Modifying Teac FD-235 C291 U5

[RiP]

I have found this article but it's a bit different than mine:
http://elgensrepairs.blogspot.co.uk/2012/10/modding-teac-fd-235-c291-u5-fdd-for.html

Hope someone can help me :hammer:

[Pat the Cat]

VERY fiddly hack. SMD resistors are a real pain to work with.

Get yourrself a few spare resistors of the same value. You are better off sacrificing the component, and concentrate on keeping the solder pads intact. Practice on a scrap electronics board before doing the mod.

The first stage is the hardest. The track cut is the next hardest.

The good news is, your board has all the same marked connectors (DS0, DS1, S6) and the other pins (IC pin 1, floppy connector pins 2 and 34). So it should work.

Surgical scalpel recommended for the track cuts - and doing SMD board work with a standard soldering iron is a real test of skill.

A magnifying glass is better than nothing, but pros use optical zoom gear and similar nicer tools.

[Amiwest]

With my soldering skills, this is the way I do it:
http://amigakit.leamancomputing.com/catalog/product_info.php?cPath=28&products_id=294

[RiP]

VERY fiddly hack. SMD resistors are a real pain to work with.

Get yourrself a few spare resistors of the same value. You are better off sacrificing the component, and concentrate on keeping the solder pads intact. Practice on a scrap electronics board before doing the mod.

The first stage is the hardest. The track cut is the next hardest.

The good news is, your board has all the same marked connectors (DS0, DS1, S6) and the other pins (IC pin 1, floppy connector pins 2 and 34). So it should work.

Surgical scalpel recommended for the track cuts - and doing SMD board work with a standard soldering iron is a real test of skill.

A magnifying glass is better than nothing, but pros use optical zoom gear and similar nicer tools.

Would you please show me on my picture?

With my soldering skills, this is the way I do it:
http://amigakit.leamancomputing.com/catalog/product_info.php?cPath=28&products_id=294

I can't order, gonna cost high for me =/

[RiP]

bump

[BLTCON0]

@RiP
Instead of modifying the floppy, get a replacement flat 34-wire floppy cable (no twists) and modify the cable.
In the following instructions, "A" refers to the amiga end of the cable and "F" to the floppy end of the cable. Recall that wire #1 is the coloured (reddish or blueish) one.

Isolate wires #2 and #34 and cut each in half, this produces 4 halves: #2A, #2F, #34A and #34F

1a) Connect (solder) halves #2A and #34F together.
1b) Discard (cut off completely) half #2F, it's not needed. Solder the ANODE of an 1N914 or 1N4148 diode to half #34A.

Strip a bit of the PVC coating from wire #8 so the metal core is exposed, without cutting the wire in half.

1c) Solder the CATHODE of the diode there.

Cut in half wires #10 and #12, this produces halves #10A, #10F, 12A and #12F

1d) Connect #10A and #12F together
1e) Cut off #10F and #12A.


1a fixes diskchange signal
1b/1c fixes ready signal
1d/1e fixes DS0/DS1 swap


With this cable, practically any off-the-shelf unmodified vanilla PC drive will work as an Amiga df0: drive.

[RiP]

Will it really work with any floppy drive?
But I want to use the original Amiga floppy drive as DF0 too.

[BLTCON0]

Will it really work with any floppy drive?

Yes, all 3.5" drives have more or less similar timings which match or exceed the ones specified in the hardware manual (some oddball 3.5" floppy drive from around 1981 might not be 100% compliant, but you wouldn't likely come across one anyway).
By timings I mean parametres such as head settle delay, track-to-track steprate, write gate-to-data gap etc.

So all you need is to route the signals where the Amiga interface expects them to be, and that's what the modified cable does (the READY signal isn't really a true READY signal but rather an imitation hack, but works well enough for instances where it's required. AmigaDOS and OS-compliant software never uses READY anyway).

But I want to use the original Amiga floppy drive as DF0 too.

Just use two cables. An unmodified straight-through cable for the original Amiga drive, and a modified one for when you want to use another drive.

If, on the other hand, you want to permanently convert a random PC floppy drive into an Amiga one, just implement the cable signal changes directly onto the drive.

For ID fixing, move the DS1 jumper (0 Ohm "resistor") to the DS0 position.

For DISKCHANGE fixing, backtrack from pin#34 and see which pin of the square FDC controller chip connects to it (verify with a continuity test). This is where DISKCHANGE is produced on the controller.

Cut the traces right behind pin#34 and pin#2 (so that they connect to nothing) and solder a wire from the FDC controller pin you just found to pin#2. This routes DISKCHANGE to the otherwise isolated pin#2.

