Update 7805 to OKI-78SR-5 for heat reduction

SmokeMonster · 07/25/2015, 05:31 PM

I have been going through my consoles and replacing their 7805 voltage regulators with the newer and more efficient OKI-78SR-5. I originally ordered four for my hottest running systems: Sega Genesis (has two 7805s), SNES, and Super Famicom.

The results were dramatic, and all of them pretty much run cool to the touch now. The 78SR-5 doesn't need a heatsink, and there is no change to the AV quality. The sync seems more stable on my Genesis, so it might have had a failing 7805. I have more ordered now for my TG16, PCE, and Duo.

Has anyone else gone this route?

ClodBusted · 07/25/2015, 06:17 PM

Since I think I'll need to replace the regulators on my Duo anyway, I'll give the swap for the those more efficient parts you proposed a try.

~~However, the link you've posted leads to a 404 site.~~ EDIT: Thanks for fixing.

SmokeMonster · 07/25/2015, 06:36 PM

The link should work now. I think Digikey is the cheapest source for them in the US.

There is also a 90-degree angled version (OKI-78SR-5/1.5-W36H-C) that is perfect for TG16 mounting.

CkRtech · 07/25/2015, 11:31 PM

I have done this on several of my consoles and figured the Turbo Duo was a no brainer. I just haven't done it yet. In fact, a Turbo Duo may benefit the most out of all consoles due to the heat issues it is known for. I may even do a temperature experiment with my unit and take measurements before and after the change and report here whenever I do the mod. One of you will most likely beat me to it.

SignOfZeta · 07/26/2015, 01:53 AM

...heat...issues...?

thesteve · 07/26/2015, 02:19 AM

Quote from: SignOfZeta on 07/26/2015, 01:53 AM...heat...issues...?

my thoughts exactly

thesteve · 07/26/2015, 02:24 AM

be aware that the 7805 is rock solid old tech, and may prove more reliable

SmokeMonster · 07/26/2015, 03:01 AM

Quote from: SignOfZeta on 07/26/2015, 01:53 AM...heat...issues...?

SNES and Genesis definitely get toasty but the NEC stuff doesn't seem to be on that level.

thesteve · 07/26/2015, 04:20 AM

well yes the SNES pushes the 7805 hard, but the other stuff not so much
the 78SR-5 however is a power converter circuit on a board to use as a replacement, but as a much more complicated circuit could prove less robust in practice

ClodBusted · 07/26/2015, 11:40 AM

On my Turbo Duo, the 7805 thingies got really hot, even so much that you can feel the heat on the plastic cover. A friend of mine who succesfully recapped my Duo even suggested I should replace the regulators with something more efficient.

Keith Courage · 07/26/2015, 12:17 PM

If it isn't broke don't fix it.

ClodBusted · 07/26/2015, 01:03 PM

Well my Duo is broken so I've got to fix it anyway.

SmokeMonster · 07/26/2015, 02:30 PM

I recap consoles that aren't broken all the time. If heat in a console can be completely eliminated using a $4 part, it's worth looking in to.

That said, the negative feedback from thesteve and Keith makes me less enthusiastic about doing this to NEC consoles.

leonk · 07/26/2015, 10:22 PM

I don't subscribe to "if it ain't broken, don't fix it" mentality.Following this logic people should wait till all the caps in their Duo/TGE leak all over the PCB and rot the traces before doing any sort of preventative maintenance.

Switching power supplies (what this is) have been here since the 80's (unlike the linear 7805 whose been here since the '40s if not earlier). It's a lot more efficient (doesn't waste electricity) and a lot more resilient (can take up to 35V input!) and puts out clean 1.5A of current(which is needed if you use FPGA based devices in your retro consoles - like everdrive)

I noticed that my Sega NOMAD with LCD mod would shut down after 2 hours of usage (using micro surface mount linear transformer) when I put this in there it ran for 8 hours before I just turned it off.

Use it, don't use it, up to you. I tell all my customers about it and they all agree with the extra fee for the upgrade.

CkRtech · 07/27/2015, 01:59 AM

Quote from: thesteve on 07/26/2015, 02:19 AM
Quote from: SignOfZeta on 07/26/2015, 01:53 AM...heat...issues...?
my thoughts exactly

from the two 7805 near the sound circuit

Keith Courage · 07/27/2015, 02:30 AM

Well, I wasn't referring to leaking caps obviously. Leaking caps can damage other things. I have yet to see any damage of any kind caused by the original 7805s. If they no longer work then of course you should change them but if they work I see no point.

thesteve · 07/27/2015, 04:33 AM

im not saying not to do it, just that the heat isnt the only consideration
a micro switcher will have a coil, diode and caps on board along with a pulse generator
the caps are likely driven to their limits as space constraints were a major consideration in the device and can fail
now in a TE i would highly recommend using something like this as it will extend battery life
35V max input is the same as the 7805

SmokeMonster · 07/27/2015, 03:53 PM

I didn't remember seeing a 7805 in the TE, does it use them as well? Extra battery life would be nice.

