Anyone have an idea what this is - Page 1
Forum section: electronics / general

author: Anks
author_rank: Frequent Contributor
timestamp: January 08, 2014, 02:55:03 pm
content: This is the pcb out of one side of a EXR exciter made for audio use. It has this massive green thing on the pcb with a footprint the same as a dip package. I was assuming it was a line balancing transformer but the unit only as unbalanced out so I'm confused. Ive look around for the schematics but not found anything in the usual places. Ive been asked to add xlr output to the unit instead of terminal block connections so would be nice if I could get it to be balanced but would like to know more out of interest.

author: IntegratedValve
author_rank: Regular Contributor
timestamp: January 08, 2014, 03:28:17 pm
content: Probably on-board power plant. LOLInside this cover could be a fuse, relay, a coupling transformer...looking at the pins on the other side may help.

author: Anks
author_rank: Frequent Contributor
timestamp: January 08, 2014, 03:35:09 pm
content: its not the power transformer i was thinking maybe coupling transformer but then it would normally be balanced out.

author: Kjelt
author_rank: Super Contributor
timestamp: January 08, 2014, 03:44:18 pm
content: Could be a lot of things, you need to reverse engineer it, measuring voltages on all the pins, looking with a scope etc.Could be a very well shielded opampnever seen it before.

author: Anks
author_rank: Frequent Contributor
timestamp: January 08, 2014, 03:59:32 pm
content: no time to reverse it its going back in the next hour. I was just curious.

author: Rufus
author_rank: Super Contributor
timestamp: January 08, 2014, 04:15:49 pm
content: It doesn't look like any kind of sensible component and I can't see much reason for encapsulating a bit of circuit in a big ugly plastic or rubber blob other than to make reverse engineering and copying harder.Looks like it was potted in an ice cube mould - lol.

author: BravoV
author_rank: Super Contributor
timestamp: January 08, 2014, 04:32:56 pm
content: Looks like a cheap method to secure against tampering or reverse engineering using epoxy potted keyboard cap.

author: Anks
author_rank: Frequent Contributor
timestamp: January 08, 2014, 04:43:12 pm
content: Well these things were considered the holy grail back when they were used. Most albums from the 80's used one

author: Stonent
author_rank: Super Contributor
timestamp: January 08, 2014, 05:12:56 pm
content: A trapezoid.

author: Falcon69
author_rank: Super Contributor
timestamp: January 08, 2014, 05:15:07 pm
content: hmm, looks like a blue petrified ice cube to me.

author: SeanB
author_rank: Super Contributor
timestamp: January 08, 2014, 05:31:07 pm
content: Did a quick google and so far as I can see the special sauce inside the cube is likely a few diodes and some capacitors to make HF distortion and then add it to the signal to "brighten" it by adding high order distortion to it. Likely there is a single opamp and a pair of clipping diodes on the inside, along with some low value capacitors to do a high pass filter, this beeing mixed with the input. This is likely as there are power rails to the blob, and a set of outputs to each amplification stage.

author: Kjelt
author_rank: Super Contributor
timestamp: January 08, 2014, 05:49:48 pm
content: Quote from: SeanB on January 08, 2014, 05:31:07 pm

author: Anks
author_rank: Frequent Contributor
timestamp: January 08, 2014, 06:05:13 pm
content: Quote from: SeanB on January 08, 2014, 05:31:07 pmPretty much what I thought but that's a bit OTT just to hide that.

author: SeanB
author_rank: Super Contributor
timestamp: January 08, 2014, 06:10:54 pm
content: Thank you Kjelt, I will be here all week.Except tomorrow, as the municipality has in it's infinite wisdom scheduled a whole day power cut. UPS batteries are not that good. Might use a generator, or go out a bit.Anks, they had a very strange idea that putting it in a blob prevented anybody from finding out what it was. They obviously never heard that you can buy epoxy remover ( also known as the worst horrible paint stripper) down at the nearest hardware store.

author: Kjelt
author_rank: Super Contributor
timestamp: January 09, 2014, 07:29:23 am
content: Indeed this won't stop the pro's but what does? The only thing you can do is patent it (even while half the world does not recognize it and goes it own way).At least this construction has made us laugh.

author: Rerouter
author_rank: Super Contributor
timestamp: January 09, 2014, 07:48:00 am
content: though arguably seeing something like that on a circuit when we open it up to repair it would drive most us to figure out what the hell it is, being so odd and obvious :/ which is why it was epoxied in the first place