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Escape Pod
Joined: Jan 15, 2017 Posts: 6 Location: Oregon
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Fri Nov 17, 2017 12:25 am Post subject:
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According to this diagram, if you measure between the neg. battery connection BN and the input pin 3 of U2 (the LM87L05) you should measure about 9volts (the full battery voltage).
If you measure from the virtual ground (between R65 and R66) you should measure around 4.5 volts at pin 3 of U2 and 0 volts at pin 2 of U2 (the GND pin)
So when you measure 4.5 volts at the GND pin of U2 than I guess you have a bad connection between pin 2 of U2 and the virtual ground connection between R65 and R66.
But to be sure you have to write from where your voltages are measured. _________________ my synth |
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Escape Pod
Joined: Jan 15, 2017 Posts: 6 Location: Oregon
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Posted: Fri Nov 17, 2017 10:21 pm Post subject:
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Thank you, Grumble I will measure those voltages and report back my findings.
Much appreciated |
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Escape Pod
Joined: Jan 15, 2017 Posts: 6 Location: Oregon
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Mon Nov 20, 2017 5:03 am Post subject:
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There is (or should be) NO connection between the GND pin of the LM78L05 and the virtual ground. _________________ my synth |
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Escape Pod
Joined: Jan 15, 2017 Posts: 6 Location: Oregon
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Posted: Mon Nov 20, 2017 8:10 pm Post subject:
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Hi, so I do have -4.5 volt between ground pin of LM78L05 so pin 2 is shorting to the virtual ground. so I reflowed the solder connections and checked the continuity and wiring. The rest of the unit functions as demonstrated on the you tube video which is really frustrating but at least I have that.So what and or where would be the next place for me to look for this bad connection. Any input or advice would be great.
As always Thank You |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Tue Nov 21, 2017 1:58 am Post subject:
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I'm sorry if I sound picky, but if you mention a voltage you have measured: always add the points you have measured the voltage between!
Quote: | I do have -4.5 volt between ground pin of LM78L05 so pin 2 is shorting to the virtual ground. |
See my problem? I have no idea where you measured this -4.5 volt...
good examples:
I measured x volt over Rn.
I measured x volt at pin n of IC u referred to GND. _________________ my synth |
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Escape Pod
Joined: Jan 15, 2017 Posts: 6 Location: Oregon
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Posted: Tue Nov 21, 2017 2:30 pm Post subject:
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Understood I will try to be more clear. I measured -4.5 v between r64 and r65 the virtual ground and pin 2 of the 78L05 if there should be no connection between pin 2 of 78L05 and virtual ground where should I look for that connection in your opinion. You have been a big help in this and I thank you |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Wed Nov 22, 2017 12:36 am Post subject:
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That is correct! since pin2 of the LM78L05 (U2) is connected to BN (that will be the - of the battery) and R64 and R65 divide the battery voltage in half.
The PT2399 "needs" a stable voltage for best performance, and that's why there is a LM78L05 to achieve just this.
So you should measure 5 volt between the neg. battery pin (BN) and pin 1 of the PT2399 (U3). If you do, the LM78L05 is connected correctly and working. _________________ my synth |
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Escape Pod
Joined: Jan 15, 2017 Posts: 6 Location: Oregon
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Posted: Sat Nov 25, 2017 10:03 pm Post subject:
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Thank you I checked it And there is 5 volt between neg bat pin and pin 1 of 78L05 so the problem lies elsewhere in the circuit. The search continues.
Thank you for helping me resolve this part of my problem I do appreciate it. |
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Dr. G.
Joined: Dec 06, 2017 Posts: 6 Location: Luxembourg
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Posted: Tue Dec 12, 2017 12:29 am Post subject:
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HI, Grumble, Escape Pod,
Your discussion of voltages/resistance from Rn to Ground is exactly why I am trying to get similar information for my non-functional noise toaster.
Hope you don't mind my hijacking your thread, but it would be really really helpful if you could share with me measured resistance from board points BN to GND, and also board point BP to GND. That is, if you happen to have a noise toaster lying around.
Many thanks,
+glenn |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Tue Dec 12, 2017 1:30 am Post subject:
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I don't have a Noise Toaster, I just made THIS _________________ my synth |
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Dr. G.
Joined: Dec 06, 2017 Posts: 6 Location: Luxembourg
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Posted: Tue Dec 12, 2017 2:35 am Post subject:
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looks really cool! |
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