Decent 6128 5v 4 Amp PSU

[Tempest1977]

Hi all,

Anyone know where to get a decent 5v 4 amp PSU for a CPC6128?

My 5v 2 amp doesn't quite cut it with a Gotek and Multiface 2 and scart power. Need something delivering more.

👍

[dragon]

I have these 5A 5v to 12 v selectable with crystals apart of that come with 8 heads to fit all connectors.

https://www.amazon.es/NIMO-Alimentador-Regulable-Universal-5-12Vcc/dp/B00AWU9QX0/

[Bryce]

https://www.ebay.de/itm/324218253955

Bryce.

[Tempest1977]

Hi, replaced PSU with 5v 4 amp supply.

Nothing has changed. Same anomaly, MF2 Stop button resets machine until about 5m of power then all good.

MF2 is detected when installing Insider Software but Stop button still behaves as above. It's like the 6128 has to build up some charge prior to normal MF2 operation.

All that is connected is an internal Gotek and the MF2.

I'm stumped. Any suggestions?

Best regards

Gavin.

[pelrun]

I guess I'll just have to keep saying it, but 5v is insufficient regardless of the current rating, as there's a significant voltage drop inside the CPC even if it's only drawing 1A. What you really need is a 5.1-5.3v supply to give the extra headroom needed.

[Tempest1977]

I got thinking about what you were saying about voltage. 5.27v is leaving the PSU @ 4amps, which is 21 watts. I checked with a multimeter.

Could this suggest there is a fault on the main board? I guess I should check the voltage on the edge connector. 

It may mean that the required voltage isn't reaching the MF2 immediately or a faulty component on the way is building up a charge to eventually power the MF2. It takes 6 minutes of power for this to happen 

[Bryce]

I guess I'll just have to keep saying it, but 5v is insufficient regardless of the current rating, as there's a significant voltage drop inside the CPC even if it's only drawing 1A. What you really need is a 5.1-5.3v supply to give the extra headroom needed.

Could you expand on that? What exactly drops the voltage inside the CPC. It is made completely with 5V parts which are all connected directly to the 5V rail. It was designed to run on 5V and it should run on 5V.

Bryce.

[poulette73]

https://www.ebay.de/itm/324218253955

Bryce.

I have bought this one, and absolutely no problem. 👍

My CPC 6128 is powered with, starts and works great with all of the below at the same time :

• Mother X4 expansion board (no external PSU) with plugged in: USIfAC II + Mulitface 2 + rom board CPC Sixrom
• External Gotek drive, or external 3" 1/2 Disk drive as needed.
• SCART for connection to a 15" TV
• Maxduino interface for CDT files

And my two Multiface 2 work without any problem (because I have one version with DC3 connector on MX4, and another version with Edge connector)

Of course I can swap / add other cards on Mother X4 without worry, and Multiface 2 still functional.

So I would forget the hypothesis of a CPC power supply problem.

The problem could be with your Multiface 2.

[Tempest1977]

I mean the voltage leaving the PSU barrel is 5.27v.

I need to check what voltage is reaching the edge connector really.

I also guess maybe a faulty MF2 is possible. Could this be a RAM issue on the MF2? The only symptom of a fault is a delayed fully operational MF2 until 5+ minutes of power.

The continuity pin to pin from the edge connector through the MF2 is all good so can't be a dirty contact.

I"m pretty new to this so not an expert.

Cheers all.

[pelrun]

Literally the resistance of the connectors inside the machine, to start. Supplying 5V at the input on my CPC's only gives me around 4.6v when putting a meter on VCC of any of the ICs, and that's with CP305 directly jumpered to take the power switch out of the path, and a shiny new DC jack soldered in. A load spike makes the voltage drop even worse, of course.

I had no end of stability issues, especially with the M4 and other peripherals until I gave my machine a bit more input voltage (initially from my bench supply but then by adjusting the output from my CTM644) and it resolved everything. (and no, putting 5V directly to the peripherals was not sufficient either.)

Sure, many people manage ok with just 5v, but the standard line of "if it's unstable you just need a psu with a higher current rating" is not always the full answer, especially when the CPC isn't actually pulling anywhere near the max current of the supply they currently have.

[Bryce]

I got thinking about what you were saying about voltage. 5.27v is leaving the PSU @ 4amps, which is 21 watts. I checked with a multimeter.

Could this suggest there is a fault on the main board? I guess I should check the voltage on the edge connector.

It may mean that the required voltage isn't reaching the MF2 immediately or a faulty component on the way is building up a charge to eventually power the MF2. It takes 6 minutes of power for this to happen

4A is what the PSU can supply, not what the CPC is using. If the CPC was pulling 4A you could smell what's damaged because it would be burning

Bryce.

[Bryce]

Literally the resistance of the connectors inside the machine, to start. Supplying 5V at the input on my CPC's only gives me around 4.6v when putting a meter on VCC of any of the ICs, and that's with CP305 directly jumpered to take the power switch out of the path, and a shiny new DC jack soldered in. A load spike makes the voltage drop even worse, of course.

I had no end of stability issues, especially with the M4 and other peripherals until I gave my machine a bit more input voltage (initially from my bench supply but then by adjusting the output from my CTM644) and it resolved everything. (and no, putting 5V directly to the peripherals was not sufficient either.)

Sure, many people manage ok with just 5v, but the standard line of "if it's unstable you just need a psu with a higher current rating" is not always the full answer, especially when the CPC isn't actually pulling anywhere near the max current of the supply they currently have.

And that's why my first suggestion is always to clean all connections and the power switch. If everything is clean and the 5V rail is still dropping to 4.6V you have one of the following issues:

1 - The cable from the PSU is either too long or the guage is too small.
2 - The PSU can't actually supply the amount of current that it claims.
3 - You have a faulty component in the circuit that is pulling more current than it should.

Raising the voltage is just hiding the symptoms, not solving the the real problem.

Bryce.

[pelrun]

1. No.
2. No.
3. No.

I do know how to check for these things, thanks. The voltage just before entering the CPC is *still 5 volts*, which invalidates every "voltage sag due to exceeded current rating" explanation.

And "clean the connections and the power switch" just completely ignores me saying that the connectors were brand new and the switch was completely bypassed, but whatever.

[pelrun]

Now don't get me wrong, I'm not trying to invalidate all the other advice - it's still absolutely the right approach to ensure your PSU has a sufficient rating, and that the connectors and power switch are all clean and low-resistance. (And low resistance means *really* low, there only needs to be 1 ohm of series resistance at 1 amp and suddenly you've dropped a full volt.)

But when those have been done and the problem persists, what are you supposed to do? Throwing up your hands and suggesting replacing the PSU repeatedly with more and more outlandish current ratings isn't exactly useful. I don't recommend bumping the input voltage until everything else has been exhausted, but it's better than running out of things to try, and it has definitely worked in my case and in others.

[Bryce]

Well you have to try and find what's dropping the voltage. So measuring points around the board can help. Removing all socketed chips to see if they are the cause will eliminate them. Measuring the resistance between the 5V input pin and the VCC of each chip will tell you whether you have a corroded trace on the PCB. Especially on old PCBs that have possibly been badly stored, a corroded trace can drop the voltage considerably.

There are lots of things you can do before giving up.

Bryce.