newlsb00 wrote on 2020-08-09, 23:02:

Hi everyone, […]
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Hi everyone,

First off, this forum has been incredibly helpful! I haven’t been able to find a clear answer to my situation, but I’ve learned a lot just reading through nearby issues.

I recently acquired a 486 rebuild from Europe and shipped it to the US where I am. Very excited, but: the PSU is a Codegen 200c AT style. The seller said it was 230v only, and so I should use a step down converter to run it off US 110v. Fine, but I can’t figure out if I can use a standard 3 prong computer power cord (the kind I have a bunch of from newer CPUs laying around) to run from the PSU to the converter. Or do I need a different power cord rated for 230v to connect the pc to the voltage converter? The PSU sure looks like it takes just the standard three prong cable I’m used to.

I’m obviously new to all this! Also, to be honest, I’m not 100% convinced the PSU isn’t the variable kind that can take 110-240v directly, but I can’t find any specs for it online. I’ll attach a photo of the PSU - it lists both voltage options on it, but separately in a way that makes me unsure..and the sticker on the back of the case says 230v (and the seller said he thinks it is 230v only). There’s no red voltage switch or anything, and I’d hate to ruin this puppy on day one!

Any help would be appreciated. (And yes, I have read many accounts of just swapping to an ATX PSU and using a converter, etc. I appreciate that and may end up doing it if I have to, but Im interested in working with what’s there first, risks and all, as seller swears PSU is in good shape, etc.)

I cannot find anyone having anything good to say about Codegen, PSU wise . Search for Codegen in the vogons forums and you will see what I mean . Even if it was able to run on US mains voltage, I would not trust it .

It's not that the PSU is unable to run on 110V due to some technical limitation, but rather because they saved the cost of a voltage switch + two wires and slapped a 230V sticker instead. It should be easy to scavenge a 110/230V switch from another PSU and make your unit support both voltages, but consider this: if they are so cheap to the point of not installing a simple voltage switch, what other components could have been victims of their cost cutting madness?

You could open it and post some pictures of the insides so we can confirm how bare it is.

TheMobRules is right about the construction details. Most AT power supplies are not auto-switching or have wide-range input, but they need an SPST switch to connect two points on the PCB to turn the full bridge rectifier into a voltage doubling rectifier. In 230V-only supplies, usually the connection points on the PCB are still there, but the wires and the switch are missing. The circuit up to the rectifier carries only half the current in 230V areas, so the components there might be unsuitable for 110V operation, this applies especially to the input fuse (changing it to rating printed on the supply for 110V operation would be easy), the interference suppresion chokes and the rectifier itself. If you are unlucky, just connecting the 110V-operation points on the PCB overloads other parts in the input circuit. Failure of chokes (might go up in smoke on high load) or the rectifier (usually blows the fuse in the supply) are not something you want to have, so I recommend against adding the 110V modification to the supply unless you know what you are doing and you made sure the AC input side can deal with the increased current.

You can run the 230V-supply on the output of an step-up transformer just fine, and you can use any connection cord that fits the output of the step-up transformer and the IEC C13 socket at the supply, as long as the cord is 250V-rated. As I am from europe, I don't know about the ratings of standard US power cords, so I can't tell you whether using them is safe or compliant, but it is likely that the insulation is strong enough for 250V.

EDIT: added warning about modifying the supply by just adding the missing connection.

Hey guys,

Thanks for these replies. Having learned more about Codegen cases/PSUs, I'm not surprised they cut corners in what sounds like a really cheap way. Definitely not confidence-inspiring. And I am not skilled/knowledgeable enough to feel comfortable modding it to take 110v in light of what mkarcher says. I'd rather just replace the PSU altogether if I would need to get that deep in.

I do have a step up/down (sorry, wasn't sure which direction up/down is measured from - going to or from the wall, so right, this would be a step up to 220v). I'm inclined at this point to just give it a go and pray for no smoke, but since TheMobRules offered to look at photos, I'll attach a couple from the PSU. I wasn't sure exactly which components would likely show signs of trouble, so here's a couple of the board at different angles. No visible corrosion or burnout marks that I could see (dirty though), but I'm definitely learning as I go here. Let me know if you look at this and think I'm about to scorch something!

Thanks!

Owch, that is a pitiful PSU. Rule of thumb is that good PSUs use a lot of big, heavy components and crap ones as few as possible small, light ones. This is right in the latter street. Those heatsinks on the MOSFETs are tiny and I'm lost for words about that mess of small caps and wide-tolerance resistors.

