Enterprise Forever
:UK => Hardware => Topic started by: Wolfgang on 2020.September.16. 11:49:54
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In both my EP64s C9 is oriented like this(minus to the left): https://www.nightfallcrew.com/gallery/enterprise-128-one-two-eight-boxed/IMG_5573.jpg
According to the schematics, the orientation of C9 should be like this (minus to the right):
https://enterpriseforever.com/hardware/ep-repair-service-)-help-with-egyptian-ep64-no-video-outputnot-strating/?action=dlattach;attach=25401;image
Why are they different?
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I am not the better knowledge source about electronics, but observing the schematics (http://enterprise.iko.hu/schematics/EP64-1~0.jpg)
[attachimg=1]
and this closer picture (https://wiki.enterpriseforever.com/images/6/60/EPprepared.jpg) without the components(thanks to Pear),
[attachimg=2]
I see the right pin of C9 tied to the central pin of U21, Ground, so the capacitor minus pin should go also to the right.
Strange to find this assembly error after so much years.
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Hmmm. Interesting. When I did my recap Ioriented my new C9 as it was on the board. + to the right. So I have the same layout as Wolfgang.
Here are the old (https://www.dropbox.com/s/7ay3ncm7e29yspz/C9%20-%20old.jpeg?dl=0). And here the new (https://www.dropbox.com/s/4sgao8okhux8qja/C9%20-%20new.jpg?dl=0).
Not to hijack the thread but maybe this error is causing my noise (https://enterpriseforever.com/hardware/noise-on-rgb-signal-suggestions/). If it is an error, that is!
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Hmmm. Interesting. When I did my recap Ioriented my new C9 as it was on the board. + to the right. So I have the same layout as Wolfgang.
Here are the old (https://www.dropbox.com/s/7ay3ncm7e29yspz/C9%20-%20old.jpeg?dl=0). And here the new (https://www.dropbox.com/s/4sgao8okhux8qja/C9%20-%20new.jpg?dl=0).
Not to hijack the thread but maybe this error is causing my noise (https://enterpriseforever.com/hardware/noise-on-rgb-signal-suggestions/). If it is an error, that is!
I actually turned the new C9 around, since it seems the correct orientation to me.
No real difference to see (yet), at least no smoke and interesting smells.:razz:
Btw., no reason to apologize, I am in the same boat. I also got an Egyptian EP and I am trying to get it up to speed. So far, I upgraded the ROM to EXOS2.4 and built my memory expansion. Now, I am fighting the missing color of the RF signal.:smt017
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Hmmm. Interesting. When I did my recap Ioriented my new C9 as it was on the board. + to the right. So I have the same layout as Wolfgang.
Here are the old (https://www.dropbox.com/s/7ay3ncm7e29yspz/C9%20-%20old.jpeg?dl=0). And here the new (https://www.dropbox.com/s/4sgao8okhux8qja/C9%20-%20new.jpg?dl=0).
Not to hijack the thread but maybe this error is causing my noise (https://enterpriseforever.com/hardware/noise-on-rgb-signal-suggestions/). If it is an error, that is!
Despite appearances, this is good orientation...
[attach=1]
[attach=2]
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Despite appearances, this is good orientation...
(Attachment Link)
(Attachment Link)
Ok. So the way it is mounted originally is the right way - despite what the schematics say? :)
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Ok. So the way it is mounted originally is the right way - despite what the schematics say? :)
ZoZo wrote here on the forum about this long ago what is the reason ...:smt017
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I don't think that the schematics are wrong.
In fact the capacitor in this image
(https://enterpriseforever.com/index.php?action=dlattach;topic=1832.0;attach=25466;image)
is strange. The - arrows point in the direction of the narrowing, opposite to the usual way. Since the visible right side of C9 seems to be metal, I would assume that this is the GND side.
