Modifying Teac FD-235 C291 U5

[RiP]

Alright, if you don't believe what I say, re-read the guide at http://elgensrepairs.blogspot.co.uk/...5-fdd-for.html and tell me where exactly pin 4 is mentioned.



So? If it wasn't connected to the IC, would there even be a point in saying "cut the trace" ? The very goal is totally *isolating* this pin from whatever false pin on the IC it may currently be connected to and then routing DISKCHANGE onto it.

Pin4 is connected to S6 which is connected to nothing. Pin2 is connected to S4 which is connected to nothing too.
Then I cut the trace from pin34 that was connected to IC and soldered the IC pin to pin2 as you said.
But I soldered pin34 to pin4 same as what he was done rather than pin8+diode you were told me.
Here's the photo: http://i.imgur.com/DoWoBwu.jpg

If it's wrong, I can solder it to pin8 with diode =/

[BLTCON0]

@RiP
The instructions I posted are generic and can be applied to any drive. I can't possibly know what signal is enabled by jumper S6 or S-anything on your specific drive, or what possibly obscure and non-standard connections some pins may have.

Hence the "dictator" instructions: either you follow them to the letter and ensure a specific behaviour for the drive, or you end up with a possibly unpredictable result.

To sum up:
0. ID jumper must be set for DS0
1. pins 2 and 34 must be perfectly isolated (if necessary, by cutting traces)
2. DISKCHANGE (from the IC) must be routed to pin2
3. READY (from the IC) must be routed to pin34. If no READY exists or is tough to discover, you can alternatively do the pins 8-34 diode trick to imitate it.

[RiP]

@RiP
The instructions I posted are generic and can be applied to any drive. I can't possibly know what signal is enabled by jumper S6 or S-anything on your specific drive, or what possibly obscure and non-standard connections some pins may have.

Hence the "dictator" instructions: either you follow them to the letter and ensure a specific behaviour for the drive, or you end up with a possibly unpredictable result.

To sum up:
0. ID jumper must be set for DS0
1. pins 2 and 34 must be perfectly isolated (if necessary, by cutting traces)
2. DISKCHANGE (from the IC) must be routed to pin2
3. READY (from the IC) must be routed to pin34. If no READY exists or is tough to discover, you can alternatively do the pins 8-34 diode trick to imitate it.

Thank you, is there anyway to fully check if the drive has modified correctly or not?

[BLTCON0]

Yes, if disk changes are properly autodetected in workbench then DISKCHANGE is correct.

For the READY signal you need some games/demos that require it in their trackloader.
I don't have a comprehensive list but the mod site you linked says something about X Copy (don't use X Copy TNG though).
Just test 10-20 NDOS games or demos, chances are at least a few of them will have READY-dependent trackloaders. If all load fine, your READY signal is OK too.

If I recall correctly, one such READY-dependent game is Skweek. I think that's what I used to test my first modded drives, but it's been more than 6 years since then :-)
A quick web search also shows Super Cars 2.

[RiP]

Thanks, then READY signal should be connected to a pin from IC too.
And how to measure 5V? I need to know the 2nd -5V to connect multimeter.

[BLTCON0]

Thanks, then READY signal should be connected to a pin from IC too.
And how to measure 5V? I need to know the 2nd -5V to connect multimeter.

+5V is measured against GND (ground), use any available ground point on the PCB (e.g. the odd numbered pins on the 34-pin connector typically are GND).

[lost_loven]

Well got a pc drive up and running.. did as described on this thread and works. Some times it says df2:unrecognizable and I have to put the floppy in a couple of times till it catchs. other than that it work good! Maybe there is a way to tweak it. Here are some pics.. should I paint it black?

 video of drive working!

https://www.youtube.com/watch?v=PdEdZjA6Nig

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lost

[RiP]

Well, diode method didn't work for other versions of FD-235.
Are you sure about pin8?

[RiP]

Ah, it was DD/HD issue. It seems they're working fine with Skweek now

[BLTCON0]

Well, diode method didn't work for other versions of FD-235.
Are you sure about pin8?

Yeah, pin8 = INDEX.

The way it's shown on the pic (using the drive's SELECT signal) is not a good idea.
The typical sequence is:
1. Select the drive
2. Enable the motor
3. Wait for the RDY signal (or for 500 milliseconds) to ensure that the motor is up to full speed

Some drives may have the motor ready in as little as 300 ms, but that's about it.
So the soonest possible after Select before the drive (motor) is actually Ready is about 300 ms, and that's not even valid for all drives. 500 ms is the accepted delay.

So, if you tie RDY to SEL, you're essentially telling the Amiga that the drive is Ready as soon as it's Selected, which is obviously not true. So an RDY-based loader will read bogus data, and it all boils down to whether the loader has a recovery procedure or not. If it has, it'll retry and retry until the motor is in full speed, at which point valid data will come through and the loader will continue.
Otherwise, if it operates under the assumption that data is always correct, you'll get a nice crash.

To the contrary, the RDY signal is always a prerequisite before the drive issues an INDEX signal (even if RDY is not externally provided, the motor-readiness state is still assessed before any valid INDEX signal is issued).

So tying INDEX to RDY, you avoid the aforementioned risk.

[RiP]

I feel the diode method makes loading slow =/

[BLTCON0]

I feel the diode method makes loading slow =/

It could happen. The diode method is only an easy approximation of the READY signal and not a true replacement.
The INDEX signal (to which the READY signal is tied to via the diode) is only active for a brief period during each disk revolution (while a true READY signal must be active for as long as the motor spins at full speed).
Most loaders, once they've started the motor, will remain in a tight checking loop for RDY, so this doesn't present any problems.
But some peculiar loader that only checks once per frame or whatever, might take a few revolutions before it 'catches' a READY signal that way.
In extreme cases this could even never happen (if the check is in perfect sync with the disk revolution, or if the loader gives up too early).

A proper READY solution (in negative logic) would be:

READY = DELAY AND MOTOR

where DELAY is a helper signal which
a) initialises as disabled
b) gets disabled whenever MOTOR gets disabled
c) replicates MOTOR with a 500 ms delay whenever MOTOR gets enabled

[RiP]

(*) If you want a true READY signal, you'll have to find which pin on the square FDC controller it's produced. The READY signal will be steady at around +5 V when no disk is in the drive (motor idle) and will drop to 0 V about half a second after a disk has been inserted (motor at full speed).
Once the READY pin on the controller chip has been identified, you can connect it directly to the (otherwise isolated) pin#34 and skip the diode altogether.

I'll try to find it

[RiP]

(*) If you want a true READY signal, you'll have to find which pin on the square FDC controller it's produced. The READY signal will be steady at around +5 V when no disk is in the drive (motor idle) and will drop to 0 V about half a second after a disk has been inserted (motor at full speed).
Once the READY pin on the controller chip has been identified, you can connect it directly to the (otherwise isolated) pin#34 and skip the diode altogether.

Are you sure about +5V ?
I found a pin which has no voltage at all but loads Skweek without any problem.

[RiP]

It seems these Teac drives have no Ready signal. Is it possible? =/
http://www.iobium.com/9100a%20tester/9100atester.htm

Edit: I think these helped me too, will test more later: