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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Electric fence "Electric Shepherd" ESB 250



 
 
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  #1  
Old December 29th 08, 04:10 PM posted to sci.electronics.repair
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Posts: 4,108
Default Electric fence "Electric Shepherd" ESB 250


Before wasting time on this, de-rivetting the step up transformer mounting
etc.
Input side measures 5Mohm, HV output side 12.7R, but looks like a standard
mains transformer.
Would this be a purpose wound transformer or an off the shelf mains
transformer that could be replaced with similar, if so what sort of voltages
and which way round ?


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



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  #2  
Old December 29th 08, 04:17 PM posted to sci.electronics.repair
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Posts: 54
Default Electric fence "Electric Shepherd" ESB 250

N_Cook wrote:
Before wasting time on this, de-rivetting the step up transformer mounting
etc.
Input side measures 5Mohm, HV output side 12.7R, but looks like a standard
mains transformer.



Shouldn't that be the other way round?


Would this be a purpose wound transformer or an off the shelf mains
transformer that could be replaced with similar, if so what sort of voltages
and which way round ?


They might have just used a low volts to mains tranny the 'wrong way round'

Ron
  #3  
Old December 29th 08, 04:27 PM posted to sci.electronics.repair
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Posts: 4,108
Default Electric fence "Electric Shepherd" ESB 250

Ron Johnson wrote in message
...
N_Cook wrote:
Before wasting time on this, de-rivetting the step up transformer

mounting
etc.
Input side measures 5Mohm, HV output side 12.7R, but looks like a

standard
mains transformer.



Shouldn't that be the other way round?


Would this be a purpose wound transformer or an off the shelf mains
transformer that could be replaced with similar, if so what sort of

voltages
and which way round ?


They might have just used a low volts to mains tranny the 'wrong way

round'

Ron



5M indicating a break associated with damp air getting in there.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



  #4  
Old December 29th 08, 05:42 PM posted to sci.electronics.repair
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Posts: 145
Default Electric fence "Electric Shepherd" ESB 250

N_Cook wrote:


Before wasting time on this, de-rivetting the step up transformer
mounting etc.
Input side measures 5Mohm, HV output side 12.7R, but looks like a
standard mains transformer.
Would this be a purpose wound transformer or an off the shelf mains
transformer that could be replaced with similar, if so what sort of
voltages and which way round ?


In the ones I built I used a standard car ignition coil ! 12 volt
battery and 1 pulse per second into it !

--
Best Regards:
Baron.
  #5  
Old December 29th 08, 07:09 PM posted to sci.electronics.repair
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Posts: 4,108
Default Electric fence "Electric Shepherd" ESB 250

Baron wrote in message
...
N_Cook wrote:


Before wasting time on this, de-rivetting the step up transformer
mounting etc.
Input side measures 5Mohm, HV output side 12.7R, but looks like a
standard mains transformer.
Would this be a purpose wound transformer or an off the shelf mains
transformer that could be replaced with similar, if so what sort of
voltages and which way round ?


In the ones I built I used a standard car ignition coil ! 12 volt
battery and 1 pulse per second into it !

--
Best Regards:
Baron.



As I cannot see how the high current side of a mains transformer could fail
I drilled out the rivets.
If originally a mains transformer, looks like one , it had primary 0.4mm
wire and secondary 0.9mm wire. 0.9mm wire has failed .
For a , by size , 50W transformer I make that 24V, 2 amp if for a 240V
transformer.
Vs = (Vp/2) * (Dp/Ds)^2 , Is = P / Vs
Fence output voltage not stated on the label. 9 seriesed 0.22 nF (no V
stated) across the output and also 4.7K, 1W dropper to 2 seriously blackened
neons in series - any guesses what that indicates as an idea of o/p voltage
?
No obvious visible reason for failure of 0.9mm wire, I would expect the
0.4mm wire to fail.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/





  #6  
Old December 29th 08, 07:38 PM posted to sci.electronics.repair
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Posts: 4,108
Default Electric fence "Electric Shepherd" ESB 250