To sum it up, I think
- the right side should be minus
- the arrow on the capacitor in the image above is wrong
- the capacitor in the image above is mounted correctly (+ left / - right)
- the silk screen on the pcb seems to be wrong
I am not an electronics expert, so please convince me that I am wrong.:)
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This is the same motherboard with the original capacitors ... The + seems to be pointing to the right...and so on all the EP motherboards I have seen
[attach=1]
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I think that Judge could be right.... and the schematic wrong.... if there is negative voltage at the left side, GND is positive.
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We are waiting for ZozoSoft.. once he told me why this is so ... :)
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We are waiting for ZozoSoft.. once he told me why this is so ... :)
I'm quivering with anticipation, waiting for his reply! ;)
I did a search on forum, looking for all references to "C9", but it didn't turn up any satisfactory explanation.
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Look at the sign on the planting scheme...
[attach=1]
[attach=2]
[attach=3]
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I'm quivering with anticipation, waiting for his reply! ;)
I did a search on forum, looking for all references to "C9", but it didn't turn up any satisfactory explanation.
Same here. :)
All available (different) schematics show the same direction.
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I can confirm that the PCB markings are correct.
On a working EP, with the ground clip of an oscilloscope probe connected to the right side of C2 (0V) and the tip connected to the left side of C2, there is approx -1v across the capacitor ie. the right side is more positive than the left side. Except for a few ms at powerup :oops: which might explain why C2 is a common failure.
[attach=1]
Here purple is 12V, blue is 5V and yellow is across C2, at power on (note different v/div for each channel.)
I was looking at power on because I thought the purpose of C2 might be to delay 12V coming up so that 5V comes up first. But here you can see that the 12V trace reaches 9V almost immediately and then goes to 12v ~3ms later, so I'm still not 100% sure! :lol:
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I would suggest looking at the waveform on an oscilloscope by inserting bipolar (https://www.google.com/search?q=bipolar+capacitor&tbm=isch&source=iu&ictx=1&fir=vK-9RHXRt3TCTM%252CALQlwcup1vA5LM%252C_&vet=1&usg=AI4_-kT_YariNkNI16KUFKOxy7FZwN0UoQ&sa=X&ved=2ahUKEwiwq6XnnfPrAhWms4sKHSnzD0YQ9QF6BAgKEEo) capacitance. Maybe it would be closer to the answer.
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On a working EP, with the ground clip of an oscilloscope probe connected to the right side of C2 (0V) and the tip connected to the left side of C2, there is approx -1v across the capacitor ie. the right side is more positive than the left side. Except for a few ms at powerup :oops: which might explain why C2 is a common failure.
Thank you for running this test ... and I assume that you really mean C9 and not C2! :)
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... and I assume that you really mean C9 and not C2! :)
:lol: yes indeed! :oops: I had TR2 in my brain... C9 & TR2 - must be the most common EP failure! :roll:
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I can confirm that the PCB markings are correct.
On a working EP, with the ground clip of an oscilloscope probe connected to the right side of C2 (0V) and the tip connected to the left side of C2, there is approx -1v across the capacitor ie. the right side is more positive than the left side.
Thanks for do it!
I remember somewhere IstvanV talked about this negative voltage.
Except for a few ms at powerup
This is the explanation why this circuit usually break at power on.
Few time I see: computer running, power off (insert another cartridge or something), power on: broken running screen (no 12V symptom).
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As Allf points out: these days you can get large-value bipolar capacitors. I don't think you could in the 1980s when the EP was designed!
I broke my EP getting the 'scope trace above :oops: so I will try and get a bipolar and give it a go when I fix it. (Between power-ons, I noticed that C9 held its charge for a long time. So I discharged it before getting a 'scope trace. Unfortunately one time (the last time :lol:) I discharged C9 while the EP was still switched on :oops: resulting in the usual TR2 problem!)
If you google "joule thief" you will get a lot more information on how this circuit works. But I could not find any other examples with the TR3/C9/R15/R16 additions - I think they are an "EP special".
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If you google "joule thief" you will get a lot more information on how this circuit works. But I could not find any other examples with the TR3/C9/R15/R16 additions - I think they are an "EP special".
