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Help Please -- very strange oscillator problem

Started by Unknown September 15, 2017
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.
On Friday, September 15, 2017 at 2:12:54 PM UTC+10, 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.
You may need a faster oscilloscope. Many weird oscillator problems turn out to be an oscillation at a higher frequency than you can see. And note that not all 2N3055s were created equal. The RCA originals had contained a lot of silicon and were slow and hard to blow up. Other manufacturers worked out how to fit the data sheet with less silicon, and their parts were faster and easier to blow up. -- Bill Sloman, Sydney
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? George H.
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.
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? -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Thursday, September 14, 2017 at 9:12:54 PM UTC-7, daku...@gmail.com wrote:
> ... 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 2N3055 is a power transistor, typically takes milliamps of base current and can deliver amps of emitter current, but at frequencies where air core coils work best, it's low in gain. It could be as simple as transistor high-frequency gain variation.
On Friday, September 15, 2017 at 12:12:54 AM UTC-4, daku...@gmail.com wrote:
> > > The problem is that one implementation works as > designed, the other does not. > >. 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.
You should be able to check most components without unsoldering. At least I suspect that is true. Without a schematic , it is really a guess. My guess is one of the transistors is not working. So how much trouble is it to swap the transistors and see if the problem follows the transistor? Dan
In article <0576d07b-8601-4b44-8adc-d4e74e87102e@googlegroups.com>, 
dakupoto@gmail.com says...
> > 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.
please show schematic here in ascii art or some website.
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
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.