Power rating of a small switch mode ps?

Worth checking the current rating of the secondary rectifiers ? Manufacturers don't tend to rate them excessively in my experience.

Arfa

A single output 5v smps? A "guesstimate" would be to multiply the input power by 0.6. If the input was 2a @ 115vac, the 5v output current would be *in the ballpark* of [(2 x 115) x 0.6] / 5 or *about* 27 amps DC.

The rated input current *should* be on the PSU label.

Just load it with an automotive taillamp and measure the voltage, that should be adequate for the PSU to regulate, you don't have to apply max load for the initial test.

What is the intended load?

is

I've fathomed out how the ps works. The 5V regulator uses only a 100mA TO92 transistor because the error is fed forward via an optocoupler to the sm oscillator. The 5V line defines the output to +/-18V as well. The original trouble was wavering 5V, which has returned, prior to replacing some more caps . In the broken mode if say 2.5V on the 5V o/p then only

+/-10V on the unloaded +/-18V lines.

Scaling linearly, an at hand 70 W smps, with its 45mm cube transformer. I would estimate volume for vol then this one with 20mm cube would be about

6W total. Allowing 1W for the few op-amp supplies and 2 relays then only 1 amp at 5V, its suppling 30 odd 74HC and 3 LSI.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Core size is also affected by the switching frequency. Is there a model number on the supply?

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

ps

regulation is

but

Its the integrated ps in the Yamaha SPX 90 , so no info with it, on thread below. When operating properly the oscillation is about 59 KHz with equal mark/space ratio, when at half-c*ck then about 40KHz short mark/ space

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Do you know how many watts the complete unit is supposed to draw?

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

SM

related to

across

thread

The consumption plate states 20W, assuming average SMPS 70 percent efficiency then 14W at DC.