That was another happy celebration - dc offset on output is tiny, maybe 60mv now.
Roger that on caps and jumper.
Agree on the logical troubleshooting. I’m mainly a dc and house AC kinda guy. Small signal AC is not my cup of tea… had no idea the BDOUT feedback loop could have such a big impact on u17. Not everyone has a Perry to guide them. Thankyou for not giving up on me.
Is it possible to swap fets or something else simple without a whole redesign to make it 1 ohm stable? No power increase needed, just one ohm stable with current sub setup would be cool.
Roger that on caps and jumper.
Agree on the logical troubleshooting. I’m mainly a dc and house AC kinda guy. Small signal AC is not my cup of tea… had no idea the BDOUT feedback loop could have such a big impact on u17. Not everyone has a Perry to guide them. Thankyou for not giving up on me.
Is it possible to swap fets or something else simple without a whole redesign to make it 1 ohm stable? No power increase needed, just one ohm stable with current sub setup would be cool.
Yes I got lucky there. Mouser shows AUIRF6215 will be in stock end of October for anyone needing any.
If you think you'll do more of this kind of work, you should learn to use your scope in differential mode. Not all amps have supplies that can be disconnected for troubleshooting and without differential mode or a battery operated scope, checking waveforms can be difficult.
I have used two probes in A-B math mode before to measure the output of a UPS in battery mode to verify it was true sine output. I’ve read the math function on this rigol is bandwidth limited but I imagine will be fine for audio amp frequency range.
Maybe I can find the bdcp version of this amp blown cheap for another project. Those do go down to 1 ohm.
Maybe I can find the bdcp version of this amp blown cheap for another project. Those do go down to 1 ohm.
Well, be aware that they're not nearly as simple as this amp and unless something has changed, only parts of the diagrams have leaked out.
To be honest, if you only need about 1kw, you can buy CHEAP class D amps from Walmart that will give you that. Look up the amp dyno tests on YT. I think some can be had for about $125.
To be honest, if you only need about 1kw, you can buy CHEAP class D amps from Walmart that will give you that. Look up the amp dyno tests on YT. I think some can be had for about $125.
Is it me or does the thermal management of this amp stink? With the heat sink facing down and the board up, with no cover, and 14.4v battery input ….
Some of the regulators are at 160F
U11 at 120f
The 5w snubber resistor is over 200F
I can’t imagine what they’d be with the cover on mounted in a trunk. Surely it’d surpass the 85c or maybe even 105c some of these components are rated at
Some of the regulators are at 160F
U11 at 120f
The 5w snubber resistor is over 200F
I can’t imagine what they’d be with the cover on mounted in a trunk. Surely it’d surpass the 85c or maybe even 105c some of these components are rated at
Maybe that’s why c59 c60 really vented… they are right next to incredibly hot regulators. I did replace them with 105c units but still this can’t be good for their health.
The maximum junction temperature of the semiconductors is just over 300°F. If the resistor isn't desoldering itself, it's likely OK.
At 14.4v, what's the DC voltage on pins 1 and 2 of the SG3526?
At 14.4v, what's the DC voltage on pins 1 and 2 of the SG3526?
That means that the regulation is likely working as it should. If it was not, that could make the regulators run hotter than normal but I think they're OK. I don't have a number for the temperature but I remember at least the two nearest the speaker terminals running too hot to touch. I don't remember seeing any discoloration of the board (thermal damage) but in some of the Rockford amps (not the BD amps), the regulators ran so hot that they discolored the board and those only rarely failed.
That may change once the cover is on and in car.
There’s only a few opamps on them. Why are they so hot with little load… maybe too high of an input voltage? They should have put them on the body heat sink. Or maybe use ldo’s and lower input voltage.
There’s only a few opamps on them. Why are they so hot with little load… maybe too high of an input voltage? They should have put them on the body heat sink. Or maybe use ldo’s and lower input voltage.
The drivers for the outputs are on 4 of the regulators. On the other two, only op-amps.
You're second-guessing an amp design that didn't have any trouble with those regulators failing. You have to remember that what seems to be hot to the human body is nothing significant to silicon and the other materials involved.
Reducing the supply voltage to 13.8 (likely more common than 14.4v) the temperatures may come down some.
The supply voltage to the regulators has to be good enough to allow the operation through the entire operating range that the amp could see.
While LDO regulators could operate at a lower voltage, they also tend to be less stable.
You're second-guessing an amp design that didn't have any trouble with those regulators failing. You have to remember that what seems to be hot to the human body is nothing significant to silicon and the other materials involved.
Reducing the supply voltage to 13.8 (likely more common than 14.4v) the temperatures may come down some.
The supply voltage to the regulators has to be good enough to allow the operation through the entire operating range that the amp could see.
While LDO regulators could operate at a lower voltage, they also tend to be less stable.
You’re right, it’s clearly good enough. Just thinking out loud…. Why not put it on the main heatsink and ditch the stamped heat sink to make it even better? I suppose I’m not so worried about the silicon bits but heat affecting the caps seeing as my specific failure mode.
Probably because there’s not enough room on the ridge that holds the mosfets and making the amp longer would be too costly.
Probably because there’s not enough room on the ridge that holds the mosfets and making the amp longer would be too costly.
Yes. Not enough room on the heatsink but they are reliable so would putting them on the heatsink make a difference?
I don't know if you work on home audio equipment but they REALLY get the regulators wrong in those. MANY have regulators that run so hot that there is nothing left to the board around the regulators but carbonized material. Many times, the only thing holding the regulators in place is the copper traces.
I've had to replace a few caps but I've also had a LOT of the amps have broken connections on the ground jumpers as well.
You could install them off of the board and bend them away from the regulators if you were really concerned but I don't think heat is a problem.
I don't know if you work on home audio equipment but they REALLY get the regulators wrong in those. MANY have regulators that run so hot that there is nothing left to the board around the regulators but carbonized material. Many times, the only thing holding the regulators in place is the copper traces.
I've had to replace a few caps but I've also had a LOT of the amps have broken connections on the ground jumpers as well.
You could install them off of the board and bend them away from the regulators if you were really concerned but I don't think heat is a problem.
A segway … what’s a practical stress test in the bench for this (or any?) amp? Would a 50hz tone for 1 hour into a resistive load just before clipping be too much ?
I don't test (long term) with sine waves. See the following:
https://www.diyaudio.com/community/threads/amp-repair-burn-in-testing.383051/post-6940308
https://www.diyaudio.com/community/threads/amp-repair-burn-in-testing.383051/post-6940308