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

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

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Best Regards:
                     Baron.
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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

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N_Cook
47K not 4.7K dropper
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N_Cook

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

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N_Cook

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.

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

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Best Regards:
                     Baron.
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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

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N_Cook
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

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N_Cook

On Wed, 31 Dec 2008 08:26:59 -0000, "N_Cook" put finger to keyboard and composed:

FWIW the following device has an open output voltage of 8kV.

Electric Shepherd ESB25 Battery Fence Energiser:

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I have an electric fence controller kit that works by charging a 7uF "dump" capacitor to 340V and then discharging it into the primary of the HV transformer. The energy stored by the cap is ...

E = 0.5 x C x V x V = 0.40J

Its output voltage peaks at 3.6kV.

The ESB25 is spec'ed at 0.08 Joules, so perhaps you can work out the required capacitor voltage (= transformer primary voltage) as follows:

V = sqrt( 0.08 x 2 / C)

Assuming V = 110V, then C = 13uF.

What is the rated DC voltage of your dump capacitor, assuming yours is a similar design?

- Franc Zabkar

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Franc Zabkar

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All boxed up now but from my listing of major devices it is 20uF, 400V Of course the 110V primary is now used as the secondary here, for th evoltage step-up. Internal construction looked the same as mains transformer.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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N_Cook

On Thu, 1 Jan 2009 08:39:30 -0000, "N_Cook" put finger to keyboard and composed:

Assuming that the energy output of the ESB250 is the same as the ESB25, then I calculate that the charging voltage should be 90VDC. This seems low for a 400V cap. Maybe you should enquire as to the actual energy rating.

FWIW, the ESB15 energiser is rated at 0.05J:

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Rutland's recommendations seem inconsistent:

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"As a very general guide, the energiser powering a permanent fence should have a stored energy of not less than 0.5 joules for cattle ..."

"Dairy cattle being strip grazed can usually be contained with a single conductor of poly wire or 12mm poly tape, powered by an energiser of around 0.25 Joules or less provided the voltage on the fence is around 2,000 - 3000volts."

BTW, if you ever need to source a replacement transformer, then maybe you could consider an old Philips FBT of the type that required a tripler. Those would have had an output of 8kV (25kV / 3), and the B+ would have been 155V or less.

- Franc Zabkar

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Franc Zabkar

8KV
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I have a problem with the ESB 55 version. I believe that the thyristor has blown. It seems to be an 82516 from ST Philips but has been discontinued. Does anybody know of an alternative??? The two neons have also blackened but I do not know what to replace them with. Could you let me know what you used please. Many thanks. Jeff.

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jeff

I have a problem with the ESB 55 version. I believe that the thyristor has blown. It seems to be an 82516 from ST Philips but has been discontinued. Does anybody know of an alternative??? The two neons have also blackened but I do not know what to replace them with. Could you let me know what you used please. Many thanks. Jeff.

++++++

I just replaced the pair with a couple of standard mains indicator ones , without any dropper, just the original dropper which probably should have a higher ohmic value. But as used outdoor, to see them flash then necessary, then probably a matter of replacing the neons when necessary

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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N_Cook

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