I need to get a rough idea of the amperage capability of a small 5V SM ps
before attaching it to its load, to simulate, just in case the regulation is
kapput.
Does anyone know how the volume of the smps hf transformer is related to
power
throughput or any other method? It uses a TOP66 of sufficient rating to
drive a few hundred watts across but the ps is relatively low power , but
unknown rating.
The one in question is only about 20mm cube

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

"N Cook" wrote in message
...
I need to get a rough idea of the amperage capability of a small 5V SM ps
before attaching it to its load, to simulate, just in case the regulation
is
kapput.
Does anyone know how the volume of the smps hf transformer is related to
power
throughput or any other method? It uses a TOP66 of sufficient rating to
drive a few hundred watts across but the ps is relatively low power , but
unknown rating.
The one in question is only about 20mm cube


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

Arfa

N Cook wrote:

I need to get a rough idea of the amperage capability of a small 5V SM ps
before attaching it to its load, to simulate, just in case the regulation is
kapput.

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.

"UCLAN" wrote in message
...
N Cook wrote:

I need to get a rough idea of the amperage capability of a small 5V SM ps
before attaching it to its load, to simulate, just in case the regulation
is
kapput.

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?

N Cook wrote in message
...
I need to get a rough idea of the amperage capability of a small 5V SM ps
before attaching it to its load, to simulate, just in case the regulation
is
kapput.
Does anyone know how the volume of the smps hf transformer is related to
power
throughput or any other method? It uses a TOP66 of sufficient rating to
drive a few hundred watts across but the ps is relatively low power , but
unknown rating.
The one in question is only about 20mm cube

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/






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
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:

I need to get a rough idea of the amperage capability of a small 5V SM ps
before attaching it to its load, to simulate, just in case the regulation is
kapput.

Does anyone know how the volume of the smps hf transformer is related to
power throughput or any other method?


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


It uses a TOP66 of sufficient rating to drive a few hundred watts across but
the ps is relatively low power , but unknown rating.

The one in question is only about 20mm cube.


--
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

Michael A. Terrell wrote in message
...
N Cook wrote:

I need to get a rough idea of the amperage capability of a small 5V SM
ps
before attaching it to its load, to simulate, just in case the
regulation is
kapput.

Does anyone know how the volume of the smps hf transformer is related to
power throughput or any other method?


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


It uses a TOP66 of sufficient rating to drive a few hundred watts across
but
the ps is relatively low power , but unknown rating.

The one in question is only about 20mm cube.


--
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

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-cock then about 40KHz short mark/ space

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

N Cook wrote:

Michael A. Terrell wrote in message
...
N Cook wrote:

I need to get a rough idea of the amperage capability of a small 5V SM
ps
before attaching it to its load, to simulate, just in case the
regulation is
kapput.

Does anyone know how the volume of the smps hf transformer is related to
power throughput or any other method?


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


It uses a TOP66 of sufficient rating to drive a few hundred watts across
but
the ps is relatively low power , but unknown rating.

The one in question is only about 20mm cube.


--
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

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-cock then about 40KHz short mark/ space


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

Michael A. Terrell wrote in message
...
N Cook wrote:

Michael A. Terrell wrote in message
...
N Cook wrote:

I need to get a rough idea of the amperage capability of a small 5V
SM
ps
before attaching it to its load, to simulate, just in case the
regulation is
kapput.

Does anyone know how the volume of the smps hf transformer is
related to
power throughput or any other method?


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


It uses a TOP66 of sufficient rating to drive a few hundred watts
across
but
the ps is relatively low power , but unknown rating.

The one in question is only about 20mm cube.


--
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

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-cock then about 40KHz short mark/ space


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


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