resilient said:Ok, editing this thing for updates.
I have signal! But it's low except in the highest position. And it seems to be correct in that position... wide open and distorted (the distortion actually sounds kind of nice!).
I have reflowed all input control solder joints, including those on the Grayhill board. Any thoughts on what might cause this low output until I get to the last setting?
JOHN5 said:Hi Mike -
I have two Copper units that I'm having some trouble with. Here's where I'm at:
Unit #1 -
-No sound except for a significant humming - - I'd describe it as a ground-related noise due to its regularity and constant presence regardless of whether an input is present (mic or DI).
-I checked resistivity w/ no op amp against my working unit (#2 - - see below) All readings check out the same. I have a spreadsheet of the readings I can send to you
-I swapped op amps with my working unit. Both my op amps work in unit #2
Unit #2 -
-Works and sounds great except for the same humming as unit #1
-I've controlled for my 500 series rack slot: I swapped another piece of 500 series gear (capi VP312DI) into the slots I had used for the hairball units. No humming from the Capi unit when using same cabling and microphones for testing as the hairball unit.
I've double-checked component placement on each and am not sure where to go next. Any thoughts?
dp said:Copper build update:
I got all the missing parts issues sorted out. I was missing the relay and its transistor and the 12k7 resistor in one of the Grayhill pots. Hairball got the transistor and relay shipped out quickly... thanks for that. The resistor I didn't discover until I was putting the Grayhill assembly together. I was easily able to put a couple resistors from my 1/2-watt MF set I use for my tube amps in series to get exactly 12k7. A little large but because of where it is on the board I was able to fit it in with no trouble.
Finished the build tonight and it works great straight-away... man that's a good feeling, isn't it?
This thing sounds fantastic. I re-tracked some vocals and was A/B'ing against some stuff I recently did with my modded-NT2 and the DIYRE CP5 with the Royal Blue colour module. They both sound really good, The CP5/Blue have a lot of high-end sparkle and some heft to it. Very clear and present. The Copper has the low-end and mid-range power you would expect from a "Neve" sound. Driven hard of course it will distort in a pleasing way. Set "on the edge" it sounds really good to my ears - the sweet spot. This thing is going to get used a lot. Have not tried the DI yet.
cmac said:I have six copper Preamps all built by myself and have not had any problems until now. I can't say how old the unit that went bad is, because I have chipped away at building these two at time over the last several years. Its has to be at least a year old, and I do use them quite often for tracking drums. Anyway, I opened up the bad Preamp unit, and it was instantly obvious what the problem was! (figured I was going to have to hit the test points to narrow down the issue) Capacitor C505 has blown its top. I will attach a picture, I think that C506 just got some gunk on it when C505 exploded, but it may be worth replacing both. The 48V light on the front still works when plugged into my lunchbox, but the unit did not pass any audio. Which now is obviously due to the cap exploding.
- I have six of these, this is the only unit that this has happened to, is it something that I did? Because I want to take care not to damage my other Copper Preamps!
- I will probably replace both C505 and C506 Caps, should I be concerned about further damage to any of the other components due to this failure?
As always, appreciate the insight!
Hairball Audio said:I would just replace those caps and see what happens. Make sure you have the polarity correct. The cap either exploded because of a 1) freak internal failure, or 2) or some crazy voltages around it that shouldn't be there.
I'd assume #1 one for now and replace and see what you get.
cmac said:I have ordered replacement Caps for C505 and C506. I really think that will do the trick but will post back the results! Sounds like an odd thing that occurred. Thanks for the quick reply.
cmac said:I received my replacement Caps for C505 and C506. I noticed instantly they appeared slightly smaller. When I removed the damaged caps from the PCB I see they are rated at 470uF/16V 105 celsius rated. The caps I ordered and Received are 470uF/16V 085 celsius rated. Its always something! I referenced the BOM to order the caps, and had not yet removed the old caps to notice the 105 C rating. Is this a problem? I can get the higher C rated ones if its necessary. Thanks much.
Hairball Audio said:Those should be totally fine.
cmac said:I replaced the caps for C505 and C506, the 48V light will light up, which tells me it is getting power. Still no signal will pass.. Any further thoughts? I am willing to hit the test points and report back. Thanks much.