Isn't there an issue with the sound caps on the Duo getting heat stressed because of their proximity to the two 7805s?

CkRtech · 07/27/2015, 07:12 PM

Quote from: Keith Courage on 07/27/2015, 02:30 AMWell, I wasn't referring to leaking caps obviously. Leaking caps can damage other things. I have yet to see any damage of any kind caused by the original 7805s. If they no longer work then of course you should change them but if they work I see no point.

Heat. The point is to eliminate (reduce) heat output. Heat is not really good for electronics, and you have two voltage regulators right at the sound circuit. Those 7805s are terrible as they are extremely inefficient and produce a ridiculous amount of heat. You could remove them both along with their heatsinks and seriously reduce just how hot the area gets during operation. Replace the caps is still an obvious part of Duo longevity, and I honestly think replacing the voltage regulators should be as well - despite the fact I haven't done it yet on mine.

I am rather shocked that you guys would oppose this, honestly. To me, it is a "duh. You obviously should do this" operation, and I am also shocked people haven't done it already. It is quite cheap and eliminates heat. Win-win

RGB32e · 07/27/2015, 09:06 PM

Quote from: SmokeMonster on 07/26/2015, 02:30 PMThat said, the negative feedback from thesteve and Keith makes me less enthusiastic about doing this to NEC consoles.

I wouldn't be concerned with their comments. The Turbo Duo systems generate a fair amount of heat with the two stock 7805s. Try leaving your finger on one of the heat sinks for a minute after the console has been on for a while!

Even Tim Worthington sells switching DC/DC converters on his site. They are modern drop-in replacements for the old 7805s. He has been incorporating switching DC/DC in a number of his products such as the Famicom-PA board and soon to be released 2600RGB. Not to mention that a switching DC/DC converter will be a requirement for the HiDefNES.

I think Tim's ability to create a competent component video circuit

, as well as his other spectacular products (AV-DRIVER

) and adoption of switching DC/DC converters in his designs trumps a few bits of conjecture. Also, if you're not using one of his AV-DRIVERs for RGB modding a Hu6260 based system, you're doing it wrong.

SignOfZeta · 07/27/2015, 10:06 PM

My PCEs (and all the other things I have that run on similar gear) have run for DECADES on these supposedly inferior parts. If there was a problem, doesn't it seem like there would have been a symptom? When will I see eventual failure? After my (now 26 year old) briefcase is 30 years old? 40 years old? Will I even be alive when this shit finally breaks?

And no, it's not analogous to failed caps. Failed caps...are *failed* caps. Having one of these regulators crap out as about as common as having a black Duo that's still operating with all its original semiconductors.

Also, heat is not fundamentally bad for electronics. Without heat they wouldn't even function. Only *excessive* heat is problematic, and just because the surface of the case is slightly warmer to the touch...that's not necessarily a problem. It's just life the universe and everything doing its thing.

The black Duos certainly aren't failing caps near the audio stage because of heat. Those are simply the first to go (probably because the electrolyte runs out quicker when it's warmer). All the caps on those machines were bad.

I'm not saying to not replace them if you want, knock yourself out, but you're not going to make me feel like a negligent fool for not de-soldering stuff off a virgin mainboard older than half the noobs on this forum based on a flawed semi-informed axiom.

PCEngineHell · 07/27/2015, 11:40 PM

I love the old trusty 7805. Got no intention of swapping it out unless one goes bad. Fact is the Duo caps near them would have gone bad anyway eventually regardless of heat generated from the 7805, because I mean its pretty normal for caps to go bad from use after like 17-20 years. If you have anything still running strong with no issue, on multiple original electrolytic caps after heavy use for that long, count yourself lucky. I have even been coming across random dry caps in Genesis model 1 decks the past few years. Was a totally common problem on arcade boards I would purchase. Caps that were nowhere near the volt regulators. Shit just happens.

ApolloBoy · 07/28/2015, 02:06 PM

I've experimented with those switching regulators before, they're neat but the problem with some of them is that they tend to emit some noticeable interference. You can bring down the interference by using an inductor though.

