[Phoca]

About 2 years ago I bought a Bugle and built it.  Initially I seem to recall it worked reasonably well (not stellar, but it ran).  Eventually I got odd noises out of it, then finally, some static on the R channel and nothing from the L channel.  I replaced one likely bad chip, but that's it.

It's always been a batter operated unit.

Left channel shows no DC voltage at the output (no signal).  Right channel shows about .9v DC on the output (no signal).  R. channel is the only one with ANY sound coming out, but it's ALL static.

In short, it's never worked exactly properly, and I'm now wanting to take time to fix it.  I had sent board photos to Jim H. and he confirmed that all solder joints LOOKED fine.  I re-did a few joints that were the worst visually, but no dice.  Chips all have the notch facing the output.  Haven't tested the op-amps (opa2134) as I'm still working on a test circuit.

Any ideas?  Thanks a ton.  I'm hoping to build a battery-powered (9v) preamp to go with the Bugle IF I can fix it.

Cheers,
Carl

[JohnR]

Hello, perhaps you meant to post this in Jim's circle?

   http://www.audiocircle.com/index.php?board=52.0

[Phoca]

Um, yep.  Thank you!

[poty]

As soon as you have a problem with both channels (although slightly different), I think you should begin to look at common circuit: batteries (are both good?), batteries' connectors, common wire (ground) to input, output and circuit parts, interconnects (from the input and output side) and so on. Check once more if you solder the opamps in the right direction. Check all voltages, mentioned in the manual schema (don't forget - the voltages measured in relation to the ground!).
If all is OK, you can begin to experimant with the "silent" channel (left). Touch with a thin screwdriver the output wire of each opamp beginning from the last (U4 from the manual) - you can use any side of R24, then R25, then R27 from the left channel to achieve that goal. As soon as the screwdriver is like antenna in this case you should hear very load hum from your left speaker. If you don't - it means the following stage has a problem.
As soon as you find the problem in the left channel you can use the method to troubleshoot the right.

[Phoca]

Thanks, Poty.  Batteries should be good but I'm not sure I recall what voltage they cut out at.  Will check the manual.  L side reads above 9v.  R side may have been at just above 7v.  All other parts should be good (interconnects work with other gear, gounds seem OK but I'll double check, etc.).  Opamps are in sockets and are properly oriented.  Again, I need to check them with a circuit I need to finish.  Will also re-check the voltages per the manual (I haven't looked at it in a while and must have forgotten they had voltages for testing) and report back if I'm still stumped.

Any ideas on the .9v on the R channel output?  That worries me.

Carl

[poty]

...L side reads above 9v.
...R side just above 7v.

It should be identical or near identical.

Any ideas on the .9v on the R channel output?

It may be the result of different batteries voltages, but it may be something else, including some bad joints in a opamps divider for example, bad opamp etc. Could you measure the DC voltages on each output of each opamp (should be 6 measurements)? It will give clearer picture about problem.

[Phoca]

OK, on first testing, I used nearly new 9v batteries (9.52v each).  9.52v at the PS lytic cap on one side (B1), nothing on the other (B2; actually, maybe it was 3v or so).  Checked continuity on B2: + of cap and battery have continuity to ground.  Neg of battery and cap read NO continuity.  By the schematic they should connect directly.  Re-soldered and I still get no connection.  The battery holder DOES have connection through to the solder side of the board (i.e with itself) so there's no problem with that.

All I can figure is that the solder joint (one of them) isn't making connection to the trace.  Will check it further, but please let me know if for some reason I'm wrong about my assumption about the neg terminal continuity.

Carl

[poty]

Yes, you are right, the negative battery lead and the electrolytic capacitor should be directly connected. You can try to use a wire to connect the solder joints together to determine if this is the problem. It could be bad trace (microfissure or so). It could be separated contact pad (from the trace).

[Phoca]

OK, so problem solved.    It was indeed a bad trace hidden by the battery holder, or rather one that got mangled at some point after initial construction (i.e. my fault, not Hagerman Tech's).  I've put in some jumpers, and it seems to work fine now.  In fact, it's quite nice, now that it's running properly.  Surprisingly fast, tight bass, clear.  No noise that I can discern (at least that isn't generated by my chinese pre-amp).  Well...other than a small pop on turn-on and shut-off.

Thanks a ton for the help!  Cheers,
Carl

P.s. Here's the trace:

[poty]

Good news! Relax and enjoy listening!