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I would like to know which are the BASE, EMITTER and COLLECTOR of the BF237 transistor. Thank you

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Here you go then:

I would like to know which are the BASE, EMITTER - e02b310.gif

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Posted on Apr 28, 2010

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1 Answer

How to test H-out transistor if it is good or defect?


All pins shorted together means the transistor is defective.

Generally, there are about 3 tests I usually do with ohmmeter to test a bipolar transistor:

1. Measure resistance from collector to emitter. If it is zero, transistor is shorted (bad).
2. Measure resistance from base to emitter. Should show conduction in one direction, but not the other.
3. Measure resistance from collector to emitter. Should show conduction in one direction, but not the other.

Nov 15, 2013 | Televison & Video

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Am I testing this horizontal output transistor correctly?


Check the resistance between collector and emitter. It should never be Zero Ohms.

Dec 01, 2012 | Symphonic Televison & Video

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When i turn on horizontal output tripping. B+ and low voltage ok


Hello
Check the LOT and Horizontal Output Transistor. If horizontal output transistor get shorted [collector to emitter or collector to base], this kind of fault will occur. Here there is nocollector to emitter short as B+ is ok. Check for collector to base leak. It is best to repalce the horizontal transistor with a new one, and switch on the Tv for a short while, say 10 seconds or so, and feel the heat of the replaced transistor. If it gets overheated, of LOT makes a whisiling of hissing sound, LOT is faulty, and shoul be replaced sith same type and number. OK.

Apr 17, 2011 | Sony PVM-14N6U TV

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Toshiba tv 32a43 power button flashes red and won't turn on


Check to see if horizontal output is shorted, But will have a damper diode, between the base and emmitter, will read 0 ohms. That's okay to check like that, Check for shorts between collector and emitter and collector and base. If ok, check for 130v dc on the collector of the horizontal output transistor.

Mar 26, 2011 | Toshiba 32A43 32" TV

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Wharfedale pro BX1360SD powered mixer intermittent fault - preamp section OK, no output from power amp (false overtemp detection? shutting down power amp??) please supply advice, circuit...


Wharfedale pro bx1360sd


I have had problems with this stereo mixer amplifier which had the symptoms of no sound output from either channel .

I opened up the unit and discovered that the amplifier was correctly amplifying my input signal up to a relay which switches the output through to the speakers .

This relay did not activate at all.

When the power switch is turned ON you should hear a click approximately 2 seconds later , if no click then there is a problem with the circuitry associated with this relay .

I traced out all the connections associated with this relay and made a circuit diagram .

The relay is a 24v relay and I will explain the way that I can see that this section of the amplifier works.

It has been designed to ;

  1. Create a slow start delay ( 2 seconds ) when the power is turned ON.

This it needed because otherwise there is a current surge and sparks from the relay turning on immediately.

  1. Thermal cutout mounted on heatsink . If the ventilation fan fails the heatsink and transistors may get too hot and the cutout will operate and cut power to the relay by going open circuit.
  2. Speaker protection from blown output transistors. There are 2 transistors q802 and q803 both 2sc1815. They are connected together emitter to emitter and collector to collector to form a differential Op amplifier I.C. If there is a blown output transistor then DC voltage will be detected by q802 and q803 and the relay will be switched OFF to protect the speakers .


Q804 turns On Q805 which turns On Q806 to activate the relay .

Voltages on transistors

Q802 and Q803 2sc1815

Base 0V Collector 12.9V Emitter 0V


Q804 2sa1015

Base 12.9V Collector 0V Emitter 15.1V


Q805 2sc1815 (driver for Q806)

Base 0V Collector 7.2V Emitter 0V


Q806 2sc1815

Base 0V at Turn ON then after 2 secs increases to 0.7V

Collector 2.8V ( transistor is activated as a switch Turned Fully ON ( saturated) to turn on the Load which is the relay .

Emitter 0V


I have replaced the following transistors to fix my amplifier q805 2sc1815 and q806 2sc1815 .If you are going to use a different type of transistor it may not work and also the lead connections of a 2sc1815 for the collector and emitter are different to those such as on a 2n2222( transposed).

