Mac Classic - will it ever run again!!

Any 680x0 based information, repairs, images, upgrades and other cool stuff that is not Atari and Amiga based but based on the Motorola 68K range of processors
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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie »

Ok, I seem to have good news regarding the Mac this morning :)

Having been left overnight, it powered up immediately, so it's looking like the IRF-BC40 MOSFET, QP2 on the schematics, was the reason for the slow start.

In retrospect, as it seems to be the main switching transistor, I probably should have replaced that first, but TBH the electrolytics on these boards are known for leaking, and in fact the first batch I did last year, about 10 in the main PSU section, were all sitting in a puddle of brown goo!

So overall, the PSU has had a pretty comprehensive refurb!!
  1. All electrolytics (PSU and Video circuits)
  2. TDA4605 (IP1, switching controller)
  3. CNY17 (QP1 Optocoupler)
  4. IRF-BC40 (Main switching MOSFET)
  5. MBR1045 (5v circuit main diode)
Items 2 to 5 were replaced based on research on the web, so sometimes you follow the advice you find, and it isn't always right, however it has helped me learn a lot about working with CRTs and a lot about switching PSUs, so it has definitely been worth the effort.

Also, changing the caps in the video circuit showed me that such a simple act can require a degree of re-tuning via the many pots, to get the picture stable on screen, plus how easy it is to upset a CRT by accidentally knocking the tuning magnets around the screen.

So, this machine is going to be temporarily parked whilst I look at Brett's STE, the final problem being that of the non working RAM expansion.

It's been quite the journey!!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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JezC
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Re: Mac Classic - will it ever run again!!

Post by JezC »

rubber_jonnie wrote: Thu Jan 13, 2022 9:33 am Ok, I seem to have good news regarding the Mac this morning :)

Having been left overnight, it powered up immediately, so it's looking like the IRF-BC40 MOSFET, QP2 on the schematics, was the reason for the slow start.
Hurrah! Good news indeed!
So, this machine is going to be temporarily parked whilst I look at Brett's STE, the final problem being that of the non working RAM expansion.
Looking forward to those pictures & the diagnostics on that STE
It's been quite the journey!!
Yes, though I'm still not sure it quite equals your battle with that Mega ST!
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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie »

JezC wrote: Thu Jan 13, 2022 11:33 am
Yes, though I'm still not sure it quite equals your battle with that Mega ST!
Yeah, the Mega had a LOT more posts at the end!!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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JezC
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Re: Mac Classic - will it ever run again!!

Post by JezC »

rubber_jonnie wrote: Thu Jan 13, 2022 11:42 am Yeah, the Mega had a LOT more posts at the end!!
I need to check my two Mega ST's before I get round to fitting the Dual TOS boards in them... :roll:
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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie »

JezC wrote: Thu Jan 13, 2022 12:07 pm
rubber_jonnie wrote: Thu Jan 13, 2022 11:42 am Yeah, the Mega had a LOT more posts at the end!!
I need to check my two Mega ST's before I get round to fitting the Dual TOS boards in them... :roll:
I would!!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Kai Robinson
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Re: Mac Classic - will it ever run again!!

Post by Kai Robinson »

rubber_jonnie wrote: Tue Jan 11, 2022 10:40 pm
Tomswork wrote: Tue Jan 11, 2022 4:56 pm Good news on the classic.

@Kai Robinson I believe he is working on a clasic ram board replacement

Tom
Indeed I'm rather pleased :)

Cool, I do have a Simm board that used to work, but has decided not to :(

@Kai Robinson are you building a replacement by any chance?
https://tinkerdifferent.com/threads/log ... nsion.106/

I did finish it - but not tested it, if you want a free PCB, and some simm sockets, you're welcome to assemble and try it :D
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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie »

Kai Robinson wrote: Sun Jan 16, 2022 1:32 am
https://tinkerdifferent.com/threads/log ... nsion.106/

I did finish it - but not tested it, if you want a free PCB, and some simm sockets, you're welcome to assemble and try it :D
Wow, that would be fantastic, thanks so much for the offer!! Are you sure I can't offer you something?

Let me PM you.

:)
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie »

Ok, so this little machine is on the bench again to try and finish off the RAM expansion problems.

I have a replacement expansion card on the way, as my current one doesn't work despite replacing the RAM with spare ICs from one of my dead Mac Classic mainboards. We'll see where we get to once it arrives, but currently booting fine from the ROM to System 6.0.3, so that's something.

Just want to get that extra RAM so I can boot to System 7 that's on the HDD.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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rubber_jonnie
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Re: Mac Classic - will it ever run again!!

Post by rubber_jonnie »

Well, the replacement RAM card arrived, I plugged it in and it didn't work. Ok, do we have a problem with the SIMMs?

SIMMS out, jumper set to none installed and we bong, and boot fine to system 7 with 2MB RAM. Cool, I'll try the SIMMs from my old card, doesn't work...

Pull the SIMMs out again and swap the jumper, and now nothing works, just a sad Mac that suggests a memory addressing problem. Waaaahhhhh!!!

:dizzy:

Will have to look at the schematics, see if I can figure out what the hell is going on here, but it's bloody annoying.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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stephen_usher
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Re: Mac Classic - will it ever run again!!

Post by stephen_usher »

Quite a few Macs are very fussy about the type of SIMM, even manufacturer and sub-model.
Intro retro computers since before they were retro...
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.
Collection now with added Macs, Amigas, Suns and Acorns.
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