Is there any update on this?

Hello.
I have an original Commodore Amiga 4000 floppy drive. Can I connect a FDD 1.76MB to my A1200NG computer? Will it be visible under Amibench and Workbench 3.2.x, 3.x, and 2.x?

From a quick re-read of the last few posts, the key point summary is:

- The system is fundamentally alive as there was/is good serial data out with DiagROM

- DiagROM highlighted a problem with the four analogue to digital inputs at Paula/8364

- You confirmed that the four analogue inputs indeed showed around 0V instead of the expected ~5V

- This suggested a problem with Paula/8364

- You bought a (used or unknown condition??) 8364 but had no serial output with that replacement part

- The supply voltage at the replacement 8364 was measured to be ~3.6V, significantly lower than expected

- There's also some kind of uncertainty around the IC sockets, with possible contamination??


This would suggest:
1. The original 8364 is still defective, sounds as though that part is still fitted?
2. The replacement 8364 is also defective, as ~3.6V measured at the supply pin suggests it's drawing excessive current, and there's no serial data output
3. The CPU, ROM, most of the data/address bus, etc, is likely OK as the serial data out looks sane


Buying an oscilloscope at this point is not likely to help, especially as you're not well experienced with using one, and I don't have the time or patience to run a 'my first oscilloscope' training course via countless posts on a public forum.  You absolutely need to know what you're looking for, in addition to knowing how to drive the instrument.

From the thread title, there was also some kind of graphics corruption thing happening.  I didn't read back far enough to recall what was going on, but it's possible there's a second problem in addition to the suspected issues with the original 8364.

The simplest way forward with diagnosing this would be get access to a working A500 or A2000 that you can test the suspect 8364 in (both the original and the replacement), and if it's confirmed they're defective, then put the working 8364 from the A500/A2000 into your A500, then see if the DiagROM output looks normal.  If it does, see if you can boot Workbench, etc.  Or see if there are further problems.

Another option is to send the A500 main board for repair.  I can do this, though freight to NZ has become more expensive.  There are some Amiga retailers in Europe who advertise repairs which may be a lower cost option.

Hi!

A couple of months passed since I last wrote under this post.

In the last reply, I said that I was going to check the DiagROM output with a new Paula. I connected the null modem cable to my A500's serial port and opened PuTTY. I got the DiagROM booting text and could easily use the menu.

This is what DiagROM gave me in System Info:

                          Information of this machine:

               Dump of all readable Custom Chipset HW Registers:
BLTDDAT ($dff000): $8098   DMACONR  ($dff002): $6380   VPOSR   ($dff004): $A000
VHPOSR  ($dff006): $9A61   DSKDATR  ($dff008): $FFFF   JOY0DAT ($dff00a): $0000
POT0DAT ($dff012): $0505   POT1DAT  ($dff014): $0000   POTINP  ($dff016): $0606
SERDATR ($dff018): $4B2D   DSKBYTR  ($dff01a): $9000   INTENAR ($dff01c): $4B2D
INTREQR ($dff01e): $1000   DENISEID ($dff07c): $0000   HHPOSR  ($dff1dc): $0090

Workmem: $0006C478 - $0007FFFD Size: 78kB   ROM size: 156kB  Order: End
Chipmem workarea: $00000400 - $0007FFFF Fastmem workarea: $00000000 - $00000000

Doing ROM Checksumtest: (64K blocks, Green OK, Red Failed)
$CED3BA58 $98C6080B $3980DA0F $003EC000 $003F0000 $003F4000 $003F8000 $00DFBCEA

CPU: 68000  FPU: NONE  MMU: NOT CHECKED
Is $1114 readable at addr $0 (ROM still at $0): NO
Is $1114 readable at addr $f80000 (Real ROM addr): YES
Is $1111 readable at addr $f00000 (expansion ROM addr): NO
Stuck buttons & keys etc at boot: BADPAULA

Serial: 9600  BPS - CPU: 68000  - Chip: 512kB  - kBFast: 0      Base: $0006C47A

I'm still getting the P1RMB/LMB stuck at boot during the DiagROM's booting process. Everything else seems to be normal as DiagROM's menu functions normally on the serial output.

However, when I try to connect my A500 to my 1084S-P1 or SCART TV, I'm not getting any video output.
Maybe the contacts on the A500's video connector should be cleaned as I didn't do it for a couple of months now, but it's really weird as I'm not getting anything on both the 1084S and SCART output of my Sony TV.

Upon researching, black screen with DiagROM inserted suggests a faulty CPU, but as I'm getting normal and healthy serial output and strong 10 short + 1 long flash from my keyboard, I think that something might be wrong with my A500's video connector, which I will firstly check.



After I read some of my older posts on r/amiga about this issue, I remembered that I used to fix this yellow screen and boot normally by pulling out Fat Agnus with a PLCC extractor, cleaning her with IPA and reinserting her into her socket. When I reinserted her, along with pressing on other ICs, the Amiga would start working again. But, after a leg broke on that original Agnus, I replaced her with a new one, tried the same trick again, but this time it didn't work. I forgot to mention this to you in earlier replies as I totally forgot about that.

Q: Maybe it's the faulty Agnus socket that's causing this yellow screen? The pins on the socket look ok, but maybe because one of the legs broke off of Agnus, I should replace the original socket with a new one as it may also got damaged when I was pulling Agnus out?

Also, I think that it's the right time to get an oscilloscope involved and look into the data/address busses.

I did some research about what kind of an oscilloscope I should buy, but I just got confused really quickly as I never used an oscilloscope before or did any research about it, so all of the specifications were kind of advanced for me.

As the 68000 operates on 7.09MHz (for my PAL A500), I found out that I should minimally use 20MHz, but ideally should go for >50MHz just to be safe.
I also found out that I should look for an oscilloscope that has a sampling rate of >200MSa/s, DC coupling, 1MΩ input impedance, X10 + short ground probe etc.
I was thinking about that maybe I should go for an oscilloscope that YouTubers like Adrian's Digital Basement use, but they cost a lot.

Q: If you maybe know, what are the important specs I should look into when buying an oscilloscope that I will use for my A500's diagnosing? Are there any minimal values of the specs I should look out for? Would you recommend a specific oscilloscope that maybe you are using?

The oscilloscope is pretty new to me, as I have never used it before, so I'm not sure if I'm doing my research right. I wouldn't like to spend a large amount of money on a oscilloscope that would be overkill and maybe could be replaced by a cheaper one that would work the same. Or maybe I shouldn't cheap out on this.

-poroxius, February 1, 2026

Unfinished Business: Fixing the Amiga Piccolo SD64's Passthrough!

After a 33 year itch, FINALLY my Amiga 2000 has my dream graphics card, a Piccolo SD64, giving it high resolution 24bit graphics! But that itch is not fully scratched, because it's passthrough is not working yet, making it quite frustrating to use. In this video I fall down a rabbit hole. Can I use my stock 15KHz video with the passthrough, can I make a suitable VGA passthrough cable, will my new Flicker Fixer card work. Lets dive in with, me and see what I find out!

Link is broken with a http:// to much and more, fixed it for ya.