I just bought a new amplifier with a separate psu. The psu according to the dealer was supposed to be 240v, however it is labelled as 220v.
I took off the cover. Inside there is a large circular thing with a label on it that says "IN: 0v-110v, BLK BRN, OUT: 0v-110v RED ORG" Below that it says "OUT 0v-16.5v <3A> BLK RED"
On the circuit board there are 8 tall round things which each say "25V, 3300uF" on them.
Could anyone please tell me based on the above what the power supply is (if possible)?
I took off the cover. Inside there is a large circular thing with a label on it that says "IN: 0v-110v, BLK BRN, OUT: 0v-110v RED ORG" Below that it says "OUT 0v-16.5v <3A> BLK RED"
On the circuit board there are 8 tall round things which each say "25V, 3300uF" on them.
Could anyone please tell me based on the above what the power supply is (if possible)?
The main input is 110V+110V = 220VAC
The output is 16.5V AC = 16.5x1.41= app. 23 V DC - 0.7V drop over the rectifier diodes = app. 22.3V DC
In your case, using this with 240V AC, the output is app. 9%higher than for 220V use, so your output will be 18V AC = 25.3 V DC - 0.7V = 24.6V DC.
As the caps are rated 25V, and the output from PSU will be higher than calculated above when unloaded, your caps will likely
in short time.
The output is 16.5V AC = 16.5x1.41= app. 23 V DC - 0.7V drop over the rectifier diodes = app. 22.3V DC
In your case, using this with 240V AC, the output is app. 9%higher than for 220V use, so your output will be 18V AC = 25.3 V DC - 0.7V = 24.6V DC.
As the caps are rated 25V, and the output from PSU will be higher than calculated above when unloaded, your caps will likely
in short time.
ACD, a few updates:
The supplier, who is very friendly and helpful, informed me this:
They just emailed me the measurements for the 255vAC test.
It looks like they measure a 0.7v drop from each diode in the rectifier.
The voltages going into the first group of capacitors is 23.9vDC, so it is within threshold of the 25v rates capacitors in your PSU.
I was then informed I will be able to get a replacement PSU with 35v capacitors rather than the 8 x 25v capacitors in mine, as per the diagram attached to this post.
The supplier said:
They will be sending out new PSUs for us, which are the v2, which have the 35v rated capacitors.
The transformers will still be 220v, but they have extensively tested it with 255v and did not experience any problems.
The LM317 regulator is able spec'd to handle the extra voltage and the first array of capacitors are also rated to operate without problems. .
Most of this goes over my head
. You have been very very helpful so far, I just want to confirm with you that the replacement PSU will be able to satisfactorily operate with 240v?
Many thanks!
The supplier, who is very friendly and helpful, informed me this:
They just emailed me the measurements for the 255vAC test.
It looks like they measure a 0.7v drop from each diode in the rectifier.
The voltages going into the first group of capacitors is 23.9vDC, so it is within threshold of the 25v rates capacitors in your PSU.
I was then informed I will be able to get a replacement PSU with 35v capacitors rather than the 8 x 25v capacitors in mine, as per the diagram attached to this post.
The supplier said:
They will be sending out new PSUs for us, which are the v2, which have the 35v rated capacitors.
The transformers will still be 220v, but they have extensively tested it with 255v and did not experience any problems.
The LM317 regulator is able spec'd to handle the extra voltage and the first array of capacitors are also rated to operate without problems. .
Most of this goes over my head
. You have been very very helpful so far, I just want to confirm with you that the replacement PSU will be able to satisfactorily operate with 240v?Many thanks!
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I can understand why you are confused..........
I did make that mistake in my calculation, so the Voltage is "only" 23.9 Volts after the rectifiers!
The specified Voltage from the toroid are when it's loaded (delivering current to a load), but unloaded the Voltage will be higher....
They may have tested it with 255VAC and the caps may have survived this for a short test period if the PSU was loaded (so output Voltage was lowered), but in the long run the caps will be at or over their specified Voltage limit (like running a car over the max recomended RPM all the time)..
Why do you think they change to 35V caps in v2 ??
Because they know there is a problem there......
The Voltage is no problem to the LM317 as it can handle 40V DC.
With 35V caps your supply will have a long life
I did make that mistake in my calculation, so the Voltage is "only" 23.9 Volts after the rectifiers!
The specified Voltage from the toroid are when it's loaded (delivering current to a load), but unloaded the Voltage will be higher....
They may have tested it with 255VAC and the caps may have survived this for a short test period if the PSU was loaded (so output Voltage was lowered), but in the long run the caps will be at or over their specified Voltage limit (like running a car over the max recomended RPM all the time)..
Why do you think they change to 35V caps in v2 ??
Because they know there is a problem there......
The Voltage is no problem to the LM317 as it can handle 40V DC.
With 35V caps your supply will have a long life
Hi,
the tolerance for mains voltage here in the UK is 240Vac +6% -10% That's a range from 216Vac to 254Vac.
Co-incidence that they tested to 255Vac.
I suspect your Austrailian power companies have a similar tolerance to us in the UK.
It is usual to have a single transformer that covers the whole range of 220/240Vac. If it is a dual primary it can also do 110/120Vac making it suitable worldwide on a universal transformer.
If the equipment is sensitive to voltage then you will find adjustable tappings or a switch that converts from 220 to 230 to 240 on the equipment.
Some even have 5Vac tappings for fine adjustment. This adjustable arrangement is much less common now.
The manufacturer of your PSU should have specified 35Vdc or 40Vdc capacitors for this duty. The checking/approvals system failed in letting this one through to the customer.
the tolerance for mains voltage here in the UK is 240Vac +6% -10% That's a range from 216Vac to 254Vac.
Co-incidence that they tested to 255Vac.
I suspect your Austrailian power companies have a similar tolerance to us in the UK.
It is usual to have a single transformer that covers the whole range of 220/240Vac. If it is a dual primary it can also do 110/120Vac making it suitable worldwide on a universal transformer.
If the equipment is sensitive to voltage then you will find adjustable tappings or a switch that converts from 220 to 230 to 240 on the equipment.
Some even have 5Vac tappings for fine adjustment. This adjustable arrangement is much less common now.
The manufacturer of your PSU should have specified 35Vdc or 40Vdc capacitors for this duty. The checking/approvals system failed in letting this one through to the customer.
AndrewT said:
http://en.wikipedia.org/wiki/Mains_electricity
You'll find 230 +10% -6% = 240 +6% -10% to the nearest volt; it's a fudge to "harmonise" throughout the civilised world without anybody needing to change anything.
And as people have said, mains transformers are very commonly marked as yours and are fine on 110V, 120V, 220V, 230V or 240V mains depending on the country they end up in.
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