Agree ! those heatsinks are so much smaller than one of my lower mid grade 200watt AT supplies, and not mounting most of the caps flush with the pc board is a give away of cheap labor. Also it appears yours is lacking a few inductors that most have...
newlsb00, here is what a better (but still not best) quality 200w looks like, I have a 250w with heatsinks near double the mass of this one.

Yeah, that unit is really anemic, I doubt that wimpy transformer can do even 100W. Other problems:

• Tiny heatsinks
• No line filter components
• No thermistor
• The 12V line is rectified by a couple of soldered discrete diodes!
• The capacitors are probably junk
• Thin cables

In short: do not use. You're better off getting a decent PSU, even if it's used. Look for brands like Delta, Astec, Lite-On (usually OEM PCs had solid power supplies, but check that it's not a proprietary design). Or if you have a spare ATX PSU you can just buy an adapter and use that (assuming it's of reasonable quality).

Crap.

Ok, thanks for the quick diagnosis, everyone. I'm convinced.

Out of curiosity: from the threads I've read here, group consensus seemed to be that it is better to go ahead and use a modern ATX (even if it is pretty overpowered for what this 486 needs) and converter than to risk buying an older or even a "new" AT. (And it isn't just you all - I was excited to see this "new" Athena AT PSU on ebay, with 700+ sold (https://www.ebay.com/itm/Athena-Power-AP-AT30 … 5gAAMXQ01tRTOc-) until I read the second review entitled, "Burst into flames"...yikes.)

Is that right? TheMobRules, you seemed to suggest maybe worth trying to find a used one from a decent brand, which seems easier in some ways, but obviously I don't want to end up right back here...I just can't tell how representative the horror stories are.

There are risks to using excessively overspecced PSUs . Have a look at his thread . Re: ATX to AT PSU requirements for AT Socket 7 with Pentium MMX 200 MHz???

IMHO, one of the safest bets is probably to get a good quality new and relatively low power ATX PSU with sufficient specs on 5V (I will let others chime in on what is actually required for a 486) and use it with an ATX to AT converter .

darry wrote on 2020-08-14, 01:23:

There are risks to using excessively overspecced PSUs . Have a look at his thread . Re: ATX to AT PSU requirements for AT Socket 7 with Pentium MMX 200 MHz???

IMHO, one of the safest bets is probably to get a good quality new and relatively low power ATX PSU with sufficient specs on 5V (I will let others chime in on what is actually required for a 486) and use it with an ATX to AT converter .

Agree that a low power ATX (like 250w) plus adapter would be a good replacement, specially if it has both -5v and -12v. 20A on+5 and 10A on +12v is good for any 486 or Pentium but could be under powered for higher end Athlons, etc. I have a HEC 250BR that works great for 386, 486 and Pentiums with just an adapter w/switch as it has both -5 and -12 (so no V reg converters needed). Saw a few on fleabay for $30 +/- (should buy another, they also have a power switch built into back of the psu) added: will pull it out of the case and show a picture of it guts, it is easy to disconnect off the AT case adapter... give me a few minutes....

darry wrote on 2020-08-14, 01:23:

There are risks to using excessively overspecced PSUs . Have a look at his thread . Re: ATX to AT PSU requirements for AT Socket 7 with Pentium MMX 200 MHz???

IMHO, one of the safest bets is probably to get a good quality new and relatively low power ATX PSU with sufficient specs on 5V (I will let others chime in on what is actually required for a 486) and use it with an ATX to AT converter .

I've had great luck with well designed, good condition PSUs that are in the 250-300W range which are NOS or working pulls from OEM machines. The ones from Acbel, Lite-on, and Delta are really nice.

gdjacobs wrote on 2020-08-14, 20:20:

darry wrote on 2020-08-14, 01:23:

There are risks to using excessively overspecced PSUs . Have a look at his thread . Re: ATX to AT PSU requirements for AT Socket 7 with Pentium MMX 200 MHz???

IMHO, one of the safest bets is probably to get a good quality new and relatively low power ATX PSU with sufficient specs on 5V (I will let others chime in on what is actually required for a 486) and use it with an ATX to AT converter .

I've had great luck with well designed, good condition PSUs that are in the 250-300W range which are NOS or working pulls from OEM machines. The ones from Acbel, Lite-on, and Delta are really nice.

I prefer a real AT and do know Delta made some very good ones. Some of the early Seasonic and Antec were good but they also were a bit of a hit and miss depending on the model. Never heard of Acbel, but recall PC Power and Cooling made some great AT PSU back in mid 90's, rare to find now.

How about running a Pico PSU with an ATX to AT converter ?
This is really a question for the PSU experts, not a recommendation .

Not an expert, but I wouldn't try the Minibox pico PSU.

