RAD SSL 4K E-Series Channel Repair

[dapolk]

Hi,

I recently purchased a pair of Rhoades Audio Design SSL 4k E-Series Channel strips w/ 18V PSU off Ebay.

Patched them in and one of the units didn't pass any audio, neither Line nor Mic In. I heard something loose inside and opened it up, turns out the Channel Amplifiers Card (CF82E241) was totally disconnected from the edge connector that links it to the PSU and rest of circuit! The card has a screw hole going to the case...no screw in sight.

I was shocked but then relieved to think I had an easy fix - plugged the card back into the edge connector and powered everything on again...but the unit started smoking so I immediately powered down.

I've built a few pieces of gear and am comfortable doing that, but am not knowledgable enough to know how to go about troubleshooting this. I was wondering if just one component got fried, and if there was an easy enough way to identify it and replace it cheaply. I want to say the bit of smoke came out of the area around the right-side of the amplifier card. Having inspected the cards, I don't see any components that look damaged to me.

Would very much appreciate any help in figuring out where to look, or ideas of what exactly might've happened in the circuit.

 

[dapolk]

more pics

 

[dapolk]

pic of full unit

 

[scott2000]

...Lot of stuff going on in there.....

I'd probably start with the power supply....make sure nothing funky is happening there.....

I guess there is a schematic for this somewhere???


What's up with those marble charred colored boards??? Is that some kind of funny design feature??? I hope....

 

[radardoug]

Do the sockets have the proper keying for the boards? Maybe you got the board in the wrong place.

 

[Walrus]

Looking at the picture, bottom right hand corner of 241 card, looks very much like the 22 Ohm resistor R14 is burnt.
This means a short on the positive rail somewhere(IC, capacitor), or as Radardoug says, the board was not correctly keyed when inserted.

 

[dapolk]

Hi all,

Thanks a lot for the help. The card only snaps into the socket when aligned properly, there's a spacer at a point along the edge that guides it. I can't force it another way.

I found a schematic for the 82E01 Input Amp Card - looks mostly identical
http://www.tenmilecreek.net/images/SSL/ssl_82E01.pdf

R14 and R15, both 22R on the +/- rails, read 32R and 28R.

I took some isopropyl alcohol to R14 and took another pic - definitely looks a bit toasted, but would the reading be much different if that were the case?

 

[Walrus]

The resistors have Gold bands for tolerance, so 5%. If R14 is reading 32 Ohms then it is definitely toasted!
Even the other at 28 Ohms is well outside spec and probably a bit burnt.

If the card is seating correctly in the edge connector, then as I said, the most likely cause would be an IC or capacitor.
You could try removing all the IC's from their sockets on that card and then powering on again. If no smoke, then that would confirm an IC failure.  If still smoking, it's probably a capacitor. Then it's just a case of narrowing down to which IC/capacitor.