Orban 111b Spring Reverb - Low level and distortion

Hi,

A while ago I bought an Orban 111b off ebay. It was sold as working, but alas it does not.

The left side has a relatively low level and distorts and breaks up slightly when fed signal. The right side is worse. The output is extremely low and can only be heard when cranked up. The right side also distorts severely and the input signal can barely be heard over the distortion.

From what I have managed to research I think it could be the lm381an IC or the limiter module, however as one side is worse I suppose it may be something else!?!

From my understanding these are pretty decent units, so I would love to try it out properly! If anyone has any ideas or input it would be greatly received.

Thanks

I don't know their reverbs but I've worked on one of the compressors. It was nicely made and easy to service.

One idea - I'd check for old electrolytic caps in the signal path. Dried out electros sound horrible.

Manual is on the orban website with schematics..

Thanks for the replies. I have changed four electrolytic caps all of which were in the EQ signal chain I believe. It has not changed anything.

I have the manual and schematics but am rather new the wonderful world of DIY and repairs so do not really know how to track down the fault.

Even without a signal going in, the output distorts if I hit the springs.

"Even without a signal going in, the output distorts if I hit the springs."

means you have a problem with the output stage, there's three caps per channel to suspect here C145, C116 & C125 for the left and C146, C115 & C124 for the right...
If you have access to a scope (even a free soundcard based software) you may try to watch the signal before and after those caps... If not, change them since they are cheap, and see how it works... As you're there you can also change the input caps: C101 & 102 and C103 & 104

Looking to the schemo I can't say if C101, 102, 124, & 125 are litycs, bipolar or other type... check them anyways...

Axel

Thanks Axel. I changed C301, C302, C303 and C304, but I'll have a look and see if I have any suitable replacements for the ones you mentioned and give it a whirl!

Looking at http://www.waltzingbear.com/Schematics/Orban/111B.htm

C117 and 118 are also electrolytics in the signal chain, although the numbers are a bit blurry on my screen.

Of course, it could be sick / misbiased transistor, but go for the easy stuff first. It'll benefit from recapping anyway.

also , check you pots

Thanks again for everyones input. I'm going to order a few caps as there are some I do not have and I guess you're right that it will benefit from recapping either way. I'm pretty sure the pots are fine. The volume, tone etc do change when they are turned. When I've changed the caps I'll give you an update. Cheers.

[quote author="heelis"]... but am rather new the wonderful world of DIY and repairs[/quote]

You probably know this, but you (normally) only need to swap the electrolytics. Worth saying it before you get your wallet out. :wink:

[quote author="zebra50"]Looking at http://www.waltzingbear.com/Schematics/Orban/111B.htm

C117 and 118 are also electrolytics in the signal chain, although the numbers are a bit blurry on my screen.[/quote]

C117 & C118 are indeed the ones I miss spelled as C116 &115... It was late, and numbers were a lot blurry!

To make it clear, let's say that we're talking about the cap between the spring's output and the positive input of the opamp (can't even read its part number!)

Axel