ZX Spectrum internal circuit looks something similar (just it is also have a negative voltage for 4116 chips, until the 128K version).
It is have a lot of problems, then lot of component changes during the motherboard versions:
ISSUE 2:
[attach=1]
ISSUE 3:
[attach=2]
ISSUE 3B:
[attach=3]
ISSUE 4A/B:
[attach=4]
ISSUE 5:
[attach=5]
ISSUE 6:
[attach=6]
Spectrum 128K:
[attach=7]
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So, by using a bipolar capacitor we can improve the situation?
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So, by using a bipolar capacitor we can improve the situation?
It is possible a bipolar capacitor would make the circuit more reliable... but not yet tried!
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It is possible a bipolar capacitor would make the circuit more reliable... but not yet tried!
I look forward to hearing your results!
I can see that Nichicon makes a 100uf 10V bi-polar electrolytic (6.3mm x 12.5mm), part number UVP1A101MED ... but it is radial and not axial. Is there room for a radial capacitor in the C9 location?
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The radial ones seem to be a bit big so I have a radial one on order, but it has not arrived yet. (I wonder if the bipolars are just two normal capacitors internally, wired + to -.)
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I look forward to hearing your results!
I can see that Nichicon makes a 100uf 10V bi-polar electrolytic (6.3mm x 12.5mm), part number UVP1A101MED ... but it is radial and not axial. Is there room for a radial capacitor in the C9 location?
The radial capacitor can also be perfectly soldered. It must be laid.
Sorry for the Google translation... :oops:
[attach=1]
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The radial ones seem to be a bit big so I have a radial one on order, but it has not arrived yet. (I wonder if the bipolars are just two normal capacitors internally, wired + to -.)
Oops sorry typo - it is the axial ones that seemed big, so I have radial ones on order, even though the PCB is for axial. The voltage rating makes a difference to the size (as well as uF of course), the original is 100uF 6.3v but I could not find a 100uF 6.3v bipolar axial, only radial. I will find out if they can be made to fit when they arrive!
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...the original is 100uF 6.3v but I could not find a 100uF 6.3v bipolar axial...
Sorry, but the original is 100uF 10v ... 6.3v in the schematic drawing, but 100uF 10v in reality.
[attach=1]
I ordered these. If you solder it horizontally, I think they will be appropriate ... Size(mm) L 16 x D 10
[attach=2]
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Sorry, but the original is 100uF 10v ...
Thanks. On my EP it was 6.3V, but of course these are prone to failure and might have been replaced in the past, so it might not have been the original original! :lol:
Now I see your picture, I remember it was black not blue :???:
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I can see that Nichicon makes a 100uf 10V bi-polar electrolytic (6.3mm x 12.5mm), part number UVP1A101MED.
I looked again, and I don't think that the UVP1A101MED capacitor would be a good choice because it has a high-ESR ... whoops! :oops:
I ordered these. If you solder it horizontally, I think they will be appropriate ... Size(mm) L 16 x D 10
(https://enterpriseforever.com/index.php?action=dlattach;topic=1832.0;attach=25541;image)
Thanks for posting that picture, the Nichicon MUSE series that you found (the UES part numbers) seems like it should be a great choice, even though they are a bit larger than the original Philips capacitor.
I look forward to hearing if you have any problems with physically fitting the new capacitor in that location.
For anyone whose distributor carries them, alternatives in the same Nichicon MUSE series are ...
UES0J101MPM 100uF 6.3V, 8.9mm x 11.5mm
UES1A101MPM 100uF 10.0V, 10.0mm x 12.5mm
UES1E101MPM 100uF 25.0V, 10.0mm x 16.0mm
Thanks. On my EP it was 6.3V, but of course these are prone to failure and might have been replaced in the past, so it might not have been the original original! :lol:
Well, the motherboard schematics do show a 6.3V rating for the 100uF C9 capacitor, and from the voltage readings that you took, a 6.3V capacitor *should* be fine (with my limited understanding of safety margins).
