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 Forum index » DIY Hardware and Software » MusicFromOuterSpace.com designs by Ray Wilson
Echo Rocket problem
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Escape Pod



Joined: Jan 15, 2017
Posts: 6
Location: Oregon

PostPosted: Thu Nov 16, 2017 10:56 pm    Post subject: Echo Rocket problem
Subject description: 78L05 not regulating
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Hi All,
I'm having trouble with a newly finished MFOS Echo Rocket. I'm hoping someone here who can shed a little light on this as I am stumped. The problem is there is no echo at all I've check and double checked the wiring and component values when checking the voltage points I found 4.3 volts at the 78L05 input pin and 4.3 volts at the ground pin. Since this is using a virtual ground splitting the 9 volt from the battery I expected this but the 78L05s output drops to .82 volts thus under powering pt2399 echo chip. I'm wondering if the 4.3V at the ground pin of the 78L05 is correct and causing it to not regulate. The oscillators all work as expected in Rays demo. I don't have a lot of experience with virtual grounds in this kind of Design. Any assistance from you builders and techs would be much appreciated. The schematic is below
Thank you all in advance


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Grumble



Joined: Nov 23, 2015
Posts: 777
Location: Netherlands
Audio files: 23

PostPosted: Fri Nov 17, 2017 12:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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.

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Escape Pod



Joined: Jan 15, 2017
Posts: 6
Location: Oregon

PostPosted: Fri Nov 17, 2017 10:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Sat Nov 18, 2017 11:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Grumble, I measured the points and you are absolutely correct I am getting
9v the full voltage between bat negative and pin 3 as well as 4.5v between virtual ground as well as 4.5v at ground pin on the LM78L05 so now my challenge is finding the bad connection between virtual ground and ground pin on 78L05. Any thoughts I'm adding another schematic and other info I meant to include on the first post
Thanks again


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Grumble



Joined: Nov 23, 2015
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Location: Netherlands
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PostPosted: Mon Nov 20, 2017 5:03 am    Post subject: Reply with quote  Mark this post and the followings unread

There is (or should be) NO connection between the GND pin of the LM78L05 and the virtual ground.
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Escape Pod



Joined: Jan 15, 2017
Posts: 6
Location: Oregon

PostPosted: Mon Nov 20, 2017 8:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

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: 777
Location: Netherlands
Audio files: 23

PostPosted: Tue Nov 21, 2017 1:58 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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Escape Pod



Joined: Jan 15, 2017
Posts: 6
Location: Oregon

PostPosted: Tue Nov 21, 2017 2:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
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Audio files: 23

PostPosted: Wed Nov 22, 2017 12:36 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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Escape Pod



Joined: Jan 15, 2017
Posts: 6
Location: Oregon

PostPosted: Sat Nov 25, 2017 10:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Tue Dec 12, 2017 12:29 am    Post subject: possible hijacking Reply with quote  Mark this post and the followings unread

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: 777
Location: Netherlands
Audio files: 23

PostPosted: Tue Dec 12, 2017 1:30 am    Post subject: Reply with quote  Mark this post and the followings unread

I don't have a Noise Toaster, I just made THIS
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Dr. G.



Joined: Dec 06, 2017
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PostPosted: Tue Dec 12, 2017 2:35 am    Post subject: Reply with quote  Mark this post and the followings unread

looks really cool!
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