Forums

Help Please -- very strange oscillator problem

Started by Unknown September 15, 2017
George Herold <gherold@teachspin.com> writes:

> On Friday, September 15, 2017 at 12:12:54 AM UTC-4, daku...@gmail.com wrote: >> Could some electronics guru please help ? I have >> two identical(same resistor, capacitor values) >> implementations of an astable multivibrator. I am >> using the 2N3055 and each transistor drives a coil >> each of a bifilar coil, whose common terminal is >> connected to a 12 Volt 2A(max) DC power supply. >> The coils is air core. >> >> The problem is that one implementation works as >> designed, the other does not. To check if the >> oscillator is working, a pickup coil is placed >> in the vicinity and the output of this pickup >> coil is monitored via an oscilloscope. >> >> I have observed that the base voltage on one of >> the two transistors is getting 10 V pulses, >> while the the voltage on the other transistor >> base is 0.2 V. I have un-soldered and checked >> the resistors, but they are fine. I have replaced >> the two capacitors, with two new identical ones >> but no luck. >> >> Any hints/suggestions would be of immense help. >> Thanks in advance. > > 0.2 V on the base sound like a blown transistor, have you tried replacing > them?
Don't the coils need protection diodes across them? -- John Devereux
On Fri, 15 Sep 2017 22:43:28 -0700 (PDT), dakupoto@gmail.com wrote:

>On Friday, September 15, 2017 at 8:24:29 PM UTC+5:30, Jim Thompson wrote: >> On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: >> >> >Could some electronics guru please help ? I have >> >two identical(same resistor, capacitor values) >> >implementations of an astable multivibrator. I am >> >using the 2N3055 and each transistor drives a coil >> >each of a bifilar coil, whose common terminal is >> >connected to a 12 Volt 2A(max) DC power supply. >> >The coils is air core. >> > >> >The problem is that one implementation works as >> >designed, the other does not. To check if the >> >oscillator is working, a pickup coil is placed >> >in the vicinity and the output of this pickup >> >coil is monitored via an oscilloscope. >> > >> >I have observed that the base voltage on one of >> >the two transistors is getting 10 V pulses, >> >while the the voltage on the other transistor >> >base is 0.2 V. I have un-soldered and checked >> >the resistors, but they are fine. I have replaced >> >the two capacitors, with two new identical ones >> >but no luck. >> > >> >Any hints/suggestions would be of immense help. >> >Thanks in advance. >> >> A schematic would be helpful. >> >> ...Jim Thompson >> -- >> | James E.Thompson | mens | >> | Analog Innovations | et | >> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | >> | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | >> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | >> | E-mail Icon at http://www.analog-innovations.com | 1962 | >> >> I'm looking for work... see my website. >> >> Thinking outside the box...producing elegant & economic solutions. > >I would be happy to supply a schematic, but then would >need an email address. This Google group does not allow >attachments.
Go to my website, click on the envelope icon. Do NOT attach anything, just send an E-mail. I will reply with an E-mail address you can use to send the schematic. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website. Thinking outside the box...producing elegant & economic solutions.
On Fri, 15 Sep 2017 22:43:28 -0700 (PDT), dakupoto@gmail.com wrote:

