AKG BX 20 problems

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First post! I found this thread doing a Google search, I believe this may the largest collection of AKG reverb users in one  forum. I have a recently acquired BX20E and it seems to work as expected, other than a bad amp card that causes the system to oscillate at high decay times. If I swap the cards, the problem travels with the card. Should be a straightforward project. The tanks seem to work as expected, and each have a wonderful sound, however they do sound notably different from each other. Is this normal? I can's seem to find info on that detail. After reading this thread, I of course wondered if the difference could be a bad coil, but the descriptions I see here are of an obvious failure where a single echo is heard. Can anyone shed light on this?

About the coil recreation discussion.  I wonder if Dan Kennedy would be interested in taking on this engineering project?
 
Got another one here that needs one replacement coil. If it ever happens i'm in for a replacement or more than one to have spares.
 
I quote myself again:

gyraf said:
We'll need some more info to get going:

- Good in-scale close-up pics of the coils for mechanics.
- Measurements on a known-good coil: Free-air inductance and DC resistance for the two windings.
- Measurements from any coil: Individual coil length, width, outer and inner diameter. If possible, an estimate of wire size.

Jakob E.
Click to expand...

...once we have this information, there is a chance of remaking the coils..
 
Here's what I can offer -

I've got a bad coil here as well as a currently open tank.  I'm willing to do the necessary measurements and also sacrifice this bad coil.

I've got between 184 and 209 ohms DC on any of these coils.  If anyone can seriously clone them I'm happy to donate this bad coil to the cause.

-Tim
 
Some interesting documents I got from AKG.    Unfortunately no winding information for the coils but interesting nonetheless.

Also, since these documents are in German, I've attached a translation cheat-sheet created by our own DerEber.

Regards,

MR

PS - looks like one attachment per post?  You'll be seeing a couple more posts from me then...
 

Attachments

  • 3714_001.pdf
    103 KB · Views: 70
Hey Yammer (and anyone else that may be able to help me out),

Just wondering if you were able to figure out why your channels sound different. I have a BX20 and channel 2 is a lot darker and also emits some static intermittently. I've swapped cards and the problem stays with channel 2. I plan on recapping the unit. So far I've only replaced the two caps in the power supply. The coils measure ok on the multi-pin connector. Is there something else I should look at?

Thanks for your time.

Trevor

yammer said:
First post! I found this thread doing a Google search, I believe this may the largest collection of AKG reverb users in one  forum. I have a recently acquired BX20E and it seems to work as expected, other than a bad amp card that causes the system to oscillate at high decay times. If I swap the cards, the problem travels with the card. Should be a straightforward project. The tanks seem to work as expected, and each have a wonderful sound, however they do sound notably different from each other. Is this normal? I can's seem to find info on that detail. After reading this thread, I of course wondered if the difference could be a bad coil, but the descriptions I see here are of an obvious failure where a single echo is heard. Can anyone shed light on this?

About the coil recreation discussion.  I wonder if Dan Kennedy would be interested in taking on this engineering project?
Click to expand...
 
Hello first time poster here with a 'mono' BX 20 also...

My tech took things apart and has all of the necessary measurements of the coil etc - we just need somebody with the skills to build it!

I know I and many others would be prepared to pay fairly extortionate prices to get our beloved reverbs back up and running!
 
Another AKG BX20 echo... umm *ahem* REVERB unit owner.

In need of coil. Someone wind some! Or maybe group DIY should group buy a known working bx20 and split the cost of parting out the coils.  8)
 
Hey,
Nice community of broken coil people ;)
I'm about to buy a bx20 with an unknown condition! The owner offer fairly cheap price without testing it. I hope it's in working condition!
First, what do you recommend for transporting it?shoud I open and foam it?
Second, Is it possible to check the coils without opening the capsule? I can take my multimeter there...

looking forward for the coils group buy...
 
Hi Aref,
You can measure the coils resistance on the connector of the springs tank.
The values are around  +/- 200 ohms each.
This is clearly explained in the service manual...  :)
Best,
Guy
 
Development (since years) is still in progress, but I'm proud to show first results.
BX20_coils.JPG

BX_20_coils_springs.jpeg



My BX 20 got wrapped from spiders but the first listening tests are phenomenal.
BX20_SpiderWeb.JPG

I'll keep you updated
 

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