464 Plus 10MHz oscillation but no 4MHz clock

[Overkill]

I have the 10MHz oscillation but no 4MHz clock.

Just so there is no confusion, I have another thread about another board.

The ASIC has voltage, I get the 10MHz to the ASIC but there is no clock output.  I'm assuming it's a dead ASIC, but just in case, I thought I'd see what you all think

[Bryce]

Where are you measuring 10MHz? The Plus has a 40MHz clock source, which the ASIC divides down to 4MHz (and should be measurable on pin 125).

Bryce.

[Overkill]

I found a 10MHz (sine looking) near the crystal, I must admit I was confused as I thought it was a 40MHz crystal. 
 
I will check again.

[abalore]

I found a 10MHz (sine looking) near the crystal, I must admit I was confused as I thought it was a 40MHz crystal.
 
I will check again.

The sine looking is more because of the precision of your oscilloscope. Is it capable of sampling 40 Mhz at all?

[Overkill]

Yes, maybe it is my oscilloscope, it's just a multifunction hand-held.

[Overkill]

Sorry, I'm new to this scope, you are right, it goes up to 10MHz (embarrassing )
 
It's good that the scope still shows the sine wave though 😊  

[Overkill]

Where are you measuring 10MHz? The Plus has a 40MHz clock source, which the ASIC divides down to 4MHz (and should be measurable on pin 125).

Bryce.

I can confirm 40MHz OSC1 at the ASIC, no 4MHz out.  Has to be a dead ASIC? 

[Bryce]

Where are you measuring 10MHz? The Plus has a 40MHz clock source, which the ASIC divides down to 4MHz (and should be measurable on pin 125).

Bryce.

I can confirm 40MHz OSC1 at the ASIC, no 4MHz out.  Has to be a dead ASIC?

If your scope states 10MHz, then it's only going to manage a sinewave at that frequency and it's also just a harmonic of the 40MHz that it's displaying. Either way, it's telling you that there is a signal there, so if pin 125 is showing nothing with the same scope, the ASIC is unfortunately an ex-ASIC, ie dead.

Bryce.

[abalore]

Have you tested CLK16 and CLK1 outputs?

[Overkill]

Have you tested CLK16 and CLK1 outputs?

I just checked, there is no CLK1 or 16, also the ASIC stays stone cold.

I might try replacing the ASIC, but not sure if I can handle the soldering

[abalore]

Have you tested CLK16 and CLK1 outputs?

I just checked, there is no CLK1 or 16, also the ASIC stays stone cold.

I might try replacing the ASIC, but not sure if I can handle the soldering

If you already have a replacement ASIC it's done. With a hot air gun it's easy stuff.

Take the motherboard to some smartphone repair service and they will do in a minute.

[andycadley]

Before desoldering anything, do you have an actual known working Plus cartridge in the cartridge slot? Not some expansion connected device that loads CPRs etc.

I'm not sure if the ASIC generates the Z80 clock or not if ACID verification fails, but it's possible it doesn't.

[abalore]

Before desoldering anything, do you have an actual known working Plus cartridge in the cartridge slot? Not some expansion connected device that loads CPRs etc.

I'm not sure if the ASIC generates the Z80 clock or not if ACID verification fails, but it's possible it doesn't.

The ACID chip itself requires the 4Mhz signal. So it's unlikely the ACID verification can be done without it.

[Overkill]

If you already have a replacement ASIC it's done. With a hot air gun it's easy stuff.

I have another faulty board that had trace damage, see My other thread, although it could be a faulty ASIC on that board aswell, although I don't think it is.

I have a hot air station, would it be as simple as heating it up to remove it, and then heating the replacement, or would extra solder be needed?

[Overkill]

Before desoldering anything, do you have an actual known working Plus cartridge in the cartridge slot? Not some expansion connected device that loads CPRs etc.

I'm not sure if the ASIC generates the Z80 clock or not if ACID verification fails, but it's possible it doesn't.

Tried with different working cartridges.

[abalore]

If you already have a replacement ASIC it's done. With a hot air gun it's easy stuff.

I have another faulty board that had trace damage, see My other thread, although it could be a faulty ASIC on that board aswell, although I don't think it is.

I have a hot air station, would it be as simple as heating it up to remove it, and then heating the replacement, or would extra solder be needed?

I made this rework several times just using the remaining tin in the footprint. In case it's needed you can add some 0.3mm wire or solder paste. I recommend you to watch several SMT rework videos on YT before proceeding, there are many useful tips. Also don't be hurry in the process, take your time heating up the components to prevent thermal shock damage.

