My Falcon went to black screen

[mikro]

Yes, asking Rodolphe for an advice is a good idea. In fact, we had diagnosed one Falcon fault exactly like that.

[exxos]

As we tested with the VIDEL deactivated it can be the CPU or the COMBEL that are faulty...

That doesn't prove the Videl is working, just its likely not responsible for the Address line issues. It may still be faulty.

You could try forcing those address lines to 0V with wires on the expansion port. With address lines all 0V, Combel should decode ROM address and set ROM CE low. If it does not do that, then Likely Combel is faulty.

[christophe.griard]

Yes obviously you are right for the VIDEL : it could also be faulty...

I did not fully understood for forcing the 0V on the two pins that are at +5V : you mean make a connection between a pin at 0V on the expansion port and the two other pins that are currently at +5V to force them at 0V?

What does mean "CE" low?

[exxos]

you mean make a connection between a pin at 0V on the expansion port and the two other pins that are currently at +5V to force them at 0V?

Yes. A1 and A2 I think it was...

What does mean "CE" low?

ROM CE pin 3.

When Ax are all 0V, ROM CE pin 3 should go to 0V also. If it does not, then likely Combel is faulty.

[christophe.griard]

Yes it was A1 and A2.

Ok well understood. I will try this (probably tomorrow morning) to force A1 and A2 to 0 and I will keep you uptodate.

[christophe.griard]

Hello,

I made the proposed test.

I first checked that without any modification, I still had +5V on pin 3 of ROM and that pin 47 and 48 of expansion port were still at +5V : it was the case.

Then I put ground on pin 47 and pin 48 of expansion port (see below picture; I checked that I really had 0V on pin 47 and 48.

But pin 3 was still High (+5V) and was not Low... I made several tests with the same result (it was easy to measure pin 3 of ROM as there is on the motherboard a small hole linked to a track that is connected to pin 3 of ROM... I alos checked that in that case in CPU pin 22 and 59 I had 0V instead of 5V.

Independantly of the fact that in that case all Ax addresses on expansion port are all Low, the Flacon does not succeed in booting... So it seems from your opinion that COMBEL is probably faulty (even if it does some good job in dividing frequencies 16, 8, 4 Mhz from the 32 MHz oscillator...

[exxos]

Independently of the fact that in that case all Ax addresses on expansion port are all Low, the Falcon does not succeed in booting... So it seems from your opinion that COMBEL is probably faulty (even if it does some good job in dividing frequencies 16, 8, 4 Mhz from the 32 MHz oscillator...

The Falcon will not boot with those lines Ax lines to ground..Plus these tests are without RAM and ROM anyway.

The test is to see if pin 3 of ROM goes 0V when all Ax lines are zero.. so you say not.. so you can only check direct on combel that XROM2 is connected to pin 3 of ROM.. if yes.. then I can only assume Combel is faulty, plus maybe the Videl and CPU.. but difficult to tell.

[christophe.griard]

Continuity test done between XROM2 (pin 199 of COMBEL) and pin 3 of ROM : less than 1 Ohm => XROM2 and ROM pin 3 are connected...

[christophe.griard]

Hello Exxos,

For your information, I just received the RAM and the two reset switches that I ordered from you.

I'm still waiting for COMBEL and VIDEL to have them soldered and see if that solves the problem (I hope it will ...): they arrived in France and they should be at my house soon.

One question: I am looking for a company that has the skills to solder such SMD chips.
From your practice with the SMT rework company you are used to working with, I wanted to know if you could give me an order of magnitude for the price to have these two chips soldered ?

Thank you very much for your feedback Exxos.

Have a good end of the day.

[exxos]

I use this company https://www.exxosforum.co.uk/forum/viewt ... 9809#p9809. You can deal direct, but because of virus, it may be some weeks before they are able to do work again. I guess they would charge about £50 to change both chips.. Of course you have postage in the mix.. And you must only send motherboard to them as they are not familiar with dismantling computers etc.