Getting READY signal from a TEAC FD-235HF-B391 floppy drive

[JonB]

I'm having lots of fun today.


I bought a TEAC FD-235HF floppy drive to replace one I had damaged, that runs in a PCW 9256. The old drive has a ready modification and there is an external board that changes DS0 to DS1 so the floppy's DS setting doesn't need to be altered.


The problem I have is, the B series 235HF doesn't have a jumper block other than DS0/1 selection and I can't see how to get a proper READY signal out of it. I have studied how-tos and pictures of TEAC ready mods, but none of them look right (as in, AMIGA RDY mod = short pins 30 & 34, not a proper RDY).


The PCB looks like this: http://i298.photobucket.com/albums/mm242/salax54/TEACHACK2.jpg (here an Amiga hack is installed with pins 34-30 shorted). There are no markings that suggest RDY. The drive uses a ROHM BH9521KS2 controller and so far I haven't found a data sheet or pinout for it. One of its pins should generate RDY. Just can't tell which.


Anyone have an idea? (I have to use a 235-hf because the adapter PCB will only fit on the back of this drive.)

[JonB]

A better picture of the drive PCB.

[Bryce]

Strapping pins 30 and 34 together is just feeding the READ signal back down the ready line. That's far from a proper ready signal. Unfortunately it's usually impossible to find datasheets for these type of parts, your only hope is to probe the pins.

Bryce.

[JonB]

Sigh. Out with Mr Rigol, then.


RDY is TRUE when? On the insertion of a disk?

[Bryce]

Ready is true when the disk is inserted and the disk has achieved the correct RPM.

Bryce.

[JonB]

Sadly, another disaster.


The old drive has failed (or the interface or adapter or something). So I now don't know if the machine works.


What a horrid day.

[JonB]

Oh well, looks like it is all over.


Am getting 3/4 beeps on the floppy drive, and swapping over to the 3" drive (as A:) also gives 3 beeps. Add that to the broken power supply and it looks like this 9512 is for the scrapper.

[JonB]

Interesting.


This seems to act like READY, but it is doing READY for drive B as well. In other words, CP/M can't detect a missing disk in Drive B with this mod in place when a disk is also in A:.


That white ribbon cable goes to the drive motor. Not sure what I have connected Pin 34 of the floppy connector to.


There are other pins that act like RDY on the controller chip, but they all stop the boot process: after the boot track and EMT file have loaded I get a blank screen, then when I disconnect Pin 34, it continues, but halts with "drive not ready".

[Bryce]

But...... What?

Bryce.

[JonB]

But, I wanted to type the rest of the post on a proper keyboard, rather than the iPad I took and uploaded the picture with..

[Audronic]

@JonB


? Did you cut the track to Pin 34 ?


If you cannot find more detail ( I don't have any here ) you could try :-
Leave the track cut as is. Run a wire from the disk insertion Micro Switch (Right hand side of drive)
to pin 34 on the edge connector.
It may be a (Non Standard) way of getting a signal that (Perhaps) emulates a Ready signal.
" No correspondence will be entered into " 


Good luck      Ray

[JonB]

Yes, that's the first thing I did...


The problem is really that these TEAC drives exist in so many different variants, that it is difficult to find ready mods for all of them. I have an idea, though. I could gate this signal I found with DS to produce a better ready signal that does not interfere with drive B:.

[Audronic]

@JonB


This will honour the Ready Signal, and  if you pull the disk all the way out CPM will be happy, it won't affect the other drive.
Ray

[JonB]

@Audronic : You probably wont approve, but in the end I decided to go with the "pseudo ready" signal from the motor ribbon. I did try to build an AND gate out of transistors, then I realised (after several failed attempts) that DS is inverted and I am not sure whether the motor signal is inverted or not. I could probe them to find out but I got a bit fed up with it as it is delaying the IDE project I'm working on. So for now, it's bodged. The machine is OK and the "ready" seems to work as before (even DISCKIT is happy).


I am sure I will revisit this at some point, because I'm a perfectionist.


Thanks @Bryce and @Audronic for your advice.

[Bryce]

For future reference. Here's some simple methods for making cheap and nasty logic gates while you are experimenting.

Bryce.

[JonB]

Nice, but I don't understand the AND / NAND circuits. The diodes look the wrong way round on the inputs. Wouldn't they prevent both inputs from reaching the circuit?

[Bryce]

No. It doesn't need to reach anywhere, it only has to be at a certain potential. Take a look at the attachment. In the first and second pictures: The left side of one or both diodes is connected to 0 (GND), the diode is dropping 0.6V, so the rest of the 5V has to be dropped across the resistor. So the point where the output is connected has to be 0.6V = "0" output. In the third picture, the left side of both diodes has been raised to 5V, so the current doesn't have a path to GND and no (very little) voltage is dropped across the resistor. As neither diode goes to GND and hence no voltage drop is possible, the voltage on the right side of the diodes is still almost 5V (via the resistor) = "1" output.

Build them for yourself and give it a go.

Bryce.

[JonB]

A great explanation, Bryce - thank you!

[Bignumbas]

I just got one of these drives a 7291-U5 revision
According to a German Amiga site you cut track to pin 34 and join it to pin 10 on the controller chip.
http://www.pitsch.de/stuff/amiga/tepe/teacfd235hf7291.jpg
This site was linked from here
http://www.buchty.net/casio/fz1-diskdrive.html

   
• Rev. 6291 (BH95060GKS2): Select Drive 0 via jumper; cut trace from floppy connector pin 34 to floppy controller and rewire pin 34 to the controller pin 10 (RDY#).

   
   
• Rev. 7291-U5 (BH95060GKS2): There's two solder-jumpers for selecting the drive ID, solder it to DS0, rest see 629
• And section 8 here: http://www.pitsch.de/stuff/amiga/floppy.htm#A6
• 
  Do not do the pin 2 connection unless you are goin to put it in an Amiga
  Hope this helps you find a solution
  happy reading 

[rpalmer]

I notice from the original picture the locations S7, S5, S4 and S3 (as well as P1,P2, P3, TP4/TP5) are possible jumper settings.

[Bryce]

I notice from the original picture the locations S7, S5, S4 and S3 (as well as P1,P2, P3, TP4/TP5) are possible jumper settings.

TP are Test Points used for testing and calibration during the manufacturing process.

Bryce.

[1024MAK]

For future reference. Here's some simple methods for making cheap and nasty logic gates while you are experimenting.

Bryce.

Or you can use one of the neat one function SMD logic chips, no ectching of the PCB needed if you are good at crafting the simple layout with a modellers cutting disc in say a PCB drill or Dremel.

Mark