SignOfZeta · 07/28/2015, 02:20 PM

If there is anything the PCE could use less of, it's noise. I was half expecting someone to say these new regs would reduce noise, that would actually be worth it. If they make the sound chip squeal even more, not interested.

SmokeMonster · 07/28/2015, 02:29 PM

It must depend on the application and the regulator type, because in my Genesis and SNES/SFC it is the exact same AV quality with no added noise at all (via Scart RGB at least).

Mine aren't stock though, as I've pulled the RF box from all them and they're recapped with high quality caps. Any modicum of signal noise is very apparent in my setups (GBS-8200 and an LKV362A) and I compared the modded SNES to the unmodded SFC for a few weeks before going ahead and doing it too.

I have absolutely no idea how they fare in a TG16 or Duo though.

MNKyDeth · 10/18/2015, 10:00 AM

Bringing this thread back.... cough....

Has anyone tested these in a Duo yet?

Basically I am about to order some for my Genesis this week as I am recapping that machine now. Do these have any adverse effects on the Duo?

From what I gathered from the discussion here is that they should be fine with the possibility of adding noise but even that could just be a one off event.

Also, I assume if I switch to these in my console I can still use the original power supply "Wall Wart" without any issues?

SignOfZeta · 10/18/2015, 03:08 PM

UPDATE: All my shit is still running.

PCEngineHell · 10/18/2015, 03:25 PM

Yeah same update for me, anything with a 7805 in it is still working fine.

NightWolve · 10/18/2015, 06:41 PM

Quote from: RGB32e on 07/27/2015, 09:06 PM
Quote from: SmokeMonster on 07/26/2015, 02:30 PMThat said, the negative feedback from thesteve and Keith makes me less enthusiastic about doing this to NEC consoles.
I wouldn't be concerned with their comments. The Turbo Duo systems generate a fair amount of heat with the two stock 7805s. Try leaving your finger on one of the heat sinks for a minute after the console has been on for a while!

...

I think Tim's ability to create a competent component video circuit , as well as his other spectacular products (AV-DRIVER ) and adoption of switching DC/DC converters in his designs trumps a few bits of conjecture. Also, if you're not using one of his AV-DRIVERs for RGB modding a Hu6260 based system, you're doing it wrong.

As Steve is an actual trained electrical engineer unlike most here commenting, his point is worth considering and looking into more before rushing in. He also designed a transistor-based YPbPr/Component circuit released free for us fans to build ourselves unlike most others which hide the design and only sell the final product to the public, not to mention he fixes NEC consoles all day long no matter the problem. I wouldn't dismiss his opinion as mere conjecture. He's certainly got more credibility than you as someone who's been here for years versus a one-time poster that came and went...

SignOfZeta · 10/18/2015, 06:49 PM

I know not much at all about electronics, but it's not conjecture to say "my shit is decades old and still works". It's just a plain fact, so plain it's hard to ignore.

Fidde_se · 10/22/2015, 01:29 PM

I don't care much for the heat issue but there is a much more important factor here and it's the factor that sometimes the 7805 breaks and shorting inside and letting the input voltage go directly to the output, and with it burning every circuit and carts/hucard you put in it.. How many games would you try before you realise it's acctually killing them? It's not what you first would expect, just some dirt on the cart right? Let's try another one...

I don't know if this particular regulator has this protection built-in, it of course depends on the quality of the 7805 to begin with but I'v seen this happening on famicoms on several occasions.

NightWolve · 10/22/2015, 01:42 PM

Yeah, that's a great point to raise. So definitely, I would recommend replacing your 7805 regulators on 15 to 20-something year old systems! The older they are, the closer to burnout they are! In the meantime, make sure there is fuse protection, that's precisely what it's for!!!

My SNES suffered from a 7805 breakdown/burnout, that's why my fuses kept popping, and when I ran out of 1 amp fuses, I tried a higher rated one after believing I solved a shorting problem, I was wrong though... As a result, one of the SRAM chips was damaged since the full 10-12 VDC from the power supply was sent into the motherboard for a split second... :/

I since fixed the system by desoldering the 7805 and implementing a 5 VDC mod, where my external power supply is a hacked 5.31 VDC 2 Amp, regulated model. It's an even 5 Volts after passing the power switch and hitting the motherboard counting the wire resistance and length, etc. So no more heat sink inside the SNES, regulation is all outside and this model is pretty sophisticated, so I'm betting it probably has protection. Nonetheless, I soldered 2 metal clip holders for standard glass fuses and bought a 40 pack from eBay, so the fuse protection is back with proper rating. SNES normally has a ridiculous one-time fuse that has to be resoldered off/on, it looks like a diode/resistor.

