H5 SIMM socket issues

[SciFi9000]

I just got a newly purchased phoenix H5 working but noticed that the SIMM socket is really flaky, sometimes it boots and sometimes it boots into a black screen with white boarder. I tried reseating the SIMM several times, but it just got worse, so i tinned the contacts on the SIMM with solder to thicken it up for better contact and that helped some, but still really flaky, more off than on.

Then i decided to just plug the module in and not clip it down, and it became stable and boot into GEM every time, but when trying to access my GOTEK, it would begin to load and then bomb or freeze. I tried all sorts of things including swapping out the DMA, and other chips but nothing helped. Then out of desperation, i set the jumpers to 2Mb instead of 4mb and that solved everything, everything works, the GOTEK loads and everything runs. No matter what i do, no matter how hard i plug in the SIMM module, I can't get it to be stable (read the GOTEK) when set to 4Mb.

Is anyone else having issues with the SIMM slot? I don't know if it's just the slot or the memory as well. For now, I have it stable by leaving the memory set at 2Mb and the sim not locked down. This is a brand-new board, and I only just got it running,. it shouldn't have this Issue.

[exxos]

Tinning the SIMM contacts with solder was not a good idea. It makes the module thicker than the socket is designed for, and clipping it down forces the socket contacts open, which can leave them permanently sprung and giving poor contact even with a good module. That alone would explain the socket getting worse each time it was reseated. That SIMM really should not go back in any socket now, as it can damage that one too.

It is also worth saying that the socket may well be damaged now, between the repeated reseating and the tinned SIMM being forced into it, and it may need replacing. The fact that it only works when the SIMM is pushed or strained in a certain way also suggests the pressure is flexing the board enough to make something nearby connect, such as the RAM jumpers or a poor joint elsewhere, rather than the socket being the original cause.

The fact it works at 2MB and fails at 4MB does not point to the socket anyway. It points to the second bank, which means the RAM jumpers, the MMU and its socket, the joints around that area, or the SIMM itself. So the way forward is:

- Use a known good, untouched SIMM.
- Run a full RAM test on a diagnostic cartridge at 4MB and post the result.
- Post clear close up photos of the MMU socket, the RAM jumpers and the joints around the SIMM area, both sides of the board.

[SciFi9000]

Hi thanks for your time and reply. I think you missed the point though. I tinned the sim contacts because it wasn't making good contact to begin with. If it had been working, I would not have resorted to this at all. Also, the things I did (leaving the SIMM unclipped and tinning) improved things. I can now actually boot into GEM whereas before, I couldn't most of the time right from the 1st instalment, and when it did boot (after much unplugging and re-plugging), the slightest movement would cause a bomb or freeze. Now it is rock solid, except I can't go above 2Mb. To imply that my actions caused the failure is backward. The socket was obviously not good to begin with - and possible the SIMM but that's a guess. Also, de-tinning the SIMM contacts is just some flux and solder braid away. Please send another socket and I will desolder the old one and solder the new one, that seems fair. Is anyone else having this issue? I thought I saw a post where someone said it stopped booting on them all of a sudden

On another topic. I can't get the MIDI output working on my MT32 pi hat. It works fine on my other Atari st, but dead silent on the H5. Is there a jumper or something I don't know about? I used 2 brand new MIDI sockets not harvested ones, and the soldering looks good under a magnifier. I'm thinking maybe the built in MIDI synth somehow bypasses the external MIDI?

Another issue. I can't get TOS 2.06 working. I bridged the solder pads located between the PLCC CPU and oscillator, and moved the jumper to use 104 and 206 decoder (the red LED illuminates on boot now). In this mode I can boot from TOS 1.04 as before, but when i set the ROM select jumper to open, it just hangs on a white screen on boot. Do I need to do something else? Do I need to install decoders or are they built in? I am using the dual TOS ROM I bought from your shop.

I don't want to come across as frustrated, I'm not, this is good fun. I am just trying to troubleshoot. I hope you understand that.

