Help needed Output Transistors blown

[Rossy]

Hi can anyone help me please?
i have a Non branded Amp called Pro-240
4 Transistors have blown
and 1 resistor
the numbers on the transistors are A940
only info i can get is this
A490 C2073
TO-220 PNP

http://216.239.59.104/search?q=cache:fmGy2WEOheIJ:www.elite-ent.com.hk/php/pdf/To-220/A940(TO-220).pdf%3FPHPSESSID%3D597428d6d3003a87c0d6ecd071850b87+transistor+A940&hl=en&ct=clnk&cd=1&gl=uk&lr=lang_en

i am strugeling to get this in the UK or find an equivilant

please help

Thanks

 

[Bone]

What's the power output of this amp and do you have the circuit?

This is an odd transistor ( The full part no is 2SA940 ) for a power amplifier it looks like its supposed to drive a TV or Monitor. Full data sheet at: http://pdf1.alldatasheet.com/datasheet-pdf/view/2524/MOSPEC/2SA940.html


The C2073 which I assume is the NPN complementary part - again full part no is 2SC2073 data at: http://pdf1.alldatasheet.com/datasheet-pdf/view/2537/MOSPEC/2SC2073.html

This may help you find replacements

Tony.

 

[Netlist]

A970 is in fact 2SA970. You could substitute it with MJE15031 which is easily available and a very reliable device.

/Hugo

 

[Rossy]

Hi thanks for reply
i do have the PCB out and can post a picture of the circuit
the other numbers on the Transistors that have blown are as follows
There is a Italic F at the top am assuming thats the brand
then in a embosed circle (U) then 537
then underneath A940

this is all the info i have on the amp
PA DJ Amplifier - "PRO 240" 480 Watt

Art Nr: AW1248244



480 Watts power!

High performance amplifier with 19” width, 2HE

High power and fidelity paired with a convincing design!

Fits in every system as easy as winking (19” standardised)

Ideal for monitoring, PA use, parties etc.



Stable 19” steel-body, 2HE

Powerful 2x106W RMS at 8 Ohm

Frequency 20-45.000Hz

Distortion factor >0,3%

Signal-to-noise ratio 80dB

Separated mixer for volume left/right

Peak and Protection LEDs

Front-sided on/off switch

Back-sided high-performance ventilator

Input over 6,3mm jack

Speaker output with golden 4mm screw plug terminal, PA cable or Jack

Safety switch (short-circuit-resistant)

Dimensions B x H x T: 485 x 95 x 270 mm

Weight 9 kg

 

[Rossy]

A970 is in fact 2SA970. You could substitute it with MJE15031 which is easily available and a very reliable device.

/Hugo

Hi it was A940
but thanks for help

thanks

 

[Rossy]

Think ive found them what luck

http://cgi.ebay.co.uk/2SC2073-TOSHI...ryZ36332QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[Rossy]

Hi the 2SC2073 is NPN like you say but the original is PNP will this matter?
thanks

 

[Netlist]

Hi it was A940

This of course was a typo.

Hi the 2SC2073 is NPN like you say but the original is PNP will this matter?
thanks

You need to replace NPN with NPN and PNP with PNP.
So, previous posts is still valid. You can replace 2SA940 with MJE15031.

If the amp doesn’t contain 2SC2073, you need not to bother.
If it has, MJE15030 is a good substitute.

/Hugo

 

[Rossy]

Hi thanks for that
there is a few variations in teh data sheet but with MJE15031 as the Mhz is 30 but on my A940 it is 4 will these mater

thanks

 

[Netlist]

It could be that the amp will oscillate and you will need a scope to watch if it does. A schematic would be real handy but I'm afraid you will not have that.
As for now, try posting a clean picture of the amps inners, concentrate on the output stage.

/Hugo

 

[Rossy]

Hi this is the left Channel that has blown
thanks
there is a 220R resistor (fuesable) that has blown and will need replacing all other componants check out apart from the 4 transistors
But i am having dificulty finding compliments for the MJE15031 here in the UK

An externally hosted image should be here but it was not working when we last tested it.

 

[Netlist]

Are all the output transistors A940?
Also, please post a picture of the underside of the PCB.

/Hugo

 

[Rossy]

Hi thanks for Helping me 😉

Ok all 8 Transistors are A940 4 for each channel
i circled the 4 that have been blown and the 1 resistor

An externally hosted image should be here but it was not working when we last tested it.

 

[Netlist]

So all you need is MJE15031.
Replace the 2SC1815 as well just above the 220R resistor.
Check the other small transistors, all are 2SC1815 and 2SA1015.
I don't know of any suppliers in the UK, you could try Farnell. They sure have the MJE15031 and 2SC1815.
As for the 2SA1015, you could replace it with BC212, also available at Farnell but not pin compatible.

/Hugo

 

[Rossy]

Thats great i will order them up

just a couple of things will i be ok with the MJE15031 although the Mhz is 30 rather than 4

and the resistor 220R what wattage would you expect it to be 1watt? colour code is red red black black brown

thanks

 

[Netlist]

I would try. Some frequency compensation could be added to prevent oscillation (you'll need the experts for that).
As for the resistor, 3611127 from Farnell will do fine as you only have to buy in quantities of 5.

/Hugo

 

[Rossy]

Hi thanks for the help
i found this web site that hass all componants i think?

could you check the resistor for me?

thanks

also could you check 2SA839

thanks

 

[Netlist]

Also, check the resistor near the burned one. 4k7?
All emitter resistors - the ones on the 2SA940 rightmost pins - need checked together with the 33R base ones.

/Hugo

 

[Rossy]

Hi pulled all the legs up for the resistors all seem fine apart from the one that i took out

thanks for all your help

great guy 😉

 

[Netlist]

2SA839 will do fine if you can get it.
I gave you the part# of the resistor at www.farnell.co.uk.

/Hugo