exxos's Atari, Amiga & retro forum

Robson wrote: 01 Jun 2020 11:58 I'll check those connections and the IDE board way as well. I don't have a 50pF cap...that's all I'm missing for it.

How annoying! Let us know how you get on.

Had some time to check things today.

No more white screen, I lost all outputs completely.

Findings so far:
I had to fix the reset, that now works .BERR is high as it should be. But HALT goes low immediately and stays.

Took a a step back and checked:
Reflow all sockets and checked smds.
2k, 1K resistance values around the 68000 port, not shorts.
All clocks to main ICs are good.
Swapped cpu, mmu, glue, dma, shifter, 68901 -same thing.
Address/data lines go high.

Have you seen my troubleshooting page ? https://www.exxosforum.co.uk/forum/viewt ... =78&t=2362

FIRST POWER UP VOLTAGE TEST.

D1,D2,D3 are low when doing this test (pins 2,3,4).

Robson wrote: 04 Jun 2020 22:25 Had some time to check things today.

No more white screen, I lost all outputs completely.

Findings so far:
I had to fix the reset, that now works .BERR is high as it should be. But HALT goes low immediately and stays.

Address/data lines go high.

Do you have a scope or logic probe? They are much better indicators of what is going on on the address pins than a multimeter. Also, if you have another working ST to compare against it's a really valuable asset as you know what to look for from a working machine.

As well as the section exxos mentioned, have a look at my Mega 4 thread here: https://www.exxosforum.co.uk/forum/viewt ... =18&t=2163 as there is an awful lot of troubleshooting done and results posted. Kept me busy that machine! I know it's a long lead, but there is a lot of expert advice in there.

Where are you with the IDE interface? If you have the IDE interface with its own CPU and ROM on board (Remove the onboard ROM and CPU) in one of the expansion sockets and it boots, then you are looking at an onboard ROM issue. That's how I figured out my LS11 was a problem. This is what I mean about the IDE interface: https://www.exxosforum.co.uk/forum/viewt ... 100#p34381

Are you still getting zero diag cart output over serial?

The other thing that occurred to me is the dual boot ROM. Which version were you using again? TOS 1.02/1.04? Or did you have a TOS 1.04/2.06 combo? If it's the latter set the ROM jumper next to the ROM socket to the opposite of what you have now as it won't boot to 2.06 unless you have extra hardware or the IDE board holding the ROM.

Hey,

I was a bit tired and fed up last night but want to get this up and running. Sooner than later, there are many projects stacking up - I thought it will be a walk in the park (ha-ha). Not what I expected for sure, the solders looks clean I was really keen to do a nice job so I'm disapointed slightly.

I have the tools (scope, LA, probe, no problem with that), repaired many STs before. Sharing the experience (and reaching out for help at the same time) here even though most of you've already finished. So feel free to ask, link, anything I appreciate that.
I know it should work as an ST so expecting that behaviour but there might be some board specific things I'm not aware of so better to check with the wider community.

IDE board: I had no luck with that either. There was a short under the 44header between (5v and gnd), so the LED doesn't come on anymore. Instead of troubleshooting the board (short is fixed now) I ordered another one to build and fix this later (maybe needs a new pld anyway ). I might need to send the chip back to exxos to check, reprogram, whatever works. Not the main concern now but definitely needs to be looked at.

I used the 1.04/2.06 combo, so as the DIAG TOS but also the diag cart is plugged in so that should take control but the boot doesn't get to that point.
1 random character appears sometimes on serial but that's just garbage.

Hoping to check few more things later today.

Robson wrote: 05 Jun 2020 09:46
I used the 1.04/2.06 combo, so as the DIAG TOS but also the diag cart is plugged in so that should take control but the boot doesn't get to that point.
1 random character appears sometimes on serial but that's just garbage.

Hoping to check few more things later today.

When I had a ROM problem, both on my H4 and my Mega4, the Diag cart wouldn't start, hence my suggestion to use the IDE card and rule out the onboard ROM.

If your onboard ROM is set to 2.06, it won't work, and I think all you'll see is a white screen, hence my suggestion to swap the ROM selection jumper.

Also worth checking is the jumper settings: https://www.exxosforum.co.uk/forum/viewt ... ers#p29130

If these are incorrectly jumpered you'll have problems too.

I pulled all address busses to gnd along with AS/UDS/LDS - and data bus shows the correct 0110 0000 0010 1110 ($602E) state.

DTACK - LOW

At LS11:
ROM0 - HI
ROM1 - HI
ROM2 - LOW
ROM CE - LOW

I do have the white screen back.

Seems like double bus error.

RDY is always low at DMA (FCS goes low after reset).
MFP resopnds with DTACK.

Was just looking at the photos of your h4. I got new glasses so I can see better. The wire on the button of the memory socket looks off. I'm not sure what but I would take a look at it.

Tom