help! troubleshoot eros

[redneckdent]

Eros has been assembled.  Resistances check, but when I plug in, the frontmost two LEDs on the A channel do not light, and I get 225V instead of 170V at OA pad on A channel.  I have double and triple checked to no avail.  Would reversing leads on the resistor from C1 to T9 do this?  Any suggestions?  Thanks!

[Paul Joppa]

Check R2A (120K 2W) and the orientation of the two LEDs on the "A" side board. It seems likely that either the LEDs are not getting power (one end is grounded through the 120K R2A) or the LEDs are shorted - look for solder bridges as well.

Trust me, a good magnifying glass and bright light - and lots of time - are essential tools for debugging a PC board.  :^)

[redneckdent]

Reversed LED as suspected.  Thank you Paul.

[Paul Joppa]

Those LEDs are a pain - very hard to see the stripe! If we could find anything else as good for the task we'd dump them in a minute.

[redneckdent]

It's not like you didn't point out very clearly in bold type that directionality on those things was the number one troubleshooting problem.  I should've paid better attention!  Sounds quite nice though...  dropped in some teflon Vcaps (0.47uF) and just about to get em really good and broken in.  I even threw on my wood bodied Denon 103R cart that only outputs .25mV.  I had to jack up the gain on my preamp to 12dB from 0dB, so there's so a slight bit more noise for sure, but damn it sounds good! 

[Grainger49]

PJ, I'm looking forward to the purchase of an Eros.  Might I use a Sharpie to black the "silver end lead" near the body of these when unpacking?  That way I don't have to use the big magnifier when I am assembling?  My only worry is the Sharpie ink might affect the soldering.

[Paul Joppa]

It would surprise me if the ink affected the solder, but I've been surprised before and expect to be again ...  :^)

Try it and find out. You can always get Eileen to send out some more LEDs, or buy a bunch from Mouser and have them on hand.