MP-F75W schematics available?

[croissantking]

I have an MP-F75W floppy drive that seems to have a failed circuit board - it doesn’t drive the stepper motor properly. When power is applied it buzzes endlessly but doesn’t turn, almost as if the current is rapidly alternating and it’s trying to go in one direction and then the other.

I tried swapping a good motor in and it does the same thing.

I swapped the HA13421 chip with a spare but it didn’t help.

Does anyone have a copy of the schematics for this drive to help diagnose the circuit?

 

[codevonlux]

I only have schematic on 800K drive. Parts around stepping motor should be the same. There is nothing else between controller chip, HA13412 and the motor and you already swapped two of them.

Could you check the TRK0 signal from the zero track detector? At power up the stepping motor will keep running until TRK0 (pin2 to the detector assembly) turns 5V

There is also possible that the 5V(C) and 12V(C) which only turn on when controller is out of power saving mode is not turning on. You can try to replace all the power transistors (2SB624-BV4 marked BV4 or V4) and driving transistor DTC114EK (normally marked 24)

 

[dochilli]

Schematics...

 

[croissantking]

Odd, I don’t see a HA13412 chip.

 

[lobust]

Odd, I don’t see a HA13412 chip.

Looks like the CXA1035 is it - U3.

IC's rebranded at some point during the production lifecycle?

 

[croissantking]

Looks like the CXA1035 is it - U3.

IC's rebranded at some point during the production lifecycle?

Or could there be more than one version of the board…? I don’t see the BV4 chips @codevonlux mentioned.

 

[codevonlux]

There are many many different versions. 2SB624-BV3 is shown in above Bomarc schematics. They are interchangeable

 

[lobust]

Or could there be more than one version of the board…? I don’t see the BV4 chips @codevonlux mentioned.

Very likely, but the pinout matches the HA13421 so the schematic is probably useful to you even if not exactly right.

 

[surfer150]

May somebody share me the capacitor values for C104, C106 and C107? Thank you

 

[cgp]

Here's one list: https://quagmirerepair.com/replacem...7XaeDQRt3tdpqK8dkrb9guE_Gsj2Qkx1zj35oHYFdqgHV

I got a fairly economical set from Console5.com.

 

[s_pupp]

C101 47uF 6.3V
C102 22uF 16V
C104 0.47uF 50V
C105 10uF 6.3V
C106 1uF 50V
C107 10uF 16V

Because ceramic capacitors like the Console5 set can lose a large amount of their capacitance in the setting of a DC bias, it might be worthwhile using an alternative. I use aluminum polymers for all but the 1uF and 0.47uF caps, for which I use tantalums. You just need to check the dimensions of the aluminum caps before ordering - the frontmost 10uF cap needs to be pretty short.

 

[surfer150]

Thank you very much!!!

 

[cgp]

Actually, the Console5 kit doesn't include any ceramics - as the quagmirerepair.com page might imply - they're all aluminum electrolytics of decent quality.

[Though I'm certainly not a spokesman for Console5 .. see https://tinkerdifferent.com/threads/a-mostly-successful-iisi-restoration.3912/ for some details of my floppy drive restoration.]

 

[s_pupp]

Actually, the Console5 kit doesn't include any ceramics - as the quagmirerepair.com page might imply - they're all aluminum electrolytics of decent quality.

[Though I'm certainly not a spokesman for Console5 .. see https://tinkerdifferent.com/threads/a-mostly-successful-iisi-restoration.3912/ for some details of my floppy drive restoration.]

I mistakenly assumed the link was to Console5's page - I didn't see that it was to quagmirerepair.
Console5's page is here.
As you say, they are aluminum electrolytics.
I recapped my wife's Classic with Console5 caps and, as you say, they were all of decent quality.

 

[campbellashe]

@croissantking, did you ever figure out this problem. I have a similar issue with my buzzing stepper motor. I swapped a good stepper and similar issue.

 

[croissantking]

@croissantking, did you ever figure out this problem. I have a similar issue with my buzzing stepper motor. I swapped a good stepper and similar issue.

No, the drive is sitting on a shelf being sad.

 

[croissantking]

But I do plan to revisit it. I also need to get a new eject gear.