Mac Classic - will it ever run again!!

[stephen_usher]

It's a pain that the board needs +12V, +5V, -5V and -12V too! I don't know what the minimum required to boot is.

[rubber_jonnie]

It's a pain that the board needs +12V, +5V, -5V and -12V too! I don't know what the minimum required to boot is.

Me either, I forgot it's been too long!!

[stephen_usher]

With respect to the HDD not powering up. That sounds like there's a short on the +12V line.

[rubber_jonnie]

With respect to the HDD not powering up. That sounds like there's a short on the +12V line.

My thoughts too.

Pages 21-23 of the Dead Mac Scrolls are showing some good tests that I need to work through as they pretty accurately describe the symptoms I'm getting. Every page says analogue board, so this is something that has failed since I started to look at it.

[Tomswork]

Does a atx extension cable plug in most of the connector is the same you may need to move some of the wires

Tom

[Tomswork]

@rubber_jonnie

On the analog board have you reflow all the connectors and wires goings to yoke tube neck and flyback pins look for cracks around those as well


Tom

[rubber_jonnie]

@rubber_jonnie

On the analog board have you reflow all the connectors and wires goings to yoke tube neck and flyback pins look for cracks around those as well


Tom

I think I did, but I'm going to check again because it has been moved into and back out of storage since I last looked and my memory is hazy.

I'll have to see what I can do re extending the cable, I simply don't have a spare ATX plug I don't think. It is 'kind' of workable ATM but I will do all the suggested analog (I just realised I was calling it analogue!!) board checks and check all of the neck board wiring too.

[stephen_usher]

Looking at the 3rd party schematics for the Classic, it doesn't look like the -12V and -5V are used on the board and the +12V is only for the floppy connector and serial ports, so you should be able to power the board from +5V only externally and then take the v-sync, h-sync and video from pins 4, 5 and 6 of the power connector. (+5V on pins 2 & 3, Ground on pins 10, 11, 12, 13 and 14)

I do dislike the way that the 3rd party schematics are done. The +5V, +12V, -12V and -5V symbols are extremely confusing and able to be misinterpreted.

[stephen_usher]

Does a atx extension cable plug in most of the connector is the same you may need to move some of the wirea

Tom

Beware that the Classic connector and SE/30 aren't compatible and there are a bunch of functions, such as sound, which go through the connector which the SE/30 doens't have. It looks like there's no -5V input on the classic, it's generated from the -12V line.

[stephen_usher]

Looking at this, personally I'd solder wires to the ground and +5V points on the underside of the board and power it from a bench power supply initially. You can then get the two syncs and video and try to see if it's outputting anything.