On Sunday 10 June 2007 16:15, Tony Duell wrote: I read this and for some reason the part number MB8877 comes to mind. Is that it by any chance? -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

On Tuesday 12 June 2007 13:32, Chuck Guzis wrote: I think I first ran into that working on the Osborne 1. :-) -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

On 12 Jun 2007 at 20:15, Tony Duell wrote: I should be more careful in my writing. The WD1793 takes a +12 and +5 supplies, while the MB8877 requires only +5 (the other pin is NC). A MB8877 will replace a WD1793, but not necessarily vice-versa. In my particular situation, I've replaced WD1793s with MB8877s, never the other way around. Thanks for catching that. Cheers, Chuck

My pictures of VCF East are online: http://sturgeon.css.psu.edu/~mloewen/Oldtech/VCFEast-2007/ Mike Loewen mloewen at cpumagic.scol.pa.us Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/

Roberto Bazzano wrote: Did HP||WD||Fujitsu patent that? I sure could use it in the car. I'd rather not run additional wire for +5V. Will it work with high voltage too? I've always wanted to put a 51J-4 in my car. == jd "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." -- Benjamin Franklin, 1759

There is a MB8866 on the board. No MB8877 at all. Roberto

On Tuesday 12 June 2007 20:55, Chuck Guzis wrote: I've never heard of the 178x parts, only 177x and 179x. What's that one all about? -- Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, ?a critter that can be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters" - Information is more dangerous than cannon to a society ruled by lies. --James M Dakin

Many chips on my controller have only HP house codes. In particular, there are three 40 pin chips, with codes: 1820-2099, MB8866 (this has an "F" as logo, may be it's Fujitsu or Fairchild, I don't know), and an Intel D8291A. Then there are four smaller chips (24 pins? I didn't count them...) marked: 1818-1834 and 1818-1835 (these are on sockets: may be they are roms?), and two 1818-0701. Then, the smallest chips (14-18 pins) with hp house codes are: 1820-2075 1826-0210 1820-1197 1820-1216 1820-1202 1820-1112 1820-1422 1820-2058 1820-0325. Others are standard ttl chips, with both hp house code and standard ttl code. The controller board code is 82901-66503 REV. B I'll do it. I've checked almost all points in the circuit, and I didn't find any -Ve supply. Also, PSU only gives +5 and +12 volt. Thank you very much. Roberto

I have now found my HP dual 5.25" drive, and it's a 82901. I have, of course removed the cover and extracted the controller board. I;ve not looked at it properly yet, but the pinout of that chip appears at a glance to be _very_ close to that of the WD1793 (closer to that than the WD1771, for example). More data when I've done a little tracing. [...] That one suprised me last night, becuase I couldn't understand why there'd be a DTL chip on this board. Am I correct it's a type for 1810-0325? That appears on my board _and on the board of one of the disk drives _ and is a 150 Ohm resistor array (terminator for the floppy drive cable). I am pretty sure the read clock VSO (and part of the PLL circuit?) is the sea of discrete transsitors at the front edge of the board. There's a twiddlepot which presumably sets the read clock frequency, but I'd not turn it yet. HP used a lot of strange circuitry in this sort of thing. Current mirrors and the like. But let's at least prove your drive has problems in that area befroe worrying. -tony

Maybe, maybe not :-). I've not traced out any scheamtics yet, but the read circuit is not simple. When tracing out connections to that MB8866 chip, I found the read data line from the drives [1] goes through what appears to be a delay line made of L's C's and a 74LS14 chip. The problem could be in that area. Or it could be in the VCO circuit, or even (let's hope not) in the MB8866 chip itself. [1] The 34 pin drive cable is the standard Shugart pinout, of course. The drives (HP9130 IIRC) are Tandon drives, built to HP spec, with gold-plated PCBs, and the like. I don;t know which company actually made and asembled the PCBs. FWIW, the older 9885 8" drive has a Shugart 800 mechanism with HP electronics (this PCB is not a copy of the standard one. The service manual for that unit actually mentioned this fact, and gives Shugart part numbers for some of the mechancial bits. I don't know what tests you made, but it's not uncommon for theere to be transsitors with bace and collector linked together in this sort of circuit. So in-cricuit tests may bot be relevant. Most of the transistors seem to be 2N3904 (NPN) and 2N3906 (PNP). but there's at least one with an 1855-xxxx number, that may well be a FET. -tony

On pin 26 there is absolutely nothing: it's always low. I traced it back, and found that there is nothing because pin 11 of LM361 (output 1) is always low. I didn't go back it yet. Also, I replaced all transistors and nothing changed. Roberto

A quick look at the PCB (and I'll admit I've not removed it, only looked for likely signals) suggests the -ve supply comes as follows : The master clock (8 MHz oscillator package) is divided down to 500kHz by the 'b' side of the '393 next to it, then divided down further to 31.25kHz by tghe 'a; side of that chip. The 'a' and 'b' sections of the '26 next to that are the drivers for the -ve supply. Yo ucan't see any obvious signal at the output of the 'a' section. it may well drive the base of a transsitor or something (it is an open-collector output, so this would be OK). The 4 transistors in front of the power conenctor are some kind of totem-pole output stage producing a 12V p-p square wave with a freqeucny of 31.25kHz from this signal (and the 12V supply input, of course). In front of that are a couple of electrolytic caps and some diodes. These form a charge pump circuit, giving the -ve supply. You should see -9.5V on the right hand (not earthed) end of the front-most capacitor of the pair. I've not traced any more.... -tony

I've now taken my unit apart, and spent the afternoon investigating the controller board (for my own interest, I hasten to add :-)) I was right aobut the clock, The -ve PSU is driven by the QD output of the 'a' section of that '393. I assuem this is present and correct (31.25 kHz). It drives one input of each of sections 'a' and 'b' of the '26. The other inputs are tied high (to +5V). This is an open-collector buffer. The 4 transsitors I thought were the driver are. The otuput of that goes to a 2-diode, 2-capacitor charge pump circuit. A very similar circuit was used in some other drive units -- I think the 9133A uses something like it (with '06 buffers, not '26?)> HP did actually publish that part of the cirucit -- I have a paper copy of the 3.5" disk driv eservice data that includes the PSU schematics, including this circuit, but not the clock generator/divider (which is, however, trivial to trace). I don't know if there's anything applicable on http://www.hpmuseum.net/ but i might be worth taking a look if you get stuck. That sounds correct. The emitter of that 2N3904 is grounded. so you'll only see 1 diode-drop of swing there. It's pulled up to +12V by an 8.2k resistor, that's what provides the base current for the 2N3904 when the output is turned off. Do you have a 'scope? If so, look at the collecttors, coveniently on the metal cans, of the 2N2222 or 2N2907 (they;re linked together). You should see a 12V p-p square wave here (switching between ground and +12V essentially. If not, suspect the transistors, If that signal is prensent, check the charge pump compoentns. Now I've looked at the PCB, I can confirm these 2 points are linked by a PCB trace. If there's voltage on the capacitor nad not on the LM361, you've got an opne-circuit there, but I think that's very unlikely. -tony

Here you can download the full service manual: http://www.z80ne.com/82901-90031_HP_82901_&_82902_Service_Manual_comple… It's uploading now: it'll be ready in 10 minutes (it's 37MB size). I sent it to HPMuseum also. Thank you. Roberto

Yes, they are two TM100-2. I downloaded a few files in the past, but I don't remember where. If you want, I can send them to you: they are 8 MB in total. No, mine hasn't it. Roberto

Excellent! fx : blushes You don't need to thank me. I'm just pleased another old HP machine is running again... -tony