Welcome, Guest. Please login or register.


« previous next »
Pages: [1] 2 3 4   Go Down

Author Topic: Capacitors - wrong orientation? (Read 5026 times)

Offline Wolfgang

  • Beginner
  • *
  • Posts: 37
  • Country: de
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Firefox 80.0 Firefox 80.0
    • View Profile
Capacitors - wrong orientation?
« on: 2020.September.16. 11:49:54 »
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?
 
Logged

Online gflorez

  • EP addict
  • *
  • Posts: 3069
  • Country: es
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 80.0 Firefox 80.0
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #1 on: 2020.September.16. 12:52:21 »
I am not the better knowledge source about electronics, but observing the schematics



and this closer picture without the components(thanks to Pear),



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.
« Last Edit: 2020.September.16. 13:00:35 by gflorez »
Logged

Offline John Fante

  • EP fan
  • *
  • Posts: 140
  • Country: dk
  • OS:
  • Mac OS X 10.15.6 Mac OS X 10.15.6
  • Browser:
  • Chrome 85.0.4183.102 Chrome 85.0.4183.102
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #2 on: 2020.September.16. 17:51:13 »
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. And here the new.

Not to hijack the thread but maybe this error is causing my noise. If it is an error, that is!
Logged

Offline Wolfgang

  • Beginner
  • *
  • Posts: 37
  • Country: de
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Firefox 80.0 Firefox 80.0
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #3 on: 2020.September.16. 18:25:11 »
Quote from: John Fante on 2020.September.16. 17:51:13
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. And here the new.

Not to hijack the thread but maybe this error is causing my noise. 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
« Last Edit: 2020.September.16. 22:31:00 by Wolfgang »
Logged

Offline Judge

  • EP user
  • *
  • Posts: 389
  • Country: hu
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Chrome 85.0.4183.102 Chrome 85.0.4183.102
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #4 on: 2020.September.16. 19:26:05 »
Quote from: John Fante on 2020.September.16. 17:51:13
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. And here the new.

Not to hijack the thread but maybe this error is causing my noise. If it is an error, that is!

Despite appearances, this is good orientation...

25465-0

25467-1
Logged
Üdv.Judge

Offline John Fante

  • EP fan
  • *
  • Posts: 140
  • Country: dk
  • OS:
  • Mac OS X 10.15.6 Mac OS X 10.15.6
  • Browser:
  • Chrome 85.0.4183.102 Chrome 85.0.4183.102
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #5 on: 2020.September.16. 20:45:01 »
Quote from: Judge on 2020.September.16. 19:26:05
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? :)
Logged

Offline Judge

  • EP user
  • *
  • Posts: 389
  • Country: hu
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Chrome 85.0.4183.102 Chrome 85.0.4183.102
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #6 on: 2020.September.16. 22:16:29 »
Quote from: John Fante on 2020.September.16. 20:45:01
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
Logged
Üdv.Judge

Offline Wolfgang

  • Beginner
  • *
  • Posts: 37
  • Country: de
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Firefox 80.0 Firefox 80.0
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #7 on: 2020.September.16. 22:26:21 »
I don't think that the schematics are wrong.
In fact the capacitor in this  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.:)
Logged

Offline Judge

  • EP user
  • *
  • Posts: 389
  • Country: hu
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Chrome 85.0.4183.102 Chrome 85.0.4183.102
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #8 on: 2020.September.16. 23:06:31 »
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

25469-0
Logged
Üdv.Judge

Online gflorez

  • EP addict
  • *
  • Posts: 3069
  • Country: es
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 80.0 Firefox 80.0
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #9 on: 2020.September.16. 23:31:02 »
I think that Judge could be right.... and the schematic wrong.... if there is negative voltage at the left side, GND is positive.
« Last Edit: 2020.September.16. 23:44:16 by gflorez »
Logged

Offline Judge

  • EP user
  • *
  • Posts: 389
  • Country: hu
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Chrome 85.0.4183.102 Chrome 85.0.4183.102
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #10 on: 2020.September.17. 00:22:04 »
We are waiting for ZozoSoft.. once he told me why this is so ... :)
Logged
Üdv.Judge

Offline elmer

  • EP fan
  • *
  • Posts: 144
  • Country: us
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 80.0 Firefox 80.0
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #11 on: 2020.September.18. 05:02:35 »
Quote from: Judge on 2020.September.17. 00:22:04
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.
Logged

Offline Judge

  • EP user
  • *
  • Posts: 389
  • Country: hu
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Chrome 85.0.4183.102 Chrome 85.0.4183.102
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #12 on: 2020.September.18. 08:00:14 »
Look at the sign on the planting scheme...

25479-0

25481-1

25483-2
Logged
Üdv.Judge

Offline Wolfgang

  • Beginner
  • *
  • Posts: 37
  • Country: de
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Firefox 80.0 Firefox 80.0
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #13 on: 2020.September.18. 11:06:51 »
Quote from: elmer on 2020.September.18. 05:02:35
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.
Logged

Offline BruceTanner

  • EP lover
  • *
  • Posts: 550
  • Country: gb
  • OS:
  • Linux Linux
  • Browser:
  • Firefox 68.0 Firefox 68.0
    • View Profile
Re: Capacitors - wrong orientation?
« Reply #14 on: 2020.September.18. 17:01:26 »
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.

25485-0
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:
Logged
Pages: [1] 2 3 4   Go Up
« previous next »

SMF 2.0.15 | SMF © 2013, Simple Machines XHTMLRSS

Page created in 0.078 seconds with 39 queries.

Linode Follow ep4ever_news on Twitter