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Hi all, I have just acquired a Color Classic and thought I would take the PRAM battery out until I have time to clean up the machine in case it leaks. To my surprise when I opened it up it has this pin setup where the PRAM battery goes. Does anyone know what the 3 pins are for, I am assuming...

Thanks Marcelv, when you say C33 and C36 which are you referring to as the International board doesn't have these ? And yes my next step was to look at Q12, is there way to test it before going down the replacement path ?

Hi all, Does anyone know of a version of this doc (especially the power circuit section) for the 240v international board for the 512k Analog board ? I am still trying to diagnose a flup flup issue.

Yes I have already tried that.  I have used this LB with a 128k analog with same response and the 128kbLB with this AB and it works fine.  So it's something on the LB.

No change unfortunately,  I used a tantalum and then an electrolytic. the sequence is as follows : 1. power on - vertical bars 2. reset switch - boot ok with bong. 3. power off 4. power on - boots ok with bong 5. power off 6. power on - boots ok with bong point 4& 6 only work if they...

I have taken C9 out of the board to test it.  it is just showing an open circuit on the multimeter when I test for capacitance.  I have a spare non-working Mac Plus board,  is there a glass bead cap on here that I can transplant,  too hard to read so I need some experience to tell me - please...

Have done some of my own research.  Glass bead caps it appears.  I assume I can replace this with a ceramic cap of 4.7uf 35v ?

So I replaced LM311 without any change.  I am now thinking it might be C9 as per the image above.  In my understanding if C9 isn't working properly then the -ve won't be presented to pin 3 and therefore LM311 won't create the reset signal.  But if the reset switch is pressed (SW2) then it will...

I would start with the chips that have traces passing by any caps so UK11, UK12, UJ11, JI12, UG12, UE11.  these should all have D and A connections and pass but eh group of caps  around C9.  I started with identifying any visual damage, and then looked at the traces around that and started...

Yes they have been replaced and the analog board is fine.

I would also check traces between components not just between components and CPU.

I had a similar problem see link below.  Check your Dxxx and Axxx data traces between IC's.  I see you ahem recapped the board,  mine was caused by a broke trace near C9.

Agree.  I have ordered a new LM311 chip so lets see what happens.  I did some more testing last night and it seems that after resetting once and then using a multimeter on pin 7 to see what was being sent,  the machine then started working normally after a few times of on/off's but then resorted...

And yes Sound is working ok to give a bong.  I will do testing on the LM311 today to see what it is doing at startup.

Found it here - http://www.digibarn.com/collections/diagrams/mac-512klogicboard/index.html

Assume it's the LM311 chip.

Thanks this makes sense.  Just need to find now what pulls RESET and HALT low creating the RST circuit.  On the schematic it looks like the circuit above the IWM chip on the Schematic but it is too fuzzy to read.  Does anyone have any clarity on this ?

So some progress but only accidental. I have checked all the connections coming off the CPU and traced them to other chips and performed some general continuity testing across the Logicboard today from what I can read on the very fuzzy Schematic of the 128/512k board.  (Note : I actually found...

Thanks this is really helpful,  I will study over the weekend.  brings back many memories of Assembler coding at university ! Any easy way to test the CPU without a scope ?

I am trying to diagnose a problem with vertical bars on a 512k and want to know if anyone has seen a documented boot sequence for a 128k/512k Mac so I can work through the sequence. I don't have any visual issues on the logicboard so I am down to trying to work out which chips may have problems...