shoestring
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Posts posted by shoestring
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Baking soda will work. The important thing is to paint them after cleaning or they start rusting pretty much straight away. I used PCB lacquer after wet sanding the metal plate of the a1200 keyboard.
But there are better ways.
https://retrohax.net/extreme-refurbishing-episode-4-vampiric-amiga-500/
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15 hours ago, Pinball freak said:
Ok never mind about the led lights, on the underside it has broken traces wich need to be fixed !
So now an hour later, i can say i fixed that problem, the power led is working again
Yes this is a common failure point on A500 keyboards. I knew there wasn't an issue with the motherboard when you measured the signal from the status ( pin 7 )
Starts off as a dry joint due to constant mechanical stress from the A500 enclosure when the two slits for the LED casings are mis-aligned during reassembling. Eventually the traces on the solder side can fail.
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Happy days. So if there is a broken leg on one of the custom chips then you can solder another leg from a donor chip if it has enough metal exposed. Some people use a dremel to expose more of it if its snapped at the base of the chip.
http://www.ukvac.com/forum/missing-chip-pin-tips_topic350953.html
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Sounds like a faulty Agnus ( 10 flashes plus 1 long ).
He is right when he said that you cannot put 8371 Agnus in rev 6 board. You need an additional refresh circuit which goes near the trapdoor on the motherboard. The 8371 isn't able to refresh some ram chips ( 44256 ) properly. Some early rev 6 had the 8371 but needed the refresh circuit.
Why not just test the 8372a in your original board ?
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16 hours ago, Pinball freak said:
Well, as i am not familiar with the screen color codes, i would say Green. It is a deep alien snot green
So i am thinking in the direction of bad ram.
Well it seems like a memory problem. But clean those 8371 leads and PLCC leads first before you do anything else.
Don't bother swapping CIAs until you address the ram issue.
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That gouge is the least of your worries. Give those leads a good clean, there's some corrosion and oxidisation taking place on almost all pin leads. They're likely not making a good connection to the PLCC.
Use some rubbing alcohol or brasso and a fine toothbrush or cotton ear bud. Don't scrub accross the chip.
I'd consider doing this first before looking at the chip ram.
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I'm get a crisp picture from the A1200, not confident I'll benefit much with such a cable but I can only try it out and see. My only complaint is the slight vertical banding I see which is likely associated with the pixel clock of the LCD which I should be able to adjust on the display or OSSC.
11 hours ago, Daedalus2097 said:That's my thinking too. Butchering the socket wasn't the way to do it though ?
They are brittle, easy to destroy. But thankfully spare PLCCs in a variety of different sizes are still easy to source nowadays and are of good quality. As for the GARY socket, he/she could have at least trimmed it down neatly with a file so that it ends up flush with the end of the chip, that's what I'd have done after removing those extra pins had I ran short of suitable spares.
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13 hours ago, Daedalus2097 said:
Well, it's not as simple as that. Many TVs need additional signals to correctly configure the SCART input. Sometimes this can be done manually via the TV controls, but on many TVs there's no option. In these cases, you also need power connections from the Amiga's RGB output and some resistors at some point on the cable, otherwise the TV might not display the SCART signal, or might try to show the composite input instead. See my link above for what is the de facto standard these days for an Amiga SCART cable.
Additionally, there are multiple ground connections, and while you don't strictly need more than one ground connection, the quality of the signal will be improved by using proper grounding - Individual screen for the red, green and blue signals and a separate digital ground for the sync line.
Well now I'm curious, I built my own SCART cable to use with the OSSC but didn't use independent grounds ( except for the audio ) or any other components in the schematics from the links above. But now I'm going to build another one to see if the display can get even better.
QuoteIt's the NTSC/PAL select pin, and it's relatively common to mod A500s to allow NTSC and PAL running. But IIRC this Agnus is too old for that mod to work, so it's pointless. Regardless, the socket doesn't look healthy all the same with the nearby pins and they could indeed be causing issues. Likewise with the Gary socket; if someone's using such inappropriate parts, they're probably not taking all that much care with the job and there's a good chance there are issues in the area.
It's possible they had upgraded to an 8372a at some point but put the old one back in.
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Also, GARY has had some work done to it with the bigger machined pin socket installed. So you probably find your broken pin somewhere there.
You could try applying some pressure to the chip to see if it makes a difference
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Well, the AGNUS socket looks a bit fucked up. Looks like the low data select pin ( if i have my orientation correct ) is damaged. Don't know how this even worked when you saw it. Get your money back
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If it has a SKART input then it should accept the Amigas video signal. Only 5 wires are needed on the 23 pin connector ( video ground, red,green,blue and csync ).
The rca audio cables from the SKART end of the cavle just taps the output from the back of your Amiga into your TV which has internal speakers.
Does the new machine have any drive activity despite the white screen?
No drive click then. Are you still using the old power supply ?
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14 hours ago, Daedalus2097 said:
Yep, but /Reset isn't being asserted so it's unlikely to be the reset circuit.
Needs to be confirmed.