>On Friday, September 15, 2017 at 8:24:29 PM UTC+5:30, Jim Thompson wrote: >> On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: >> >> >Could some electronics guru please help ? I have >> >two identical(same resistor, capacitor values) >> >implementations of an astable multivibrator. I am >> >using the 2N3055 and each transistor drives a coil >> >each of a bifilar coil, whose common terminal is >> >connected to a 12 Volt 2A(max) DC power supply. >> >The coils is air core. >> > >> >The problem is that one implementation works as >> >designed, the other does not. To check if the >> >oscillator is working, a pickup coil is placed >> >in the vicinity and the output of this pickup >> >coil is monitored via an oscilloscope. >> > >> >I have observed that the base voltage on one of >> >the two transistors is getting 10 V pulses, >> >while the the voltage on the other transistor >> >base is 0.2 V. I have un-soldered and checked >> >the resistors, but they are fine. I have replaced >> >the two capacitors, with two new identical ones >> >but no luck. >> > >> >Any hints/suggestions would be of immense help. >> >Thanks in advance. >> >> A schematic would be helpful. >> >> ...Jim Thompson >> -- >> | James E.Thompson | mens | >> | Analog Innovations | et | >> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | >> | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | >> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | >> | E-mail Icon at http://www.analog-innovations.com | 1962 | >> >> I'm looking for work... see my website. >> >> Thinking outside the box...producing elegant & economic solutions. > >I would be happy to supply a schematic, but then would >need an email address. This Google group does not allow >attachments.
We use something like Dropbox, or a photo posting site. Or make an LT Spice schematic and include the .ASC text in a post here. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On 2017-09-15, dakupoto@gmail.com <dakupoto@gmail.com> wrote:
> Could some electronics guru please help ? I have > two identical(same resistor, capacitor values) > implementations of an astable multivibrator. I am > using the 2N3055 and each transistor drives a coil > each of a bifilar coil, whose common terminal is > connected to a 12 Volt 2A(max) DC power supply. > The coils is air core.
Sounds like a blocking oscillator. this circuit? https://en.wikipedia.org/wiki/blocking_oscillator
> The problem is that one implementation works as > designed, the other does not. To check if the > oscillator is working, a pickup coil is placed > in the vicinity and the output of this pickup > coil is monitored via an oscilloscope.
12V kind of high for that circuit, it generates lots of reverse base voltage which will damage transistors.
> Any hints/suggestions would be of immense help. > Thanks in advance.
this might be worth a look https://en.wikipedia.org/wiki/royer_oscillator -- This email has not been checked by half-arsed antivirus software
On Sunday, September 17, 2017 at 1:31:33 AM UTC+5:30, Jasen Betts wrote:
> On 2017-09-15, dakupoto@gmail.com <dakupoto@gmail.com> wrote: > > Could some electronics guru please help ? I have > > two identical(same resistor, capacitor values) > > implementations of an astable multivibrator. I am > > using the 2N3055 and each transistor drives a coil > > each of a bifilar coil, whose common terminal is > > connected to a 12 Volt 2A(max) DC power supply. > > The coils is air core. > > Sounds like a blocking oscillator. this circuit? > https://en.wikipedia.org/wiki/blocking_oscillator > > > The problem is that one implementation works as > > designed, the other does not. To check if the > > oscillator is working, a pickup coil is placed > > in the vicinity and the output of this pickup > > coil is monitored via an oscilloscope. > > 12V kind of high for that circuit, it > generates lots of reverse base voltage which > will damage transistors. > > > Any hints/suggestions would be of immense help. > > Thanks in advance. > > this might be worth a look > > https://en.wikipedia.org/wiki/royer_oscillator > > -- > This email has not been checked by half-arsed antivirus software
Thanks, yes I have did have in mind a Royer oscillator in mind in the past, but shelved it after I could not find a straightforward way to implement the transformer with the feedback coils. My existing problem is that one implementation of my oscillator workd fine, but the identical copy does not.
On Saturday, September 16, 2017 at 7:07:46 AM UTC+5:30, bitrex wrote:
> On 09/15/2017 11:02 AM, John Larkin wrote: > > On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: > > > >> Could some electronics guru please help ? I have > >> two identical(same resistor, capacitor values) > >> implementations of an astable multivibrator. I am > >> using the 2N3055 and each transistor drives a coil > >> each of a bifilar coil, whose common terminal is > >> connected to a 12 Volt 2A(max) DC power supply. > >> The coils is air core. > >> > >> The problem is that one implementation works as > >> designed, the other does not. To check if the > >> oscillator is working, a pickup coil is placed > >> in the vicinity and the output of this pickup > >> coil is monitored via an oscilloscope. > >> > >> I have observed that the base voltage on one of > >> the two transistors is getting 10 V pulses, > >> while the the voltage on the other transistor > >> base is 0.2 V. I have un-soldered and checked > >> the resistors, but they are fine. I have replaced > >> the two capacitors, with two new identical ones > >> but no luck. > >> > >> Any hints/suggestions would be of immense help. > >> Thanks in advance. > > > > Schematic? > > > > > > It's probably a variation on this circuit: > > <http://www.seekic.com/uploadfile/ic-circuit/s2012121103631509.gif> > > which in my experience is a PITA to get to work correctly at the best of > times. It's bad don't use it
No, my circuit is is a loosely related to the last one at : https://electrosome.com/astable-multivibrator-transistors/
On Saturday, September 16, 2017 at 8:43:39 PM UTC+5:30, Jim Thompson wrote:
> On Fri, 15 Sep 2017 22:43:28 -0700 (PDT), dakupoto@gmail.com wrote: > > >On Friday, September 15, 2017 at 8:24:29 PM UTC+5:30, Jim Thompson wrote: > >> On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: > >> > >> >Could some electronics guru please help ? I have > >> >two identical(same resistor, capacitor values) > >> >implementations of an astable multivibrator. I am > >> >using the 2N3055 and each transistor drives a coil > >> >each of a bifilar coil, whose common terminal is > >> >connected to a 12 Volt 2A(max) DC power supply. > >> >The coils is air core. > >> > > >> >The problem is that one implementation works as > >> >designed, the other does not. To check if the > >> >oscillator is working, a pickup coil is placed > >> >in the vicinity and the output of this pickup > >> >coil is monitored via an oscilloscope. > >> > > >> >I have observed that the base voltage on one of > >> >the two transistors is getting 10 V pulses, > >> >while the the voltage on the other transistor > >> >base is 0.2 V. I have un-soldered and checked > >> >the resistors, but they are fine. I have replaced > >> >the two capacitors, with two new identical ones > >> >but no luck. > >> > > >> >Any hints/suggestions would be of immense help. > >> >Thanks in advance. > >> > >> A schematic would be helpful. > >> > >> ...Jim Thompson > >> -- > >> | James E.Thompson | mens | > >> | Analog Innovations | et | > >> | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > >> | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > >> | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > >> | E-mail Icon at http://www.analog-innovations.com | 1962 | > >> > >> I'm looking for work... see my website. > >> > >> Thinking outside the box...producing elegant & economic solutions. > > > >I would be happy to supply a schematic, but then would > >need an email address. This Google group does not allow > >attachments. > > Go to my website, click on the envelope icon. Do NOT attach anything, > just send an E-mail. I will reply with an E-mail address you can use > to send the schematic. > > ...Jim Thompson > -- > | James E.Thompson | mens | > | Analog Innovations | et | > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | > | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | > | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | > | E-mail Icon at http://www.analog-innovations.com | 1962 | > > I'm looking for work... see my website. > > Thinking outside the box...producing elegant & economic solutions.
I did all that, but when trying to send the email with the schematic as attachment, I got an error message that the mail server was not responding. Please take a look at a fairly close relative of my oscillator, the last one at : https://electrosome.com/astable-multivibrator-transistors/
On Sat, 16 Sep 2017 23:45:36 -0700 (PDT), dakupoto@gmail.com wrote:

