Replacing Hafler 9130 transistors- 2 techie question

[reiver]

I was soldering in new caps on my Hafler 9130, and damaged the rt channel. When I started playing music I heard a pop and lost the music. I now have .400 DC offset on that channel but the bias is fine. I figure I overheated a transistor at the input because that was where I was soldering. There is no DC offset trimpot so I suspect Hafler matched the transistors at the factory, so....


- If I replace Q1 with a new 2N5550 I plan on also replacing Q2 to keep the parts "matched". Should I also replace Q3/4 to keep everything "matched"?

- To keep characterics/imaging the same between the channels, should I also change the same transistors in the other channel, even if they are ok?

After 20 years of modding this will be my first time replacing a transistor....thanks for any input. See the attached image.

-Bryan

 

[Tube_Dude]

Are you sure that you haven't left any solder bridge at your intervention area ?

Haven't you put the capacitors backwards?

 

[reiver]

The only caps I changed were small value film caps (220pf, etc). Could be I have a short, I'll double check tonight for solder bridges...I was getting pretty tired and didn't want to mess it up more.

The "pop" and suddenly no music made me think of a transistor going though....

 

[Tube_Dude]

The "pop" and suddenly no music made me think of a transistor going though....

Or a solder bridge "making connection" with the vibration or warm up dilatation of the PCB...

Inspect the new capacitor for internal short, also...

 

[reiver]

The cause...

Well, I took my meter and checked Q1 and it didn't seem shorted.

I, ummm, then noticed, ummm, that one of the fuses on the board had blown. I replaced it and the problem mysteriously vanished(!) DC offset is fine and it sounds excellent now.

Thanks for the tips on looking for shorts....as it slowed me down from ordering transistors I didn't need.

Cheers, Bryan

 

[Tube_Dude]

Re: The cause...

Well, I took my meter and checked Q1 and it didn't seem shorted.

I, ummm, then noticed, ummm, that one of the fuses on the board had blown. I replaced it and the problem mysteriously vanished(!) DC offset is fine and it sounds excellent now.

Thanks for the tips on looking for shorts....as it slowed me down from ordering transistors I didn't need.

Cheers, Bryan

Sometimes is good to take some time ...

Cheers