Now the 100uF capacitors at C11 and C12 are there to help smooth out the +5V power supply lines, and if you apply the normal x2 safety-factor for those, then I can understand why 10V capacitors were used for C11 and C12 instead of the 6.3V capacitors on the schematic.
Then from an ease-of-manufacturing standpoint, if they were buying 10V capacitors for C11 and C12, they would just use the same 10V capacitor for C9, even if it didn't need that rating.
I guess that we won't really know for sure until someone is brave enough to try a 6.3V bi-polar for C9! ;)
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I found it here... (https://www.ebay.com/itm/2-10pcs-NEW-Nichicon-MUSE-BP-ES-Bi-Non-Polar-Bipolar-Hi-Fi-Capacitors-4-7-100uF/321588547877?ssPageName=STRK%3AMEBIDX%3AIT&var=510472180382&_trksid=p2060353.m2749.l2649)
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I found it here... (https://www.ebay.com/itm/2-10pcs-NEW-Nichicon-MUSE-BP-ES-Bi-Non-Polar-Bipolar-Hi-Fi-Capacitors-4-7-100uF/321588547877?ssPageName=STRK%3AMEBIDX%3AIT&var=510472180382&_trksid=p2060353.m2749.l2649)
Cool, eBay to the rescue! ;)
It looks like you can get the smaller voltage ones here (https://www.ebay.com/itm/Nichicon-UES-Bi-Polarized-Bipolar-MUSE-6-3V-50V-1uF-1000uF-Audio-Capacitors/183247490013).
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It looks like you can get the smaller voltage ones here (https://www.ebay.com/itm/Nichicon-UES-Bi-Polarized-Bipolar-MUSE-6-3V-50V-1uF-1000uF-Audio-Capacitors/183247490013).
Damn it! :evil: I didn't find this. It doesn't matter now. Thanks! :lol:
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I ordered these from eBay UK: https://www.ebay.co.uk/itm/Nichicon-UEP-EP-6-3V-100V-0-47uF-6800uF-Bi-Polarized-Bipolar-105-C-Capacitors/183792363878 (https://www.ebay.co.uk/itm/Nichicon-UEP-EP-6-3V-100V-0-47uF-6800uF-Bi-Polarized-Bipolar-105-C-Capacitors/183792363878). By coincidence this is the same make as all the other electrolytics in my EP, so they match :mrgreen::lol:. (I don't have the blue sort, but they look original, the solder joints look un-disturbed. :?: Also TR2 looked original.)
Anyway it is working fine. No difference that I could see on the start-up oscilloscope traces that I posted before.
It was easy to fit the radial capacitor in the same space as the original axial capacitor:
[attach=1] [attach=2]
I don't know if this has fixed the C9 / TR2 weak point, but I have turned mine off and on 50 times and it is still working!
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It was easy to fit the radial capacitor in the same space as the original axial capacitor:
Yes! I did the same. On this motherboard, all capacitors are originally radial.
[attach=1]
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Thanks. On my EP it was 6.3V, but of course these are prone to failure and might have been replaced in the past, so it might not have been the original original! :lol:
FYI, I finally opened up my EP64, serial #71370 (so fairly late manufacture), and it also uses 6.3V 100uF capacitors for C9, C11 and C12.
In this case they are all old-style axial, and Unicon brand (another decent-quality Japanese manufacturer).
That is on an issue 4 motherboard, which unfortunately has 300ns video RAM, so I presumably won't be able to change to a 6MHz clock unless I replace those. :(
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That is on an issue 4 motherboard, which unfortunately has 300ns video RAM, so I presumably won't be able to change to a 6MHz clock unless I replace those. :(
Often chips are faster than the official rating, so you might be lucky.
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Hello Elmer.
About serial numbers, I don't know if you have took a look to the inventory of machines from Zozo's page (http://enterprise.iko.hu/inventory.htm).
On it you can observe how the EP64 numerations are different from the EP128 ones. You also can see how there are very big gaps on the EP64 list.
