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General Category => Technical Support => Topic started by: rewk on 20:17, 22 July 21

Title: GX4000 rather warm: voltage regulator replacement ?
Post by: rewk on 20:17, 22 July 21
Hello,

My GX4000 is getting rather warm, due to the 7805 voltage regulator. I guess it's normal, however I wondered whether it would be worthwhile to replace it with a DC/DC converter TSR1-2450. It should allow for a lower temperature inside the case. And hopefully, increasing the life expectancy of this nice little console. :)

Has anybody here already done this ?

Title: Re: GX4000 rather warm: voltage regulator replacement ?
Post by: tjohnson on 22:38, 22 July 21
What PSU are you using, original one is 11v now many use 12v so it's disipating 7v.  Apparently you can use 9v on many and it will still work.  Another alternative is use the 5v but you'll need to the din output, scart doesnt work when powered via the 5v socket.  Not sure I would bother trying anything else.
Title: Re: GX4000 rather warm: voltage regulator replacement ?
Post by: rewk on 23:11, 22 July 21
I'm using the one recommended for using the C4CPC, that is a 9v. I couldn't find the original PSU anyways. That's why I though it was strange that the voltage regulator was getting warm. It's just warm, nothing really wrong, looking at the size of the heatsink there. But better safe than sorry. My main concern was to get my old GX-4000 going for as long as I can.

Maybe it was already warm when i played with it 30 years ago, but I really can't remember.

It's a French model, without composite video circuitry. The motherboard is quite empty on the top left corner. :)

These voltage regulators I got require testing though (AliEpress...)
Title: Re: GX4000 rather warm: voltage regulator replacement ?
Post by: pelrun on 11:21, 23 July 21
Linear regulators work by converting the excess voltage to heat. So getting warm is pretty much to be expected, and the whole unit getting warm just means the heat is being successfully transferred away instead of building up internally.

A switching regulator will certainly work in it's place, heck, the one you listed is specifically advertised as being a drop-in replacement for a 7805. Go for it, but only if it really bothers you.
Title: Re: GX4000 rather warm: voltage regulator replacement ?
Post by: Bryce on 12:38, 23 July 21
The GX4000 circuit isn't optimised for a switching regulator, so you may end up getting artefacts or glitches on the screen with the TSR1-2450. The high frequency noise it creates also isn't ideal for the IC's without additional filtering.


The 7805 is a much better choice and it's meant to get warm/hot. I'd stick with that.


Bryce.
Title: Re: GX4000 rather warm: voltage regulator replacement ?
Post by: rewk on 14:24, 23 July 21
The GX4000 circuit isn't optimised for a switching regulator, so you may end up getting artefacts or glitches on the screen with the TSR1-2450. The high frequency noise it creates also isn't ideal for the IC's without additional filtering.


The 7805 is a much better choice and it's meant to get warm/hot. I'd stick with that.


Bryce.


Thanks for you input. Looks like I won't try to mess with my console, then. ;)





Title: Re: GX4000 rather warm: voltage regulator replacement ?
Post by: pelrun on 14:51, 23 July 21
The GX4000 circuit isn't optimised for a switching regulator, so you may end up getting artefacts or glitches on the screen with the TSR1-2450. The high frequency noise it creates also isn't ideal for the IC's without additional filtering.
I know you're not a fan of switching regulators, but I do think you're overstating the problem dramatically. I've *never* seen any glitches when using them myself, even the crappy low-frequency ones. And I've used plenty in other rather more sensitive digital hardware in my day job. A CPC is pretty easily satisfied.
Title: Re: GX4000 rather warm: voltage regulator replacement ?
Post by: Bryce on 15:57, 23 July 21
It all depends on when the device was designed and what type of psu it was designed for. I have seen artefacts due to using a SMPS, but the hidden danger is the spikes that are stressing the IC's the entire time. SMPS pass high frequency spikes into the circuit. The CPC range was designed at a time when this problem didn't exist. If you have a device full of IC's that have a max voltage of 5.25V as is typical for TTL and RAM IC's and they are getting hit with 5.5 or 6V spikes all the time, then you are killing them slowly without knowing it. Modern equipment have the correct filters to block these spikes, but the CPC range was designed for a linear regulated PSU, so there is no HF filtering.

Of course it's not my GX4000, so I won't be offended if people ignore my advice, I'll also be happy to fix their CPC when it suddenly dies without warning.

Bryce.

P.s. I am a huge fan of SMPS's due to their size and efficiency. In fact I use them all the time in my designs, but only in conjunction with the correct filtering.