Another*SERVICE NOTE* for older BGW amps revolves around the use of MOLEX multi-pin connectors to attach the power modules to the amp's wiring harness. (The larger BGW amps use octal plugs / sockets and are subject to the same time mediated malady.)

I have a large group of BGW 150 (1 RU height) amps that I use to drive JBL 2404 "Baby Cheek" tweeters. They would intermittently hiss, pop, and fart... I looked at the amps' output on the oscilloscope with an 8 ohm dummy load driven by a 1 KHz sine wave. I drove the amp at 75% rated power. With the cover off the amp, I poked around looking for noise sources -- I used freeze-it spray to see if any active component had 'gone thermal." NO DICE!

Remembering some tube type troubleshooting, I tapped the output modules and saw some noise spikes on the oscilloscope. I thought maybe the thermal paste on the power devices a degraded, so I spent two hours removing and renewing the thermal transfer paste. Powered up the amp, and the noise trace was still there. Out of frustration I tapped the 16 position MOLEX connector with a 1/2" diameter wooden dowel. BINGO -- the noise trace changed in direct relation to the tapping.

After power down, I used two pairs of slip-joint pliers to *GENTLY* separate the male and female connectors from each other. I examined the connectors and found them to be nickel plated -- and dull and grungy. I then sparingly used (one drop per receptacle / pin) some MARVEL MYSTERY OIL on both the female socket receptacles and male pins. I made and broke the connections four times and then powered up and tested the amp as above. Result -- no noise traces at all when when the MOLEX connectors were tapped. The amps sound clean, crisp and noise free.

Lesson -- look at the condition of the removable connectors first when tracing down intermittent amplifier noises.