Hard drive: 1A
CDROM or fdd: 1,5A (assuming they won't operate together at the same time)
Chipset/ram could take 2-3A I guess, 10-15W motherboard power
486 CPU: 1A
GPU: 0,5A
I/O: 0,5A
Sound card 0,5A
Having two fans blowing air around at 5V (not 12v, for silence) or adding another HDD and you'll be over 8A already.

A normal 5volt 486 won't use over 1A, but get to a P1 and it may be 3A. Get a P2 or P3 and it may take 5A already. A 72 W socket A Athlon could get up to almost 15A, so you can do the maths on what you need.

The Minibox pico PSU 160XT can only deliver 8A continuous, so for any 486 that would be on the edge already. Not my comfort zone...

Back in the P1/P2 era Intel motherboard manuals used to specify expected power consumption for an average system with 1 hard drive, 1 optical drive and so on. Even though those where specs for Intel motherboards I don't think it would be too different for other brands, and could be used as a rough guideline to determine how viable the Pico PSUs would be.

Horun wrote on 2020-08-15, 02:38:

I prefer a real AT and do know Delta made some very good ones. Some of the early Seasonic and Antec were good but they also were a bit of a hit and miss depending on the model. Never heard of Acbel, but recall PC Power and Cooling made some great AT PSU back in mid 90's, rare to find now.

Indeed, I have an AT supply built by Delta that's a real peach.

There's an important fact to understand about computer hardware, especially with respect to power supplies. You must be aware of the difference between the brand name on the part you're buying and the manufacturer. For example, PC Power & Cooling was an aftermarket brand. They contracted with manufacturers like Seasonic, FSP, and Super Flower to produce PSUs with engineering input from themselves and the OEM. This is the same for most of the brands on the market with some doing a lot of customization and others essentially using an off the shelf OEM design. Some manufacturers have a variable level of workmanship (depending on the time period, customer demands and oversite, phase of the moon, etc.), others do uniformly good work, and not a few are always terrible. As a result, most of the brands who sold PSUs have exhibited variability in performance (stability, electrical noise, protection features) and build quality to a greater or lesser degree.

Companies like HP, IBM, and Dell sold whole fleets of PCs to business customers which provides two benefits to us. First, the customers tended to emphasize reliability as it factors into total cost of operation. Second, the systems deployed (and retired) were in huge numbers. This results in a significant supply of PSUs on the market, sometimes with unimpressive stats on the labels, that were well designed and constructed by some of the biggest and most capable OEMs in the world - the kind of OEMs for whom Corsair are too small to care about.

This is all super helpful, and I appreciate the diverse opinions. I've ordered one of the HECs recommended above, as I found one that looked well-maintained for $10.

I'll also keep an eye out for a Delta OEM AT as well, though, since they seem to be pretty widely endorsed. I don't know where to look other than ebay, though, and it is really hard to discern the shape they are in just from looking at the outside case in a photo or two.

One last question for the group: besides the obvious (smoke, fire, burning smell, etc.), are there any clear warning signs for when you've got a PSU that is about to go out on you? As in, when the CPU is chugging along, are there typical but non-obvious indications that you'd see or hear or notice and think: uh oh, I need to replace that PSU - or is it all from just eyeing the condition of the PSU internals?

newlsb00 wrote on 2020-08-16, 15:59:

One last question for the group: besides the obvious (smoke, fire, burning smell, etc.), are there any clear warning signs for when you've got a PSU that is about to go out on you? As in, when the CPU is chugging along, are there typical but non-obvious indications that you'd see or hear or notice and think: uh oh, I need to replace that PSU - or is it all from just eyeing the condition of the PSU internals?

The most reliable indication is system instability. Part of the reason for going with a better, more complete PSU is that they include protection circuitry which shuts down power if it steps outside specifications. Even in the event of failure, a PSU should never take downstream hardware with it.

gdjacobs wrote on 2020-08-16, 20:29:

The most reliable indication is system instability. Part of the reason for going with a better, more complete PSU is that they include protection circuitry which shuts down power if it steps outside specifications. Even in the event of failure, a PSU should never take downstream hardware with it.

Yep ! Good PSU and good Battery Backup UPS will sacrifice themselves instead of the equipment they are powering. Had a APC Pro 1500 take one for my PC, file server and printer a few years ago during a bad lightning storm. And it was still under warranty so free replacement, but still Cheaper (and easier) to replace a good PSU or UPS instead of whatever you have it attached too.

A good inspection of the insides of a PSU will tell you a lot specially if you cannot find detailed specs about it having OCP, OVP/UVP, SCP, etc