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  1. P

    How to drive a 12v 40w heating pad

    My wife asked me to make a honey heater. They are normally pretty basic with a wooden box and 2 40w light bulbs. However when our desktop washing machine broke I grabbed the opportunity as its a ready made cabinet. I found a really cheap 240v thermostatic controller with temperature probe and...
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    Help understanding this circuit please

    Trying to repair this uplighter LED array for a friend. I am suitably puzzled. Mains at 230Vac comes in via 2 fuses and I measure 211VDC at the pins of the bridge rectifier. I can then follow the circuit from the positive terminal of the bridge rectifier via 28 LEDs in series to the negative...
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    Mosfet marked q812 & d8528n

    From a saw controller
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    Simplest mosfet circuit with ghosts....

    So this is the simplest Mosfet circuit possible. Its in a shower pump I bought as a backup. The mains input (230vAC) comes to one side of the mosfet (BTA08 600b). A feed to the gate goes via a resistor (12k) and two reed switches which are triggered closed by magnetic floats in the pump. The...
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    Hep please - what resistor size.

    I am flummoxed. This is a commercial circuit from a pump. It incinerated the resistor and the thyrstor. The thyrsitor is correct but when i connect the pump and energise the reed switch it works once or twice then the thyristor burns out. The only variable is the resistor size. Its on a 240V AC...
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    Truly embarrassed - help what have I done wrong

    Talk about feeling stupid. This is the simplest of circuits. a BTB08-400B was used to switch a water pump via two reed switches that are triggered by magnetised floats in the pipes. The reed switches feed via resistor to the gate. So turn the tap on the flow starts and the floats rise triggering...
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    What is this...no markings

    Trying to get a simple world clock to work consistently. The pcb is really simple. This is close to the only discrete semi ( a c9013 transistor) other tgan the main chip. Its has no markings and is about 5mm duameter and 9mm tall. Initially I thought it was a capacitor across the main battery...
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    Thyristor/triac gate resistor size

    So I have a 230v a.c. supply switched pump that uses the exact circuit below. After a major failure the resistor was fried. I am puzzled by my calculations as the resistor in the circuit was no where near the wattage. I take the 230v a.c. and tb at gives me a peak of say 330v. The gate current...
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    field stop IGBT G20T65D equivqlent help please

    Hi am trying to repair a potters wheel with electronic control of a 180V DC motor. Can anyone help me find a more available equivalent to the main power semiconductor which is marked G20T65D HT H0601. Any help greatly appreciated
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    smd component marked UL25 in a SOT223 type package

    Trying to repair a non-responsive 12V DVD player from my car. Found a shorted area (looked like a burnt out piece of fluff) that appears to have damaged a resistor and so I suspect the closest semi as well. The semiconductor is in a SOT223 type package (though appears larger with the actual unit...
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    Power connector - looks like a B on its side

    Trying a repair and found its the 12v chassis socket. Its like a figure of * but with only one indent so looks like a capital (upper case) B on its side. Half the problem in finding a stockist is knowing what it is called. Can anyone help please
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    GYS Flash 50.12HF Battery Charger & Support unit capacitor value

    Just beginning the investigation so I appreciate its a long shot but trying to identify a burnt component value. So this went bang after it was moved. Amazingly I have checked the components around the incineration and so far all appear to have survived....apart from one multi layer ceramic...
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    Need a new multimeter - any thoughts

    So as a hobbyist i use the multimeter all the time. Unfortunately the display on my relatively cheap (then) Maplin sourced meter is giving up. I've been amazed just how cheap digital meters are nowadays. Does anyone have experience of Angeng meters - they are selling an amazingly low priced...
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    Pure Oasis DAB radio switches itself back on..

    So with decent battery voltage the Pure Oasis digital radio will switch off....then with a modest delay will switch itself back on. The switch itself is a momentary push to connect and appears to be working correctly. Although a trained electronics engineer I last practised in the era of TTL so...
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    Swingline nail gun semi ideas please

    So had a bug in the system - literally. My nail gun shorted across the thyristor (a S6010L) to Q1 via a bug that took out the electrolytic C1 (50uf) and Q1 - amazingly despite fireworks everything else tests OK. The clue that the cap is gone is one half blasted out (!) and half of Q1 no longer...
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    Bang & olufsen Penta amp repair - circuit diagram needed

    4 years ago I started the repair of a B&O Penta 6602 amplifier from the base of a speaker. Got the main circuit behaving but found a problem in the input board. Unfortunately having just dug the circuit board out from the heap of other projects I realise I don't have the right diagram. The...
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    B & O Penta amplifier repair and Tr equivalents

    Hi all, just taken on a project - a 150w B&O amplifier from the base of a Penta loudspeaker. The ouput uses 3 cascaded pairs of SC3281 and SA1302. The unit was blowing the main power fuse - suggesting one or more of these transistors had gone short circuit. With nothing on the resistance...
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