[Overkill]

If you already have a replacement ASIC it's done. With a hot air gun it's easy stuff.

I have another faulty board that had trace damage, see My other thread, although it could be a faulty ASIC on that board aswell, although I don't think it is.

I have a hot air station, would it be as simple as heating it up to remove it, and then heating the replacement, or would extra solder be needed?

I made this rework several times just using the remaining tin in the footprint. In case it's needed you can add some 0.3mm wire or solder paste. I recommend you to watch several SMT rework videos on YT before proceeding, there are many useful tips. Also don't be hurry in the process, take your time heating up the components to prevent thermal shock damage.

How did you do yours? do you heat it up and keep nudging the chip to see if it's loose, then pick it up with tweezers?

[abalore]

If you already have a replacement ASIC it's done. With a hot air gun it's easy stuff.

I have another faulty board that had trace damage, see My other thread, although it could be a faulty ASIC on that board aswell, although I don't think it is.

I have a hot air station, would it be as simple as heating it up to remove it, and then heating the replacement, or would extra solder be needed?

I made this rework several times just using the remaining tin in the footprint. In case it's needed you can add some 0.3mm wire or solder paste. I recommend you to watch several SMT rework videos on YT before proceeding, there are many useful tips. Also don't be hurry in the process, take your time heating up the components to prevent thermal shock damage.

How did you do yours? do you heat it up and keep nudging the chip to see if it's loose, then pick it up with tweezers?

Yes. Since you are removing a broken part, you don't have to worry too much about overheating it, but still need to be careful to not damage the PCB, so don't put the gun closer than 1 cm to the PCB and don't move the IC until it's really loose. What I do is to move the gun around the IC pins with a small nozzle of about 4mm, at 400 degrees, at a distance of about 2 cm. And in the meantime I gently pull the part up with tweezers until it goes out with no effort. Try to remove the IC vertically, without sliding it horizontally over the board. It takes a bit so be patient. For this procedure some people use solder flux, I don't use it. Of course take all the cautions, at the very least have a suction fan with filter near so you don't breath harmful gases, or do it in a very well ventilated place.

When you successfully removed the IC, make a visual inspection of the footprint so there are no bridges or broken pads or traces. Then put the new IC in place. It should fit well on top of the tin left by the old IC, because it makes a kind of mold of the pins. Then heat up again with the air gun or go pin by pin with a small tip soldering iron.

And that's all. If you don't find yourself confident, take it to some phone/console repair service as I said previously. It's a easy job for them.

[Overkill]

If you already have a replacement ASIC it's done. With a hot air gun it's easy stuff.

I have another faulty board that had trace damage, see My other thread, although it could be a faulty ASIC on that board aswell, although I don't think it is.

I have a hot air station, would it be as simple as heating it up to remove it, and then heating the replacement, or would extra solder be needed?

I made this rework several times just using the remaining tin in the footprint. In case it's needed you can add some 0.3mm wire or solder paste. I recommend you to watch several SMT rework videos on YT before proceeding, there are many useful tips. Also don't be hurry in the process, take your time heating up the components to prevent thermal shock damage.

How did you do yours? do you heat it up and keep nudging the chip to see if it's loose, then pick it up with tweezers?

Yes. Since you are removing a broken part, you don't have to worry too much about overheating it, but still need to be careful to not damage the PCB, so don't put the gun closer than 1 cm to the PCB and don't move the IC until it's really loose. What I do is to move the gun around the IC pins with a small nozzle of about 4mm, at 400 degrees, at a distance of about 2 cm. And in the meantime I gently pull the part up with tweezers until it goes out with no effort. Try to remove the IC vertically, without sliding it horizontally over the board. It takes a bit so be patient. For this procedure some people use solder flux, I don't use it. Of course take all the cautions, at the very least have a suction fan with filter near so you don't breath harmful gases, or do it in a very well ventilated place.

When you successfully removed the IC, make a visual inspection of the footprint so there are no bridges or broken pads or traces. Then put the new IC in place. It should fit well on top of the tin left by the old IC, because it makes a kind of mold of the pins. Then heat up again with the air gun or go pin by pin with a small tip soldering iron.

And that's all. If you don't find yourself confident, take it to some phone/console repair service as I said previously. It's a easy job for them.

Thanks for all the info, I think it's worth me having a go.  I'll let you know how it goes