ADA Preamps > MB-1

MB-1 Problems

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WillIsAPill:
Greetings,

I hope someone can provide some guidance.

I have an MB-1 which I purchased in the early 90s and have been using regularly all this time.

About a month ago when I powered up the unit I am getting a very loud buzz from the device (around an A# if it matters).

Solid State only patches do not have the buzz. If I plug in XTR out and use the 'pre' setting no buzz, 'post' setting I get a buzz. Clearly somewhere in the circuit path for the tube stage there is a failure.

EDIT: It is possible to hear the bass tone under the hum, but faintly, if that helps.

I went ahead and replaced the tubes. Groove Tubes (russian) were all the had available at the local store.

Sadly, after replacing the tubes the buzz persists unchanged on any patch using the tubes.

It seems ADA is gone and I am at a loss at to how to further isolate this problem to a particular component (obviously with the sketchy hope of replacing it).

Can someone provide a more formal troubleshooting guide?
What is the chance of obtaining replacement electronics?

I should mention, this device is a key part of my 'sound' and has been tweaked beyond count over the decades. Losing the device is going to devastating. I am in the middle or recording some parts which were started with the MB-1 in the chain. In short, I am screwed right now. Any help would be appreciated.

Thanks

MarshallJMP:
Hey

Seems like a busted cap in the high voltage power supply.Do you have some soldering skills?

Take a pic of the inside of your MB-1 and mail it to me.This way i can tell you what you need to replace.

rnolan:
Hey Will, MJMP will no doubt get you sorted  :thumb-up: so don't despair. I feel the same about my MP2 (so I've bought 2 more). One mod you might consider (as is really worth while) is a MDRT (Machinator Designed Replacement Transformer) MJMP got some new stock recently but they'll go fast I suspect as lots of MP1 users were wanting one (http://www.marshalljmpmodshop.net/miscellaneous_parts_and_replacement_tubes.htm).

WillIsAPill:
Hi, thank you so much for the reply.  Sorry for the delay in replying, had some issues come up.

Here is a link to the board for my MB-1. If not clear I can take more of course.

http://postimg.org/image/8tamjkzwb/

I have not touched a soldering gun in 35 years, however, it is theoretically possible that I could perform a soldering operation depending on the difficulty.

Any help is greatly appreciated.

EDIT: Fixed link.

rnolan:
Hey Will, here to help if we can  :thumb-up: . MJMP and others will know better but looked to me like the CAP very top left didn't look happy ?

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