2SC1618 question

[Low_Boy]

Sumitomo 2sc1618. Could this pin out be possible or did I buy another junk part. Dath sheet shows different. No pins marked. My tester shows the mounting plate as the collector.

 

[Low_Boy]

Pin out is correct. I pulled the old transistor and cross checked.

 

[Low_Boy]

Next question. The one I thought was bad had a 118 HFE. The replacement has a 45 HFE. The original tested good. But i see signs of heat in the power supply in the washington. Is that common?

 

[Tallman]

According to the spec sheet it might be okay.
http://html.alldatasheet.com/html-pdf/268611/ISC/2SC1618/114/2/2SC1618.html

 

[sp5it]

If it works must be heat. No worry, critical temperature for this transistor is 150 degrees C.
Mike

 

[Handy Andy]

May just need Capacitor replacements - ESR on those can "Drag down" the loading on a power supply and cause the very thing you're having. Caps eventually will act more like resistors with higher and higher values, in series to take and release a charge, but lower and lower values in parallel to store and filter - eventually they'll look like dead shorts and refuse to take a charge or even hold it.

Old parts, time for fresh replacements - that sort of thing...

Might want to do that before you need another tophat (TO-3) replacement - which those caps will take their frustrations out on soon enough.

 

[Low_Boy]

I have had this radio a long time and actually only ran it off the 12 volt with my power supply. Internal power supply does work I think I'm going to put all the old Parts back with the exception of capacitors and resistors thanks.

 

[Handy Andy]

So, if you didn't use it, what caused the "tempering" and discoloration?

Was the external power thru the rear jack panel or something just tied in and run that way?

Because if say a battery charger was used, and the output of the regulator was never bypassed - you'd see a similar effect from the power dissipation the built in regulator offered to provide extra filtering and regulation - only it (any voltage variance slightly higher than the "Sense" loop the internal regulator used - as dissipated in the input - which was on it's output - instead.

Ok, the reason why this comes up was from experiences in replacing those Uniden - style 3-pin connectors that used a built in detent that used a "Cherry switch" - when you plugged something into the external power jack it automatically turned off the lines from the internal power supply feed - but not always! The switch and or internal power supply - if left plugged into the wall - kept the radio powered all the time and eventually the owner began hearing of complaints of a hum in his audio and eventually the internal regulator failed - and he couldn't understand why...

 

[ExitThirteen]

If there is a disc capacitor labeled "104" that's tied across the case and 1 of the pins of the 2SC1618, remove it. That disc cap has a high failure rate, which in turn shorts out that transistor between the collector and base. Also, replace the 3300uf/35V filter capacitor if you have not done so already. Those two things should restore operation if the 2SC1618 was not damaged or previously replaced.


~Cheers~

 

[Low_Boy]

Thanks Exit 13. I will remove the Cap. Both transistors checked good so I reused them. Will there be noise coming from the power supply with the Cap removed?

Andy.. The ESR's on the two capacitors were SKY HIGH. That is where the heat was probably coming from.