• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

2385 reconnect PS00 to P400 pin question

One probe on the top blue line, the other on the lower blue line. If i wiggle the post above the top blue line, i loose connection.
 

Attachments

  • PXL_20260831_203136623.jpg
    PXL_20260831_203136623.jpg
    109.6 KB · Views: 9
That connection from blue line to blue line is NOT on the carbon trace, it is on the wiper trace which is just a copper (brass) conductor. It may just be a feed through rivet to connect the trace to the post. You can just try to apply some flux and solder to that hole and where the hole mates with the trace and you should have a good connection. The CARBON (resistive) trace is the 1/2 black trace above it. When you move the slider the contact on the slider connects the soldid trace to the one above it. If you are on the half that has both traces as copper, then there is no attenuation (resistance). If you keep sliding it over, then you start to hit the resistive material and it effectively adds more resistance to the signal path. The other channel is just the opposite. If your slider is positioned to the right, then there is the most resistance on the other channel to attenuate the audio on that channel.

If the problem is the continuity between the two blue lines, then it should be a simple fix by adding some solder.

Apply solder here:
1788219713993.png
 
Last edited:
I used flux and filled the hole with solder, no change when i wiggle the post and use one probe on soldered hole and one probe just below it on the copper trace i loose contact. Meter drops and comes back
 

Attachments

  • PXL_20260901_000958129.jpg
    PXL_20260901_000958129.jpg
    86.5 KB · Views: 7
I think that you need to put some solder where the green circle is between the feed through and the copper trace. That should connect the circle feed through to the copper trace. You should be able to narrow down exactly where you lose conductivity using your meter and probes. That is where the solder is needed.
1788225544965.png
 
Last edited:
The blue line on the photo shows where i loose connection, it appears to be a break in the wiper trace. Is it possible for solder to stick to the trace?
 

Attachments

  • PXL_20260901_112914881.jpg
    PXL_20260901_112914881.jpg
    77.6 KB · Views: 7
That is either copper or brass so it should be solderable, but you need to clean it well first.
  1. First, clean both the trace and the feed through with 99% Isopropyl alcohol and a Q-tip
  2. Next, try to clean both with a pencil eraser and see if the oxidation is removed. If not use a extra fine piece of sandpaper. (careful not to scrub too hard).
  3. Clean again with alcohol & Q-tip
  4. Apply solder flux to both areas
  5. Heat the joint and apply a SMALL amount of solder and let it flow between the joint
  6. Test again with DMM
  7. If good, then clean again with alcohol and Q-tip
 
dankik said:
That is either copper or brass so it should be solderable, but you need to clean it well first.
  1. First, clean both the trace and the feed through with 99% Isopropyl alcohol and a Q-tip
  2. Next, try to clean both with a pencil eraser and see if the oxidation is removed. If not use a extra fine piece of sandpaper. (careful not to scrub too hard).
  3. Clean again with alcohol & Q-tip
  4. Apply solder flux to both areas
  5. Heat the joint and apply a SMALL amount of solder and let it flow between the joint
  6. Test again with DMM
  7. If good, then clean again with alcohol and Q-tip
Click to expand...
I cleaned the area with 99% alcohol, let it dry, then used a clean eraser rubbed untill not black anymore, re cleaned with 99% alcohol ..let dry added flux, heated down on copper trace. solder runs up to connector but doesnt stick to trace. Do i need more heat on copper trace?
 
sendust said:
Do i need more heat on copper trace?
Click to expand...
Maybe there is a coating on the copper trace. Try to sand it just enough to scuff it up a bit with very fine sandpaper, clean, then try again. Yes, you might need more heat.
 
dankik said:
Maybe there is a coating on the copper trace. Try to sand it just enough to scuff it up a bit with very fine sandpaper, clean, then try again. Yes, you might need more heat.
Click to expand...
I have 2000 grit paper. I'm using 360 c for Temp. Should l go higher?
 
2000 should be OK, just a few scrapes to remove any oxidation or maybe coating on the board. I typically use 350C so you are OK with 360C. If you have a broader soldering iron tip it might help get some heat on the board.
 
I tried a wider tip, scraped a bit with an exacto blade, sanded with 2000 grit, cleaned again with alcohol, dried and applied flux. heated just the copper trace, the hotter it got the more the solder runs up to the connector, nothing at all sticks to the trace.
As per in the photo, can i clean and sand where the circle is and try and install a very thin jumper wire to connector?
 

Attachments

  • PXL_20260901_201321628.jpg
    PXL_20260901_201321628.jpg
    103.4 KB · Views: 2
I wonder if it is aluminum? Maybe you can use some conductive epoxy?
What kind of solder are you using (60/40, 63/37 flux core...) hopefully not lead free?

1788294758764.png
 
So I can just clean and sand a little over the solid trace and use the syringe to apply a line to the connector from trace.
 
sendust said:
So I can just clean and sand a little over the solid trace and use the syringe to apply a line to the connector from trace.
Click to expand...
As far as I can tell, that's what it says to do. Then let it dry. Try not to get it too far down the trace so it won't interrupt the sliding piece.
 
Ive used the silver paste and am pretty sure this has solved my intermittent issue.
I will now put the unit back together and try to find with the scope where the left channel distortion originates.
Im not sure if there is a different way to set up the oscilloscope to see the distortion, as of now right and left look identical, is this possible it is a output transistor ?
 
Ages ago, I think that you performed a test where you connected an external audio source to the Main In L/R jacks and I think you said that that was OK.
You can also connect the Preamp L/R outputs to another amplifier and listen for the distortion to see if it is coming from the Preamp.
You don't need the scope for either of these tests. Also, to make sure it is not your speakers, connect the L output to the R speaker and R output to the L speaker.
 
I connected my 2385 to my 2275 using 2385 pre out and 2275 main in. I moved the speakers to the 2275 main, I played music through the aux of the 2385 and turned up volume.
I found no distortion on right or left channel.
 
From that test, it sounds like the 2385 Preamp is good and both of your speakers are good. Looks like your balance control repair worked.
Now you need to try the reverse, 2275 Pre-out to 2385 Main in.
 
dankik said:
From that test, it sounds like the 2385 Preamp is good and both of your speakers are good. Looks like your balance control repair worked.
Now you need to try the reverse, 2275 Pre-out to 2385 Main in.
Click to expand...
I reversed it , 2275 pre out to 2385 main in, 2275 aux for music, speakers on 2385 main. volume up on 2275 no distortion right or left
 
You must log in or register to reply here.
Back
Top Bottom