Newbie here and I got a mess and in over my head. [resolved]

[rayjrop]

Hello,
        I had gotten all the resistance and voltage checks correct. I had some trouble with the white center pin on the rca jack, reheated it and was okay.
        Turned it on with my AQ Firefly Cobalt and while being careful with the volume (apparently not enough) it went full volume. This has been a problem with others and me in the past!
        I believe it did some damage:       
                                                            1}  White, left channel failed, no sound now-o ohms, reheat solder connection, it goes to 94K and when it cools it goes back to 0. I may have overheated the
                                                                  joint and hurt the volume pot?   
                                                            2}  All resistance checks are okay except 6U and 10U, they should be zero and both are now 2.4K ohms, sounds like it hurt the resisters or ...?

        I am thinking I need a new volume pot and....?
        Not fun. I hooked up everything correctly, but I do have a tendency to overheat the joints.
        Any help will be appreciated.

 

[Paul Birkeland]

Hello there,

Could you post your voltages on terminals 1-10?

Are you using a 1/4" to 1/8" adapter by chance? 

It is extremely unlikely that you need a new volume pot.  It's a lot more likely that there's a wiring or soldering issue in your kit.

-PB

 

[rayjrop]

Hello again,
                    Yes I am using a 1/8" to a 1/4"adapter as I am using the Sennheiser HD-600 as it is fitted with an 1/8" plug.
The voltages are within spec.
1) 88.7v
2) 167.8v
3) 0v
4) 167.0v
5) 96.0v
6) 0v
7) 108.3v
8) 0v
9) 113.6v
10) 0v
So I did have everything within spec and now after the incident I have 6U,10U and the left channel center pin are out of spec as stated above. Soo...if it was a wiring or soldering issue, why did it work before? Maybe something was weak and needs to be resoldered? I will recheck wiring and resolder the joints at the volume pot? What about the 2.4KOhm readings at terminal 6 and 10 that are supposed to be 0 ohms?
Thank you!

 

[Paul Birkeland]

6U and 10U will go back into spec if you unplug the 1/4" to 1/8" adapter.

When you say "it went full volume", does that mean that you had the Crack turned down and the amp played at full output on its own?  Was it in one or both channels? 

Something like this is most likely a solder joint issue usually. 

You said you had 0 ohms, now 94K, but I don't know what that is in reference to. Is this the center pin of the left RCA jack?

 

[rayjrop]

Nice to see the resistance of 6 and 10 go back to zero once I took the 1/4" x 1/8" adapter out!

I believe the crack was just under half volume and the laptop/dragonfly cobalt went to full volume, as it does sometimes.
I do believe both channels were working up to that point. the headphones were in my lap at the time as I was having dragonfly/laptop issues. I fixed that.

Yes, I did have 94K ohms on both left and right center pins. then I didn`t on the left center pin around the time of the incident.
So, I thought I would resolder the white wire that come from the center pin on the upper left lug off the volume pot.
I resoldered, and when it was still warm, I got the 94K back and as it cooled, I lost it back to zero ohms. I did this a few more times and same thing 94K back to zero as it cooled.
This makes me believe the pot may be damaged, possibly from too much heat from the soldering iron. I did burn the end of the white insulation a bit.
So, I resoldered both white wires on the top of the volume pot with no change in readings.
I checked the ohms on the top middle center lug. and as I turned the volume knob to max, it progressively turns from 0 to 94k at full volume, with 0 ohms on the top left tab. Does that tell you anything?

 

[Paul Birkeland]

Are you getting 0 or are you getting OL? Could you post some build photos? 

What resistance value do you get from terminal 3 to the outer upper and outer lower lugs on the volume pot?

 

[rayjrop]

Hi,
    I am getting 0L, open circuit on the left center rca jack.

Terminal #3 resistance to:
                                              the outer upper lug I am getting 0L, open circuit.
                                              the lower outer lug I am getting 95.2k ohms.
Here are some pics

 

[rayjrop]

2 more pics

 

[Paul Birkeland]

I would go ahead and replace the volume pot.

 

[rayjrop]

I can just desolder the joints, reattach using the same wires and resolder and should be good to go?
So, I apparently overheated the pot I take it.
Thank you for your time and patience. I really appreciate it.
Those instructions are top notch, best I have ever seen, ever.
I hope everything turns out okay, if not we will give it another whirl.
I will let you know.

 

[Paul Birkeland]

Yes, that will work.  It's not a matter of overheating necessarily, but rather that flux probably got in there and disrupted the connections.  Just be sure not to forget to put back the jumper between the ground lugs on each level.

 

[rayjrop]

Hello Mr. Birkeland,
                                  I thought why not try to clean the pot, what do I have to lose?
I unhooked the pot from the plate, but not the wires and sprayed some electrical cleaner in every open orifice there is, then some WD-40 and back to the cleaner.
No luck, did it a few more times, nope. then I resoldered the connection a couple more times and the resistance stabilized. YES!
After that, I uninstalled my Tidal and reinstalled it and got that right. I got it working nicely at 24bit 96000Hertz. 44100 not so good.
At first it seemed thin, harsh and bright, but after a few songs or so everything seemed to fall right into place.
To me it is dead quiet, well-balanced right to left, no buzz, no haze, musical, very impressive. Four and a half hours later I am still listening... this amp loves to sing!
Can't wait till tonight to listen again. Next is the power cord then the speedball, then a better dac and maybe HD800S, lol. The dragonfly cobalt is doing okay. Schilit dacs seem praised.
I think I did a great job on building it, I just got carried away on that one joint and put too much solder and flux on it and apparently flooded the pot with flux like you suggested.
Well, this is the first step in this great hobby!
Thank you, Paul!
Surely appreciate it.
Sorry to make this long, but I am just glad it worked out.