BGW Legacy Amp Service Note

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11-25-2017, 04:22 PM
loach71

BGW Legacy Amp Service Note

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.
01-08-2018, 08:03 AM
Rudy Kleimann

Vintage Crest amps too!

Crest Audio was started by former BGW employees, and a brought a lot of the same thinking into their amp designs, like their 'overbuilt' power supplies.

Your suggestions really apply to all cable connectors, be they for power or signal paths.
01-08-2018, 08:20 AM
Rudy Kleimann

Contact cleanup tips & tricks

On low-voltage contact points, oxidation can produce a "diode effect" that can make for a nasty sound quality due to the fact that the oxidized surface is resistant to current flow below a certain voltage level.

My personal favorites for contact clean-up and treatment is:

For power path:
Cramolin red liquid
CorrosionX spray

For signal path:
Caig DeOxIt spray (red or gold) (contains Cramolin)
Cramolin Red liquid
Caig MCL (blue) spray for sliders.

Use pipe cleaners on female XLR connectors etc.
Twist two or more pipe cleaners together for larger jacks.

Q-tips are generally useful on male connectors. Watch for any cotton fiber lint left hanging around.

Use toothpicks for stubborn spots and to remove lint etc.

Scotch-Brite cloths can be helpful too but take care not to remove the surface plating, especially silver or gold plating. Note: silver oxide IS conductive, and gold doesn't oxidize, so concentrate on dirt removal more than polishing the silver on these connectors. Use the non-abrasive blue pads if you can find them.

Gun cleaning brushes are especially useful, and are made with nylon or bronze bristles in a wide variety of diameters from .17", .22", and many other "calibers" up to .45" & .50"
Most are made to thread onto gun cleaning rods ( pistol rods are shorter & handiest)
Some cleaning tools are made like miniature screwdrivers with tips of different sizes & shapes.
01-08-2018, 02:56 PM
loach71

MOLEX Connectors

Quote:

Originally Posted by Rudy Kleimann

On low-voltage contact points, oxidation can produce a "diode effect" that can make for a nasty sound quality due to the fact that the oxidized surface is resistant to current flow below a certain voltage level.

My personal favorites for contact clean-up and treatment is:

For power path:
Cramolin red liquid
CorrosionX spray

For signal path:
Caig DeOxIt spray (red or gold) (contains Cramolin)
Cramolin Red liquid
Caig MCL (blue) spray for sliders.

Use pipe cleaners on female XLR connectors etc.
Twist two or more pipe cleaners together for larger jacks.

Q-tips are generally useful on male connectors. Watch for any cotton fiber lint left hanging around.

Use toothpicks for stubborn spots and to remove lint etc.

Scotch-Brite cloths can be helpful too but take care not to remove the surface plating, especially silver or gold plating. Note: silver oxide IS conductive, and gold doesn't oxidize, so concentrate on dirt removal more than polishing the silver on these connectors. Use the non-abrasive blue pads if you can find them.

Gun cleaning brushes are especially useful, and are made with nylon or bronze bristles in a wide variety of diameters from .17", .22", and many other "calibers" up to .45" & .50"
Most are made to thread onto gun cleaning rods ( pistol rods are shorter & handiest)
Some cleaning tools are made like miniature screwdrivers with tips of different sizes & shapes.

I have come to DETEST nickel plated MOLEX connectors. I am in the process of servicing six BGW 150s with intermittent noise problems. I am using the 'nuclear option' to fix this noise problem -- the replacement of the nickle plated pins and sockets with gold plated versions.
01-08-2018, 10:14 PM
Rudy Kleimann

I feel your pain... however, considering their age, the nickel plating hasn't done too poorly, has it?

I'd guess it is tin plated instead of nickel but I :dont-know:

If you have the gold connectors and don't mind the work, they'll last for the rest of your life... but if it was me I'd just clean the existing connectors with deoxit, treat them with Cramolin red, and call it good for another 30 years.

OTOH, you can just pull the connectors off the PC board & wiring harness and solder them in place... and eliminate connector issues entirely. :yes:

Quote:

Originally Posted by loach71

I have come to DETEST nickel plated MOLEX connectors. I am in the process of servicing six BGW 150s with intermittent noise problems. I am using the 'nuclear option' to fix this noise problem -- the replacement of the nickle plated pins and sockets with gold plated versions.
01-09-2018, 11:37 AM
loach71

Molex

Quote:

Originally Posted by Rudy Kleimann

I feel your pain... however, considering their age, the nickel plating hasn't done too poorly, has it?

I'd guess it is tin plated instead of nickel but I :dont-know:

If you have the gold connectors and don't mind the work, they'll last for the rest of your life... but if it was me I'd just clean the existing connectors with deoxit, treat them with Cramolin red, and call it good for another 30 years.

OTOH, you can just pull the connectors off the PC board & wiring harness and solder them in place... and eliminate connector issues entirely. :yes:

You are correct! Brian G Wachner, the designer and owner of BGW was quite picky about component selection for his products. The only design shortcoming I've seen in the early BGW products is the use of the cheaper MOLEX connectors as opposed the the gold plated variety.
01-12-2018, 11:48 AM
Rudy Kleimann

OK... but you need to re-read my post and keep in mind that you're not in a production company or service situation where you have to get the amp in and out of service and back on the road on the same day.

The long and the short of it is this: Less IS more... just get rid of the damn connectors in order to improve the reliability AND sound quality - and save yourself a ton of grief and work all in one Fell Swoop. :dead_horse: