971018  Differential story

Back in 1997, hard drives were not so cheap here in Japan.  New hard derive of 1G capacity cost about JY10,000. As a matter of fact I could not pay such money for SCSI hard drives.   According to my master of MCA,  used 5" full height drives were relatively cheap to get.  He wrote that he sometimes got 1G drive for JY1,000 in used PC market.   OK,  that was the way I liked. 

Oct. 18 
As usually, trolled around  junk shops.  Found three  ST42400ND at a shop. A clerk said they were defective and their testing system could not detect them.  I had taught by the master of MCA  that the last letter "D" in Seagate drive meant "Differential".  Paid JY3,000 for three drives. Ordered  Rancho single-differential converter to US hi-techinc.com. (  it cost me another JY5,000.  MAD level increased one step higher ). 

Nov. date unknown
Got single-differential converters from hi-tech inc. 
One was Rancho's converter and the other was labeled as "Juke Box".  Rancho converter could be
used in bi-directional, from differential drive to single-ended usual adapter and/or from single -ended
drive to differential adapter. Juke Box is a tiny card to be connected to differential hard drive directly.

Opened up my "Grandma", connected  the Rancho off from short cached SCSI 2/A  with yellow DIP terminator ( of course the terminator was pulled off ) after the small IML drive, and then connected a ST42400ND to Rancho differential end.
Hey-ho,  2G capacity would be provided for me with Rancho converter. 
"Power on ! ",  pushed the main SW.   " Go baby go, go.  go baby go go.......? "    Charming error code was displayed on the LED panel  ( don't remember it ).   Tried various combination of jumper blocks on the Rancho card.  No lucks....    Pulled off the Rancho card and powered up 5580.

  SCSI drive was not detected by the system.  5580 warned me that Spock SCSI is defective !.

The short, cached SCSI /A that I used for the test was known to be capable to handle IML drive >1G. 
And that was the only one I had back then.   I had not yet tried it with a usual single-ended narrow 
drive larger than 1G ( because I had not such a drive. All of my 3.5" scsi drives were below 500MB ).
Yes I had some of  bigger drives but they were all 5" full height shape made of DEC, Micropolise and
Fujitsu.   What the h*ll happened there.   I examined  short  Spock to every inch with my ohm meter
and found that a very little black square chip was defective.    Same part used in 16bit scsi card had
electrical connection ( sorry I don't know how to say call it ) between both end,  but the one in 32bit
Spock had no connections. A needle of my ohm meter  deflected outer ward.  The part might was 
supposed to be a FUSE with it's silk marking "F1".  What kind of fuse it was ???
I asked to the Forum and got an answer that it might be a part so called " Poli-Switch".
Few days latter I got similar kind of tiny chip and replaced it with the burnt one.
Bingo !  Specification of the chip I bought was bit different from original part but it was functional and
revived my precious love. 

Oh, well, I should talk about Rancho.  As a matter of fact I don't remember how I got rid out of the trouble.  But Rancho converter securely drove ST42400NDs. It had been sat in my 5580 for about 3
years with a ST42400ND.   I also got some differential drives latter.  HP,  Sequant ( probably HP OEM ) and Seagate.  Most of them were donated to used PC/Parts forum.

                 Someday In 2000,  I  happened to see funny drive cages pulled off from unknown 
                 server  machine at a garage shop.  I could just recognize markings " IBM", "DFxx" 
                 through punching holes of the cage.  They were not slim height drives so I assumed 
                 they should be DFHS S4F( Single Ended 50pin Fast ) or S4F ( Single Eended 68pin
                 Fast/Wide).   I  Paid  JY3.000for 3 assembly of cages and drives.
                 Back in home,  disassembled  the cages,  saw the labels on the drives saying
                 " DFHS S4E" .....grrr...they were actually First/Wide drives but.......Differential.

                 2001. Apr
                 Read message by Dan that he wanted to sell differential corvette. The part number 
                 was same with the one supposed to be functional on PS/2  (  according to Louis's page ).
                 Paid for it  through PayPAl. Received a Differencial First Wide SCSI II /A.
                 I'm ashamed.   I  have not yet checked it to drive DFHS S4Es in my 95.

               Japanese Lesson 1
                  go go;  "5"  is  "go" in Japanese.   "55" is " gojyu-go" ( say, 10 is "jyuu" ).
                               mathematically "55" should be pronounced as "gojyuu-go" . 
                               I usually call it as "PS go-go" 
                               I don't know how IBM called PS/55,  PS fifty five,  PS gojyuu-go , PS go-go .... 
                               But anyway ...   Go baby go, go. GO baby go go go go. Jophny B. Good... 
                I bet  SONY Play Station will never reach to "55" and  PS/55 will always be high above from it.

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