EP64 numbers 2000~30000, probably all expanded to 128KB by the Enterprise company, that could explain why there are so many issue 4 and 5 PCBs mixed with issue 6 ones, the usual on the 128KB EP.(There are also some issue 6 EP64s, probably refurbished in Germany and then sold to the Egypt dealer).
EP64 numbers 40000~70000...., I have a theory for this gap... at that time they were selling less Enterprise units than expected and, incrementing artificially the serials, then could give to the public impression that they had manufactured a huge amount.
I think that they restarted the serial count for the EP128 model, now lineal, the first units being mounted with the rest of old issue 4 and 5 PCBs with the defective Nick(mine for example), and then all the rest issue 6 PCBs with the improved Nick.
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This is a bit of topic but what is the difference between the different issues?
And I can confirm that the Egyptian EP64's are issue 6. At least my Egyptian EP64 is issue 6 :)
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This is a bit of topic but what is the difference between the different issues?
And I can confirm that the Egyptian EP64's are issue 6. At least my Egyptian EP64 is issue 6 :)
You are lucky then. My three EPs from Egypt are all issue 4 with the problematic NICK :(
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Zozo can say all about that.
What I have read from him is that ALL EP PCBs share the same circuit layout, with minor differences on the "fingers" of the EDGE connectors.
(https://enterpriseforever.com/index.php?action=dlattach;topic=148.0;attach=3618;image)
Starting from bottom, issue 3, 4 and 5 on the middle, and 6 the upper one.
The Issue 3 EDGE fingers were totally wrong, with excessive width, prone to cause short-circuits if not correctly aligned with the female connector . A bigger gap was added on issues 4 and 5 to fix that, and on issue 6 some of the unused pins of the Video connector were populated and gained a solder point, the planed use unknown.
There are also some differences on the custom chips mounted. Issue 3 were test EP64s fitted with Korean made Nick and Dave, first batches of chips that turned out to be malfunctioning, needing an external PCB to correct the behaviour. There are very few of these, almost all distributed to developers, not to open public.
Issues 4 and 5 mount the first batches of Austrian made custom chips, but it happened that the advanced designs were years ahead of the contemporary manufacturing techniques, and then the new Nick also didn't worked as intended. It showed bad colours on some intensive screen modes(and probably bad external colour input), some units worse than others. The cooper heat sink over Nick was then added to minimize the failure, worse on high temperature.
The new fixed Nick was introduced with the Issue 6 PCBs or a little earlier on last Issue 5.
There are other curiosities about the Enterprise PCBs, the most evident is the black lead from the Z80 to the cartridge port that can be seen on the upper side... the same cooper track already exist on the PCB, but cut on two places(on all EPs), a modification probably made to fix some insidious signal interference.
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ISSUE 3 only the first 100 non final machine which are sent to the developers and magazines. (Marked as "Not for resale")
These are not have a internal speaker circuit on the board, it is on a additional piggyback pcb.
Using Made in Korea Nick, which are very faulty.
ISSUE 4 board are originaly at the early 64K machines. But! at this time many lot of manufacturing problems. Boards which are not passed the quality check, later are repaired, and putted back to the production line. Then randomly can found ISSUE 4 board at later EP64 and also at EP128 machines.
The main interesting point of ISSUE 4 boards: these are have a FLAN company, name which are only used for a short time.
R208 and C215 missing from the PCB, soldered in the air at the modulator. Two unused pins are missing from the monitor connector.
Using Made in Austria Nick, 08-04, which are much better than the Korean version, but still have a problems. Heat shink reduce the problem. Good idea check the heat shink, because the ~35 years glue start fall apart at many machines.
This ISSUE using the bad Philips capacitors
ISSUE 5 the most common at EP64 machines. Currently never see it at EP128.
It is have a Enterprise company name. R208 and C215 placed to the pcb. The two unused monitor pins still missing.
Also using 08-04 Nick. But using the better capacitos (I'm not sure about all ISSUE 5, but what I see used the good caps).
