Author Topic: [PLEASE READ] GX4000 with original power brick and C4CPC  (Read 23792 times)

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Offline gerald

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I've just serviced a GX4000 that failed after using a C4CPC.
To make it short, the original power supply likely failed, ultimately frying the RAM.

The C4CPC consume up to 80mA more than a regular cartridge, a GX4000 is consuming about 400mA + 50mA if it has an RF modulator. This slightly exceed the rated current supply of the Amstrad provided power brick.

Therefore I urge you to stop using your Amstrad power supply with the C4CPC.

Instead :
  - use any regulated DC 9V to 12V 750mA (positive on center pin, GND on outer pin), powering the 11V entry. The 11V is used to power the 5V regulator and to drive the scart switching pin.

  - use the 5V supply input and the DIN rgb output (as if connected to a plus monitor). 5V supply may not work well with GX4000 having a RF modulator when using the SCART plug.

As a general rule, when using the 11V input, using a power supply with a voltage as low a 7.5V will work with the possible exception of the scart switching signal. Using it at lower voltage will minimise the 5V regulator(s) heating.

Failure details :
To fix it, I first replaced the main voltage regulator as it was issuing 7.5V instead of 5V. However, this happened also with the new one.
I then found that the 7805 bypass diode (to protect it when powered from a 5V supply, see attached schematics) failed in a way that feed the 11V on the 5V. So I removed that diode to discover that the RAM chip failed as well.
Once the RAM have been changed, everything worked fine. I've also replaced the diode with a new one.

Now, what happened ?
I suspect the power brick to have failed, or at least had a transient that made the diode fail, which in turn fried the RAM, which roughly protected the remaining part of the GX4000. The GX4000 jumped to 1A with the dead RAM.


Offline gerald

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The original Amstrad power supply is a 11V 500mA stabilised power supply, using a 220V AC input.
From oscilloscope trace under load, it seems to use a full diode bridge and a 3300µF filtering cap.

Powered with a 230V main, the output voltage is :
  • unloaded : 15.4V DC
  • under load (415mA) : 12.1V DC + 1V AC ripple.
With a 240V main, DC voltage would go at 12.6V, which mean about 3.8W to dissipate for the 5V internal regulator instead of 3W at specified 11V

With a 9V DC regulated power supply, the dissipated power will be reduced to 2W.

Offline dxs

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Hi, So does that mean that if we have a GX4000 without the RF output we can continue to use the original Amstrad PSU?

Offline CraigsBar

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The original Amstrad power supply is a 11V 500mA stabilised power supply, using a 220V AC input.
From oscilloscope trace under load, it seems to use a full diode bridge and a 3300µF filtering cap.

Powered with a 230V main, the output voltage is :
  • unloaded : 15.4V DC
  • under load (415mA) : 12.1V DC + 1V AC ripple.
With a 240V main, DC voltage would go at 12.6V, which mean about 3.8W to dissipate for the 5V internal regulator instead of 3W at specified 11V

With a 9V DC regulated power supply, the dissipated power will be reduced to 2W.
Mine is now safely on a 9v 1A supply and the original one is packed up back in the box.


Seems to be fine with 9v not 11, my 6v supply does not power it (well the LEDS on the C4CPC and console light, but nothing else) and I don't have a 7v supply.


Craig


Offline Ast

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Hi, So does that mean that if we have a GX4000 without the RF output we can continue to use the original Amstrad PSU?
I've asked the same question to Gerald a few days ago. His answer was it'll be better to change the power supply to not have any problems with the old one.
After that, do what you have to do!
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Offline gerald

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Hi, So does that mean that if we have a GX4000 without the RF output we can continue to use the original Amstrad PSU?
I would not recommend this, you only get a 50mA margin.

Offline gerald

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my 6v supply does not power it (well the LEDS on the C4CPC and console light, but nothing else) and I don't have a 7v supply.
6V is too low for the 5V regulator to work as it need 2V margin.
And while the GX4000 may not work at 4V, the C4CPC will : it's a 3.3V device and it regulator only need less than .5V margin to work.

Offline Crazy_Borg

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Sadly, we lost a large part of the discussion here because of the database crash.

All of my GX4000 need at least 9V at the 11V input, 7,5V is too low and results in visual corruption / game freezes.

It is possible to power the GX4000 through the 5V Monitor input if you only have a 5V power supply.
To power the RGB chip CXA1145 for the SCART output to work you have to remove the UPC78L05 (IC17) and bridge point LK7 on the pcb, which  it is marked on the pcb near the IC17.
That way you will turn your GX4000 into a french model.
I already modded a regular GX4000 this way some time ago and it worked fine, though I only testet the SCART output.

Gerald noted that the RF modulator may not work because of noise after the above described conversion, but who is using it anyway?
Where you worried just about image stability or about a complete failure of the RF modulator because of it?


words are cheap...words come and go

Offline gerald

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Gerald noted that the RF modulator may not work because of noise after the above described conversion, but who is using it anyway?
Where you worried just about image stability or about a complete failure of the RF modulator because of it?
Mostly noise. But as you said, who is still using it nowadays ?
Yes, 7V is the low limit. I think the sweet spot is 9V.
Also, the original 11V power supply will run at higher voltage with current 230/240V instead of the old good 220V.

Offline dthrone

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Is it possible to recommend a suitable replacement brick, maybe with an Amazon (or equivalent) link or something?

