge needed.)

The standalone memory test part, can be used in the cartridge. It is a 16K (27C128), or practicaly also add the BASIC ROM, then the total is a 32K (27C256).

Offline Bagpuss22

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Re: EP64 will not boot.
« Reply #4 on: 2012.September.05. 11:07:28 »
A couple of times this EP64 DID boot for a short while.

Got the "Enterprise" logo up and was able to get into basic.

This did return a good memory size, BUT after a couple of keyboard
presses it froze and died.

I am hoping this is a easy fix and not one of the more obscure
IC's like Nick or Dave  :(


Russ

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Re: EP64 will not boot.
« Reply #5 on: 2012.September.05. 11:28:01 »
If you made the new test EPROM, and if you get picture then try the Advanced test (pressing A at power up or pressing C+A when pressing Reset), it is more accurate then the original EXOS RAM test.
When all segments tested it is waiting for key press. This is for Refresh testing, you wait few minutes before pressing key, then it is will check again the previously writed pseudo random patterns.

I think it is about 99% the problem with the memory or the CPU.

Offline Bagpuss22

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Re: EP64 will not boot.
« Reply #6 on: 2012.September.06. 16:11:40 »
OK,

Decided to order all the parts, just in case I need them and get spares as well.  :ds_icon_cheesygrin:

So.....

2 x EEPROM's ordered.  Once I get them I will put EXOS 2.4 Beta on them ready for testing.

4 x Z80 CPU ordered.  Thought I would get them as they were cheap. Just incase!  :|

4164 question though.  I have sourced a place with MCM4164BP15 Ram which is fairly cheap.
Are these good enough?  I have not checked the spec of the 4164's that are already there,
If they are I might get some and spares too.

Thanks

Russ

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Re: EP64 will not boot.
« Reply #7 on: 2012.September.06. 21:17:18 »
Are these good enough?  I have not checked the spec of the 4164's that are already there,
It is good, 150ns.
150,200,300ns IC-s built in the EP machines. If you want to make 6 or 7.12Mhz turbo then the 150ns is recommended :-)

Offline Bagpuss22

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Re: EP64 will not boot.
« Reply #8 on: 2012.September.12. 01:34:56 »
EEPROMS arrived today, will blank them tomorrow and try and program them by the weekend.

Hopefully we can then start to look at getting my EP64 working again.

Yay!

Offline Bagpuss22

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Re: EP64 will not boot.
« Reply #9 on: 2012.September.17. 21:21:42 »
Starting to get a little confused!

I powered it up with EXOS 2.0 and for the first couple of times it was OK
but I glimpsed a memory error (tv had box in the way)!  :?: :?: :?:

After it has been on a few times, then it seems to stop working! :shock:

I put the EXOS 2.4 Beta 2 in and this has no effect, that is assuming I have
programmed them correctly  :oops:

I checked the voltages.

PSU output +13v, +10.5 under load.

+5A is running at +4.90
+5B is running at +5.07
+12 is running at  +11.72

Well this is testing part 1!  Need to try and find out if I have programmed the
EPROM correctly....

Russ
« Last Edit: 2012.September.17. 21:33:35 by Bagpuss22 »

Online Zozosoft

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Re: EP64 will not boot.
« Reply #10 on: 2012.September.18. 09:30:38 »
I put the EXOS 2.4 Beta 2 in and this has no effect, that is assuming I have
programmed them correctly  :oops:
But it is started when the machine working?
Try to press B key at power on it is forced the BEEP test mode.

Offline Bagpuss22

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Re: EP64 will not boot.
« Reply #11 on: 2012.September.18. 11:54:32 »
looks like eprom not programmed correctly as it did not
work in my working ep128.

Try and get it reprogrammed soon

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Re: EP64 will not boot.
« Reply #12 on: 2012.September.18. 12:08:16 »
Which IC used and which ROM file?

Offline Bagpuss22

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Re: EP64 will not boot.
« Reply #13 on: 2012.September.20. 11:04:23 »
I am using ATMEL 27C512R IC's and file EXOS24UK.ROM  ;-)

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Re: EP64 will not boot.
« Reply #14 on: 2012.September.20. 11:44:00 »
I am using ATMEL 27C512R IC's and file EXOS24UK.ROM  ;-)
Both is good.

Now needed to find the correct programing method :-)