New (broken) pedal day!

[laurie]

Nice! Progress!!

[fuzzbuzzfuzz]

Aaaand the Monacor EM-200 is almost fully working again.

I still have to replace another potentiometer that has broken off. These and all the jacks were fastened very tightly, so I think that the parts had too much physical stress for all the decades. I replaced all the jacks and the electrolytic and tantalum capacitors and resoldered every single connection. I used the magnetic foil of a 5.25'' floppy disk and mounted it on the rotating disk.

A few minutes ago I decided to power it to test if anything is working at all after all the trouble. I was very pleased to see the motor spinning - the seller said that it didn't move at all when he tested it. And then I gave it a go with my guitar. Hey, that doesn't sound half bad with the floppy disk foil! Not as lo-fi as I imagined that it would be! I have to use another foil, because there is some unbalance that is audible as a rumbling noise. I need to try to give it more tension.

Wow excellent work. Thats a big beast to work on so your methodology is paying off! Great stuff

[Pepe]

Fresh pictures! Here you can see some of the new capacitors. I used Panasonic FC and Nichicon Fine Gold (1µf) electrolytic capacitors. Also two tantal capacitors and three bipolar electrolytic capacitors had to be replaced.



I read that the units were built in Japan by Shin-Ei. Here is the motor by Matsushita from December 1977. So my unit might have been built in 1978.



Here are the heads. The two playback heads are positioned in such a way that the delay at head B is twice as long as that of head A. A control knob on the front allows to adjust the volume of both heads (counter-clockwise: head A only, noon: head A and B, clockwise: head B only).



Here you can see the floppy disk foil fixed to the metal ring.



Here is the second ring with another layer of non-magnetized foil. It is mainly for stabilisation only. Under this foil there is a pitched metal surface.



I removed the foil of the floppy disk again. I am going to test it with another foil tonight. I put the metal ring in the freezer and I hope that the new foil will have a bit more tension this time if I glue it onto the cold ring. I don't know if there will be a strong effect when it will warm up from -24°C (-11.2°F) to room temperature, but it's worth a try.

[Pepe]

The second try with a 5.25'' floppy disk was a bit better. I was able to attach it on the metal ring with more tension. But there is a remaining problem. The heads are running tightly on the floppy disk foil, apparently with higher pressure that a floppy disk drive uses. After a few minutes of operation a rumbling noise appears and doesn't go away.

People at the German synthesizer forum told me that 8'' floppy disks with single density might come closer to the quality of audio tape. I ordered a few of them, as well as a demagnetiser. Today I learned that the heads need to be demagnetised after lots of operation.

[laurie]

The second try with a 5.25'' floppy disk was a bit better. I was able to attach it on the metal ring with more tension. But there is a remaining problem. The heads are running tightly on the floppy disk foil, apparently with higher pressure that a floppy disk drive uses. After a few minutes of operation a rumbling noise appears and doesn't go away.

People at the German synthesizer forum told me that 8'' floppy disks with single density might come closer to the quality of audio tape. I ordered a few of them, as well as a demagnetiser. Today I learned that the heads need to be demagnetised after lots of operation.

Years ago... we found that Verbatim 8" floppy discs were the toughest.

Might need to back the spring tension off on the heads?

[Pepe]

Yes, maybe. But the guys at the synth forum told me that I should better keep the heads as they are.

[Pepe]

Well, ChatGPT's recommendation to try 8 inch floppy disks was completely fruitless. The non-magnetized rim of those disks is too large. The heads of the Monacor EM-200 would rub against the part between the magnetized space and this circle of small holes. So I have to stick to 5.25'' disks.



Since the metal plate is somehow askew it is causing annoying rhythmic rumbling noise due to the imbalance. Someone at the German synthesizer forum offered me to have a look at it, because he owns a workshop with the necessary tools. And he has several kinds of floppy disks at hand to try out if there is better sound quality with the use of single density, dual density (what I used) or high density disks.

The echo machine has already arrived at his place yesterday. I'm looking forward to his actions. I'd be very happy should the metal plate be rotating 100% evenly again.

[laurie]

Dang...

[Pepe]

But should the noise vanish once the metal plate is even again, then I'm happy with the sound of a 5.25'' floppy disk.

[Pepe]

The member of the German synthesizer forum has the Monacor on his workbench.