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I have FIVE of the damned Mackie SWA1501 powered subwoofers in here at the moment. Blown up amps and melted speakers. Got a stack of speakers come in, so that's covered. Noticed they are now sending out Eminence KAppa 16 ohm in place of what was in the things to start with. They should last a lot better.
Meanwhile I am getting familiar enough with the amps that I can production line them. 5200/1943 pair, an MJ15033, a couple IRF630 and one 640, a few burnt diodes in the middle. SAme stuff. Plus I had ordered bags of 100 of things like the BAV20 diodes and the 1N5245 15v zener. Ther are two +/-15v rail sets in these, both run off the same +/-25v, each set through 330 ohm resistors to the 15v zeners. Always look in the corner and down next to the big caps for burnt 330 ohm resistors. There are a coiple green LEDs that run off one set of rails.
When those resistors burn, I just replace the four resistors, the four zeners, and the four little caps. No point screwing around to see if some 2 cent part was damaged or not.
The power from the transformer comes in to a 5-post push-on at the corner. But the plastic housing is in two parts, so you can leave the high voltage disconnected asnd just power up the low voltage stuff. Handy.
SO I rebuilt one of these things, and power up. No LEDs, voltage is about 3v. BOTH sets are at +/-3v. SO what is loading me down? The diode junctions check at about .7v, nothing seems shorted. The caps are new. Each set of rails powers a 5532 op amp. They can fail, pulled the two ICs, no help. One IC has a bypass cap across it, pull that, no help. These rails don;t go to much, and nothing is loading them down. I should not be having a hard time with this, it's a plain old freaking zener power suply.
So I am looking at this bag of zeners, from Mouser yet, and it says 1N5245B 15v zener right on the bag of 100. I can't read the tiny print on the parts. SO I fired up a DC supply, grabbed a resistor and one of the diodes from the bag, and VOILA! These ain't 15v zeners in the bag. Whatever they are, they zene pretty well at 3v. Come to think of it, the little print on them looks almost like a "2v4" if my eyes ar working.
The lesson is that just because you used a trusted supplier, ordered exactly what you needed and got a nice big bag full labelled for what you expected, well that doesn;t mean that is what you got. When repairs don;t make sense, don't forget to check the parts.
Meanwhile I am getting familiar enough with the amps that I can production line them. 5200/1943 pair, an MJ15033, a couple IRF630 and one 640, a few burnt diodes in the middle. SAme stuff. Plus I had ordered bags of 100 of things like the BAV20 diodes and the 1N5245 15v zener. Ther are two +/-15v rail sets in these, both run off the same +/-25v, each set through 330 ohm resistors to the 15v zeners. Always look in the corner and down next to the big caps for burnt 330 ohm resistors. There are a coiple green LEDs that run off one set of rails.
When those resistors burn, I just replace the four resistors, the four zeners, and the four little caps. No point screwing around to see if some 2 cent part was damaged or not.
The power from the transformer comes in to a 5-post push-on at the corner. But the plastic housing is in two parts, so you can leave the high voltage disconnected asnd just power up the low voltage stuff. Handy.
SO I rebuilt one of these things, and power up. No LEDs, voltage is about 3v. BOTH sets are at +/-3v. SO what is loading me down? The diode junctions check at about .7v, nothing seems shorted. The caps are new. Each set of rails powers a 5532 op amp. They can fail, pulled the two ICs, no help. One IC has a bypass cap across it, pull that, no help. These rails don;t go to much, and nothing is loading them down. I should not be having a hard time with this, it's a plain old freaking zener power suply.
So I am looking at this bag of zeners, from Mouser yet, and it says 1N5245B 15v zener right on the bag of 100. I can't read the tiny print on the parts. SO I fired up a DC supply, grabbed a resistor and one of the diodes from the bag, and VOILA! These ain't 15v zeners in the bag. Whatever they are, they zene pretty well at 3v. Come to think of it, the little print on them looks almost like a "2v4" if my eyes ar working.
The lesson is that just because you used a trusted supplier, ordered exactly what you needed and got a nice big bag full labelled for what you expected, well that doesn;t mean that is what you got. When repairs don;t make sense, don't forget to check the parts.
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