50Hz ---> 60Hz

Anything to do with New Zealand Classic or Vintage Computing not covered in the other forums

50Hz ---> 60Hz

Postby nama on Tue Oct 27, 2015 8:08 am

Hi,
I have a bit of an issue with some old Shugart 8" (801) drives. These drives were imported from the US, and incorporate an AC transformer to power the drives.
The unique thing about the AC power supply is that it uses the mains frequency to spin the drives at a certain speed. As you may know US power is 110V @ 60Hz which allows the Drive should spin at 360rpm. In NZ the power is 220 @ 50Hz. It's easy enough to use a step down transformer for the voltage, but the frequency is a different story. 50Hz means the drive spins at 300rpm, not 360rpm

I've been looking into solutions, including:
- fabricating new pulleys and sourcing new drive belts
- Using a US inverter to convert 12V DC to 110V @ 60Hz AC, but need to find a grunty enough 12V PSU to handle the load.
- Other solutions seem to be large and industrial based, and extremely expensive.

I was wondering if anyone else has come across a similar problem and have found an affordable solution.

I may add that the drives actually work, but the disks they create can not be used on any other system, and archiving of these disks using something like Dave Dunfield's ImageDisk is not an option as the disk is unrecognisable as all the data is compressed.

Thanks for listening.

Phil
Retro computing at: http://www.neoncluster.com
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Re: 50Hz ---> 60Hz

Postby Gibsaw on Tue Oct 27, 2015 10:33 am

Oooh... I wonder if this affects USA sourced disk II's?
"dsakey" on trademe. Apple II's are my thing.
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Re: 50Hz ---> 60Hz

Postby nama on Tue Oct 27, 2015 10:46 am

5.25" and 3.5" drives don't have this issue, also some 'newer' 8" drives too...just the really old 8" drives.

Shugart 800 series drives actually came in 2 varieties. 110V @ 60Hz, and 220 @ 50Hz, and both spin the drive at 360rpm in their respective countries. The problem arrises when using a 50Hz drive in a 60Hz country, or visa versa.

Phil
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Re: 50Hz ---> 60Hz

Postby Clym5 on Tue Oct 27, 2015 11:50 am

How many amps does the drive pull under load at 110v? And how long would max (or thereabouts) load be sustained for?
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Re: 50Hz ---> 60Hz

Postby nama on Tue Oct 27, 2015 1:55 pm

According to the 'SA800/801 Theory of operation manual', a single drives maximum current is about 0.6 Amps. I have a dual drive setup, so I think about 1.2Amps...does that sound right?
As for sustained use, I probably don't use the machine for more that an hour at a time.

EDIT: Actually, looking at the manual again, I'm not sure how to read the power chart. Seems to have a bunch of different pins mentioned. the 0.6Amps is for the AC power to the drive (P4) , but the P5 pin1 states 1.7Amps and for the DC power tot he drive. So sorry, I'm a little confused how to read the chart. Wish I could post pictures. Here is a link to the manual:
http://nfggames.com/x68000/Documentatio ... ations.pdf
Page 29 shows the chart in question.

Phil
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Re: 50Hz ---> 60Hz

Postby nama on Tue Oct 27, 2015 2:54 pm

Hi, me again. I found a spec sheet here:
http://bitsavers.trailing-edge.com/pdf/ ... _Feb78.pdf
The power specs are shown as:

AC Power Requirements
50/60 Hz ± 0.5 Hz
100/115 VAC Installations 85-127V at .4A typical
200/230 VAC Installations 170-253V at .2A typical

DC Voltage Requirements
+ 24 VDC ± 5% 1.3A typical
+ 5 VDC ± 5% 0.8A typical
- 5 VDC ± 5% .05A typical (option -7 to -16 VDC)

Phil
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Re: 50Hz ---> 60Hz

Postby Clym5 on Wed Oct 28, 2015 8:24 am

The power requirements aren't that high then, that's good. I was about to say you could easily adapt a computer's ATX PSU to give 12v and 5v at however many amps you need for the inverter (most good ATX supplies give more than 10A) but you also need 24v..

I haven't been able to read through that document, but when you say "DC Voltage Requirements", is that generated internally by the disk drive or do you need to provide that? You mentioned 1 DC input, not multiple.

I'd also highly recommend a pure sine inverter for this.
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Re: 50Hz ---> 60Hz

Postby mons2b on Fri Sep 23, 2016 1:13 am

Maybe I am over simplifying it but could you just not alter the internal feed to feed slightly more volts to the drive until it gets to your required RPM. Ie a variable resister pot inside. Tune to your perfection then locktite it.
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Re: 50Hz ---> 60Hz

Postby Mark0x01 on Fri Oct 28, 2016 8:23 pm

I'd do what they probably origionally did, change/modify the size of the drive wheel to compensate.

Mark.
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Re: 50Hz ---> 60Hz

Postby nama on Wed Nov 09, 2016 8:49 am

Hi All,
After some serious searching, I was able to purchase some 60Hz pulleys for Shugart 8" drives from the US.
However, my recent projects have possibly made the need for them unnecessary.

I borrowed a Kryoflux and I was able to convert my real IMSAI 8" CP/M floppies to disk images.
I built up an 8" -> 5.25" floppy adapter cable, and purchased a Gotek floppy emulator. I then purchased a Gotek firmware upgrade so it can function like an HxC floppy emulator. It was then a simple case of converting the disk images to something the Gotek/HxC can read...bingo. A solid state solution for booting CP/M 2.2 and 1.4, without worrying that my 30+ year old 8" floppy disk will keep working.

Thanks

Phil
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Re: 50Hz ---> 60Hz

Postby tezza on Sat Nov 12, 2016 10:19 am

Great to hear about this feat of preservation Phil.

Next time I'm in ChCh I should bring my 8 inch disks for my panasonic machine and pay you a visit. I'd love to get those imaged so the software can be preserved.

>A solid state solution for booting CP/M 2.2 and 1.4, without worrying that my 30+ year old 8" floppy disk will keep working.

True. Mind you there is something about the "shuff, shuff, shuff"...wrrrr..clack" of a floppy turning in it's jacket and the drive head seeking that adds to the vintage experience. However, too often though the vintage experience is just "Bdos Err On..." these days :D
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