Offline gerald

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Is it possible to recommend a suitable replacement brick, maybe with an Amazon (or equivalent) link or something?
You should look for something like this :
9V 1.5A : High Capacity 9V Power Supply Adapter for Arduino: Amazon.co.uk: Electronics
9V 1 A : GRV 9V DC 1A switching power adaptor 2.1x5.5mm Supply UK plug: Amazon.co.uk:

Both of these have a 2.1mm centre pole that should prevent pluging them on the 5V input.

Offline chinnyhill10

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You should look for something like this :
9V 1.5A : High Capacity 9V Power Supply Adapter for Arduino: Amazon.co.uk: Electronics
9V 1 A : GRV 9V DC 1A switching power adaptor 2.1x5.5mm Supply UK plug: Amazon.co.uk:

Both of these have a 2.1mm centre pole that should prevent pluging them on the 5V input.


Don't much like the look of either of those. One of them came apart when the user got it, a reviewer on the other measured the output and found it to be unstable. Fact is most of the generic PSU's on Ebay and Amazon are dangerous poorly made tat.


The only place I can recommend for PSU's are RS. Yes they are expensive but their PSU's are both stable and unlikely to kill you or your equipment.


Plug In Power Supply | RS Components


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Offline Phantomz

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Don't much like the look of either of those. One of them came apart when the user got it, a reviewer on the other measured the output and found it to be unstable. Fact is most of the generic PSU's on Ebay and Amazon are dangerous poorly made tat.


The only place I can recommend for PSU's are RS. Yes they are expensive but their PSU's are both stable and unlikely to kill you or your equipment.


Plug In Power Supply | RS Components

Have you got a link for the best one to get from there for the Gx4000?  :)

Offline chinnyhill10

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Have you got a link for the best one to get from there for the Gx4000?  :)


Just select what you require on the left hand side, hit update and it will give you the suggestions. Double check the specs of what you are buying as they have so many PSU's in stock you need to be ware that you need a switched mode PSU with the correct input voltage and a UK plug.


You could go for a 5v adaptor if you wish which could then double up for use with a standard CPC if you have one or plan to get one.


I can't access the search thing at the moment but can try later. I can also post the RS part number of the PSU I use for my 6128 tonight.
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Offline gerald

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Offline Phantomz

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Suitable 9V 1A from RS :
5.5 x 2.1 with positive on centre pole

Euro plug :  ECP-11-9E | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply,
UK plug : ECP-11-9U | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply,
Selectable Plug : PSC12R-090 | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply,

Thank you for that.  :)

I'll get one of those for my GX4000, I've also got a 6128 Plus with a Monitor, I know you said the Monitor Power supply is ok to use with the C4CPC, but I'm not using it at the moment.
The monitor is stored away as I haven't got the space really so I'm using one of those power and scart kits that you get from ebay.

A photo of the power supply I'm using is below:

6128 Power Supply_zpszw8mmyw4.jpg Photo by Phantomz | Photobucket

Is this ok with the C4CPC in my 6128 Plus or do I need a different one?

Offline gerald

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6128 Power Supply_zpszw8mmyw4.jpg Photo by Phantomz | Photobucket

Is this ok with the C4CPC in my 6128 Plus or do I need a different one?
2.5 Amp more than enough for a 6128

Offline Phantomz

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2.5 Amp more than enough for a 6128

That's good then, only need one for the GX4000.

Thanks  :D

Offline EgoTrip

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You don't need more than one CPC. You should give me one.
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Offline dragon

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I have the nimo alm 072 multi output, and i very  happy with it.

If you compare the nimo, with a normal chinese adapter or similiar low price , the adapter always is very hot. The nimo is cold.

But it not cost 10e, it cost me around 30e,And I no longer worry about amps. He deliver 5A in all outputs. (But they have other model with minus amperes).

Offline Phantomz

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You don't need more than one CPC. You should give me one.

Yea you do  :P

Offline CraigsBar

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You don't need more than one CPC. You should give me one.
Is that where I am going wrong... Damn, I got 2 CPC's, 3 plusses and GX4000. Not giving any away tho! I dod offer to give away a JXD S7800b but no one seemed too interested. Oh well.


Craig

Offline EgoTrip

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Is that where I am going wrong... Damn, I got 2 CPC's, 3 plusses and GX4000. Not giving any away tho! I dod offer to give away a JXD S7800b but no one seemed too interested. Oh well.


Craig

Greedy 1%er >:( ;)
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Offline Phantomz

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Suitable 9V 1A from RS :
5.5 x 2.1 with positive on centre pole

Euro plug :  ECP-11-9E | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply,
UK plug : ECP-11-9U | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply,
Selectable Plug : PSC12R-090 | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply,

I decided to get one of these UK plug : ECP-11-9U | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply, ordered it yesterday in the afternoon around 14:30 and it turned up this morning just after 08:00 , so they are fast.  :)

I've tested it quick and it works fine, I don't know if it stays cool as haven't had time to play with it yet.  :-\

Happy with the service though.  :D

Offline Dr Tiger Ninestein

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I decided to get one of these UK plug : ECP-11-9U | 9V dc, 1 Output, Switch Mode, ErP Compliant, Plug In Power Supply, ordered it yesterday in the afternoon around 14:30 and it turned up this morning just after 08:00 , so they are fast.  :)

I've tested it quick and it works fine, I don't know if it stays cool as haven't had time to play with it yet.  :-\

Happy with the service though.  :D


I'm about to order one of these. Am I right in thinking that I can use this to power my gx4000 with or without the c4cpc?