Initial power on reset is also triggered by the 555 during power up. GARY will then pulse _RST and _HLT briefly to various custom chips and U37 ( 74LS32 ) which buffers the _RESET to both CIA chips and some of the IO such as the parallel port and the external floppy. I'd check GARY , the 74LS32 @ U37 and 4.7k resistor at RP101
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If you're worried about a short at the connector, then you can dial the dmm in continuity mode and look for a dead short between pins 1,2,3 and 4. ( with the machine switched off of course ).
Pin 4 is vcc so it should be 5v. Clock and data are held high ( 5v ) before any keyboard transmission begins.
The _KBCLOCK signal ( pin 1 ) is driven by the keyboard itself, _kbdata ( pin 2 ) is driven by both keyboard and the Amiga ( bi-directional ). I'd assume that _KBCLOCK should float ( not measure anything ) with the keyboard unplugged since it's uni-directional
The keyboard will only pulse _kbreset low when the user presses the ctl-amiga2 combo. So when gary sees low signal, it will assert _reset and _halt to initiate the reset process. _kbreset ( pin 3 ) should be held high by default if the user is not pressing the 3 key combo.
I don't know if a white/grey screen is with enough confidence to assume that the ks rom is passing software checks, what version of kickstart do you have ?
White or black is screen is common value in color0 register when the Amiga ( denise ) powers up and that seems to depend on the revision too. Lots of other faulty parts of the chipset can cause the machine to boot to white, grey or black screen.
Ideally I would start my troubleshooting at the reset circuit, at the 555.
After probing it with the mm, the second pin from the right ( blue ) jumps like crazy with 0.07 to 4.8 with all kind of voltages in between...It should probably be flashing. Have you checked the keyboard LED and resistor R6 on the keyboard pcb ? Might be blown or loose.
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That's pin 6 on the kb connector which is the power led +5v on the kb . Is the power led blinking on power up ?
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Without some proper tools ( logic probe or scope, eprom device programmer, ram/logic tester ) or at least a second working system, you're going to have a hard time and will probably need to shotgun it, and that's going to be very expensive looking at the price of custom chips these days.
Do you recall where the bad solder job was located ?, this might indicate where the short took place. Some photos of the board at location might help someone see something
With a short, it could be as simple as a blown resistor, logic package or even a blown trace. I've seen resistors blow in A500s just from normal use.
The schematics should help
https://amiga.net.au/files/Tech_Amiga/Commodore_A500_System_Schematics.pdf
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3 hours ago, Pinball freak said:
Do i need a donor board to have the proper cia's , because they are hard to find... Or can the chips bought on the internet ?
You have two 8520 CIAs in your current Amiga ( odd / even ). If only one is faulty you might see something different after swapping the two around in the machine. If you're lucky, the machine might even boot.
CIA responsible for I/O like kb, parallel, serial ..etc and also generating timings and interrupts.
More here: https://www.amigalove.com/viewtopic.php?t=324
I'd say your ks rom should be OK since you get a whitish/greyish screen, some code has run to a point but then the machine can't go any further due to some other h/w issue. A completely dead ks prior to v3.1 will give you a black screen.
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On 3/16/2022 at 2:58 AM, Pinball freak said:
But, if i flip the switch, the caps lock light lits up and goes out, and i get a white or greyish screen ( can't say for sure ), but that is it.
Some points.
1.If it's blinking at 1 burst per second, then that indicates a kb rom checksum failure.
2.Otherwise consider the kb self-test passes with a single flash in a normal working system.
3. Note that all Amigas will boot without a keyboard plugged in or if the kb controller is faulty.
4. As mentioned check CIAs, swap them over and see if your symptoms change to something else.
I would also swap the kickstart rom for quick troubleshooting if you have a spare lying around.
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I had a Samsung LCD TV that refused to lock on to the Amiga's display via the composite in, I have an A1200. The C64 worked fine.. so I don't know. *shrug*
Edit:
I had no problems through a 1084S and my brothers Sony CRT TV from the late 90s.
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Most modern LCDs, especially
13 hours ago, Isaac Electro said:You didn't even have to replace any of the sockets, I replaced some sockets and Stull nothing.
Most LCDs including TVs aren't compatible with the Amiga's video output signal. They do not support 15khz horizontal refresh, you can get lucky on this especially with older TVs that have a SCART input. So you might want to look into an upscaler like the OSSC which is what I use.
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Yes it does
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I don't know how I missed Krakout, played it to death.
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Too many classics to choose from. Arkanoid II - Revenge Of DOH, Ball Blasta and Batty come to mind.
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On 12/1/2021 at 6:21 PM, carlsson said:
It is on again. Tomczyk's latest YT video spurred Leonard to raise his arm.
Check out the comments section.
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Amiga CD32 RGB help
in Commodore Amiga
Posted
AFAIR there were two different types of original power supplies for the CD32, the heavier brick ( resin filled similar to ones found for a1200/a600 ) and a lighter one.
The brick is reliable and will last years, the smaller one not so much.