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| | Previous Messages | Posted By
RobertB
on 2012-07-18
01:40:43
|  Re: Getting a pair of 1551s
Richard42 wrote:
> Robert, I didn't know you had a European 1551 as well.
That reminds me to bring my 1551 to CommVEx. I can exhibit it with a Plus/4.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
July 28-29 Commodore Vegas Expo v8 -
http://www.portcommodore.com/commvex
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Posted By
Richard42
on 2012-07-16
22:53:32
| Re: Getting a pair of 1551s
Robert, I didn't know you had a European 1551 as well. I bet the 1540009-02c transformers that I bought also came out of 1541s. This transformer just barely fits in the space under the PCB. It's quite a bit bigger than the -06 transformer. It's nice that it mounts perfectly with the same screw locations.
Chicken, thanks for the link to Csory's tools. I agree that it may not be the seller's fault; the drive might have been sitting in a box for a decade before going up on ebay.
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Posted By
Chicken
on 2012-07-16
03:28:59
 | Re: Getting a pair of 1551s
Richard:
Thanks for the updates  Glad to hear you got both of them working! You should check out various tools by CSORY. His dedicated 1551 tools get the most out of the drive. I always wondered if they work on NTSC plus/4s.
Btw, those yellow dots are very common on all the socketed chips Most of my machines have them.
Side note:
The auction text said something like "Got these from a deceased relative." and "They look ok." It seems honest, not everyone is able to check everything. It's different if someone sells lots of "checked" items and then lists "untested" ones.
Hans:
Actually, ROMs do get bad sometimes. I experienced some faulty BASIC ROMs myself. (Which was somewhat fortunate because I expected a bad TED or CPU instead  )
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Posted By
RobertB
on 2012-07-16
02:05:31
| Re: Getting a pair of 1551s
Yay! More 1551s in California! Richard, you'll have to show me your 1551s, and I'll bring my 1551. Ray Carlsen put a North American p.s. from a 1541 into mine, and it works just fine.
Truly,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
July 28-29 Commodore Vegas Expo v8 -
http://www.portcommodore.com/commvex
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Posted By
Richard42
on 2012-07-15
17:15:29
| Re: Getting a pair of 1551s
Yes, the PROM chip is socketed. I don't know why someone would remove this chip and try to program anything into it; maybe it was just a normal failure due to age, contamination during manufacturing, etc. But it doesn't really matter. I'm just glad that I was lucky enough to find the problem right away and could fix it without much work.
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Posted By
Hans
on 2012-07-15
15:36:51
| Re: Getting a pair of 1551s
Hi Richard,
It's many years ago since I looked into the bowel of a 1551. From your report I assume that the faulty chip in question is socketed and not soldered to the board directly?
So my humble guess is that somebody has been playing around with it and probably made a mistake during erasing and/or burning. If I remember correctly, not all of the homemade eprom burners for the Plus/4 did provide a correct / stable burning voltage (wasn't it 21 VDC like as for the 27256 type? Can't remember exactly).
At any rate, it's naughty to have remarked the chip from "OK" (yellow) to "BAD" (black) but not to indicate this on the clad.
Isn't that very, very Ebay-like?:
"...unit powers up and the pilot lits... can't test it further...".
Regards,
Hans.
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Posted By
Richard42
on 2012-07-15
14:39:41
| Re: Getting a pair of 1551s
Hans, that's correct. I also noticed that the working drive had 3 40-pin chips with yellow dots on them; presumably this was done in the commodore factory to indicate that the chip was tested/good. The non-working drive appeared to have 2 chips with yellow dots, but on closer inspection I saw that the 318008-01 PROM chip had a (presumably yellow) dot which had been painted over with black. So it seems that someone even tested the drive before me and found that the ROM was bad. That's unfortunate; I thought that both auctions stated that the drives were good.
For kicks, I dumped the data from the bad ROM chip as well as the good one. I ran each through 'hexdump -C' and diffed the output to see what the bad rom data looked like. The binary differences showed up only in the 5th and 6th bytes of each 16-byte block, and only in four 1k blocks, starting at 0x0000, 0x1000, 0x2000, and 0x3000. This eprom is 0x4000 bytes long. In these bytes, in the bad PROM chip, the 0x04 bit is always 0. This is an interesting failure mode for that chip. I presume that it's internally an NMOS eprom but with no quartz window.
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Posted By
Hans
on 2012-07-15
07:52:55
| Re: Getting a pair of 1551s
Hi Richard,
<quote>.....drive S/N 10754 wouldn't work at first; the +4 reported "device not found" and the drive gave a repeating 2-blink code on the red light. I tried to find a service manual for the 1551 but couldn't. I did find an old PET drive service manual claiming that a 2-blink code means DOS ROM error. I pulled the EPROMS out of both drives and found that the working drive had the correct eprom data (as tested via md5 hash with a ROM that I downloaded from the web) while the non-working drive had different eprom data. I took a spare 27C128 eprom and burned it with the correct dos eprom data......</quote>
That's mysterious. Your changing the AC power supply from 220 VAC (at 50 Hz) to 115 VAC at 60 Hz certainly has nothing to do with the cloag & dagger behaviour of the floppy's internal DC circuits (to which the eprom you are quoting belongs to), and I've never heard that an eprom would change its stored data unless it's exposed to UV radiation.
