white PC ENGINE - CASING(ed) extremely HOT - is this normal?

[cheezio]

hi - RE. the large chunk of metal that sits over the on/off switch - I am guessing it is a kind of heatsink?

It's just that whilst I have had the console open for an RGB mod - I have noticed that the chunk of metal gets stupidly hot (not warm to the touch - but OUCH) after about 30 mins.

Is this normal? (or has my modding done something dodgy - I have ripped out the RF unit, and have 2SC1815 transistors on each of the RGB lines to the scart). [see here http://pcenginefx.com/phpBB/viewtopic.php?t=2026&sid=605b52aedd09145632fc1fb228d12519 ]

I am just worried that it`ll melt/set fire over long periods of use

[grahf]

Yes its ok. You'll notice that the power regulator is screwed to the heatsink. The way these type of regulators work, is they take any power input of at least 7v-some other number, and limit it down to the 5v which the system needs to operate. Any extra voltage is turned into waste heat.

Companies use these type of regulators because they are dirt cheap, and work fine when you dont care about a little wasted energy.

[cheezio]

cool - thanks for the info. I was expecting it to be warm - just not as hot as it is because it doesn't have the prongs of a modern heatsink.

Seems crazy that the system has a 9v PSU when it only needs 5v huh?

[Tatsujin]

grahf is right! the LM78M05 linear voltage regultaor is just burning the remaning 4 voltages into pure heat! its nothing than a better voltage divider!
at about 1A of current it flows, it's normal it's getting hot as hell^^

[FM-77]

Yeah, these voltage regulators are present in almost all the older consoles (NES, SNES, MD, etc). They all get really hot, and in the case of NES clones and the like they often use very small heatsinks. Not a good idea: my NES clone almost caught fire (it started smoking violently and it was extremely hot).  

[Vanquish]

so... could the pc engine work with a 7 volt or 6 volt ac adaptor?

[FM-77]

I doubt it. I couldn't run an NTSC SNES (10V) with a 9V adapter. It worked, but the sound was buzzy and the picture was flickering.

Edit: I've also tried running an NES (9V) with a 6V adapter. Same thing happened there.

[Keranu]

My PCE can get hot too like that.

[SignOfZeta]

so... could the pc engine work with a 7 volt or 6 volt ac adaptor?

My Core Grafx will run on 6v. I wouldn't be surprised if it caused AV problems though. I didn't test it much.

[cheezio]

Hmm - so if volts are being wasted, and being turned to heat - would it be a good idea to add something to use the current up?

eg - an LED, or a small fan?

or will drawing more current heat up the heatsink?

[grahf]

The regulators require a certain voltage is input. Even though they output 5v, they require at least 7v or so input. (Somebody correct me if i'm wrong since im going from memory), But if you have a higher drain on the regulator, it will require an even greater input voltage. Thats why some systems will work with a lower voltage supply (like SignofZetas coregrafx), and some require a higher input (like Seldane stated with the Nintendo systems).

An alternative to the standard regulators, are "Switching" or "Buck" regulators. Instead of just wasting the extra energy as heat, they use an IC and very rapidly switch on and off to lower voltage. There are a ton of different ICs, some with set output voltages, and some with adjustable output. Pretty much all of them require a few external caps and resistors to be used.

If your interested, a company called Dimension Engineering makes a nice SUPER tiny switching regulator circuit thats designed to be a drop in replacement for standard regulators: http://www.dimensionengineering.com/DE-SWADJ.htm
I bought one im going to use in a portable snes project of mine.

[SignOfZeta]

Hmm - so if volts are being wasted, and being turned to heat - would it be a good idea to add something to use the current up?

eg - an LED, or a small fan?

or will drawing more current heat up the heatsink?

The whole principle behind a regulator (electric, hydraulic, pneumatic, whatever) is to provide a steady suppy of something. You need to have more than what is eventually desired, so that the regulator can cut it down to what is needed. When more current is being used, the regulator will waste less into heat, and make it flow into the circuit. Its like having an extra $100 in your checking account. You don't want to figure out ways to spend it.

If you had just 5V, then a sudden demand for current would most likely cause a drop in voltage. A regulated 9V will always provide a solid 5V...unless outstripped the demands of the power supply.

[Tatsujin]

The regulators require a certain voltage is input. Even though they output 5v, they require at least 7v or so input. (Somebody correct me if i'm wrong since im going from memory),mine.

yes thats right, the LM78xx series have a drop out voltage of 2V!

http://www.it.iitb.ac.in/~it606/Datasheets/LM7512C.pdf#search=%22lm7805%22

if the input voltage falls below 7V, the output voltage can't be regulated well, will drop below the 5V and the CPU and the rest of the TTL logic will face some tremendous probs!

[cheezio]

Has anyone thought of filing down grooves into the heatsink? to increase surface area, and so help it stay cooler?

[grahf]

You could, but its not really worth it. The regulators can be bought for under a dollar (i think $1.49 at radioshack). If it goes bad, you can just replace it. Probably never will though.