[ghayslip]

I built my bugle several years ago and until recently it's been running flawlessly. Just the other day I noticed that after running for a while, the left channel begins to distort and gain drops off. Symptoms are similar to a dying battery. It takes about one full LP for the problem to appear. A year ago I converted from 9V to a pair of 12V SLA batteries. I thought one of my SLA batteries was going south so I switched back to 9V batteries but the problem is still there.

Any suggestions would be appreciated. I'm guessing that one of the left channel caps or op amps is going bad.

Gordon

[PatOMalley]

First thing I thought was to pull the cables, wipe the RCAs with contact cleaner, and hook back up.

[ghayslip]

I tried that. I first swapped RCA's, no change. Then I swapped cartridge leads, still no change. I'm pretty sure at this point the problem is in the Bugle.

Gordon

[hagtech]

Hmmm, I've heard mention of similar symptoms over the years, usually pointing to a battery issue.  I wonder if there could be some other charge buildup if one of the opamp inputs is blown (partially).  I can't quite see how this might happen, so keep chasing down power supply connections.

jh

[reuben]

Grasping at straws:

Have you moved the op amps up and down in their sockets to clean the connections?

If you left behind any flux residue from the build, now would be a good time to clean it up.

A good visual inspection (I use 10x mag) works wonders when you touch up any questionable solder joints and look for the obvious.

Regards,
Tom

 

[ghayslip]

Thanks for the suggestions. I'm going to order a fresh set of opamps and look for a loose connection. I'll follow up with a post when I find the problem.

I've got two systems and turntables so I may go ahead and build a second bugle with designer resistors & caps.

Regards, Gordon

[hagtech]

Usually it has something to do with the negative supply.

jh

[jcg0322]

Gordon,

If you don't mind paying for shipping, I will check it out for you. I will replace any bad parts for free.

Thanks,
Jack

[ghayslip]

After running for several hours without any issues I think my Bugle is fixed. Since this problem had all the earmarks of a power supply issue I decided to change out the 220uf filter caps bridging the power supply inputs and bingo, the problem went away. I suspect the left channel cap would start leaking after the circuit was energized for a while, intermittently shorting out the battery and causing distortion and loss of gain similar to a low battery.

Thanks again for all the suggestions and support.

Gordon

[robertash]

I ran into this exact same problem.  I was going to suggest you replace the filtering caps, but you did, and that's the solution I found.  I replaced the regulators, cables from the PSU, tried a different grounding scheme.  Anyway, glad to hear you found the solution.

Robert Mills