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Old 07-17-2017, 03:18 PM   #2741
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Default Re: Power supply build quality pictorial. part 2

Here's a surprising one. Modem PSU, 10v, one and a half amps. Its a bodge-job replacement for a real POS. http://www.badcaps.net/forum/showpos...postcount=1326

Case shot.

Not inspiring....

Board topside.

This is promising! Good insulation, no Brown Gorilla Snot, plenty of filtering. Looks like the board has provisions for another rail. Actual safety rated caps.

Topside-BottomWise!

No bad solder. Plenty of isolation. Not bad.

And the Money-Shot!

Decent Chemi-Con caps.
Secondary Filter: 1000uF, 16v.
BootStrap: 47uF, 50v.
Primary Filter: ? It was wrapped in yellow tape... Very large though.

Goontrons rating: B for beautiful. Needs more heat sink, and the primary cap is resting on some large resistors. More than satisfactory for its intended use. Looks Delta OEM.
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Last edited by goontron; 07-17-2017 at 03:26 PM..
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Old 07-18-2017, 12:48 AM   #2742
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Default Re: Power supply build quality pictorial. part 2

I'd guesstimate that primary cap around 47 uF/400 V.
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Old 07-18-2017, 09:33 PM   #2743
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Default Re: Power supply build quality pictorial. part 2

Quote:
Originally Posted by goontron View Post
Here's a surprising one. Modem PSU, 10v, one and a half amps.
...
Goontrons rating: B for beautiful. Needs more heat sink, and the primary cap is resting on some large resistors.
For a 1.5A adapter, the heatsinks look plentiful.

With those caps, I would have argued you give it an "A"... but it looks like it is a 2-transistor design. So in that case, "B" seems appropriate, as 2-transistor designs are not very efficient. The small cap on the primary may also be a "critical" cap... but again, I see nothing but good caps in this adapter, so that shouldn't be a problem.

A world of a difference compared to the gutless adapter you posted in the other thread.
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Old 07-18-2017, 10:10 PM   #2744
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Default Re: Power supply build quality pictorial. part 2

Quote:
Originally Posted by goontron View Post
Decent Chemi-Con caps.
Secondary Filter: 1000uF, 16v.
BootStrap: 47uF, 50v.
Primary Filter: ? It was wrapped in yellow tape... Very large though.
33-47u, 400V? Maybe 68u/400V.

Actually, since it's rated only up to 120V AC, the cap could be an 82u/200V unit.

Quote:
Originally Posted by goontron View Post
Goontrons rating: B for beautiful. Needs more heat sink, and the primary cap is resting on some large resistors. More than satisfactory for its intended use. Looks Delta OEM.
Agree! Looks rather non-RoHS-ey for 2011.
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Old 07-18-2017, 10:54 PM   #2745
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Default Re: Power supply build quality pictorial. part 2

^ That was my thought. 82uF/200v.

I gave it a nice dose of 60/40 before i welded the case back together.
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Old 08-12-2017, 07:57 AM   #2746
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Default Re: Power supply build quality pictorial. part 2

Here we are with an ebay 12V 2A power supply.
Label.

Not looking promising.
Top side.

Not bad IMO. I think they did a good job with it.
Has a nice Y-class capacitor and a PI coil on the output side. I'd take some points off for the cheap glue. The input capacitor is not original to this power supply and no, i did not replace it.
The big transistor is a STD13005 and the smaller looking one is a AZ431.
And bonus points to whoever noticed that the input capacitor is bulging.
Bottom side.

Looks like they did a decent job on isolation from the input.
The hot glue was added by me to stop one of the solder pads from being ripped up from the PCB.
Solder seems to be good.
Cap shot.

Input: 10uf 400v
Bootstap: 220uf 16v
Output: 680uf 16v
Brands: BERYL, Ltec.

Overall i'd say this thing is not bad for the price.
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Old 08-12-2017, 12:32 PM   #2747
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Default Re: Power supply build quality pictorial. part 2

Vaguely familiar to the 2-transistor 5VSB circuitry modified to 12V, compacted into a wall wart?
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Old 08-12-2017, 08:00 PM   #2748
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Default Re: Power supply build quality pictorial. part 2

The power supply is OEMed by unifive. Some of there products seem to be UL listed when looking on there website.

Last edited by ruky con; 08-12-2017 at 08:08 PM..
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Old 08-13-2017, 10:08 AM   #2749
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Default Re: Power supply build quality pictorial. part 2

Quote:
Originally Posted by ruky con View Post
Here we are with an ebay 12V 2A power supply.
Label.

Not looking promising.
Top side.
...
Overall i'd say this thing is not bad for the price.
IC1 is an optocoupler, and IC2 is in a TO-92 package. I'm guessing IC2 is a TL431 (or clone), and the output is regulated. The MJE13005 clone transistor - bipolar, not a MOSFET - should be plenty beefy for 24W. As long as its heatsink and the traces "heatsinking" the output rectifier are adequate, it looks reasonably solid.
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Old 08-13-2017, 04:32 PM   #2750
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Default Re: Power supply build quality pictorial. part 2

Quote:
Originally Posted by PeteS in CA View Post
...I'm guessing IC2 is a TL431 (or clone)...
IC2 is a AZ431.
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Old 08-13-2017, 07:55 PM   #2751
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Default Re: Power supply build quality pictorial. part 2

I may all a new wires to the output because the ones that are there are thin and are soldered across the output capacitor making the PI coil useless unlike the old wires.
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Old 08-14-2017, 12:56 PM   #2752
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Default Re: Power supply build quality pictorial. part 2

Quote:
Originally Posted by ruky con View Post
IC2 is a AZ431.
That self-oscillating discontinuous flyback circuit using a bipolar transistor as the switch and a **431 as an error amplifier has been around for nearly 40 years. It's not super high efficiency, but the low component count generally, and the lack of a large separate output inductor make it an attractive choice for small adapters.
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Old 08-15-2017, 06:41 AM   #2753
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Default Re: Power supply build quality pictorial. part 2

Quote:
Originally Posted by PeteS in CA View Post
That self-oscillating discontinuous flyback circuit using a bipolar transistor as the switch and a **431 as an error amplifier has been around for nearly 40 years.
Interesting that the design has been around for that long.

Quote:
Originally Posted by PeteS in CA View Post
It's not super high efficiency, but the low component count generally, and the lack of a large separate output inductor make it an attractive choice for small adapters.
When it comes down to adapters, i don't really care too much about the efficiency. [Unless it draws many times more power than it outputs.]

And IIRC the output inductor is usually referred to as a 'PI coil'.
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Old 08-15-2017, 02:50 PM   #2754
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Default Re: Power supply build quality pictorial. part 2

Quote:
Originally Posted by ruky con View Post
Interesting that the design has been around for that long.
...
And IIRC the output inductor is usually referred to as a 'PI coil'.
Here's a second generation single output example from Boschert, dated 1983:



Here's a first generation multiple output example from Boschert, dated 1982:



The latter was in production when I started at Boschert in 1980.

Those little inductors on the outputs are there primarily to reduce spike and ringing noise, not to filter switch frequency ripple.

Boschert's second generation discontinuous flybacks were part of a fairly large scale effort to get the pricing for their low and medium power products under $1 per watt. I don't think the first-gen OL25 was replaced, but I know second-gen XL standard products ranged from that 30W single output to a model that could do 165W convection cooled or 185W with forced air cooling. The guy who did all those designs - one guy! - was a genius.

By way of contrast in terms of pricing, in 2000 Delta Products was charging Compaq, Dell, and Apple $13-$16 for 200W-250W power supplies.
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