NotTaR of Television Sets : The horizontal output transistor substit..  
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The horizontal output transistor substitution jig trick

(From: penguin@datastar.net).

Okay, here's a good trick you can use for almost all TV work. Mount a TO-3 transistor socket on a heatsink that has about as much surface area as the skin of both fists balled up, actually the bigger the heatsink the better. Then mount a horizontal output transistor in the socket. Use an ECG238 or equivalent. Make sure you use a good mica insulator, as there will be over a thousand volts on the collector.

Solder a 1.5 foot red wire (18 gauge or bigger) to the collector, an equal but yellow wire to the base and an equal but green wire to the emitter (or use your own color codes). You may be able to salvage a ready made heatsink with socket out of an old receiver or TV. Mine came out of some old Curtis Mathes TV's. Solder a damper diode with the cathode to the collector and the anode to the emitter. Add a 200 ohm 1/4 watt resistor from base to emitter. Add these parts to the socket not the transistor, so the transistor can easily be changed if you ever need to.

Now you have a very useful test jig. If you are ever working on a TV that has a blown HOT (horizontal output transistor) you can pull out the bad part and connect this jig. Then you can run the set at low voltage.

If you have a set where the HOT is running too hot, this method often will give you some running time, hopefully enough time to find out what the problem is. Often the bad parts themselves will self destruct or heat up to where identifying them is easy. Usually a bad flyback will crack and smoke proving itself to be bad. Once your satisfied that the problem is cured, you can put the original HOT in knowing it will be safe.

Usually when I power a TV in this way (using a Variac) I'll bypass the series pass regulator with a jumper. This is easily done by finding the 180 to 330 ohm 15 to 20 watt regulator bypass resistor and putting a jumper across it. With the regulator bypassed the power supply will go to 160 volts this is why it is necessary to use a Variac and only run it at about 60 volts. It is necessary when using this brute force approach, to make sure that all of the low voltage supplies coming off the flyback are fused with fusible resistors. Most models do fuse the LV supplies, but some don't. (One particular RCA comes to mind.)   Another good trick, if your out in the field and don't have a varactor handy, is to simply pull the series pass regulator (e.g. STR30130 etc.) and let all the power just come through the 20 w bypass resistor. If the flyback is okay the B+ to the flyback will come up to about 60 to 90 volts, and in many cases you can even see a dim picture.  Anything less than 50-60 volts and the flyback is probably bad. Don't run it this way for more than a minute or two as the the resistor will be dissipating close to or more than its rated power under these circumstances. Of coarse you obviously can't use this method with switching power supplies.

Here's a good trick for the Sony TVs that use the SG-613, even though this device is a gate controlled SCR you can sub a regular HOT like the ECG238 on your test jig. I used to blow out these buggers to the tune of about $20 dollars a pop til I figured out how to use the "HOT Heatsink Jig". Now with the jig connected, the horizontal width may not open up all the way, but you can run these old Sony's like this for about 5 minutes before the HOT jig starts to get too hot. Usually if they run this long they're ok and then you can put the SG-613 in knowing that you aren't going to see a bunch of $$$ go up in smoke. I had a Sony that would run for weeks then blow the SG-613 finally put this one to rest when I changed out the horizontal output transformer which was separate from the flyback on this oldie.

Always be cautious of the high voltage on the collector of the HOT JIG.

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