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Post by mulmany on Oct 22, 2013 23:26:50 GMT -6
I built 2 vp28s with gar1731 and gar2520. On both units r15 and r11 burned up on the 1731 in the 2nd stage position. Any thoughts?
Thanks
patrick
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Post by tonycamphd on Oct 22, 2013 23:36:19 GMT -6
I built 2 vp28s with gar1731 and gar2520. On both units r15 and r11 burned up on the 1731 in the 2nd stage position. Any thoughts? Thanks patrick hey patrick welcome to the forum, wish it wasn't under bad circumstances. Did you check the orientation of Q7, Q8? |
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Post by tonycamphd on Oct 22, 2013 23:37:47 GMT -6
meaning they are not the same part, and the direction matters also, make sure the printing on Q7, Q8 is facing toward the center of each opamp, not outward.
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Post by mulmany on Oct 22, 2013 23:52:15 GMT -6
Thanks Tony,
I am just glad that it was not something really serious. The amount of smoke that those 4 resistors produced made me think I had lost my whole rack or the psu. I want a new rack from Jeff but I want it to be under better terms then cooking all my 500 series gear.
I will double check, Since I dont remember double checking the orientation I may have glazed over it.
Patrick
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Post by tonycamphd on Oct 22, 2013 23:57:47 GMT -6
Yeah, scary when stuff goes! probably gonna cost you about 70 cents in replacement parts, better save up lol! anyway, check my post previous to your last, i edited it with a little more info and posted it a second after you posted again, post up to let us know what you find out. At least they blew up on both units in the same spots, it means your consistent..seriously
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Post by mulmany on Oct 23, 2013 6:40:56 GMT -6
Lol, yeah not really worried about replacing the resistors. I can handle that.
I was actually mistaken on the resistor number... it was r14 and r15. Q7 and Q8 are oriented correctly. Double checked the 16v +- and its 15.68v to the socket.
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Post by Johnkenn on Oct 23, 2013 7:26:58 GMT -6
Tony, you're a great resource to have! Because I have NO IDEA what you guys are talking about. #sciencenerds  |
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Post by svart on Oct 23, 2013 8:47:19 GMT -6
Have a link to the gar1731 schematic?
Also, Mulmany, did you build these or buy them assembled?
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Post by tonycamphd on Oct 23, 2013 9:25:38 GMT -6
Lol, yeah not really worried about replacing the resistors. I can handle that. I was actually mistaken on the resistor number... it was r14 and r15. Q7 and Q8 are oriented correctly. Double checked the 16v +- and its 15.68v to the socket. Patrick, can you post a hi reso close up pic of one of your VP's, and one of your 1731's, and a 2520. i have a bunch of properly functioning units here i can compare them to. You must have put something?... a cap in wrong way round or confused something, because the malfunction is identical in both pieces, could figure it out quick with a pic Ok, quickly i checked VDC at +- pins at A3 opamp position, opamp removed(with my new extension card kit  ), my voltage is 31.73vdc, your waaaay low if we measured the same points, which makes it odd that'd burn up resistors...?? get those pictures happening, and it's as good as fixed broman. T |
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Post by jsteiger on Oct 23, 2013 11:53:48 GMT -6
Check the diodes for proper orientation. If you skim the opamp build threads at groupdiy.com you will probably find the answer as a number of folks have had similar issues.
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Post by jsteiger on Oct 23, 2013 11:54:33 GMT -6
Swapping the larger BD transistors and/or having them rotated 180 is the most common problem.
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Post by mulmany on Oct 23, 2013 19:56:49 GMT -6
Jeff, You got it! Swapped the BD transistors. I was just about to post pics, since i had gone through everything over at groupdiy on this problem. I must have had a brain fart when I put them in, I definitely remember checking the 139/140 markings.
Thanks Guys! You all are so much nicer then some other places I use to frequent often!
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Post by tonycamphd on Oct 23, 2013 21:32:53 GMT -6
Jeff, You got it! Swapped the BD transistors. I was just about to post pics, since i had gone through everything over at groupdiy on this problem. I must have had a brain fart when I put them in, I definitely remember checking the 139/140 markings. Thanks Guys! You all are so much nicer then some other places I use to frequent often! Patrick, real quick, so Q7 and Q8 were swapped? Just want to be clear to help the next guy. thanx T |
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Post by Johnkenn on Oct 23, 2013 22:08:03 GMT -6
Hey guys - I'm actually very proud if this thread. This is EXACTLY what I wanted to start a forum for. I have no idea what you're talking about but I love the fact that people can come on this forum and be given direction from not only the people that know what they're talking about ( tony) but the freaking designer of the product! I'm a proud (dumb) papa!! |
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Post by mulmany on Oct 23, 2013 22:21:30 GMT -6
Tony, yes I had swapped them. I checked the orientation, then dismissed your comment about them being different parts. I had remembered checking the part# to the build doc but I guess I had swapped them in the end.
Its interesting how your brain will dismiss the simplest things looking for a bigger problem. I went through the docs and double checked my part layout, diode orientation .... everything except reading the part number on the biggest part.
Ran some mixes though the pair and they sound great! Now I need to get new face plates for my original 51x vp26's and
vp25's. They look out of place next to the new design.
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), my voltage is 31.73vdc, your waaaay low if we measured the same points, which makes it odd that'd burn up resistors...?? get those pictures happening, and it's as good as fixed broman.
