Or just one of those point and shoot IR thermometers. Something is bound to be getting warm dropping that much voltage. Fortunately it isn’t enough to pop one of the bridge diodes. That’s actually a good thing! 😊
The Fasest option is an IR camera to find a short. But when elecrolitic caps in a power supply are broken can create exactly the same issue. You can load both negative and positive rails with 330K resistor and compare output voltage.
you also have the main +/- 9v regulation on that small PSU board (IC1, IC2 & Q1, contrary to what it says in the text, weirdly). how do those look? fortunately the unregulated -18v source only seems to be used in a handful of places on the main board.
If your problem is an active component being turned on when it shouldn't then that might not show on a simple resistance test. If you had an IR camera a quick view of the boards with the power on should show something dissipating heat. Also given that you have an unloaded voltage of 25V out of the bridge rectifier a rating of 25V on the capacitors seems a bit marginal.
Yup, a lot of ripple. Going to start with the electrolytic on the main power supply, then probably hit the electrolytic on the synth board. I'm *hoping* to avoid shotgun replacing everything, but we'll see how it goes...
@@JaenEngineering Yeah, I figure with a batch of electrolytic of the same age, if some are bad, and some are still good, the good are just waiting to go bad.
keep in mind that ripple is also consistent with a perfectly good linear PSU being loaded excessively. smoothing caps can't smooth if they're being drained quickly.
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Swap the synth power supply with a proper bench power supply with current limitation and use an IR camera to see where the energy is going.
Ah, good idea!
Or just one of those point and shoot IR thermometers. Something is bound to be getting warm dropping that much voltage. Fortunately it isn’t enough to pop one of the bridge diodes. That’s actually a good thing! 😊
The Fasest option is an IR camera to find a short. But when elecrolitic caps in a power supply are broken can create exactly the same issue. You can load both negative and positive rails with 330K resistor and compare output voltage.
Ah good idea! We will try that.
you also have the main +/- 9v regulation on that small PSU board (IC1, IC2 & Q1, contrary to what it says in the text, weirdly). how do those look? fortunately the unregulated -18v source only seems to be used in a handful of places on the main board.
If your problem is an active component being turned on when it shouldn't then that might not show on a simple resistance test. If you had an IR camera a quick view of the boards with the power on should show something dissipating heat. Also given that you have an unloaded voltage of 25V out of the bridge rectifier a rating of 25V on the capacitors seems a bit marginal.
Ah -- I do have access to a thermal camera! That's a good idea. (We tried the usual touch test on the chips).
Yeah, I was hoping the resistance test would suggest something simple like a shorted cap somewhere.
the flir adapter for my iphone has made finding shorts a breeze! it's expensive but saves me time in the long run
Nooooooo, I had my fingers crossed it was just the PSU.
Me too. :)
Wasn't there a fair amount of ripple on the power supply in the last video? I say replace all caps.
Yup, a lot of ripple. Going to start with the electrolytic on the main power supply, then probably hit the electrolytic on the synth board. I'm *hoping* to avoid shotgun replacing everything, but we'll see how it goes...
@@Lantertronicswhen it comes to electrolytic caps for what they cost it's best not to mess about and just do the lot.
@@JaenEngineering Yeah, I figure with a batch of electrolytic of the same age, if some are bad, and some are still good, the good are just waiting to go bad.
keep in mind that ripple is also consistent with a perfectly good linear PSU being loaded excessively. smoothing caps can't smooth if they're being drained quickly.