exxos's Atari, Amiga & retro forum

I'm not sure what to say! I must have confused things somehow.. :oops:

Although it has three holes blown in it, R1 is still giving a reading of about 20 ohms so it would have been able to function? I mean it did still work after the bang so it must have been just clinging on?

After removing R1 and R2 I have not tried to power the board up again, maybe I gave the impression that I did? In that case I can see how I may have confused things!

exxos wrote: 14 Nov 2022 13:21
R1 is in series with the mains rectifier.. With no R1.. the PSU has ZERO power. It will not function without it. Basically has the same effect of the mains fuse blowing.

R2 is a voltage suppressor where the power supply can run without it.

So either you have the wrong part number or the wrong schematic...Or you have placed a wire link over the part or something else ??

I'd agree with what exxos said, no R1 = no power.

Have you compared the layout of the components and where they trace to to the schematics to verify that you have the right thing?

I'd also check the bridge rectifier hasn't failed.

wub wrote: 14 Nov 2022 13:33 I'm not sure what to say! I must have confused things somehow.. :oops:

Although it has three holes blown in it, R1 is still giving a reading of about 20 ohms so it would have been able to function? I mean it did still work after the bang so it must have been just clinging on?

After removing R1 and R2 I have not tried to power the board up again, maybe I gave the impression that I did? In that case I can see how I may have confused things!

Personally I wouldn't trust a component that looks like it's been shot with a .50 Cal!! It might seem to work, bit I doubt it will last long.

Get new and in the meantime verify the schematics match your PSU. If they don't, then you could have ordered the wrong part.

Have you compared the layout of the components and where they trace to to the schematics to verify that you have the right thing?

Absolutely! The board is very clearly marked up. I'm sure the problem is that I implied that R1 was completely blown. I should have said that it was still giving a reading of 20 ohms and wasn't completely blown, despite looking like it should be.

I'm really sorry to have created confusion!

I have ordered a new R1, it's R2 that I am going to reuse as it genuinely does seem fine.

wub wrote: 14 Nov 2022 13:42 Absolutely! The board is very clearly marked up. I'm sure the problem is that I implied that R1 was completely blown. I should have said that it was still giving a reading of 20 ohms and wasn't completely blown, despite looking like it should be.

Yikes, so you are still using that blown part ?? if that is the case I suggest you stop doing that as it has mains voltage across it. It is certainly rather a fire risk.

wub wrote: 14 Nov 2022 13:42

Have you compared the layout of the components and where they trace to to the schematics to verify that you have the right thing?

Absolutely! The board is very clearly marked up. I'm sure the problem is that I implied that R1 was completely blown. I should have said that it was still giving a reading of 20 ohms and wasn't completely blown, despite looking like it should be.

I'm really sorry to have created confusion!

Not a problem, these things happen. I just like to be 100% certain with PSUs as they can be quite 'fighty' if you don't get things just right.

Trust me, when stuff goes boom in a PSU, it goes boom properly!

It's really difficult. If I had the money and the time, and the confidence in my skills, I would replace everything on the PCB that I could just for the peace of mind. Knowing that the mixer was very likely a fire hazard is a huge concern!

I've also got to make sure that when I make a post like this that I am much more detailed in describing what I have done and what condition the components are in. Re-reading the post I can see that I made it sound like R1 was blown, but that the board was still functioning.

Thank you for taking the time to clarify what was going on for my safety, it is genuinely very much appreciated!

And sorry to Exxos for testing his patience, I have learned a lesson today I promise!

wub wrote: 14 Nov 2022 14:05 And sorry to Exxos for testing his patience

Don't worry, that's basically a sport around here. :lol:

Don't worry, that's basically a sport around here. :lol:

lol Sounds like I'm going to fit right in then! ;)

As for my PSU, I'm going to remove and test C6 and the rectifier and, assuming that all goes smoothly, I'll see about testing all the adjacent caps to make sure everything is within spec.

I always feel like I'm on a tightrope, do I take the risk of assuming things are ok, or risk damaging something else by trying to de-solder and test? This particular PSU seems to be unavailable as a spare part so if I damage the board I could be in real trouble!

I don't want to be ignoring the advice I asked for though, so in for a penny in for a pound I guess!