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Categories | Power Supplies | Goldsource DF1726 13.8VDC 30A Linear Power Supply Help

Show all reviews of the Goldsource DF1726 13.8VDC 30A Linear Power Supply

You can write your own review of the Goldsource DF1726 13.8VDC 30A Linear Power Supply.

NR7N  Rating: 4/5 Apr 26, 2013 11:47  Send this review to a friend!
Good basic value but there is a serious gotcha that is fiaxable  Time owned: months
This a no frills high current linear power supply. It uses all discrete components and has no fan. It is a great replacement if one has switcher noise. I am using it with by Icom IC-7410 and the slight amount of noise i had with my previous switcher is now gone along with the fan noise.

It is essentially a steel black box with an on-off switch (neon lighted) two large binding posts on the front panel and pass transistor heatsinks, a fuse holder and AC cord entry on the rear. There is a handle on the case top as this power supply is heavy, about 30 lbs.

I opened up the case and found that the component quality is OK and the assembly quality OK as well. The circuit takes an "economical" approach to things but is sound. First, the rectifier assembly is fullwave and not a fullwave bridge. Each leg consists of seven 3A 200 PIV diodes in parallel giving about 21A capability to each side. This is OK and these diodes are only a few cents each. The filter cap assembly consists of six 4700 uf electrolytics instead of a single computer grade cap. This is also OK and saves more money. The regulator pass transistor assembly consists of six 2N3055 devices in hard parallel with each pair mounted on separate adjacent heat sinks. The power transformer is a massive beast that one would expect at this current level. The rest of the components are mounted on a single PCB and as mentioned previously are all discrete and readily available should the need arise.

I added a few cable ties to tidy things up a bit and touched up all the high current solder joints although I am sure that they ere probably OK (just to make sure).

I turned on the unit and the voltage came up to exactly 13.8 VDC. I ran the IC-7410 in receive (about 2.2A draw) for several hours. As one would expect from a linear PS, there was no noise in the receiver and no fan noise as it has no fan. After about two hours of running I touched the heat sink assembly and found that it was quite hot. I then ran it at 100W RF output into a dummy load and the heatsink became way too hot. I had read several reviews elsewhere about overheating and I became a bit concerned.

I measured the no load voltage at the input to the regulator and found that the no load voltage was at 29.7 VDC. At the 2.2A draw it had dropped to 27 VDC and at 23A draw it was down to 26 VDC. This means that at the 23A point the regulator was dissipating about 225W. No wonder it was hot. Even at the 2.2A pint the power dissipation was at 26W. Not a large number but it still heated up things pretty good.

I looked at the instruction sheet schematic and something caught my eye. There are several versions of this PS available for different AC input voltages. These are 110V, 115V, 117V, 120V, 220V, 230V, 240V, 110V/220V and 127V/220V. Each voltage had a box before it and mine had the 110V/220V box checked. My line voltage is typically 122 VAC and it became clear what the problem was. This version was obviously made for the Asian/Japan market where line voltage is 110VAC. Most of the ones for sale in the U.S. are this version (110V/220V).

I took an old 12VAC @ 4A filament transformer I had in the junk box and I put in a small chassis with a line cord and socket and connected the transformer to buck the AC input voltage. This reduced my line voltage to 108.5VAC (remember this has to pass only the AC line current, about 3A, not the DC side output current. I repeated the heat tests and now the PS runs nice and cool as it was designed to. At 23A draw the input to the regulator is now 19VDC so now the PS is dissipating 160W less!

This is actually a nice, quiet and basic supply but as supplied, at least for the U.S., it is the wrong version (we should have the 120VAC model). Adding a small buck-boost transformer on the AC side though solved the problem. 
Product is in production.
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