1541C unusual "Shorter Board" version - J3?

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eslapion
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Re: 1541C unusual "Shorter Board" version - J3?

Post by eslapion »

Gyro Gearloose wrote: Wed Dec 04, 2019 9:20 am Here's a new piece of information, a contributor to a vintage Tektronix forum says that the open coil is caused by too high a write current. But it's not the user who sets that, it's selected by engineering at design time. So who is right here? Is it a design flaw in the head by Mitsumi or a design flaw by Commodore?
The purpose of J6 is to change the write current.


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Re: 1541C unusual "Shorter Board" version - J3?

Post by Gyro Gearloose »

Yes indeed, there are two currents possible. Never knew that about the 1541. Interesting. I'll go talk to the Mitsumi reps again. Doubt I'll get far though.

I suppose I should look at my 2031 "big case" drive and take a look at its mechanism.

The Tek contributor mentioned that this Newtronics issue was known 30 years ago in the C= repair community but because 1541s were so cheap at the time no corrective plan was made.

He also mentions that no other C= drive model had this issue.
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Re: 1541C unusual "Shorter Board" version - J3?

Post by rmzalbar »

Very interesting! This suggests that a preventative fix might be possible if the write current can be reduced while maintaining performance. For now, I suppose, I'll be sure to use my Alps drives as destination disks for making copies.
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Re: 1541C unusual "Shorter Board" version - J3?

Post by Gyro Gearloose »

Well, the 2031 has a Shugart full height mechanism, and there's not much in common with the Newtronics or Alps drives.
I did, however, see a unique way of stepping the head back and forth.
I've seen the metal band attached to the motor's shaft like in 1541s, and I've seen the screw drive like in 3.5" drives.

But this Shugart mechanism uses a completely novel approach I've never seen anywhere else.
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Re: 1541C unusual "Shorter Board" version - J3?

Post by eslapion »

rmzalbar wrote: Tue Dec 17, 2019 2:02 am Very interesting! This suggests that a preventative fix might be possible if the write current can be reduced while maintaining performance. For now, I suppose, I'll be sure to use my Alps drives as destination disks for making copies.
On boards 250442 & 250446, the jumper configuration suggested for Newtronics causes a stronger write current. I suspect using a weaker write current could cause floppies to become unreadable fairly quickly.
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Re: 1541C unusual "Shorter Board" version - J3?

Post by Zippy Zapp »

As an update to my post above, I still can't identify any compatibility issues by switching on the track 0 sensor. I have been using this 1541C drive as my main drive every day and have used it with quite a lot of commercial software. I have also been using it for disk duplication and so far so good. I have to say it is nice to not hear any head knocking. And this drive is quieter too.

I wish I could find some concrete information on why they shipped with it turned off. The 1571s also have a track zero sensor and they do have a few issues but nothing major. It is still a mystery to me.
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Re: 1541C unusual "Shorter Board" version - J3?

Post by rmzalbar »

I did find a good mechanism+head in a horribly beat-up case, so I serviced it up and installed it into the 1541-pseudo-C. It's in near-mint condition waiting to be paired up with a C64-G that's still enroute. I do still hope to find a true 1541C logic board, but a 1571 is probably a better choice.

20200205_203502.jpg
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Re: 1541C unusual "Shorter Board" version - J3?

Post by banman »

Just browsing the eBay listings for something else and came across this......

https://www.ebay.com.au/itm/5x-New-1571 ... 56-20017-0
Screenshot_2022-10-30-14-36-00-319_com.ebay.mobile.png
Not sure if it's relevant here....
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Re: 1541C unusual "Shorter Board" version - J3?

Post by Gyro Gearloose »

Very interesting. I think the 1571 is a Newtronics D502, so those 1571 heads have some sort of parental lineage with the D500 in the 1541.

I found a similar listing for TEAC-branded floppy drive heads, much cheaper than that Australian listing with a Buy It Now price, only to receive an email stating that they couldn't find them and cancelled my purchase.

Here's another floppy head listing, also TEAC

https://www.ebay.ca/itm/154413804706?epid=732833039

Oh well. Kinda expensive and I don't see how to just slap that into a 1541 mechanism. I'm not paying 45$ US to find out ...
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Re: 1541C unusual "Shorter Board" version - J3?

Post by banman »

Hi Gyro Gearloose,


That Teac head looks like a good candidate. I wonder if anyone has ever tried to MacGyver one into a commodore drive.
I was just browsing eBay when this showed up. I have been following a hunch that was suggested by rmzalbar in another thread.

Here.....

viewtopic.php?p=23542#p23542

rmzalbar said something that I had always suspected of some eBay sellers but couldn't enunciate it.

So I have been hard at it trying to prove it. It is very difficult, it's more like observing and tracking trends, patterns in the eBay market than anything else. Maybe I am not going about my research the correct way.
I actively look for products. Sometimes I find the item I'm looking for with only a few days left on the bid (as in the above case) or the sale has already been transacted.
I wonder if some items on eBay's site don't even make to my inbox.
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