Indivision ECS V2 Screen Corruption after Warmup

Drewlio77 · Oct 29th 2022

Hi,

I have an odd issue, on my A600 (revision 1.5), after 10 minutes or so, areas of the screen become corrupted, especially during redraw or refresh. This only occurs when the ECS V2 is installed. Both video outputs are affected (the Amiga's native and the ECS V2). They display exactly the same video artifacting. I have ruled out the ECS V2 since it works fine in my other Amiga 600's and the ECS V2 or V3 form other 600's have the same issue on my troubled A600. I have also ruled out the A600n module as well. It works fine in other systems too. Since this happens with or without the accelerator card attached, I doubt if it's a PSU issue. It is most likely heat related, but all chips seem about as warm/hot as my other systems. Plus, the fact if the ECS V2 is removed, the corruption is gone. I am going to recap the board since it needs it anyway, some caps show some signs of leakage. Though I doubt this will resolve the issue. I want to continue to use the ECS V2, since its Video output is amazingly clear compared to other Scan Converters I have or tried.

My question is, what lines on the A600's Expansion connector does the ECS V2 get its video from? This may help me diagnose the issue better. If anyone has any ideas of what could cause this, any help would be appreciated.

Jens · Oct 31st 2022

Quote from Drewlio77

My question is, what lines on the A600's Expansion connector does the ECS V2 get its video from?

Video is generated from DMA data that's flying by. Indivision ECS V2 completely emulates the Denise chip.

However, I suspect something else hat's going on. Please take a picture of your Agnus chip in the troubled computer - does it have a Vbb designation?

Drewlio77 · Oct 31st 2022

Jens,

Indeed, it does (image attached). What does VBB strand for? And is this a known issue the ECS V2/V3?

Jens · Nov 2nd 2022

Vbb designation means that the negative bias voltage (which is needed locally on the chip) is bonded on a pin of the chip, so the outside world can add a capacitor. This was cutting-edge at the time, and pretty common these days.

However, the original schematics of the A600 did not account for VBB-type Agnus chips, although the majority of computers is equipped with these Agnus chips. Schematics were never updated, though, so the Vbb voltage (about negative 3 volts) is present on the trapdoor connector, where the A604n routes the signal to the 48-pin socket that is meant for Indivision, because the original Agnus has a clock output on that pin, and when I designed the A604n, I figured that an additional clock will be handy on a flicker fixer.

What I suspect is that the A604n unit that you have there was not modified to cope with this quirk: We are now cutting the connection to the 48-pin socket, so the negative bias voltage does not arrive on Indivision.

Can you take pictures of the top and bottom side of the A604n? The bottom side may be sufficient if you also post the warranty ID; this will let you keep the Indivision unit on (no danger/wear to/on the pins).

Drewlio77 · Nov 2nd 2022

Jens,

I believe this card did not come with a warranty ID sticker, though I can't say this with exact certainty. I did remove the QC sticker on the bottom of the card to better see the traces. Regardless, both images are attached (Top and Bottom). Thanks for responding, your hardware is top notch and can't be left in limbo like this

Jens · Nov 2nd 2022

If this card really came without a warranty ID sticker, it's *very* old, probably from the very first production run in 2013. In that case, you need to cut the trace to pin#35 of the 48-pin socket - this will separate the negative bias voltage from Indivision ECS, and your screen corruption will be gone.

The trace to pin#35 of the socket is on the bottom side. The best place is near pin#35 itself, as there's only the GND plane near it, and you can't damage any nearby traces.

Drewlio77 · Nov 2nd 2022

Jens,

Sounds good. I'll give it a shot. I have done similar work before; this should go well (knock on wood). I'll report back with my results.

Drewlio77 · Nov 3rd 2022

Jens,

Success! Thanks for the time you took to help me resolve this issue; it is greatly appreciated.

Sincerely,

Allan V.