On 08/16/2017 10:40 AM, Tony Duell via cctalk wrote: > > I have just looked at it, and unfortunately it is of no help with this > question (I assume that if manuals for other versions of the FD235 > exist, they will be similar). Most of the manual is replacing mechanical > parts, doing the head alignment, etc. There are schematics of the > spindle motor and the logic PCB in the manual, but the latter is one > big ASIC (containing all the digital circuitry, the read channel, etc) > with a few passives hung off it. There is no theory-of-operation > of that IC, or block diagrams in the manual, alas.
Exactly--there have been many versions of the PCB for the 235HF. The schematic that I have (obtained back in the day via Teac's "FAX on demand") mostly show a large anonymous ASIC. Same for the 235J (ED version). This probably also obtains for most other 1.44M drives as well--though if I looked, I might get lucky. AGC and bandpass filtering wouldn't be unexpected, however. --Chuck
