English Amiga Board


Go Back   English Amiga Board > Support > support.Hardware > Hardware mods

 
 
Thread Tools
Old 08 December 2020, 18:15   #41
solarmon
Registered User

solarmon's Avatar
 
Join Date: Dec 2018
Location: UK
Posts: 1,379
I got the some of the adapter boards printed through JLCPCB and it seems to be working as expected.
solarmon is offline  
Old 08 December 2020, 18:22   #42
solarmon
Registered User

solarmon's Avatar
 
Join Date: Dec 2018
Location: UK
Posts: 1,379
What I would like next is to make an adapter for the other way around - so that a 26-pin slim Citizen drive can be used in a normal 34-pin floppy drive controller/interface.
solarmon is offline  
Old 08 December 2020, 22:19   #43
solarmon
Registered User

solarmon's Avatar
 
Join Date: Dec 2018
Location: UK
Posts: 1,379
Quote:
Originally Posted by solarmon View Post
What I would like next is to make an adapter for the other way around - so that a 26-pin slim Citizen drive can be used in a normal 34-pin floppy drive controller/interface.
Actually, the current adapter will work in this direction too - since it is the same pin mappings. It is just that the connectors are not in a convenient position.

I just tested the adapter with with a Citizen slim drive connected to my A500 motherboard and it is working as expected.
solarmon is offline  
Old 10 December 2020, 04:24   #44
MiaM
Registered User

 
Join Date: Jun 2018
Location: Gothenburg/Sweden
Posts: 17
Some general things re the various turns this thread has taken:

The circuit on a regular external drive for an Amiga does two things:
A) Identifies to the Amiga that there is a drive connected, and if it a 40 or 80 track.
B) Latch the motor signal so the Amiga can turn on and off the drive motors individually without having a separate motor wire for each drive

As the interface does nothing else every wire except for the motor signal should be connected directly between the actual drive and the 23-pin connector(s). This makes it easy to measure or visually inspect the pcb and the connectors to tell which pin is which.

For testing purposes you can disconnect the motor signal to the drive and connect the motor pin on the drive to ground. The motor should spin all the time (or in many cases all the ime when a disk is inserted). If your drive works fine with the motor constantly running but won't work with the regular motor wire connected, then there is something wrong with the motor latch circuit. If your drive won't work even with the motor signal grounded, there is something wrong with the pinout, with the drive itself or possible termination of the signals. For a 3.5" drive termination is unlikely to be an issue. However if you connect an old 5.25" drive, like say the huge Tandon drives found in the original IBM PC and PC/XT, you need to replace the 150 ohm termination resistor packs with higher resistance ones (say 1-2k, can be built using a "component adapter" where you solder resitors, or you can push individual resistors in the socket for the terminator pack).

If you need a replacement interface pcb for an external drive, the german language book Amiga Hardware Tuning has a DIY solution using two readily available 74xx chips. Although the book is in german, the schematics and the pcb layout should be usable even if you can't read german.

Btw if anyone decides to order new PCBs based on the Amiga Hardware Tuning book, please please consider changing the layout to support two drives. Only half of each of the 74xx chips are in use, so the chips can already handle two drives but the traces of the PCB is missing. Back in the days three decades ago I used one of those interface PCBs and added a bunch of bodge wires to be able to use it with two drives. IIRC I wired the 34-pin PCB mounted connector the way it is wired on a PC floppy controller, with a twisted flat cable for two separate motor signals (and of course two separate drive select signals)..

Another advice: If you must feed the drive and the computer from different power supplies, make shure the mains power ground of both power supplies are connected to each other. In some countries this statement doesn't make any sense since every socket has been grounded since many years. However in other countries you can still find ungrounded sockets. For example here in Sweden the regulation requiring grounded sockets everywere came into effect in the mid 90's so we still have a lot of homes with ungrounded sockets. Just use a grounded power strip for all your computer stuff.

The reason for the grounding issue is that the mains filer on many switched power supplies leak a small current from the mains to the low voltage side. The current is small enough to not harm humans, but if you connect your drive to your amiga and the signal wires make contact before any of the ground wires this small leakage current can damage the chips in the drive, the drive interface and in the Amiga. This migh be an explanation of why one of the Amigas early on in this thread did display DF1:BAD DF2:BAD and DF3:BAD.
MiaM is offline  
Old 10 December 2020, 15:06   #45
solarmon
Registered User

solarmon's Avatar
 
Join Date: Dec 2018
Location: UK
Posts: 1,379
@MiaM

Thanks for the tip about the "Amiga Hardware Tuning" book. I found a copy at:

https://archive.org/details/amiga-hardware-tuning-de/p

For quick reference, the information about the external controller is from page 156, with the schematics on page 160.

I think I will also try to build this board using KiCAD.
solarmon is offline  
Old 20 December 2020, 13:05   #46
solarmon
Registered User

solarmon's Avatar
 
Join Date: Dec 2018
Location: UK
Posts: 1,379
This is an adapter that allows you to use the Citizen slim drive as a 'normal' drive.



It just plugs in the back of the Citizen drive on the 26-pin connector and presents a normal 34-pin data and power connectors.

The KiCAD and Gerber files can be found at:

https://github.com/solarmon/PCB-Proj...%20(Design%20B)
solarmon is offline  
 


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
WTB: SCSI-1 50 Pin Hard drive christopherpm MarketPlace 2 08 July 2013 06:05
Wanted: SCSI hard drive (50-pin) 8bitbubsy MarketPlace 9 18 May 2011 23:01
23-pin to 9-pin video cable pinout MagerValp support.Hardware 9 22 August 2008 16:00
Amiga 2000 Floppy header keyed? (Broken pin #4) TjLaZer support.Hardware 1 13 June 2007 08:50
VGA Adapter 23 pin -> 15 pin High Density @UAE support.Hardware 11 16 October 2006 14:32

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +2. The time now is 22:41.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Page generated in 0.07597 seconds with 14 queries