No Sound from Right Channel

[Paul Birkeland]

Well, the solder joint that gives people the most trouble is the middle leg of each MJE5731A, but that will typically leave the input and output pads at roughly the same voltage when you don't get it well enough soldered.  When you look at the top side of the board, if you see that the solder has flowed through all the holes in the board and up around the legs of those transistors, the joints are probably OK.

Beyond that, if this kit sat around in an area with high humidity for more than six months, the HLMP LEDs may have accumulated some moisture which can cause them to be damaged when you go to solder them.  This is a very unlikely scenario, but it happens once or twice a year.

Lastly, it's possible that you have a broken jumper wire on that board.  You can gently tug on them with your needlenose pliers to be sure they are all still in once piece.

Beyond that, I would suggest just purchasing a fresh board/resistors/transistor/heatsink/mounting kits.

[ScottAstroNut]

Hi Paul,

Well, I thought I had it! For a moment...

I resoldered the MJE5731A'a again, but they looked fine to begin with. No change.

I inspected the jumper wires, but they seemed fine to me. Still, just to be sure, I completely replaced the jumper wires. It seemed to work! The voltage on terminal 11 now read 145V, and terminal 17 read 88V. It looked a little low, but still not bad, so I decided to give it a go on my stereo system.

Plugged everything in, double checked the connections... put on a source... turned on the BeePre then the Kaiju. Put on some John Fogerty, then turned up the volume carefully. It worked! Sweet music came out of both speakers... for about 30 seconds! Then, the left side (the side with the suspect PCB) cut out and all I could hear was a loud static sound in that channel. Turned everything off. Waited a bit, then turned it back on... still more static in the left channel.

Unless you have other ideas, I think at this point I am ready to try a new board and associated components. How much is that going to cost?

Scott

[ScottAstroNut]

Oh, and just to answer your other question... this kit sat around for all of ONE day before I opened it and began building. No waiting for me on these delicious Bottlehead kits!

However, I'm not impatient, either. I tried to take my time, allowing finishes to dry and cure, and double-checking everything as I did the wiring. Still, I made two wiring mistakes on this kit, neither of which could, I think, have damaged the C4S board.

Just a bit frustrated at this point that this one is taking so long to get up and running. The thirty seconds of good music that I heard with the BeePre just wet my appetite for hearing more!

Scott

[Deke609]

When you swapped boards, did you unsolder the connecting wires at the board or at the chassis? If you swapped connecting wires too, then maybe try replacing those as well?

[ScottAstroNut]

Hi Derek,

I unsoldered the wires at the board, not on the chassis. I carefully removed the wires, then used a desoldering tool to clean up the pads. The wires currently connected to the "bad" C4S board worked previously with the other C4S board. I can resolder again, but I also think that it is time that I tested the transistors. I'm wondering if one or more of them are bad? Seems strange to me that it would work for all of about thirty seconds, then cut out when I turned the volume up a bit. Seems to me that a bad power transistor would cut out if the power got too high, rather than a solder joint. Still...

Thanks!

Scott

[Deke609]

Yeah, that does seem weird. Since you obviously know your way around a soldering iron, why not replace all the transistors? Mouser, DigiKey, etc. could have the replacements at your door on Monday.  Faster than waiting for a new board.

[Paul Birkeland]

I would do one more board swap, since you had some success with new jumper wires.  It's also possible that in swapping the boards, you may have a wire on one side of the amp that's also damaged.  I think you're pretty close to being up and running.

[ScottAstroNut]

OK, I'll give it a try.

Keeping my fingers crossed.

Scott

[ScottAstroNut]

No go. Switching the boards resulted in the voltages going back to the incorrect values they were before, with only a volt or two on terminal 2 and terminal 6 reading high like it did before.

What's more, my probe slipped while testing the (now) good L channel and I shorted out a capacitor. I think it's OK, but it definitely zapped. First time I have done that in a long time.

I think that I had better put down the probe and the soldering iron for a while! At this point I feel like we are chasing the problem in a circle.

Any further suggestions? Thanks!

Scott

[Paul Birkeland]

No go. Switching the boards resulted in the voltages going back to the incorrect values they were before

Did the bad voltages follow the board or stay put? 

[ScottAstroNut]

Hi Paul,

The bad voltages followed the bad board.

Scott

[ScottAstroNut]

At this point should I simply order a new C4S board (and perhaps a new capacitor, just in case)?

Thanks,

Scott

[Paul Birkeland]

Yes, a new board and the parts that go on it.  Definitely do not replace any capacitors.

[ScottAstroNut]

OK. Will do.

Thanks, Paul, for all your help.

Scott

[ScottAstroNut]

Well, the new C4S board arrived today.

I very carefully assembled and soldered the board and attached it to the rest of the BeePre. I then redid ALL of the resistance and voltage tests. All values were close to spec!

Keeping my fingers crossed, I put the BeePre back into my stereo system. Turned on my Eros 2, the Rega P6, the BeePre, and then the Kaiju. I held my breath as I dropped the needle on to the record...

Hallelujah!!! Sweet music appeared out of BOTH speakers!!! And GOOD music, too!!!

I haven't had time to critically listen to the BeePre yet, but that will be coming later this evening. I can hardly wait!

I can't tell you how relieved I am that we solved this problem. Paul and Derek, thank you SO MUCH for your help with this! I am extremely grateful!

All best wishes,

Scott