512k with 800k floppy...Arrrrrgh!!!!!

[namaman]

I am repairing a Mac 512k upgraded with an 800k drive upgrade. The symptom was it does not boot from any known good system floppy (the floppy works on my Mac128k upgraded to 800k floppy). I have another spare drive which actually booted the system disk on the 512k, but did not eject.
After some probing around, I decided to remove the Q7 transistor from the non booting drive and installed it on the non ejecting drive, and I was finally able to get the eject working. Yay a fully working drive! I installed it tested it a number of times and went to bed happy.
This morning I powered up the 512k and the drive is dead, just like the original drive. No booting the system (at least eject is working still)
Heads are clean, so I'm stuck and not sure what to do now.
Was wondering if the motherboard is killing the drive(s)????
Wondering if anyone has any suggestions

 

[namaman]

Oh..both drives have been lubed and are actuating smoothly

 

[thecloud]

Possibly dumb question, but have to ask... is this system disk at least System 3.2/Finder 5.3? That's the earliest version that will let you boot a 512Ke. (512Ke was the nomenclature for a 512K with an 800K drive and the upgraded ROMs.)

 

[namaman]

Thanks for the reply.
ok...so I actually got it working. I adjusted the voltages on the system as they were a bit high (5.85V and 13.1V) and wiggled the drive cable and now the drive is working again!!!
However, I have seen slight anomalous behaviour. If the machine has been left off for a bit, and I insert the boot floppy, it attempts to load (thats good) but often fails on the first boot attempt. It does seem to work the second try and all subsequent attempt after that...until it's been left off for a while, and then it's game on again...could just be a coincidence.
Anyway, it's all so fickle!

 

[68kPlus]

Have you fully recapped it and cleaned all of the analog board? Apparently inconsistent boots can be a symptom of a weak power supply, meaning your board might need recapping or could have some corrosion in places. Worth checking!

 

[namaman]

Have you fully recapped it and cleaned all of the analog board? Apparently inconsistent boots can be a symptom of a weak power supply, meaning your board might need recapping or could have some corrosion in places. Worth checking!

No, unfortunately I have not done this. Mostly because if I do it to this 512k machine, then I will 100% feel compelled to do it to my Mac 128k, and Mac plus too...that's a bit of a financial commitment. lol
...sometime soon for sure.

 

[mikes-macs]

that's a bit of a financial commitment.

Anything vintage Mac is.

 

[68kPlus]

Anything vintage Mac is.

Yup... I've spent a ton on caps and I don't even have THAT many Macs. $200 for a flyback transformer? Jeez....... sold.