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Old 19 May 2018, 11:05   #1
jurassicman
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2 A600 motherboards with issues, need advice!

Hello,
I have 2 A600, both have been recapped but they still have an issue each.

The first one had problems with the audio as soon as I bought it. You could hear a bad noise in the background like a "scratching sound" after just a few seconds. Once recapped this noise disappeared but the audio is still "weird". I tested the 4 channels with a few tester tools (Kaf Sys Test and Amiga Test-E) and the first channel seems ok, the second and the third are lower and a bit "awkward" while the fourth is higher but still "weird". What could cause this?

The second had many issues, it has been literally saved from the bin, it needed a lot of work but it seemed to be ok at the end. Just recently, I tested mouse/joystick ports with a few port testers and I have noticed that both, port 1 and port 2 have the same issue. When you go UP with a Joystick it actually goes UP and LEFT. Using the mouse you can't notice this behavior. All the other directions and buttons work well, if you go left it goes left.

Please, any hints on what I can do? I'll probably have to send both the motherboard to a technician but, if possible, I would like to know earlier what are the causes of the problems.
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Old 19 May 2018, 12:57   #2
Chucky
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my guess is damage due to leaking caps. so recapper didn't do a check and repair??
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Old 19 May 2018, 15:28   #3
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Quote:
Originally Posted by Chucky View Post
my guess is damage due to leaking caps. so recapper didn't do a check and repair??
Yes, leaking caps could be a cause.
The motherboards have been recapped by two different technicians.

The one that repaired the A600 with sound issues told me that he found a broken track near the capacitors between the PSU plug and the PCMCIA slot and he rebuilt it but he didn't notice other broken tracks.

The other card needed much more work and I think that the technician that repaired (and recapped) it simply didn't notice the issue with the mouse/joystick ports. I can't even say if this issue happened just recently or if it was already present when I got the card repaired about six months ago since, as I said, the issue isn't noticeable when using a mouse...
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Old 21 May 2018, 11:11   #4
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Hello!

Does anyone have an idea about what to do in order to fix the issues I explained in my first post? Thanks in advance!
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Old 21 May 2018, 11:52   #5
MigaTech
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The motherboard with the audio issue could be down to failing op amps. If the cap replacement was done correctly then op amp is the next area of inspection.

Also if any traces have been damaged this could cause problems, on the -12v feed if it isn't getting correct voltage, specially on A1200, then the audio sound output is distorted. Is the PSU you are using good?

As for the second motherboard, have you checked for dry joints on those ports? It maybe just something simple like reflow of pin contact to logic board.
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Old 21 May 2018, 13:22   #6
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@MigaTech

Thanks mate, your hints are really precious.
I'll ask the technician that recapped the motherboard with audio issues if he can inspect both the cards, as per the PSU I'm pretty sure that it's more than fine since I'm using a 500W PC Power Supply converted to Amiga but I'll do the same tests with another PSU just to be sure.
Thanks again for your help!
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Old 22 June 2018, 20:23   #7
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I've just found out that the A600 mainboard with the joystick/mouse port issue works perfectly with a standard, not recapped, Commodore PSU (to be more precise a Black PSU with 3A in the +5V, 500mA in the +12V and 100mA in the -12V).

With two different PC converted PSUs (one with 5A in the +5V, 2.5A in the +12V and 0.5A in the -12V, the other, a Vultech GS-500M 500W PSU with 16A in the +5V, 10A in the +12V and 0.5A in the -12V) I have the UP = UP+LEFT issue with both, mouse and joystick ports.

How can this be possible? Bad capacitors? Looking at the mainboard I can't say if all the necessary capacitors have been replaced.
Please, let me know if you have any hints!
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Old 22 June 2018, 20:35   #8
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i personally think that using a PC PSU is a wrong idea. Better use a recapped original PSU.
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Old 22 June 2018, 20:49   #9
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Quote:
Originally Posted by dlfrsilver View Post
i personally think that using a PC PSU is a wrong idea. Better use a recapped original PSU.
Really?

I'm not an expert but I always read that this PC converted PSUs are the best you can find for your Amigas, especially if they have many expansions cards like Blizzard PPC, Vampire, etc...

To be honest 16A in the +5V and 10A in the +12V seems a lot to me but could this be "dangerous" for the mainboards?
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Old 22 June 2018, 21:03   #10
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Main problem with PC PSUs is that generally only high end ones (80 plus gold rated or higher) are fully independently regulated and will support very low loads without stability issues. Capacity is never the problem. EDIT: low end PSUs also can have high ripple that is still inside ATX spec but too high for Amigas.
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Old 22 June 2018, 21:39   #11
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I can understand that PC converted PSUs can have stability issues with very low loads but with those two PSUs I don't have the joystick/mouse issue using the A600 mainboard with "weird noise".

That's way I think that the problem is the A600 mainboard and not the PSUs but I could be wrong... honestly I really don't know what to do...
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Old 22 June 2018, 22:41   #12
Toni Wilen
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Direction issue is weird because direction signals are pure digital. If mouse works without weird jittering, it probably is timing issue somewhere in Denise or multiplexer TTL chip that is located between joystick ports and Denise. (Which does not really help much..)

If you have joystick in both ports and push both joystick up and then release one, does it "mirror" left direction change to other port?
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Old 23 June 2018, 23:23   #13
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Hi Tony, thanks for the help.

Unfortunately today I was very busy and I couldn't do the test you suggested. I'll do it tomorrow and I'll update this thread.

Just for reference, this seems the first PC Converted PSU I tried.

The second, as said, is a Vultech GS-500M.
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Old 02 July 2018, 21:45   #14
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Quote:
Originally Posted by Toni Wilen View Post
Direction issue is weird because direction signals are pure digital. If mouse works without weird jittering, it probably is timing issue somewhere in Denise or multiplexer TTL chip that is located between joystick ports and Denise. (Which does not really help much..)

If you have joystick in both ports and push both joystick up and then release one, does it "mirror" left direction change to other port?
I've finally got time to do the test.

If I use two joysticks and I go UP with both of them they go "UP+LEFT" but if then I use only one joystick the other isn't mirrored. However doing the test with two joysticks together I sometimes got weird movements... using a single joystick the only issue is "UP+LEFT".

I've also checked the movement with two games. Using R-type if I go UP the ship goes straight UP but with Worthy if I go UP the character goes "UP+LEFT"...

Sorry for not having replied earlier.
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