Atari 810 rear board redesign?

[spinnaker15136]

I have the original Atari 810. The one with the problem rear board. Other than the Grass Valley upgrade, was anyone tried to do a redesign?

 

I might try and give it at least a look anyway. But first I would like to understand the over all issues with the rear board. From what I understand it was the RPM circuit that was unreliable. Was this pretty much the main issue?

 

I am thinking it might be possible to redesign the rpm control section only. Patching in control lines from the side board might be challenging.

[+Nezgar]

Looking at service manual tech-tips, and the And the FAQ there's some other hints to issues of the pre-grass valley upgrades, there's quite a few changes:
https://mcurrent.name/atari-8-bit/faq.txt
http://atariage.com/forums/topic/254378-complete-list-of-techtips-change-orders-mods-etc/?p=3543286

• The WD1771 controller chip had inadequate internal data separation, which is where the daughterboard came in to address that. Improves the drive's ability to distinguish between data pulses and clock pulses on the disk, lowering the chance of a misread.
  • The Western Digital WD1771 disk controller does in fact include a FM (single-density) data separator on-chip. Being an early integrated circuit design, the data separator is not particularly high-performance. This is referenced in the WD1771 datasheet, page 17: "NOTE: Internal data separation may work for some applications. However, for applications requiring high data recover reliability, WDC recommends external data separation be used." Source: http://www.glitchwrks.com/2014/01/30/cromemco-4fdc
• The stepper motor circuit voltage was upgraded to a regulated 12V DC.
• The increased power requirements from 20W to 30W meant the power adapter was upgraded to the 31VA 9VAC supplies, according to the FAQ analog 810's originally came with a 15.3VA supply! (C014319)
• The redesigned power board contains a redesigned power supply, a tachometer/speed Switch I.C. (frequency to voltage converter) added to the tach circuit to stabilize the motor speed.
• The separate analog board major changes are to the Read/Write circuitry: Operational amplifiers ("op-amps") and discrete transistors in place of transistor arrays, and a multiplexer chip for switching the Read/Write amplifiers.

I've never had my hands on one of those early drives, but the early history is sure interesting...

[spinnaker15136]

Looking at service manual tech-tips, and the And the FAQ there's some other hints to issues of the pre-grass valley upgrades, there's quite a few changes:

https://mcurrent.name/atari-8-bit/faq.txt

http://atariage.com/forums/topic/254378-complete-list-of-techtips-change-orders-mods-etc/?p=3543286

• The WD1771 controller chip had inadequate internal data separation, which is where the daughterboard came in to address that. Improves the drive's ability to distinguish between data pulses and clock pulses on the disk, lowering the chance of a misread.
  • The Western Digital WD1771 disk controller does in fact include a FM (single-density) data separator on-chip. Being an early integrated circuit design, the data separator is not particularly high-performance. This is referenced in the WD1771 datasheet, page 17: "NOTE: Internal data separation may work for some applications. However, for applications requiring high data recover reliability, WDC recommends external data separation be used." Source: http://www.glitchwrks.com/2014/01/30/cromemco-4fdc
• The stepper motor circuit voltage was upgraded to a regulated 12V DC.
• The increased power requirements from 20W to 30W meant the power adapter was upgraded to the 31VA 9VAC supplies, according to the FAQ analog 810's originally came with a 15.3VA supply! (C014319)
• The redesigned power board contains a redesigned power supply, a tachometer/speed Switch I.C. (frequency to voltage converter) added to the tach circuit to stabilize the motor speed.
• The separate analog board major changes are to the Read/Write circuitry: Operational amplifiers ("op-amps") and discrete transistors in place of transistor arrays, and a multiplexer chip for switching the Read/Write amplifiers.

I've never had my hands on one of those early drives, but the early history is sure interesting...

 

I am beginning to think this would be a huge undertaking for such a project.

 

I have someone sending me a couple of PC drives. I am thinking the best thing to do is try to build an interface for them and fit it to an 810 case. I could probably leverage the work done like the folks that did SD Drive Max for the SIO part.