Ricoh RTC diode in Amiga 4000

8bitbubsy · 06 May 2012, 09:58

Some of you might have seen this big 1N5817 diode connected from the VCC pin on the RTC to an SMD component on many Amiga 4000 motherboards -- any idea what this fix really does? My rev B Amiga 4000 mobo never had this one, and I was wondering if I should install this diode myself...

Here's a picture of what I mean:

FOL · 06 May 2012, 11:19

Quote:

Originally Posted by 8bitbubsy

Some of you might have seen this big 1N4001 diode connected from the VCC pin on the RTC to an SMD component on many Amiga 4000 motherboards -- any idea what this fix really does? My rev B Amiga 4000 mobo never had this one, and I was wondering if I should install this diode myself...

Here's a picture of what I mean:

I cant remember what it fixed but it does fix something. Have'nt done one for a while now, hence I cant remember what it fixes.

I think it was a fix to stop a boot related problem.

8bitbubsy · 14 March 2013, 11:40

Bumping this thread.. Can someone with an A4000D (which has this diode) check what diode type it really is? The number starting with 1N. I'm not sure if it was a 1N5817 after all...

Turran · 14 March 2013, 12:32

Dont know if this helps:

@28/05/10
Very strange problems may create a defective Ricoh 5C01 real time clock IC, as red screen, yellow screen, or not boot at all.
Also recently encountered a very strange problem was as follows.
In an A4000 who boot normaly from cold start and work perfect, if someone push off and on again the mains switch, has as result a dark grey screen. After two minutes with the machine OFF, when the restart all work perfect again!!! This was repeated.

The problem was the Ricoh ic. For some reason degrade its suply voltage from +5v, to 1.77v!!!! This was happened only if someone shut and then restart the machine from a previews working condition.

At first I think cause the ic was defective, but later discover cause in some pcbs, must add a 1N4001 diode from D178, to Ricoh ic at pin 20. The cathode of diode must connect at pin 20 of ic.

Source: http://www.amibay.com/showthread.php?t=6896

8bitbubsy · 14 March 2013, 13:22

Thanks!

Anyways LOL I just noticed something... On all Amiga 4000D's, the L and R label is wrong... It should say R and L, but instead it's swapped.

Turran · 14 March 2013, 13:29

Same with mine and another one I know of =) Labels are correct, color is not.

pandy71 · 14 March 2013, 18:49

Quote:

Originally Posted by 8bitbubsy

Bumping this thread.. Can someone with an A4000D (which has this diode) check what diode type it really is? The number starting with 1N. I'm not sure if it was a 1N5817 after all...

Check reverse current for 1N5817 - it doesn't look good - IMHO this can't be Schottky as reverse current in Schottky diode is to high.

nobodyii · 15 March 2013, 09:54

The diode is in original state 1N5817.

pandy71 · 15 March 2013, 16:00

reverse current for this diode is around 1mA - battery can be drained quite fast...

Jope · 17 March 2013, 08:50

Quote:

Originally Posted by Turran

Same with mine and another one I know of =) Labels are correct, color is not.

Just about all of them have the colours reversed. As a result I remember having a big arguement as a kid with an a4000 owning friend regarding whether red is right or not. :-D

06 May 2012, 09:58	#1
8bitbubsy ProTracker Nerd Join Date: Sep 2009 Location: Norway Age: 23 Posts: 1,123	Ricoh RTC diode in Amiga 4000 Some of you might have seen this big 1N5817 diode connected from the VCC pin on the RTC to an SMD component on many Amiga 4000 motherboards -- any idea what this fix really does? My rev B Amiga 4000 mobo never had this one, and I was wondering if I should install this diode myself... Here's a picture of what I mean: __________________ Amiga 4000 rev B [040 25MHz - 16MB fast RAM - 2MB chip RAM - kick 3.1 - Picasso IV] Amiga 2000 rev 4.2 [030 25MHz - 8MB fast RAM - 2MB chip RAM - kick 3.1 - Picasso II] Amiga 1200 rev 2B [030 50MHz - 16MB fast RAM - 2MB chip RAM - kick 3.1] Last edited by 8bitbubsy; 14 December 2012 at 17:43.

14 March 2013, 11:40	#3
8bitbubsy ProTracker Nerd Join Date: Sep 2009 Location: Norway Age: 23 Posts: 1,123	Bumping this thread.. Can someone with an A4000D (which has this diode) check what diode type it really is? The number starting with 1N. I'm not sure if it was a 1N5817 after all... __________________ Amiga 4000 rev B [040 25MHz - 16MB fast RAM - 2MB chip RAM - kick 3.1 - Picasso IV] Amiga 2000 rev 4.2 [030 25MHz - 8MB fast RAM - 2MB chip RAM - kick 3.1 - Picasso II] Amiga 1200 rev 2B [030 50MHz - 16MB fast RAM - 2MB chip RAM - kick 3.1]

14 March 2013, 12:32	#4
Turran Registered User Join Date: May 2012 Location: Stockholm / Sweden Age: 38 Posts: 341	Dont know if this helps: @28/05/10 Very strange problems may create a defective Ricoh 5C01 real time clock IC, as red screen, yellow screen, or not boot at all. Also recently encountered a very strange problem was as follows. In an A4000 who boot normaly from cold start and work perfect, if someone push off and on again the mains switch, has as result a dark grey screen. After two minutes with the machine OFF, when the restart all work perfect again!!! This was repeated. The problem was the Ricoh ic. For some reason degrade its suply voltage from +5v, to 1.77v!!!! This was happened only if someone shut and then restart the machine from a previews working condition. At first I think cause the ic was defective, but later discover cause in some pcbs, must add a 1N4001 diode from D178, to Ricoh ic at pin 20. The cathode of diode must connect at pin 20 of ic. Source: http://www.amibay.com/showthread.php?t=6896 Last edited by Turran; 14 March 2013 at 12:38.

14 March 2013, 13:22	#5
8bitbubsy ProTracker Nerd Join Date: Sep 2009 Location: Norway Age: 23 Posts: 1,123	Thanks! Anyways LOL I just noticed something... On all Amiga 4000D's, the L and R label is wrong... It should say R and L, but instead it's swapped. __________________ Amiga 4000 rev B [040 25MHz - 16MB fast RAM - 2MB chip RAM - kick 3.1 - Picasso IV] Amiga 2000 rev 4.2 [030 25MHz - 8MB fast RAM - 2MB chip RAM - kick 3.1 - Picasso II] Amiga 1200 rev 2B [030 50MHz - 16MB fast RAM - 2MB chip RAM - kick 3.1]

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14 March 2013, 13:29	#6
Turran Registered User Join Date: May 2012 Location: Stockholm / Sweden Age: 38 Posts: 341	Same with mine and another one I know of =) Labels are correct, color is not.

15 March 2013, 09:54	#8
nobodyii Registered User Join Date: Jun 2010 Location: Germany Posts: 18	The diode is in original state 1N5817.

15 March 2013, 16:00	#9
pandy71 Registered User Join Date: Jun 2010 Location: NL/PL Posts: 498	reverse current for this diode is around 1mA - battery can be drained quite fast...

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