-----Original Message----- From: owner-classiccmp(a)classiccmp.org [mailto:owner-classiccmp@classiccmp.org]On Behalf Of Tony Duell Sent: Tuesday, February 26, 2002 23:16 PM To: classiccmp(a)classiccmp.org Subject: Re: Teac FD-55B Floppy Oddity drives were but in dinking the other), applied, but it the drives in on +5 or transistor could be I am not sure quite which version my schematic applies to (it says 'FD55(L)' on it), but it appears the head load solenoid pulls in on 12V and holds on 5V. The head load solenoid conencts to the 2 pin connector J4. Pin one goes to the open collector driver (part of U8), and is grounded whenever the solenoid is 'in'. Pin 2 goes via a diode (CR1) to +5V and via a transistor (Q4) to +12V. THe idea is that U8 will ground one end of the solenoid and Q4 will be turned on briefly when the solenoid is to pull in (thus applying 12V to the solenoid, CR1 being reverse biased now) and then Q4 turns off (U8 still grounds the other end of the solenoid), allowing it to hold in (5V power suppled via CR1). across it, out twitch when it's motor select). If the solenoid is mechanically OK, I'd suspect Q4 (assuming it's the same circuit). If that's OK, then I guess U6 (a custom logic gate array) is defective -- it controls the head load circuitry (and a lot of other things) -tony

-----Original Message----- From: owner-classiccmp(a)classiccmp.org [mailto:owner-classiccmp@classiccmp.org]On Behalf Of Tony Duell Sent: Wednesday, February 27, 2002 15:40 PM To: classiccmp(a)classiccmp.org Subject: Re: Teac FD-55B Floppy Oddity I do know that sensor, and the 4 Sounds like it might be the same drive. It was late when I posted last night, and I didn't notice that the track 00 sensor uses pins 4,5,6 of J4 also. Pins 1 and 2 of J4 go to the load solenoid. The schematic has 'P/N 15532001-XX' printed on it. Can you find that number on the PCB? It uses 2 ASICs, 1922-00 (mostly digital circuitry, looks to have about 48 pins) and 7556-00 (analoge read/write circuitry, looks to have 30 pins). -tony

-----Original Message----- From: owner-classiccmp(a)classiccmp.org [mailto:owner-classiccmp@classiccmp.org]On Behalf Of Tony Duell Sent: Wednesday, February 27, 2002 17:43 PM To: classiccmp(a)classiccmp.org Subject: Re: Teac FD-55B Floppy Oddity 7556-00, but a The quality of printing is so bad, that the 30 pin ASIC could well be 7358-00.... I suspect this is the same board. used in the to pull down 4 sections for the head stepper, one for head load, one for the front panel LED. That LED is not going to take much current -- I guess the driver was used 'because it's there'. The head load section has an input on pin 2, output on pin 15. It's shown as a NAND gate on the schematic. One input of all the gates in U8 goes to pin one, which is tied high. On the 1922-00 chip, look at pin 42 (HL output, goes to pin 2 on U8) and pin 41 (HOD -- this is the drive to Q4 to apply 12V to the solenoid to pull it in). My guess is that pin 42 should essentially follow the head load signal from the controller and pin 41 should provide a pull-in pulse whenever head load goes from deasserted to asserted. Q4 is a PNP transistor. Emitter to +12V, collector to the 'top' end of the load soleneoid. CR1 (diode) between +5V and the collector (this is to provide the +5V holding supply when Q4 is cut off). There's a couple of resistors in package RA6 -- seem to be 2k2 each. One from pin 4 to pin 3 (this is connected between the base and emitter of Q4), the other from pin 4 (base of Q4) and pin 5 (to pin 41 on the ASIC). It's all pretty simple... Incidentally, there's a similar circuit for the head stepper motor using transisto Q3 nad diode CR3... -tony

-----Original Message----- From: owner-classiccmp(a)classiccmp.org [mailto:owner-classiccmp@classiccmp.org]On Behalf Of Tony Duell Sent: Wednesday, March 06, 2002 21:37 PM To: classiccmp(a)classiccmp.org Subject: Re: Teac FD-55B Floppy Oddity 42 is staying to load with I am puzzled... If pin 42 is alwys low, then there's no way the head can ever load (U8 a would be turned off, so the output will be floating, so no return path for the load solenoid). (or ever was) DS0/DS1, etc), So am I... itself. There 'UR', 'ML', on that block start is what I It's a bit odd, and as far as I can see (it's getting late, so I might be missing something), the jumper config you have can't work. The motor-on line (pin 16) goes to one side of the HM jumper. The select line (common of DS0, DS1, DS2, etc) goes to one side of the HS jumper (head load on select, I think). The other sides of those 2 jumpers are linked. Makes sesne so far, we'd want this signal to load the head. Invert that with U3f (it's now an active high signal). We'll call this 'H' for the moment. Take motor_on again (straight from pin 16). AND it (remeber it's active low, so it's really an OR) (U2d) with one side of the ML jumper (also puled high by a resistor). ML is not fitted, so the output of UD2 is essentially motor on. Now invert that with U3d. Call this 'M'. Now AND H and M with U2b. So far so good. The only problem is that the output of U2b goes to the SM jumper and nowhere else. The other side of the SM jumper is pulled down (47K resistor in RA4), then goes to pin 40 (HSM) of the 1922-00 ASIC. So without the SM jumper fitted, it can't do a darn thing. My schematic has the HM, IU (pin 4 is In Use, not Head Load (which is what you get idf the HL jumper is fitted instead)) and SM jumpers drawn it. Might be worth fitting at least SM and seeing what happens. -tony

I am not sure quite which version my schematic applies to (it says 'FD55(L)' on it), but it appears the head load solenoid pulls in on 12V and holds on 5V.