PeteS in CA
Badcaps Legend
Last Activity: 06-06-2025, 01:44 PM
Joined: 08-10-2005
Location: San Jose, CA
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One of the transistor pins, the emitter, may be connected to Return, so it should have 0V. So the problem is "upstream" from the base, possibly in the LM723 circuit as [i]CapLeaker[/i] suggested. I suggest tracing the circuit back to that IC, possibly starting with whether the IC has Vcc.One of the transistor pins, the emitter, may be connected to Return, so it should have 0V. So the problem is "upstream" from the base, possibly in the LM723 circuit as [i]CapLeaker[/i] suggested. I suggest tracing the circuit back to that IC, possibly starting with whether the IC has Vcc.One... -
Adding to what stj posted, MOVs are damaged by every surge they absorb. With every surge, the firing voltage decreases a little. Eventually, with many surges, the firing voltage drops to or near the nominal line voltage, at which tome conduction becomes continuous and the MOVs short and/or explode. Depending on the surges' intensity and frequency of occurrence, it may take years to reach the point of self-destruction, but if there are surges it is a question of "when", not "if".Leave a comment:
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Looks like it's available through Mouser and Digi-Key, but in Croatia? It's made by On Semi. IIRC (from ~45 years ago) that part is higher than the common maximum voltage for a PNP BJT....Leave a comment:
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Concur. That thing is on the order of 25 tears old, and cleaning it will help see what is what. The PCB looks singed under 1 or more of those 2W resistors. Have you verified the 2N5038 is not shorted or open?
Judging by the model number and the BJT switch device (2N5038), that looks to be a 3T designed by Boschert Inc., ca 1980, when I worked there (Robert "Bob" Boschert was, then, VP Engineering), though not with that project. You may have to create your own schematic. Boschert was bought by Computer Products, which merged with (IIRC) Zytec to form Artesyn, which was bought...Leave a comment:
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The part marked "1R5" is a 1.5uH inductor. The part marked "BABCNA" is a DC-DC converter IC; another member may be able to let you know what part number it is.Leave a comment:
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Curtis Instruments motor controllers are designed in their division in Livermore, California. [url]https://www.curtisinstruments.com/products/motor-controllers[/url]https://Curtis Instruments motor con...trollers[/url]Leave a comment:
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It looks like it might be a discontinuous flyback design. If my guess is correct, VR1 (TO-92 package), located a bit above T2 in your picture, might be a TL-431. While this is nominally a programmable reference IC, it can also be used as a comparator with a reference on one input, and through an opto-isolator or transformer (T2?) to turn of the switch device. Thus a TL-431 (or TL-430) can be the controller.
I don't have a schematic, but if the switch is not turned off, it might remain on long enough for the main transformer core to saturate, blowing the IRF840 and input fuse.Leave a comment:
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This may seem odd, but since the P/S is probably more than 20 years old, there is the possibility that:
* Output caps you replaced now have capacitors that are "too good", their impedance is too low, causing instability;
* Output caps you did not replace are high impedance, causing instability.Leave a comment:
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I've had very good experience with Nichicon HE, Chemicon KZE, Panasonic FM, and Rubycon ZL series, but those might be "too good" (too low impedance, possibly causing stability problems) in older VCRs.Leave a comment:
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Given polymer caps' low impedance and where those 'lytics were in the output filter circuit, the 'lytics really should not have been terribly stressed. Those Asia'X caps were pretty awful, and a decent P/S mfr should have known to use decent 'lytics for output filtering.Leave a comment:
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These are fairly mature and have similar characteristics:
Nichicon PW series
United (Nippon) Chemicon LXZ series
Panasonic FC seriesLeave a comment:
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This picture is of ceramic capacitors with quite a few safety agency logos:
[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"Ceramic-Capacitor-DCF-Y1-X1-Capacitor-Y-Capacitor-Capacitor-Y-.jpg","data-attachmentid":3590389}[/ATTACH]...Leave a comment:
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If those blue ceramic caps near the top tight of your picture are DC-rated instead of safety agency-approved and rated for an AC voltage, remove them, and if you can replace them with proper Y-caps.
While the heatsinks look possibly OK for 250W-300W, the 330uF input 'lytics and output inductor probably limit the realistic output power to 150W-200W. 470uF or 560uF input 'lytics would be needed for input filtering adequate for 250W or 300W, but that output inductor would have to have a larger core and probably heavier gauge wire, and the output caps might not be adequate for those power...Leave a comment:
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The PM series is Nichicon's RoHS-compliant version of the PL series. It was introduced, AFAIK, in the early 2000s. I first saw them in 2005, and in the several prior years I had been at a company making military power systems, so how long before 2005 the series had been around, I'm not sure. FWIW, Nichicon's PS series (if it's still around) is the RoHS-compliant version of the PR series.Leave a comment:
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On the plus side, users would not have to worry about Y-caps that are not safety agency approved....Leave a comment:
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Given the age, if it is an electrolytic I'd suggest Nichicon PS, PM, PJ, or PW series, in that order of preference, whatever fits. I'm not sure whether polymer caps were coming into use in 1996.Leave a comment:
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Is 5VSB OK? DC voltage and ripple?Leave a comment:
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How comparable are the turn-on, and turn-off times and the input capacitance? Those may also be critical parameters.Leave a comment:
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Supermicro's main board model numbers reflect the generations of Intel's processors. e.g. X6 was followed by X7 which was followed by X8 and so on. "20 years old" sounds about right for an X6 main board, making it approximately contemporary with Win XP, which MS stopped supporting and updating long, long ago.
X10 generation main boards were in their prime around 2016. While that's "just" 8 years ago, X13 and X14 generation main boards are most of current sales. BIOS updates to X10 main boards have probably been limited for a couple of years to just fixing security...Leave a comment:
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It might do 200W continuous without launching. Efficiency will probably be in the 70% range, maybe 75%. If those output inductor cores get hot they will degrade pretty fast.Leave a comment:
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