Guest sachu Posted April 22, 2009 Report Posted April 22, 2009 Possible that the LEDs on the boards are not oriented correctly.
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 Well it didn't last long, I gave it the 10 minute warm up before final tweaking then smelled some faint smoke... switched it off, reset the trimpots to zero on the board I was working on and now nothing lights up I killed it.
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 yeah, got 30V coming in... 0.3V going out of the sigma. *sigh*
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 Indeed! Pars, how would I know if the sigma was made for 24 or 30V? I was measuring 30 at the terminals
Guest sachu Posted April 22, 2009 Report Posted April 22, 2009 Indeed! Pars, how would I know if the sigma was made for 24 or 30V? I was measuring 30 at the terminals It depends on the transformer you are using as well as the value of R10. If R10 is 10kohm then it is wired for +/-24Volts If R10 is 6.81kohm then it is wired for +/-30Volts At which terminals were you measuring 30 volts?
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 the outputs to the boards, and the input, input had a smidgen more volts. It was like 30.xx in and 29.xx going out I think I had my 65mv, my 4.5v, my 0 dc offset and was just resetting offset after the 10 minute thermal drift period.
Guest sachu Posted April 22, 2009 Report Posted April 22, 2009 the outputs to the boards, and the input, input had a smidgen more volts. It was like 30.xx in and 29.xx going out I think So your S22 is working fine then....you are getting +/-30 volts DC on all the 4 outputs, in your case you need 3? The input is of course in AC volts..right? SO what did you smoke out?..one of the B22 boards?..the ground channel or the amp channels?
Guest sachu Posted April 22, 2009 Report Posted April 22, 2009 yep, 30v ac in, 30v dc out Well that's good..just need to debug the amp boards..connect them up one at a time and go through the amb checklist for each then..unless you know which particular board you smoked
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 It's the sigma that got smoked, not the boards, it's only outputting 0.3V now.
Guest sachu Posted April 22, 2009 Report Posted April 22, 2009 It's the sigma that got smoked, not the boards, it's only outputting 0.3V now. oh...bollocks!!.. replacing burnt silicon is never fun.
Fungi Posted April 22, 2009 Report Posted April 22, 2009 The good news is that the B22 is safe. The bad news is that you have no working power supply for your new baby.
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 heh, looking at the sigma shows no obvious signs of toast which is a pity because at least I'd have something obvious to replace Everything looks perfect.
Nebby Posted April 22, 2009 Report Posted April 22, 2009 Now you get to experience the joys of electronics troubleshooting and replacing blown parts!
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 only if I can figure out what's blown... I have no idea what to even check.
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 (edited) Hah, D5 is looking suspicious... and it was in the right area. It's the smallest whatever on the board and it's giving an add reading. Meter set to 200Kohms it's constantly rising from a -48kohms??? What the hell is that thing? *runs off to check ambs site again... *EDIT* D5 not C5 Ok, looks like it's a 12V zener diode, and a very important one. I don't know how to test it, any clues? Edited April 22, 2009 by Smeggy
Beefy Posted April 22, 2009 Report Posted April 22, 2009 Check the output resistors first - R12, 13, 14 and 15. I recall reading on Head Wize that they are almost like fuses when you short the outputs. Though they are only 0.47 ohm resistors; many multimeters are not accurate that low. Hah, =c5 is looking suspicious... and it was in the right area. It's the smallest whatever on the board and it's giving an add reading. Meter set to 200Kohms it's constantly rising from a -48kohms??? What the hell is that thing? By measuring the resistance, you are actually charging the capacitor. It causes funky readings.
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 (edited) see above, I wrote C5 instead of D5. The zener reads .759 on my diode setting looks like R12 and 13 are popped, 14 and 15 are reading 0.4 Edited April 22, 2009 by Smeggy
Beefy Posted April 22, 2009 Report Posted April 22, 2009 Check. NFI to answer your question regarding testing it. What I do know is that it is just a few cents to replace.
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 Cheers Beefy, you identified a couple of bits already
Smeggy Posted April 22, 2009 Author Report Posted April 22, 2009 Further testing, with the sigma powered by itself I'm reading 1.6V +/- R12 and R13 are reading 41V one side, 1.6V the other. R14 and 15 are reading -1.6V at both ends of the resistors. The LED is glowing faintly, but glowing. many of the checkpoint voltages on the board seem fine, others not so.
amb Posted April 22, 2009 Report Posted April 22, 2009 R12 and R13 are blown. Replace them and re-check the voltages. Don't connect the amp boards until you get the PSU fixed first. Then, connect the amp boards one at a time to set them up.
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