Blown fuse on EME-156 V drive

[mikeyp]

Hi all

First time post here so hi.

My grandpa has given me his Sinclair ZX Spectrum +3 which has the Amstrad 3" floppy drive. That works great I'm pleased to say.

I would however like to archive all his disks using my greaseweasel. I have therefore bought loose 3" 180k drive model EME-156 V.

I had to make up my own 34-26 pin cable to connect the floppy drive. I then successfully read out 2 disks before the N11008 fuse on the 12V rail blew.

I have hooked up my bench power supply after the fuse at 12V limited to 500mA and the drive continues to work as expected, drawing at most 90mA when reading a disk.

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My current plan is to image the disks like this for now and replace the fuse with a 400mA running current, 800mA trip current (same as the old) self resetting polyfuse so I don't have to worry about it in future. That will take care of daft shorts etc. and still protect the circuit without resorting to a bridge.

Let me know if you think this is a sensible or silly idea please.

Thank you

[SerErris]

Is that fuse on the drive, or on the greaseweazle?

I am asking because I cannot see any fuse in the schematic of EME-156. I could not find a EME 156V schematic, but I would be surprised if they have added a fuse on the drive to protect the motor, which is the only component utilizing the 12V rail.

If it is about the greasweazle, not familar with it, but I could not see, why the replacement fuse you are talking about should be wrong. It is a fuse which is auto resetting and one could argue why they not have that in place in the initial design.

[mikeyp]

Thank you. I will proceed with the replacement then.

It is definitely the drive not the greaseweazle. The greaseweazle only supplies 5v not 12 which has to be obtained from another power supply.

Yes. It's an odd one. I haven't see a 156 with a short board before either. Q3 bottom left of the first image is blown and you can see the fuse in the second image.

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[mikeyp]

Just thought I would update that the fuse swap was successful and the drive is fully working again.

Thank you.

[Bryce]

Did you swap that capacitor beside it too? It looks a bit bulgy in the picture. Maybe that's what took the fuse out?

Bryce.

[mikeyp]

I didn't swap it. It's actually flat and fine. Just a play of the light.

[Bryce]

I think I would have changed it anyway. There are very few things that could have blown the fuse and it's one of them. It's old and capacitors degrade over time.

Bryce.

[mikeyp]

I see. Will do. Thank you again. I appreciate it.