Mac Classic - will it ever run again!!

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Tomswork
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Re: Mac Classic - will it ever run again!!

Post by Tomswork » Thu Sep 03, 2020 6:55 am

@rubber_jonnie

Any signs of happy mac beep

:girldance:

Tom

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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie » Thu Sep 03, 2020 9:05 am

Tomswork wrote:
Thu Sep 03, 2020 6:55 am
@rubber_jonnie

Any signs of happy mac beep

:girldance:

Tom
Sadly not I'm afraid :( I've just not had the time.

The CPU has power, and using a spare one, it no longer gets ridiculously hot, and neither does the ROM. I have good power at all pins on the power plug. Continuity on the new CPU socket looks fine too, and no shorts between pins. Also, the /halt and /reset lines are high, which is a good sign.

No beep though and actually no display either, so next up I will check the solder connections for the wiring harness on the analog board, make sure all the moving around hasn't done anything to them. I need to find out more about how it should work, at the moment I don't even see the tube light up :(
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
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Tomswork
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Re: Mac Classic - will it ever run again!!

Post by Tomswork » Thu Sep 03, 2020 3:46 pm

Hmmm no tube glow is almost always a solder problem on the connector of the analog board. And again the capacitors could have leaked. No beep could be anything.

Tom
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Re: Mac Classic - will it ever run again!!

Post by stephen_usher » Thu Sep 03, 2020 6:20 pm

You did plug the speaker in, didn't you? I often forget on the SE/30. ;-)
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ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie » Thu Sep 03, 2020 11:19 pm

stephen_usher wrote:
Thu Sep 03, 2020 6:20 pm
You did plug the speaker in, didn't you? I often forget on the SE/30. ;-)
Yep, I nearly forgot at first, but did plug it in.
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie » Sun Jan 03, 2021 11:06 am

Ok, so I seem to be back here again, and thinking of the Mac and seeing if I can get it going again.

The problems I have at the moment are:

1. I don't know if the logic board is good.
2. I don't know if the analog board is good.

Since I have no good way of testing the analog board, other than seeing if it is delivering the correct voltages, I'd like to rule it out.

The line of reasoning goes like this:

1. I have a PSU that I can use to deliver all of the voltages (5, 12, -12) though I suspect only 5v is needed to run the show, in a similar manner to the Atari ST.
2. The video output seems to be composite going by the main connection on the logic board.
Connector.JPG
Connector.JPG (19.19 KiB) Viewed 149 times
Is it therefore possible to connect the logic board to a composite display, powered by my external PSU?

Or is the composite signal not a true one, but an Apple composite that doesn't work as expected? Or would I also need to combine the hsync/vsync signals from the plug with the composite out to make it work?

@Tomswork you seem to be quite clued up on these machines, do you have any thoughts?
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

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olivier.jan
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Re: Mac Classic - will it ever run again!!

Post by olivier.jan » Sun Jan 03, 2021 3:22 pm

Hi,
Do you have access to a scope to look at this composite signal ? If it looks ok, you’ll be able to rule out a logic board failure.
Even with a cheap logic analyzer, plugged on composite, Hsync and Vsync you should be able to recognize a video signal (need to change the thresholds though as you might get something between 0v and 1v with a sync around 0.3v).
I have two Classic sand managed to get one to work properly. Fixed both logic boards, but still fighting with the second analog board and it’s always a bit scary with all the high voltage. Need to replace the MOSFET, it’s an usual issue with the analog boards.

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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie » Sun Jan 03, 2021 3:36 pm

olivier.jan wrote:
Sun Jan 03, 2021 3:22 pm
Hi,
Do you have access to a scope to look at this composite signal ? If it looks ok, you’ll be able to rule out a logic board failure.
Even with a cheap logic analyzer, plugged on composite, Hsync and Vsync you should be able to recognize a video signal (need to change the thresholds though as you might get something between 0v and 1v with a sync around 0.3v).
I have two Classic sand managed to get one to work properly. Fixed both logic boards, but still fighting with the second analog board and it’s always a bit scary with all the high voltage. Need to replace the MOSFET, it’s an usual issue with the analog boards.
As it happens, I am just going through the Bomarc schematics and wiring up the edge connector at the front of the board for power and was then going to get the scope going on it with out having to hook up the display, then see if I get what looks like a composite signal on my scope. I'll also have a look at the address, data, /HALT and /RESET lines, see what they're doing.

I did recap the analog board (Caps were ALL leaking), and it seems to be generating the correct voltages, but clearly it has a part to play from a video generation aspect.

I'd heard the AB opto-couplers could be problematic, so I was intending to replace that, but not heard about the MOSFETs. I'll have to look into that, though I guess if I'm getting correct voltages, then I suspect it's ok.

Do you have parts you can specifically recommend for the opto-coupler and MOSFET? Or do you just replace like for like? I'm pretty new to Mac Classic repairs, so still learning.

Appreciate your help.
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

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olivier.jan
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Re: Mac Classic - will it ever run again!!

Post by olivier.jan » Sun Jan 03, 2021 5:46 pm

Didn’t change the opto-coupler on the analog board, but I should have a look on the defective one. The MOSFET is an IRFBC40 which you can find easily at Mouser or other.
The caps are totally crap on these Analog boards, they leak a lot. Mine was put on storage in 2004 fully working, got it back 2 years ago, it blows fuse each time I turn power on.
Did a full recap, but still blows fuse :cry:
The other one didn’t turn on, but after full recap it works (nearly) perfectly. Only small issue, when turned on the display is stretch horizontally but after 30s-1min it finally gives a proper picture. I know which part to change, but not urgent.

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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie » Sun Jan 03, 2021 6:27 pm

olivier.jan wrote:
Sun Jan 03, 2021 5:46 pm
Didn’t change the opto-coupler on the analog board, but I should have a look on the defective one. The MOSFET is an IRFBC40 which you can find easily at Mouser or other.
The caps are totally crap on these Analog boards, they leak a lot. Mine was put on storage in 2004 fully working, got it back 2 years ago, it blows fuse each time I turn power on.
Did a full recap, but still blows fuse :cry:
The other one didn’t turn on, but after full recap it works (nearly) perfectly. Only small issue, when turned on the display is stretch horizontally but after 30s-1min it finally gives a proper picture. I know which part to change, but not urgent.
Thanks, I will take a look for that Mosfet, you never know.

Out of interest, I connected the edge connector at the front of the board to my bench PSU, so 5v, 12v & -12V.

I can at least power on and probe the thing without having to fight with the stupidly short AB cable and a lingering fear of death by electrocution!!!

So it seems my theory is at least in part correct.

I am seeing a signal on the composite out pin, but need to get some pics (I stupidly forgot), but there is definitely something there.

In addition, I'm seeing the correct 22.3Khz hsync, and the correct 60Hz vsync values at the main connector. I believe it is possible to combine these with the composite signal to work with VGA in monochrome, so I'm having a look into that too.

I also had a probe around the CPU and found the /RESET & /HALT lines to be 5v, and drop on reset, returning to 5v as expected, and /BERR was also looking fine staying high as expected.

What was a bit concerning was that there didn't seem to be any activity on the address and data lines. I need to get pinouts for everything and check what's going on at the other chips, though the RAM did seem to have activity on the address pins which is potentially a good sign.

It is doing something, I just need a display other than the original CRT so I can see what's going on.

I found the attached notes too, which I thought might be useful for people in the same predicament as me!
Attachments
Classic Mac Repair Notes.pdf.txt
(527.73 KiB) Downloaded 5 times
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

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