ISSUE 6 same with ISSUE 5, just the two unused pins putted back as spare at monitor connector.
This version used mostly at 128K machines, only few 64K machines (randomly) have it.
Possible both are 08-04 and 08-47 Nick chips. Not a 100%, but usually the dark green ones have a 08-04 and the light green have a 08-47, but exist a exceptions for a both. In a few ISSUE 6 EP64 I found a 08-47.
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It hasn’t left me calm for many years to see what the Issue 1 and 2 motherboards might have been like.
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If the Issue 3 were only 100... maybe these were the prototypes, no more than 10 or so.
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If the Issue 3 were only 100... maybe these were the prototypes, no more than 10 or so.
But we would have at least 1 photo of them... :-)
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Remember its first name: Damp Proof Course.
The first phases of development were strictly secret....
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Remember its first name: Damp Proof Course.
The first phases of development were strictly secret....
THEN. :-) But there could have been photos, recollections at the time that could be put together before being ISSUE3. But we don't know ...
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Not so long ago Tutus was honoured to ask Nick Toop (https://enterpriseforever.com/summaries-from-the-hungarian-topics/interview-with-nick-toop/msg78307/#msg78307) some questions.
On his answer he narrates how painfully was his exit from Enterprise Computers LTD:
".....when I was constructively forced out of the company was one of the saddest periods of my life and I do not like to think about it. I was also obliged to erase all personal copies of the design which is sad as I had various enhancements in mind and would love to be able to implement my design with these enhancements in a modern CPLD...."
This mean to me that all people involved on the project had such obligatory clause in their contracts.
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I replaced the C9 capacitor on my 64/128 motherboard with a bipolar one. Working perfectly.
[attach=1]
[attach=2]
[attach=3]
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I replaced the C9 capacitor on my 64/128 motherboard with a bipolar one. Working perfectly.
Excellent, that is great to see. :)
I am very jealous of that beautifully clean motherboard! ;)
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I replaced the C9 capacitor on my 64/128 motherboard with a bipolar one. Working perfectly.
The electronics supplier in Poland currently only has a voltage of 6v3 (at a reasonable price) in stock, which I do not want to order. What is the voltage at the poles of the bipolar capacitance?
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What is the voltage at the poles of the bipolar capacitance?
I put a 6.3v bipolar in my EP128, so far no problems. On an oscilloscope the voltages across it are exactly the same as with the original mono-polar (if that's the right word!) ie. goes briefly to 1V at power-up and then drops to a steady approx -1.25V - see my 'scope traces earlier in this discussion, I could observe no difference.
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Bruce was faster. :) I measure -1150mV at the poles. My capacitor is a Nichicon 100uF 25v.
The output 12V is only 11.95V ... but still the picture is very nice.
[attach=1]
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Thank you for your answers. I ordered 6V3 bipolar capacitors...
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I also replaced the C9 capacitor in my main machine with a bipolar one.
[attach=1]
The original capacitor was a Rubycon 100uF 10v, This capacitor is 99uF even after 35 years. The Japanese know something ... :smt023
[attach=2]
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The original capacitor was a Rubycon 100uF 10v, This capacitor is 99uF even after 35 years. The Japanese know something ...
Yes, I have never found problems with this type of capacitors.
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Huge thanks to Wolfgang for starting this thread and to everyone else for the comments. A while ago, when I repaired my Enterprise 12V, I was following the schematic diagram rather than the PCB markings and this thread explains why I kept blowing transitors!!! :cry:
It never occurred to me that the circuit diagram was wrong. I have now installed C9 with minus to the left. Fingers crossed this will work.
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Fingers crossed this will work.
There will be no danger, man!
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explains why I kept blowing transitors!!!
One note: rare fault, but if the L1 are broken then the TR2 will dead again, and again... (I about after 5 transistors found the problem at L1...)
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One note: rare fault, but if the L1 are broken then the TR2 will dead again, and again... (I about after 5 transistors found the problem at L1...)
Thanks for the tip. I wound a new L1 myself so hopefully that will be okay.