Last yr my Orange failed and my local amp guy fixed it by replacing an Opamp chip soldered directly to the board. Now its gone again and I think I can fix it myself Is there any reason not to use an 8 pin socket instead for easy replacement of the chip? Theres only one 8 pin chip that I can see (https://uploads.tapatalk-cdn.com/20180326/fe7a1746b9b1676ca5b2ad689e0d712f.jpg)
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Sure you can socket the ic.
First off, I would prove that the ic is bad.
Quote from: Jazz P Bass on March 27, 2018, 01:01:03 AM
Sure you can socket the ic.
First off, I would prove that the ic is bad.
Yes that is the first step. If it is to be replaced, what are pros and cons to using a socket rather than soldering chip to board?
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Quote from: flester on April 08, 2018, 07:20:18 AM
Quote from: Jazz P Bass on March 27, 2018, 01:01:03 AM
Sure you can socket the ic.
First off, I would prove that the ic is bad.
Yes that is the first step. If it is to be replaced, what are pros and cons to using a socket rather than soldering chip to board?
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Sorry I see you answered that already.
Any tips on how I would see if the ic is bad or not. Or should I seek professional help?
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You really need to find out why it is failing. If you replace it odds are that it will fail again.. Op amps don't just fail for no reason!
It was never stated exactly what is wrong with amp.
"Doesn't work" does not lead to the opamp.
Quote from: Jazz P Bass on April 08, 2018, 11:54:59 AM
It was never stated exactly what is wrong with amp.
"Doesn't work" does not lead to the opamp.
Fair points. I think I will go back to the previous repair and not mess with it myself
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If it failed once and it fails again following the same scheme:
A lot of ancient/recent FX/boutique amp designs use an unprotected TL072 or similar as input stage.
Often the poor input transistor gate is hard-tied to the phone tip without any protection. Suggestion: Insert a series resistor of 4k7 or 10k between Tip and OpAmp, connect two antiserial Zener diodes 2,7V from OpAmp input to GND.
From now on spikes or DC thumps from connecting DC ring-switched active basses/guitars are swallowed by resistor and zener. The gate junction stays alive a bit longer. And once somebody starts to unsolder an OpAmp: A socket is always handy.
One fine day you may want to swap a TL052 in. Or what ever crosses your mind...
Had another look at this. The signal comes and goes when I move the Overdrive and or Gain knobs. I assume this could be an issue with pots or with whatever they are controlling? No schematic but I could almost draw one. See video here https://flic.kr/p/HX8P4L
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I didn't have any luck with the video, but from the sound of your description, those pots might just need to be cleaned.
Quote from: g1 on April 13, 2018, 02:10:03 PM
I didn't have any luck with the video, but from the sound of your description, those pots might just need to be cleaned.
Yes hopefully that might be all it needs. Surprising how simple the circuit seems by the way. TDA2030 at the heart of ir. Should I be discharching caps before working on it or is that just for tube amps?
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You dont need to worry about discharging caps as voltage across them not large enough to be a hazard in small SS amps. Just make sure amp is unplugged when you delve inside. To clean pots, get hold of some contact cleaner spray (Servisol or similar - not WD-40!) Fit the small tube (looks like a straw) into the nozzle and spray for a second or two inside the pots. There should be a small vent hole in the body of the pots into which you poke the tube and spray. Give the jack sockets a blast while you are at it. This is best done by inserting a jack plug to open the spring contacts before spraying. Good luck.
Quote from: solderer25 on April 14, 2018, 02:51:59 PM
You dont need to worry about discharging caps as voltage across them not large enough to be a hazard in small SS amps. Just make sure amp is unplugged when you delve inside. To clean pots, get hold of some contact cleaner spray (Servisol or similar - not WD-40!) Fit the small tube (looks like a straw) into the nozzle and spray for a second or two inside the pots. There should be a small vent hole in the body of the pots into which you poke the tube and spray. Give the jack sockets a blast while you are at it. This is best done by inserting a jack plug to open the spring contacts before spraying. Good luck.
Overdrive pot needs replacement for sure. It is marked B250k but I believe B can be linear or log depending on market? All the pots (gain, overdrive, volume, low, mid, high) are B which guess means probably log?
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If the control is marked 'B250K', then it is a linear 250K control.
Quote from: wetty on April 11, 2018, 02:25:56 PM
If it failed once and it fails again following the same scheme:
A lot of ancient/recent FX/boutique amp designs use an unprotected TL072 or similar as input stage.
Often the poor input transistor gate is hard-tied to the phone tip without any protection. Suggestion: Insert a series resistor of 4k7 or 10k between Tip and OpAmp, connect two antiserial Zener diodes 2,7V from OpAmp input to GND.
From now on spikes or DC thumps from connecting DC ring-switched active basses/guitars are swallowed by resistor and zener. The gate junction stays alive a bit longer. And once somebody starts to unsolder an OpAmp: A socket is always handy.
One fine day you may want to swap a TL052 in. Or what ever crosses your mind...
I replaced the Overdrive plot and broke the pcb traces in the process. I then replaced the broken trace with a wire link (connected to R7 as shown). When I ove the pot slightly I get either a weak output with a missing sound, or a loud bassy buzz, or a proper overdrive sound. All connections to the pot seem sound. Could there be an issue somewhere other than the pot?(https://uploads.tapatalk-cdn.com/20180803/0edfd130aa79a1838d622f37d3a26270.jpg)
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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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Picture now attached(https://uploads.tapatalk-cdn.com/20180803/c8ae4f5f30c6f261f0b931a50242f288.jpg)
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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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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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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.
Thanks. I will try those checks.
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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.
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?
(https://uploads.tapatalk-cdn.com/20200513/1645e605443e1651c3626fd6e05c91cc.jpg)(https://uploads.tapatalk-cdn.com/20200513/56a07e89e65a73f675fff1fa240909f6.jpg)
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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?
(https://uploads.tapatalk-cdn.com/20200513/1645e605443e1651c3626fd6e05c91cc.jpg)(https://uploads.tapatalk-cdn.com/20200513/56a07e89e65a73f675fff1fa240909f6.jpg)
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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.
You're right about cleaning up my soldering. Yes, its lead-free solder. And I will continue checking the ground connections.
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:
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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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.