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-   -   amiga 1200 cold start video problem (http://eab.abime.net/showthread.php?t=99922)

C_K_A 06 December 2019 09:36

amiga 1200 cold start video problem
 
3 Attachment(s)
Hello.
My English is not very good. So I used GoogleTranslate. I apologize in advance for the mistakes.


I have a strange video problem on my amiga 1200 computer. Motherboard model 2b

When the workbench screen arrives during a cold start, the image disappears.

I tried it by starting the amigatestkit with gotek driver. The same thing happened in the video test section.

The computer can be restarted with a reset when the video signal is absent. After a few reset attempts, everything returns to normal.

Hardware connected to the computer, aca1233n, compact flash hard drive and gotek drive.

The Amiga 1200 has recently been refurbished. New capacitors installed.

This problem has been repeated before. At that time, I carefully cleaned the motherboard with isopropyl alcohol, the problem had disappeared.
(there is dust and solder paste on the motherboard)

I'm gonna clean it up again, there may be points I missed.

What should I do if this doesn't work?

I think this fault is a capacitor problem, but I don't know which one.


I am using amiga with os3.9 bb4.
The power supply I use is meanwell RT65B.
You can also watch the youtube video below.
https://www.youtube.com/watch?v=koLF7A7LKSA

solarmon 06 December 2019 09:57

Does the same issue happen without the ACA1233n connected?

It could be a timing issue with the ACA1233n:

http://wiki.icomp.de/wiki/ACA1233n

Quote:

the ACA1233n features a new A1200 motherboard interface. Some A1200 main boards have been delivered with the wrong timing components and require modification for reliable use with accelerators (A1200 capacitors E123C and E125C may need to be removed). With the new improved interface, the ACA1233n is less likely to require these board patches. Although this has been tested extensively, timing patches may still be required.
I had a similar stability issue (but not with an ACA1233n) and I had to remove E123C and E125C on my A1200 rev 2B to resolve the issue:

http://eab.abime.net/showthread.php?t=98149

C_K_A 06 December 2019 10:27

Quote:

Originally Posted by solarmon (Post 1363483)
Does the same issue happen without the ACA1233n connected?

It could be a timing issue with the ACA1233n:

http://wiki.icomp.de/wiki/ACA1233n



I had a similar stability issue (but not with an ACA1233n) and I had to remove E123C and E125C on my A1200 rev 2B to resolve the issue:

http://eab.abime.net/showthread.php?t=98149


Yeah, I forgot to write. I dismantled e123 and e125.

solarmon 06 December 2019 10:36

Oh, OK.

Has the expansion connector pins (connecting to the ACA1233n) on the motherboard been cleaned?

Does the same issue happen without the ACA1233n connected?

C_K_A 06 December 2019 11:02

The contacts you mentioned are pretty clean. I had suspected it before and I had cleaned it with pencil eraser and ipa.

I took the Aca1233n card and tried it. There was no problem.
I re-inserted the card and the amigatestkit video test again resulted in a black screen.

Thank you. I think there's something wrong with the card, or the incompatibility is still going on.

solarmon 06 December 2019 11:24

The picture you have of the card seem seems show the soldering of the pins is not that great.

Please could you provide better photos of the card so that we can see the state of it.

C_K_A 06 December 2019 11:50

4 Attachment(s)
I tried to take a detailed photo of the card.

solarmon 06 December 2019 11:59

Might just be the lighting and shadows, but the soldering on the under side of the board does not look good at all. I would try to clean that up and make sure that there are no shorts and cold joints.

utri007 06 December 2019 12:05

General rule is, if you have weird problems, first thing to check is PSU. I think it doesn't offer enough juice?

Would it be that you need a new PSU?

C_K_A 06 December 2019 12:10

Quote:

Originally Posted by utri007 (Post 1363506)
General rule is, if you have weird problems, first thing to check is PSU. I think it doesn't offer enough juice?

Would it be that you need a new PSU?

I have another psu. But it also meanwell RQ65

I'm gonna try with that power supply.

solarmon 06 December 2019 12:16

Both Meanwell RT-65B and RQ-65 are both rated at 5A for the 5V supply. So both should be OK.

However, do check if there is any ripple or fluctuations in your AC power source.

solarmon 06 December 2019 12:19

Also, make sure you have the latest MMU libraries installed:

http://wiki.icomp.de/wiki/ACA1233n#Download

Daedalus 06 December 2019 14:20

A common issue with newer expansions on the A1200 is the connector not being 100% positive with its positioning. Try move it 1-2mm out again, but straight. It helps with a lot of boards that otherwise don't start.

C_K_A 08 December 2019 22:30

1 Attachment(s)
Hello again,
I've examined it because you suspect the PSU.
I found a problem with the potentiometer used to separate the 5v current in the Meanwell power supply.

pressure on it gave random voltages. Usually 5v and under was going. I cleaned it with contact spray. I set 5V to 5.07v. I tested it like this for two days. For now, my problems have disappeared. I will continue to investigate again until it appears again.

Thanks for your help.


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