>On Saturday, September 16, 2017 at 8:43:39 PM UTC+5:30, Jim Thompson wrote: >> On Fri, 15 Sep 2017 22:43:28 -0700 (PDT), dakupoto@gmail.com wrote: >> >> >On Friday, September 15, 2017 at 8:24:29 PM UTC+5:30, Jim Thompson wrote: >> >> On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote:
[snip]
>> >> Go to my website, click on the envelope icon. Do NOT attach anything, >> just send an E-mail. I will reply with an E-mail address you can use >> to send the schematic. >> >> ...Jim Thompson
[snip]
> >I did all that, but when trying to send the email with the schematic as attachment,
I never got you initial E-mail (without any attachment) ??
>I got an error >message that the mail server was not responding.
That would be _your_ E-mail server.
> >Please take a look at a fairly close relative of my oscillator, the last one at : >https://electrosome.com/astable-multivibrator-transistors/
Check to see if you have the diodes reversed. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website. Thinking outside the box...producing elegant & economic solutions.
On Sat, 16 Sep 2017 23:30:45 -0700 (PDT), dakupoto@gmail.com wrote:

>On Saturday, September 16, 2017 at 7:07:46 AM UTC+5:30, bitrex wrote: >> On 09/15/2017 11:02 AM, John Larkin wrote: >> > On Thu, 14 Sep 2017 21:12:45 -0700 (PDT), dakupoto@gmail.com wrote: >> > >> >> Could some electronics guru please help ? I have >> >> two identical(same resistor, capacitor values) >> >> implementations of an astable multivibrator. I am >> >> using the 2N3055 and each transistor drives a coil >> >> each of a bifilar coil, whose common terminal is >> >> connected to a 12 Volt 2A(max) DC power supply. >> >> The coils is air core. >> >> >> >> The problem is that one implementation works as >> >> designed, the other does not. To check if the >> >> oscillator is working, a pickup coil is placed >> >> in the vicinity and the output of this pickup >> >> coil is monitored via an oscilloscope. >> >> >> >> I have observed that the base voltage on one of >> >> the two transistors is getting 10 V pulses, >> >> while the the voltage on the other transistor >> >> base is 0.2 V. I have un-soldered and checked >> >> the resistors, but they are fine. I have replaced >> >> the two capacitors, with two new identical ones >> >> but no luck. >> >> >> >> Any hints/suggestions would be of immense help. >> >> Thanks in advance. >> > >> > Schematic? >> > >> > >> >> It's probably a variation on this circuit: >> >> <http://www.seekic.com/uploadfile/ic-circuit/s2012121103631509.gif> >> >> which in my experience is a PITA to get to work correctly at the best of >> times. It's bad don't use it > >No, my circuit is is a loosely related to the last one at : >https://electrosome.com/astable-multivibrator-transistors/
The circuit shown does have a stable state: both transistors saturated and nothing going on. But it's impossible to analyze a circuit defined as loosely related to some other circuit. There is an interesting, recurring psychological effect in our business: people describe the way a circuit can work, and ignore the many ways that it might not work. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sun, 17 Sep 2017 09:24:16 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

[snip]
> >There is an interesting, recurring psychological effect in our >business: people describe the way a circuit can work, and ignore the >many ways that it might not work.
Indeed! I have a client right now arguing with me about such a "state machine". ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I'm looking for work... see my website. Thinking outside the box...producing elegant & economic solutions.