[dhollister]

Hi folks,

I finally got around to building the bugle power supply I ordered a couple months ago.  It seems I built everything correctly.  It puts out about 14.8V.  Then I connected it to the Bugle and no sound.

First, I noticed that I managed to wire the +/-15V backwards when going to B1/B2 on the bugle.  Ugh.  So I reversed them.  Still no sound (and a second blown fuse).  Double-ugh.  I then noticed that I had wired it backwards -- the -15V went to the "+" side and the ground went to the "-" side on the battery connector.  I hadn't even had that much to drink!  I guess that's what I get for trying to follow how to wire the thing based on a picture somebody posted somewhere.

Anyway, I then reversed that connection.  Now the fuses don't blow anymore, the LED stays lit, and I seem to be getting voltage on the bugle, but still no sound.

Any thoughts on what might be going on?  Is it possible I blew something?  I seem to see voltage on each of the op-amps and even on the outputs.  I'm not sure if that's normal or not.  I suppose I'm just out of my league.

Thanks for any help!

David

[hagtech]

What voltages are you reading on the opamp supply pins?  What voltage at output?  Are opamps in backwards?

jh

[dhollister]

What voltages are you reading on the opamp supply pins?  What voltage at output?  Are opamps in backwards?

jh

Hi Jim,

Thanks for the response.  The bugle was working fine with battery sources before this, and I haven't changed anything there, so I'm sure the opamps are fine.  I'm not sure which pin I was reading on the opamps, but it was the same pin on all three and I was reading somewhere around 13.5 V.  If it matters, I can go back tonight and check the voltages on the right pin (if I didn't hit the right one -- I just picked one at random).

The voltage I was reading on the outputs was also in the neighborhood of 13.5V I think (I'm going by memory and am at work at the moment).

David

[dhollister]

I haven't found out the problem yet, but I am definitely seeing 13-14V on every pin on every opamp.  I checked my other bugle which is still a battery powered one and it looks more normal (only voltage on two pins).

I then looked at the switch I had removed to convert the battery powered bugle to use the power supply.  Those connection points are rather small and after installing a switch, removing it and installing two short pieces of wire to act as the jumpers, I may have created some sort of connection between a couple of the points.  I see infinite resistance between the two pins on the upper row, but there is definitely a non-infinite resistance between the two lower points.  There is a bit of flux there which I will try to remove, but I think the bigger problem is the damage done to the circuit board with the brute force of removing solder with my iron and a desoldering braid.

Would it be possible if there was some sort of leakage at those connection points that would cause what I am seeing (voltage on every pin on every opamp)?

Sorry if I'm being somewhat vague.  I can discuss software acronyms and technology with the best of them, but circuitry just isn't my strong suit.

Thanks again,

David

[hagtech]

Take the opamps out first.  Then debug the supplies.  Seems you might be missing the neg supply, or maybe have driven it positive.

jh

[dhollister]

Take the opamps out first.  Then debug the supplies.  Seems you might be missing the neg supply, or maybe have driven it positive.

jh

Hi Jim,

Here is what I found out last night.  I believe the supplies are wired correctly.  I seem to get -14.9/+14.9 V across the jumpers that I put in.  The problem may be that one of the switch connectors has lost the metal ring around the outside which makes it impossible to form a solder joint there.  I'm wondering if that's why I'm losing my negative voltage (it's the other side of the jumper position from where the -15V comes in).  If that is the problem, I have no idea how to fix it, or if it is even fixable.  After messing with it long enough I finally did get a wire soldered across it, but I fear it's just not making a connection with the trace that leads up into the guts of the board.

David

[dhollister]

I decided to give it one last try this morning.  I tried to gently add a bit more solder between the switch pin and the trace.  Like I said earlier, the metal ring that connects to the trace had been removed after so many times messing with the bugle (putting a switch on, taking it off, wiring it to an external switch, then undoing it to connect the power supply).

Anyway, after doing that, I finally saw 0 resistance from that pin to the pin on the other end (where an opamp would go).  I plugged the opamps back in and did some voltage readings.  It looked more normal, so I plugged it in to my system and voila!  Music, sweet and powerful (gotta love Dire Straits' Love Over Gold).

I guess my next step is to get this frankenstein into a chassis of some sort.

Jim, my next beer will be a toast to you  

Cheers,

David