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Orange Crush 12 repair

Started by flester, March 26, 2018, 06:10:15 PM

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flester

I did break the earth connection to chassis as shown in this photo but am fairly sure the issue was there before that

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flester

Picture now attached

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flester

I'm having another go at this as I have a bit of time on my hands. I didn't do anything with the opamp but replaced the gain and overdrive pots and repaired some broken pcb traces. I'm left with the following issues.
1. At low levels, with overdrive at zero, a. Pretty good clean signal with a lot of hiss via internal speaker.
b. Signal disconnects intermittently.

3. At higher levels, signal sort of drops out as the note fades l. Sound clip below
https://drive.google.com/file/d/1k-Kf7-oBOZkOzntB7SPu0VswwtfftZrZ/view?usp=drivesdk

Any ideas? I can show bits of my schematic if I can get it finished

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flester

Correction:.
1.At low levels, with overdrive at zero, a. Pretty good clean signal with a lot of hiss via internal speaker.
b. Signal disconnects intermittently when using headphones

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joecool85

Quote from: flester on May 13, 2020, 06:12:18 AM
Correction:.
1.At low levels, with overdrive at zero, a. Pretty good clean signal with a lot of hiss via internal speaker.
b. Signal disconnects intermittently when using headphones

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Sounds like an intermittent ground issue.  Go over any solders/connections that go to ground.  Also, sometimes speaker outputs etc don't go direct to ground but rather pass through a 0.1 ohm resistor or similar.  If this is the case, you can cause issues by sending it straight to chassis with an uninsulated jack.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

flester

Thanks. I will try those checks.

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phatt

If it crackles when you wiggle the the Hphone plug then check for cracked solder pads on the PCB at the Hphone socket terminals.
Phil.

flester

No crackles when I wiggle any of the pots or jacks.
Joe, your mention of ground connections focused me. I think I soldered the overdrive pot, middle leg incorrectly to ground. See before and after photos below. What do you think?


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joecool85

Quote from: flester on May 13, 2020, 12:23:04 PM
No crackles when I wiggle any of the pots or jacks.
Joe, your mention of ground connections focused me. I think I soldered the overdrive pot, middle leg incorrectly to ground. See before and after photos below. What do you think?


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Kinda rough soldering job on a few joints there.  I would suggest reheating any joints that don't look clean.  Are you using lead free solder?  If so, turn your heat up.  If not, you still may be running too cold, but just don't turn it up quite as high.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

flester

You're right about cleaning up my soldering. Yes, its lead-free solder. And I will continue checking the ground connections.

joecool85

Quote from: flester on May 14, 2020, 04:44:40 AM
You're right about cleaning up my soldering. Yes, its lead-free solder. And I will continue checking the ground connections.

Honestly, I would consider purchasing some leaded solder.  It makes repairs like this WAY easier.  Just wash your hands when done, and no licking the solder.   :dbtu:
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com

flester

Thanks for the tip. I now have some lead solder and it is indeed easier to use.

I decided to use wire links instead of repairing the broken traces and have good connections now. I am left with 2 issues, which I can live with but would be nice to fix if possible. One is that there's still quite a lot of hiss.  Also the overdrive still goes crazy from about half way up, after which I get a very loud low frequency buzz.  While half way is more than enough overdrive for me most of the time,  theres obviously still something wrong.
The pot is new, works smoothly as measures correctly (250K linear). All pots have been cleaned with contact cleaner. Could this point to the opamp or the clipping diodes?

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joecool85

Quote from: flester on May 15, 2020, 02:22:10 PM
Thanks for the tip. I now have some lead solder and it is indeed easier to use.

I decided to use wire links instead of repairing the broken traces and have good connections now. I am left with 2 issues, which I can live with but would be nice to fix if possible. One is that there's still quite a lot of hiss.  Also the overdrive still goes crazy from about half way up, after which I get a very loud low frequency buzz.  While half way is more than enough overdrive for me most of the time,  theres obviously still something wrong.
The pot is new, works smoothly as measures correctly (250K linear). All pots have been cleaned with contact cleaner. Could this point to the opamp or the clipping diodes?

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Sounds like poor grounding to me.  Alternatively, possibly a short between traces as this can cause the gain issue you are having.
Life is what you make it.
Still rockin' the Dean Markley K-20X
thatraymond.com