47K not 4.7K dropper


  #7  
Old December 30th 08, 10:54 AM posted to sci.electronics.repair
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Posts: 4,108
Default Electric fence "Electric Shepherd" ESB 250

Well I would not have believed it unless personally witnessed.
As the o/c must be on the outer layer of the transformer, I stripped off the
cloth tape. There is indication that damp air has got in this unit but not
flooding or internal drips. But in the middle of this outer layer, with no
sign of corrosion or damp under the tape , generally, there is one spot of
blue green corrossion and a small break in the 0.9mm wire.
Maybe a spot of acidic something at that point on assembly and then years of
damp air. Bridging the break gives resistance of the winding of about 0.2
ohm.
Powering on a variac, could not take higher than 150V (saturating) so
assuming it is 110V transformer ( or problem on the original pimary ) output
read 4.7V ac , no load, for 110V ac input.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


  #8  
Old December 31st 08, 12:09 AM posted to sci.electronics.repair
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Posts: 145
Default Electric fence "Electric Shepherd" ESB 250

N_Cook wrote:

Well I would not have believed it unless personally witnessed.
As the o/c must be on the outer layer of the transformer, I stripped
off the cloth tape. There is indication that damp air has got in this
unit but not flooding or internal drips. But in the middle of this
outer layer, with no sign of corrosion or damp under the tape ,
generally, there is one spot of blue green corrossion and a small
break in the 0.9mm wire. Maybe a spot of acidic something at that
point on assembly and then years of damp air.


I have seen that type of failure in several instances, not just on
transformer windings ! PCB traces as well. I belive that acid flux has
been used locally and spattered during soldering. Possibly onto the
tape and then transfered to the wire.

Bridging the break gives
resistance of the winding of about 0.2 ohm.
Powering on a variac, could not take higher than 150V (saturating) so
assuming it is 110V transformer ( or problem on the original pimary )
output read 4.7V ac , no load, for 110V ac input.


I'm a little surprised that it could be a 110V Txf... Or is it a unit
made in the USA ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


--
Best Regards:
Baron.
  #9  
Old December 31st 08, 09:26 AM posted to sci.electronics.repair
external usenet poster
 
Posts: 4,108
Default Electric fence "Electric Shepherd" ESB 250

Baron wrote in message
...
N_Cook wrote:

Well I would not have believed it unless personally witnessed.
As the o/c must be on the outer layer of the transformer, I stripped
off the cloth tape. There is indication that damp air has got in this
unit but not flooding or internal drips. But in the middle of this
outer layer, with no sign of corrosion or damp under the tape ,
generally, there is one spot of blue green corrossion and a small
break in the 0.9mm wire. Maybe a spot of acidic something at that
point on assembly and then years of damp air.


I have seen that type of failure in several instances, not just on
transformer windings ! PCB traces as well. I belive that acid flux has
been used locally and spattered during soldering. Possibly onto the
tape and then transfered to the wire.

Bridging the break gives
resistance of the winding of about 0.2 ohm.
Powering on a variac, could not take higher than 150V (saturating) so
assuming it is 110V transformer ( or problem on the original pimary )
output read 4.7V ac , no load, for 110V ac input.


I'm a little surprised that it could be a 110V Txf... Or is it a unit
made in the USA ?

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/


--
Best Regards:
Baron.


Back working with proper bridged repair, new neons etc . I'm asuming 8KV (it
is actually mentioned on the label) , at least it fires a neon via 100M ,
(0.1G ) dropper, I will dig out EHT divider today. The casing screws mayvbe
UNC which may indicate USA but label has UK address. Electric Shepherd
printed on the PCBs


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/





  #10  
Old December 31st 08, 03:50 PM posted to sci.electronics.repair
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Posts: 4,108
Default Electric fence "Electric Shepherd" ESB 250

1000:1 EHT divider to scope showed about 1.5V pulses which presumably is
consistent with no load 8KV. Left the bank of Cs and neons in circuit ,
giving about 1.5Kv peak pulse.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



 




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