In my opinion this can only mean that the 1551 never has been operational before you fixed it with a rewritten eprom. Strange....
Regards,
Hans.
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Posted By
MIK
on 2012-07-14
23:30:07
 | Re: Getting a pair of 1551s
Congrats on getting the drives working! Just shows, if you know what your doing it is worth the effort. Enjoy!
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Posted By
Richard42
on 2012-07-14
18:41:32
| Re: Getting a pair of 1551s
Another update.
Today I got the 1540009-02C (120/240v) transformers, so I took apart both of my German 1551 drives. I found that drive S/N 10754 had the newer-looking (open windings w/ solder lugs) 1540009-06 transformer, which I previously wrote about, while drive S/N 11476 had an older-looking 1540009-03C transformer (paper+glaze covering the windings with, red/blk/white primary wires and no solder lugs). This transformer looked just like the -02C transformers so I thought maybe it was also 120/240v, but I tested and alas it is also 220v/240. I swapped in the -02C transformers in both drives. I had to also swap in the (taller) support brackets for S/N 10754, because the -06 transformer is smaller than the others and has shorter brackets. I put 1A fuses in both drives and used heat-shrink to make it all nice, and, viola both drives power up.
Unfortunately drive S/N 10754 wouldn't work at first; the +4 reported "device not found" and the drive gave a repeating 2-blink code on the red light. I tried to find a service manual for the 1551 but couldn't. I did find an old PET drive service manual claiming that a 2-blink code means DOS ROM error. I pulled the EPROMS out of both drives and found that the working drive had the correct eprom data (as tested via md5 hash with a ROM that I downloaded from the web) while the non-working drive had different eprom data. I took a spare 27C128 eprom and burned it with the correct dos eprom data, and viola, I now have 2 German 1551 drives which work properly here in the US with 120v mains.
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Posted By
Richard42
on 2012-07-13
12:32:42
| Re: Getting a pair of 1551s
Just for anyone who is interested in the Commodore 1551 drive:
The German drives which I received each have a Commodore 1540009-06 power transformer. This transformer can only be wired for 220v or 240v primaries. Luckily I found this guy on the web:
http://4sale.sbszoo.com/xformers_2sec.htm
I purchased two 1540009-02C transformers from him; these are used in the 1541 drive, and can be wired for either 120 or 240v. They appear to have the same physical dimensions as the -06 transformer, and hopefully they will have sufficient current output to power the 1551 drive as well. With a little bit of luck I will swap out the transformers and use a 1.0A fuse instead of a 0.5A fuse and the German drives will work here in the US.
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Posted By
Richard42
on 2012-06-08
22:51:38
| Re: Getting a pair of 1551s
Hans, sorry for the outbid. Those are the auctions that he won for me. Ebay won't even let me bid on them, since the seller will only deliver to Germany. Seems a lot of the 1551s selling on ebay lately have been either in the UK or Germany with no worldwide shipping option. Thanks for the information about the power supply and wire colors. I am an electrical engineer so it shouldn't be a problem to rewire the transformer. Sorry to hear about your dead +4. I also got a dead one a couple of months ago and the seller was gracious enough to refund me the entire cost and keep the machine. I gave it to a local commodore enthusiast who said he was making a couch out of dead plus/4s.
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Posted By
Hans
on 2012-06-08
15:21:38
| Re: Getting a pair of 1551s
Your friend got those on Ebay Germany yesterday?
Ebay item No. 170850614744 and
Ebay item No. 170850612995.
HRMPF! I was outbid on both of them!
Anyway, yesterday wasn't my day. The Plussy which was delivered yesterday afternoon was described in the Ebay offer as usual:
"....found this item in the attic....can't test it....no warranty...."
Oh yes. Untested. I tested it, and:
Windows: blue screen
Faulty Plussy: black screen.
Just another one with a blown CPU and/or TED....
Well, that's life.
Richard, congrats to your purchase. If 1551s in are really that rare in the US, I'd rather take them both and keep them. If they're OK, their value is going to increase, in particular when they're so rare.
Please keep in mind that the machines, since originating from Germany, are laid out for 220 VAC pover supply. You can change the internal transformer to the US standard 115 VAC by replacing some leads (I've seen that on a C64 web page but can't recall the WWW address right now). -
The power cord you're getting along with the 1551 is colour coded to the European standard. When you replace the plug, please follow these codes:
Live wire: US = black / Europe = brown
Neutral wire: US = white / Europe - blue
Ground wire: US = green / Europe - green/yellow
Regards,
Hans.
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Posted By
Richard42
on 2012-06-08
13:41:36
| Getting a pair of 1551s
Everyone in the US knows how impossible it is to find 1551 drives here. I have a friend in Germany who just bid on and won 2 ebay.de auctions for 1551 drives. He will take delivery of the drives and send them on to me in California. If someone is interested I may sell the second drive, since I only really need one. It won't be cheap though, I think the total bill to get both of them here will be around $320-350.
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