Thanks, Simon

[exxos]

Before we go any further, how did you diagnose the SIMM socket as the problem in the first place? Unless there was a RAM test or some actual measurement behind it, it is an assumption, and from what you describe I do not think the socket is the likely cause.

A board that will not boot, then bombs or freezes with the slightest movement, points far more towards bad connections on the GLUE and MMU, or a socketed chip not making proper contact. Pressing on the SIMM flexes the board, which can make or break those connections, so the socket gets the blame for something happening elsewhere. The fact it is solid at 2MB and fails at 4MB fits that too, as the second bank is handled by the MMU.

So what I need is:

- Take the GLUE, MMU and CPU out of their sockets and check them under a magnifier for bent, flattened or dirty pins, and check the socket contacts at the same time.
- Check all the joints on those sockets under the magnifier too.
- Post a clear photo of all your jumper settings, including the RAM jumpers.
- Run a RAM test on a diagnostic cartridge at 4MB with a known good, untouched SIMM.

Once we have that, we will know what is actually at fault, rather than replacing parts in hope, which is about as reliable as blowing on a cartridge.

[SciFi9000]

Hi thanks for the reply. It is very, very obvious without doubt that it is the SIMM socket. Before I tinned the SIMM, it would stabilise while I was putting pressure on the SIMM, but the second I took my hand off the SIMM the screen would go white, or show black vertical stripes on a white screen or just crash. When i managed to get it to boot without holding the SIMM firmly in place (rare), just simply brushing the SIMM would cause it to crash. The PLCC sockets are rock solid. I know you need convincing, but I'm here looking at it and touching it. There is no doubt as all. After tinning the SIMM contacts, it is rock solid and it boots every time, as long as I don't clip it down (with the 2Mb limit as set by the jumpers). Time and time again it was any interaction with the SIMM that made it either work or crash (pressing the SIMM in place while booting made it work ok until i let go.. then it would freeze or etc). When it boots, I can tap on the PLCC sockets all day and cause no issues, also, the harvested chips are tested solid on a working ST. It's equally likely that the SIMM socket is bad as any other socket, so why not accept that I'm here interacting with it and am thoroughly convinced that it's the SIMM? I have done much troubleshooting and I am reasonably experienced.

I'll recheck the MMU for bent pins etc as you suggest tomorrow (i'm about to go to bed). That may be a possibility for the 2Mb limit, but so would a bad simm socket, but I'll test all possibilities. I have a schematic I can consult for the pin (A9 I believe from memory.. no pun intended).. i'll check the actual pin number on the MMU

Please remember I didn't know it was the SIMM at 1st, I went through all the usual troubleshooting steps including reseating all chips and checking jumpers. It became obvious it was the SIMM as soon as i touched it after it managed to boot up on it's own. I must iterate again, it is very obvious where the problem is. Also remember that I only just unpacked the whole thing this week. ALl I did with the SIMM is plug it in and clip it down. It started having problems almost immediately (though I didn't know what the problem was originally).. I spent hours chasing it thinking it could be jumpers, other chips etc as you are thinking.

Regarding the diagnostic test. I can't load any software in 4Mb mode due to memory crashes, it boots into GEM and seems stable, but as soon as i try to load software, it bombs. If i set the jumpers to 2Mb, I can load sysinfo from my Gotek and everything tests fine (at 2Mb). I had removed the chips several times, that's how I discovered that it was a SIMM issue. If you still insist on my sending you a photo of the jumpers I can do that but it's late and I'm off to bed. Let me know if you are not convinced and I will do it tomorrow.

I did bridge the 2 solder pads as per your instructions (I have read them). I also successfully rotated the opamp chip (i lifted 2 pads unfortunately in the process but successfully repaired them.) The audio works fine and sounds really good.

Kind regards, Simon

[Steve]

@SciFi9000 is it possible that the SIMM could also be at fault? Did you have another to try, before deciding to tin it?