Fusion FP-505: TIP36C Problem

[theAnonymous1]

OK, well I guess the problem WAS caused from a solder bridge all along. It was so tiny I didn't notice it at first. I only saw it when I got in real close to desolder the TIP35.

This tiny spec was definitely not from me, so I don't know how sub channel ever worked at all with it being there. The bridge connected the base of one of the TIP35 to the positive rail of the 4-channel amp section power supply.

The sub channel appears to be working fine now. There is only 14mv offset on the output. I just need to reconnect the preamp board and run a signal through it now.

Thanks again everyone; especially Perry.

[I Am An Idiot]

WOW somebody knows how to use the Macro setting on their camera. Chances are the amp did work fine at one time, It looks a lot like it was mounted to the back of a seat and driven a bit too hard, causing the solder to melt and gravity took it from there.

[theAnonymous1]

I put everything back together and the sub channel is playing music.

Not a bad little amp for $20. Gotta love DIY repairs.

Or maybe it should be called DIYWHFP (do it yourself with help from Perry).

[ppia600]

Wow, so someone must have tried to repair it before? Glad you got it figured out.

[theAnonymous1]

Originally posted by ppia600
Wow, so someone must have tried to repair it before? Glad you got it figured out.

I don't think so. It didn't look like it was ever taken apart before. The seller said he was the original owner and bought it new ~2 years ago. He said it started going into protect recently so he put it up for sale.

The solder bridge was also making the positive rail of the sub channel supply high at 53v somehow. I had measured this before I found the bridge. Now both rails measure 47v.

Next time I try to repair an amp I will be sure to look twice for even the smallest solder bridges.

[I Am An Idiot]

Originally posted by I Am An Idiot
Chances are the amp did work fine at one time, It looks a lot like it was mounted to the back of a seat and driven a bit too hard, causing the solder to melt and gravity took it from there.

I agree with Anonymous1, I don't think it has been repaired or attempted before. I am sure that when the bridge was created by the melted solder and the gravity, it took out the TIP36s. Then it became a Sold As-Is Ebay item.

[ppia600]

Originally posted by I Am An Idiot



I agree with Anonymous1, I don't think it has been repaired or attempted before. I am sure that when the bridge was created by the melted solder and the gravity, it took out the TIP36s. Then it became a Sold As-Is Ebay item.

I would believe that if it weren't for the super clear photo he provided. If you look closely it appears there is a huge glob of solder melted onto the top of the original solder on the board, it looks as some novice at soldering was trying to add solder to make the connection better somehow and the curve on the top looks to be where they were trying to smooth it down a little. If it was indeed mounted in a vertical fashion as the photo appears, the solder wouldn't have expanded toward the direction of the camera lens and then trickled down just enough to touch the other leg. You can actually see flux in between the original solder mass and the second glob applied to the top, mainly on the left in the picture. Just because the seller told you he was the original owner or that it wasn't repaired before doesn't mean its true.

[jol50]

Think I saw that amp on there but did not know much about them. The guts look similar to some others I have seen.

I have found a lot of solder bridges in cheap amps that have hand soldering. I swear some of them have a pound of solder on the board. Does not seem like it would have worked with it there when new so something put it there.