what grounds ? speaker returns are secondary driven to +/- 25.
run a simple two wire line input, I would not connect anything else yet
standard to use just a variac and an isolation transformer for SMPS tests for safety with grounded test equipment, else yer just stuck with battery powered test gear.
note remember this product says Class II > no earth connections!
run a simple two wire line input, I would not connect anything else yet
standard to use just a variac and an isolation transformer for SMPS tests for safety with grounded test equipment, else yer just stuck with battery powered test gear.
note remember this product says Class II > no earth connections!
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Really... wow that's a surprise. Don't know what to suggest now... we really need to see it all drawn out to get a handle on how its configured.
Hi,
At the beginning of your thread you mentioned that if you used a variac to slowly bring the voltage up it worked OKAY with no problems. Pin 8 of the SG2525A it is the soft start of the chip. In the data sheet it is showed a 5 uf capacitor connected to the pin. I would check the size of the capacitor that they are using in your amplifier. Depending of the size and I would add some more capacitance and see what it does. By adding more capacitance it will slow down the start up same thing your are doing with the variac. Just a suggestion.
At the beginning of your thread you mentioned that if you used a variac to slowly bring the voltage up it worked OKAY with no problems. Pin 8 of the SG2525A it is the soft start of the chip. In the data sheet it is showed a 5 uf capacitor connected to the pin. I would check the size of the capacitor that they are using in your amplifier. Depending of the size and I would add some more capacitance and see what it does. By adding more capacitance it will slow down the start up same thing your are doing with the variac. Just a suggestion.
tauros suggestion could be worth trying. Perhaps just add a 1uf in parallel as a trial.
I wondered if there might be some sensing of the flyback pulse off the tranny as its method of determining an overvolts condition. What is very odd when you think about it is that SMPS are usually configured to work from anywhere from about 90 to 265 vac. That's the beauty of them, they make regional voltage requirements a thing of the past.
I wondered if there might be some sensing of the flyback pulse off the tranny as its method of determining an overvolts condition. What is very odd when you think about it is that SMPS are usually configured to work from anywhere from about 90 to 265 vac. That's the beauty of them, they make regional voltage requirements a thing of the past.
OK, added 1uf. Starts up ok warm. I was sometimes able to do warm restarts prior to adding the cap. I want to wait for a cold cold start to see what it does...looks promising tho...
After 10 minutes, starts up ok. Has a 5 - 6 sec delay now before coming on...looks like this was it...
I used a 1uf / 25V cap....didn't think to check the voltage...datasheet says chip has a 40V supply voltage, but pin 8 soft start volatge is 2.5v, so I guess I am ok......
I used a 1uf / 25V cap....didn't think to check the voltage...datasheet says chip has a 40V supply voltage, but pin 8 soft start volatge is 2.5v, so I guess I am ok......
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That sounds quite promising. Test it thoroughly though... try it after say 12 hours. Six seconds is a long time as a delay, I wonder if its fiddling rather than fixing the issue but if it works 🙂 and it should be a safe (for the PSU) solution.
Was the delay much less with just 5uf, and now the added 1uf has increased it dramatically ? Is the 5uf cap an electrolytic ?
Was the delay much less with just 5uf, and now the added 1uf has increased it dramatically ? Is the 5uf cap an electrolytic ?
Whoops, correction - The original 5uf was a smd, the new 1uf was a tantalum...
The delay with variac at 110 was a bit quicker - maybe 2 - 3 seconds...with no variac - full mains - I could not gauge the delay, as it was, well, infinite🙂
The delay with variac at 110 was a bit quicker - maybe 2 - 3 seconds...with no variac - full mains - I could not gauge the delay, as it was, well, infinite🙂
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Intriguing. I don't know what to advise really for this without actually working on one for real. The tant should be fine in that location. If it works reliably and you are happy then I'm tempted to say leave it.
Give it a thorough test... if its OK then make the fix permanent 🙂
(I'll look in tomorrow and see how its panned out)
(I'll look in tomorrow and see how its panned out)
Funny, I told some EE's at work about my capacitor AC voltage dropper and they looked at me like I was crazy...
Caps as droppers are fine when the load is constant. Its an old technique and was sometimes seen in TV's and the like as a means of dropping the voltage to a series chain of valve heaters. It worked because the desired heater current was known and a constant.
Hi,
There are some transformeless battery charger that used the capacitor method directly from the 120 ac volts. Do a google "Transformeless battery charger" and you will find out some circuits using the capacitor method. I think this practices are unsafe. You can get shock easily.
There are some transformeless battery charger that used the capacitor method directly from the 120 ac volts. Do a google "Transformeless battery charger" and you will find out some circuits using the capacitor method. I think this practices are unsafe. You can get shock easily.
Yes, its good that you emphasise the dangers.
They can be very dangerous indeed if the safety implications are not fully understand. Essentially there is no isolation between the output side and live incoming mains. Result... the potential 😀 for a serious shock hazard.
They can be very dangerous indeed if the safety implications are not fully understand. Essentially there is no isolation between the output side and live incoming mains. Result... the potential 😀 for a serious shock hazard.
Bah! The fix is sporadic...every now and then it does not wanna start. I removed and measured that original cap - its only .1uf. Nowhere close to the 5uf in SG3525 datasheet. When I drop in a 5uf cap, it never starts.
It appears the over-voltage limit on smps section of module has somehow been dropped from 132vac to 114vac. I will have to look more closely at the datasheet...
It appears the over-voltage limit on smps section of module has somehow been dropped from 132vac to 114vac. I will have to look more closely at the datasheet...
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