ProTip: Your TurboDuo has a 3 Amp fuse by default, but it's highly recommended to replace that with a 1 to 1.5 Amp fuse as 3 Amps is WAY too high and something might get damaged in a breakdown situation like this!

Vimtoman · 10/22/2015, 04:57 PM

It may have a 3A for inrush current reasons.

NightWolve · 10/22/2015, 05:08 PM

Desh had been running his with a 1 Amp per the "turbo tip" mentioned, wasn't sure if that was too low though and would need to be replaced with a 1.5 Amp as that's what the SNES uses, but the lower the better if it works out.

But yeah, you don't want to get stuck with too low of a choice and have it be popping all the time. The maximum stated draw is 1000 mA on the Turbo Duo power supply, and I thought I read from Steve the draw of the system was at ~850 mA, not sure, so a 1 Amp fuse could be OK in principle, but a safer bet would be a 1.5 Amp fuse and for the issue you mention.

Pretty sure Desh reported it worked out, but longer testing and by more people would be needed to learn if it really should be at 1.5 Amps instead.

SignOfZeta · 10/22/2015, 06:17 PM

Quote from: Fidde_se on 10/22/2015, 01:29 PMI don't care much for the heat issue but there is a much more important factor here and it's the factor that sometimes the 7805 breaks and shorting inside and letting the input voltage go directly to the output, and with it burning every circuit and carts/hucard you put in it.. How many games would you try before you realise it's acctually killing them? It's not what you first would expect, just some dirt on the cart right? Let's try another one...

I don't know if this particular regulator has this protection built-in, it of course depends on the quality of the 7805 to begin with but I'v seen this happening on famicoms on several occasions.

That's a good point, I never thought of that, however I'm going to go ahead and wait until at least one other person can prove that this ever happened to them before I replace a part. The odds of this tragedy befalling me seem to be about equal to the chances of me accidentally shoving my soldering iron straight through the PCB; nearly but not exactly zero.

Some guys here have refurbished dozens if not hundreds of PCEs. Has anyone scene this?

thesteve · 10/22/2015, 09:43 PM

i have not, not even on SNES with dead 7805
per the internals it looks like it could happen, but if you're concerned about it drop a zener across the output to short in case of overvoltage

NightWolve · 10/22/2015, 10:00 PM

Quote from: thesteve on 10/22/2015, 09:43 PMi have not, not even on SNES with dead 7805
per the internals it looks like it could happen, but if you're concerned about it drop a zener across the output to short in case of overvoltage

Normally, with what he's referring to (and what happened to my SNES), the fuse saves the day anyway when the 7805 goes bad, no ? It's just that somebody not correctly guessing why the fuse burned, puts another one in, only to see it burn again but keeps going before diagnosing the real problem that leads to damage.

Does the NES not have an internal fuse ??

wilykat · 10/26/2015, 11:17 PM

http://www.freeinfosociety.com/electronics/schemview.php?id=2405

schematic shows no fuse. So when that 7805 fails, it will cook NES and turn it into blob of melted plastic and silicon.

In all of my time, I have had only one failed 7805 in a Commodore disk drive, it had burned open and not providing anything. Out of maybe 1,000 7800 series and similar regulators I've checked. I did have to replace a few in Atari 2600 because it was giving low voltage with original 30-year old regulators. I have not had one short out or blow fuse.

Atari Lynx didn't use such regulator, they used a transistor and 5.7v zener diode in emitter-follower design. When either of those fails, there is nothing to prevent 9v from getting dumped into the entire system. 5v mod (originally on German site, English writeup on Atariage forum) fixes this with a real regulator or a 7805-compatible switching regulator chip. All of my Lynxes uses the 5v mod.

Still it'd be good to check anyway.

NightWolve · 10/26/2015, 11:26 PM

Quote from: wilykat on 10/26/2015, 11:17 PMhttp://www.freeinfosociety.com/electronics/schemview.php?id=2405
schematic shows no fuse. So when that 7805 fails, it will cook NES and turn it into blob of melted plastic and silicon.

Huh, that's bad. Would be a good thing for NES owners to mod a fuse slot in appropriately then. Or do a 5V mod with a modern, regulated power supply. The issue with that though is you may get strange behavior in the system, as I have observed when I did the 5V mod to my SNES. Weird background artifacts at times and what not, minor stuff, but it doesn't work exactly the same if you remove the 5V regulator and directly bring in a clean 5V USB-style power supply to that motherboard location. Guess you'd have to be as experienced as Steve to figure out why...