whats the besy way of testing Sanken LEXAM SAPM01 transistors??.

[joeyuk]

been given a e faulty pionner surround amplifier

theres a problem keeps comming up with error was told power output stage is damaged.

i have had a look at the power transistors question is the transistors are Sanken LEXAM SAPM01 audio transistors.

i have noticed they are not like normal 3 pin power transistors which you can test with a dmm on diode function for shorts but these have 5 legs how do i test these as not come across these type before?





can someone please advize.

thanks

[jackinnj]

They are diode incorporated MOSFET's -- you can get replacements form Profusion in the UK. Here's the datasheet;

http://www.profusionplc.com/static/i...ts/sapm01n.pdf

[joeyuk]

thanks any ideas which number pins i need to test ? as theres 5 on this transistor.

[jackinnj]

If I have what appears to be a blown MOSFET I disconnect the source, connect the gate and drain together and apply a current controlled (200mA, 500mA is fine) 12V source to the drain-gate junction, measure the voltage from the DG junction to S -- these flavor of MOSFET's turn on at between 3 and 4 volts, so you should get a reading in the vicinity of 4V if they are working.

I have never blown out the temperature sensing diode in Sanken's bipolar transistors, but it is important that the current flowing through them is at the level specified by the company, elsewise they will experience thermal runaway. In this case it would appear that you should lift pin 4 of the P-channel device, measure the resistance from pin 4 to 5. Reconnect to the circuit and measure the voltage across the pin 4 and 5 -- which will give you the forward current (should be 3mA).

I can't find these transistors at the usual 2 suspects for Sanken -- ProfusionPLC and Allegro.

[joeyuk]

thanks jackinnj

is there a simple was of testing them with a dmm?

as thats how i uselly test transistors but im a bit puzzled with these concidering they have 5 legs.

[jacco vermeulen]

Originally posted by jackinnj
can't find these

Looks like the duo is heading to become a different kind of Legend in it's own time.

[joeyuk]

any ideas how i can test these on my digital multimeter guys?

do i test same as normal 3 pin power transistors? as the 5 leg type in throwing me.

im getting "amp error" so wanted to check power output transistors.

[janneman]

Originally posted by joeyuk
any ideas how i can test these on my digital multimeter guys?

do i test same as normal 3 pin power transistors? as the 5 leg type in throwing me.

im getting "amp error" so wanted to check power output transistors.

One obvious test is for shorts between any two pins. If you're lucky ( ) that will be the case (disconnect the pins from the board before doing this).

Also, the build-in emitter resistor may be open-circuited, this happens often with the MOSFET itself still being OK. If that is the case you can put in an external emitter resistor and you're good to go.

Other than that I don't know of a simple way to test MOSFETs with a multimeter.

Jan Didden

[joeyuk]

ok just a update guys.

i was getting "amp error" soon as i switch on amp, checked the sapm01 they all measure the same so think they are ok.

i then removed AWX8411 small board which is connected to main transformer and the amplifier come on as normal ??

all i can find about the AWX8411 small curcuit is its a VH TR ASSY, not sure function of this small board.

looked at the 2 transistors checked with diode function and seem ok?

heres a few pics of the small board and also pinout where it connects on transformer.

the small curcuit

rear of curcuit


pinout connection off transformer


anyone any ideas why is comming on when this board is dissonnected and i get amp error when it is connected?

[joeyuk]

anyone any ideas what the VH TR ASSY circuit is used for ?