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Power up problem with alesis rs300 (ra300)


you have more than likely damaged some transistors.
the resistors have burned because of excessive current.
there are 2 typesof transistors,bipolar and mosfet
a bipolar transistor has 3 pins.1) base 2)emitter 3)collector.
an NPN is tested with the + meter lead on the base , and a PNP transistor with the - lead on the base.
TESTING
base to collector should read .5 to .6 v drop in one direction and open in the other with a digital meter on the diode check function.
base to emitter about the same,but slightly higher than the collector.
if base to collector is .5v then base to emitter is .52 or so.it is always higher than the base collector number.
between emitter and collector will read open in both directions.
if there is a short on any lead combination,the transistor is blown.
npn transistors operate on the positive rail power supply,and pnp on the negative rail.
typically a 150 watt amp will run + - 65vdc.
the transistors running on the plus side are npn and on the negative pnp.
most pnp output transistors are green.,but some are black,
so we must go by the numbers on the transistors, eg.A1076 is a pnp,B755 is a pnp and all transistors that have a C or D eg. D424 are NPN transistors. all A and B numbers are PNP and all C and D numbers are NPN.
MOSFET transistors have 3 pins 1)gate 2)drain 3)source
the source goes to power like the collector does. the drain is like the emitter,and the gate switches it on like the base does.
testing a mosfet is a different procedure.
a mosfet with k then a number e.g. k135 is a positive device like npn.
a mosfet with j and a number e.g. J50 is a negative device like pnp.
a mosfet reads open source to drain both directions.
for a positive (k number device) the plus meter lead goes on the source.,the black meter lead on the drain. on the diode test function.
jump a wire from the source to the gate for 1/2 second and remove the jumper while leaving the other two meter leads connected to the source and drain.The mosfet should switch on and the meter should show a short.that means the mosfet switched on.About 5 seconds later,the resistance from drain to source should go open.
for a p channel mosfet,it checks the same,except that the black meter lead goes on the source and gate .
a mosfet will stay switched on longer than the voltage applied to the gate,if it is driving a high impedance device such as a meter.
a bipolar transistor will not stay on when voltage is removed from the base lead.
i hope this has been of some help.

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1 Answer

Rear projection mitsubishi vs5042 no high voltage


Are you talking about the LV power supply or the HV power supply? The terminology your using is related to the horiz drive circuit. Have you checked the B+ off the regulator which should be about 120v or, it will on the pc bd for the correct voltage. Do you have sound? If you do then you will have to use use your scope to see if you have proper drive at the base of the Horizontal Output Transistor. Then we can go from there. Oh, by the way I can tell by the voltage readings you stated both of those transistors of turned off.

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1 Answer

I can here them but they can't hear me


Hello,

I have the TRU9585 with 4 hansets. We used them for about 3 months, worked great. One day, I can hear caller, caller can't hear me. Problem was a defective transistor in base unit. Part number C2120, small 3 legged device near bottom of unit. Replaced it with generic NPN transistor from Radio Shack. Caution...should only attempt repair if you have worked on electronics before and can solder...Also C2120 configuration is not standard, configured emitter-collector-base instead of emitter-base-collector...Good luck!!!

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Pioneer vsx-9900s


Hey man,... no worries.

Were any fuses blown? Check this first and foremost before you do anything else. If there were blown fuses, you then (if you are familiar with how), need to check the output stages for shorts. NOT generally to ground as you have suggested.... but more between the center and outside pins (collector emitter short we are looking for here) To check the output transistors properly, you need to unsolder leg and check each of the output transistors junctions base emitter, and base collector, and also collector emitter for any leakage. Once you find the offending channel(normally there is only one), you need to then carefully check the driver transistors also. Pay attention to low value resistors about the output stages, small signal and zener diodes and if they are there, any power diodes. If you are unsure of the condition of a part, then replace it to be sure :)

Hit me back and let me know how you go.

regards
Graeme

Apr 24, 2008 | Audio Players & Recorders

1 Answer

Tv repair


you can try to check if the problem is near flyback transformer
you ha to disconnect the power cord , open tv and locate power
transistor for generate high voltage it is near the big four connector 
cable the transistore you have to dissolder from board and check
with multimeter if it is shorted or not in this way base to collector
junction about 500 or more base emitter the same  collector to emittor open - delfo

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