Alpine 3502 not turning on?

[crooner2264]

could something else cause the capacitor to blow ?

 

[crooner2264]

could the orientation be marked wrong on the board?

 

[Perry Babin]

What's the DC voltage on the pads for that capacitor?

 

[crooner2264]

I took some before and after pictures of the driver board before changing out the capacitors. the markings on the board are consistent with the way I installed the replacements.

 

[crooner2264]

I am not sure how to do that. the capacitor immediately explodes when I power up.

 

[crooner2264]

should i reassemble the amplifier and leave that capacitor out, then test across the 2 points?

 

[Perry Babin]

You can leave it out and measure the voltage. Two voltages. One on the positive terminal. The other on the negative terminal. Black probe on one of the non-BTL speaker terminals.

 

[crooner2264]

Ok, did that. r145 which is a 150 ohm resistor started to smoke. I shut the amplifier down and tested that resistor by removing 1 leg..spec says 150 reading = 167.1 ohm

 

[crooner2264]

ok, pulled q119 and q120 . 1 of them measured wrong. Both tested with the diode function and also with my transistor tester...1 shows up as a diode and the other reads PNP transistor.

 

[crooner2264]

2SC2824 npn Transisor

 

[crooner2264]

i meant npn transistor

 

[Perry Babin]

So, what are you saying about the transistors you pulled?

Are you sure that the bias isn't set too high? The pot could be intermittent.

Has it been pulling excess current during the time when it's been blowing the caps and burning the resistor?

 

[crooner2264]

I need to find a replacement for the 2sc2824 npn transistor.

 

[Perry Babin]

There are a lot of transistors that should work. From your description of the test results, I'm not convinced that it's defective. Was one junction leaking, shorted or open?

How much space is there above the transistor? Would a TO-220 transistor fit?

 

[crooner2264]

Yes, a 220 case would fit. what would you recommend?

 

[Perry Babin]

I'd suggest an MJE15030. I used them a lot as drivers and never had problems with them (oscillation, distortion, bias problems...).

Note that the pin configuration is reversed so you have to install facing the opposite direction.

If you have something on hand, try it.

If you can, try to measure the rail voltage. You should be able to measure it in a second or so if you connect your meter before you power up.

 

[crooner2264]

rail voltage without the driver board loading it down is 30 pos and 30 neg dc volts

 

[crooner2264]

what I have on hand is a pair of tip31c with 158hfe and 162hfe

 

[Perry Babin]

Try it but I think a rail voltage reading might be important, first.

 

[crooner2264]

i also have some mje340