Watch for 'unknown' chips in power supplies!

[japlytic]

In a few power supplies I have seen, there is a proprietory chip (usually the SMPS controller) in them. These supplies can be unreliable.

They included an LC-B400ATX and similar models (with a chip simply marked '2003') and an LC-A400ATX (with a chip marked 'DR0183'). The proprietory chip in these supplies had no evidence of the markings being sanded off.

The replacement power supply in my computer has a popular TL494 SMPS controller.

You should be suspicious of power supplies having an proprietory SMPS chip , and only buy supplies with a well-known SMPS chip (eg. TL494/KA7500, SG/LT3524, SG/LT3525, UC3842 etc.)

If you have any supplies with proprietory SMPS controllers (which you cannot identify the manufacturer of), please post it here!

[PeteS in CA]

Re: Watch for 'unknown' chips in power supplies!

Both Delta Products (I used to work for them) and Astec, very good P/S mfrs, use in-house-design ASICs in some of their products. One of Delta's ASICs that I'm aware of combines a PFC controller and a PWM controller in one chip. The other Delta ASIC I've seen is a secondary-side supervisor, combining OVP, current limit, sequencing, and possibly the error amplifier in one chip. Custom isn't necessarily bad.

[japlytic]

Re: Watch for 'unknown' chips in power supplies!

I have seen a custom chip in an Astec supply before.

We should only avoid the not-so well-known manufacturers with power supplies containing custom chips (mainly Chinese), and if we do buy power supplies with custom chips, only buy them from the larger (and more well-known) manufacturers.

[Newbie2]

Re: Watch for 'unknown' chips in power supplies!

I have seen a TL494 chip in a generic 250W PSU before, but I don't know if it's a genuine chip or a counterfiet that looks identical. Pics later.

[Rainbow]

Re: Watch for 'unknown' chips in power supplies!

I see often Daewoo DBL494 which is TL494 compatible. I've bought some original TL494 for PSU repairs - they're cheap here.

[linuxguru]

Re: Watch for 'unknown' chips in power supplies!

TL494 or KA7500 are commodity parts with many second sources, and they're fairly rugged - I haven't seen a failure yet, though I suppose it does happen.

[Rainbow]

Re: Watch for 'unknown' chips in power supplies!

Yes, they're reliable. They fail only when the supply voltage goes too high - which happens when aux supply fails in some PSUs. Then usually some of the pins short to ground internally. If it happens when the power is on, it can easily damage other PC components.

[Newbie2]

Re: Watch for 'unknown' chips in power supplies!

I just checked the chip in the generic 250W power supply and it was TL494CN.

Plus I checked the chip in an Enermax EG301P-V 300W power supply and the chip was an ST LM339N chip.

I discovered Digikey sells both of those chips, which is a relief for me.

The only custom proprietary chip I saw was the ones in L&C power supplies.

I couldn't get pics just because my camera doesn't have macro mode.

[PeteS in CA]

Re: Watch for 'unknown' chips in power supplies!

The LM339 is a quad comparator, a good GP jellybean part. Lots of companies make it; National Semiconductor designed it back in the 70s.

[yanz]

Re: Watch for 'unknown' chips in power supplies!

My Aibo 360w PSU has a chip marked:

2003
BA110130431E

[linuxguru]

Re: Watch for 'unknown' chips in power supplies!

If it has a controller marked 2003, it's a Deer/L&C. The only saving grace is that lots of things tend to fail in a Deer before the controller fails - so the 2003 chip is usually OK.