Solder a diode between pin#8 and the otherwise isolated pin#34 (cathode on pin#8, anode on pin#34). This imitates (*) READY on pin#34, and the conversion is complete (**).


(*) 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.

(**) You can also fix the HD detection switch permanently to the DD position, so the drive behaves as a DD drive at all times.

[lost_loven]

oooo so doing this.. I have a couple of dead 1010 drives I can modify up and make a pc drive fit nicely ... these should do the trick Eh!

http://www.ebay.ca/itm/Lot-of-25-1N4148-Diode-Fast-Switching-DO-35-/112055861781?hash=item1a170cc215:m:mn4vJ_JWTVCMcGxGTYG2QnQ

[BLTCON0]

@lost_loven
Yes, AFAIK the 1010 uses a separate PCB to implement the motor flip-flop/ID mechanism, much like the majority of later Amiga external drives. So all you'd need do is replace the drive with an Amiga-converted one and find a way around the fascia differences.

OTOH the A1011 (and the identical A1411 of course) uses custom Chinon FB-354 revD drives with a 24-pin interface and integrated flip-flop/ID circuitry, so they're a different story (no interface PCB there so it has to be re-implemented if replacing with another drive).

[RiP]

If, on the other hand, you want to permanently convert a random PC floppy drive into an Amiga one, just implement the cable signal changes directly onto the drive.

For ID fixing, move the DS1 jumper (0 Ohm "resistor") to the DS0 position.

For DISKCHANGE fixing, backtrack from pin#34 and see which pin of the square FDC controller chip connects to it (verify with a continuity test). This is where DISKCHANGE is produced on the controller.

Cut the traces right behind pin#34 and pin#2 (so that they connect to nothing) and solder a wire from the FDC controller pin you just found to pin#2. This routes DISKCHANGE to the otherwise isolated pin#2.

Solder a diode between pin#8 and the otherwise isolated pin#34 (cathode on pin#8, anode on pin#34). This imitates (*) READY on pin#34, and the conversion is complete (**).


(*) 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.

(**) You can also fix the HD detection switch permanently to the DD position, so the drive behaves as a DD drive at all times.

Thank you very much, I just connected pin 34 straight to pin 4 same as here:
http://elgensrepairs.blogspot.co.uk/2012/10/modding-teac-fd-235-c291-u5-fdd-for.html

And it worked! I feel it's quite faster than A2000's floppy drive, just need to cover the HD/DD hole :laughing:

[BLTCON0]

Thank you very much, I just connected pin 34 straight to pin 4

That would be pin 2

And it worked!

Yes and no.

It worked because pin2 was probably not connected to anything in the first place in your drive (it's normally used for DENSITY SELECT which not all drives are factory configured to support).

So now you're getting a duplicate of DISKCHANGE on pin2 too (where the amiga expects it) and still getting it on pin34, where the Amiga expects the READY signal.

Now, as I said, under AmigaDOS the READY signal is not used for its intended purpose, and trackdisk.device won't bother ID-ing a DD 3.5" drive connected as df0: (which would normally employ the READY signal), so as long as you have this half-modded drive connected as df0: and only use it under Amiga DOS, you'll get by fine (*).

But with any demo/NDOS game that uses READY, you'll have problems unless you take all the steps.

 I feel it's quite faster than A2000's floppy drive, just need to cover the HD/DD hole :laughing:

It isn't, it only feels that way because it's quieter (unless of course the original drive had a considerably dirty head and kept retrying until it got a successful reading). Otherwise the operating parameters are more or less identical.

(*) At the very extreme, a PC drive can be made to work as df0: only and under AmigaDOS with no modifications at all. Just short SEL0 and SEL1 (cancels installing an external drive) and isolate pins 2 (DISKCHANGE) and 34 (READY). As said, under AmigaDOS "ready" is not required, and DISKCHANGE can be emulated with the synonymous CLI command. The only thing to remember is having the boot disk pre-inserted upon power-up/reset and the DISKCHANGE command copied to RAM: so it's readily available for any disk (all made much easier if booting off a hard drive).

[RiP]

Cut the traces right behind pin#34 and pin#2 (so that they connect to nothing) and solder a wire from the FDC controller pin you just found to pin#2. This routes DISKCHANGE to the otherwise isolated pin#2.

That would be pin 2

But pin2 is connected to the IC :confused:

[BLTCON0]

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.

But pin2 is connected to the IC :confused:

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.

[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 =/