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Yep. Both of the two-transistor push-pull circuits have to deliver the same power to the output combiner. Leaving off that capacitor guarantees that one half the amplifier is putting out less than the other half. That imbalance tends to totally toast the resistor inside the output combiner toroid, and eventually the wires on the combiner as well. The combiner only sees the difference in wattage between one pair and the other. If they're equal, the difference is zero and the combiner runs cool. But the bigger the difference, the hotter the combiner resistor will get.

Very first item offered on this web page is a 1000pf Semco-style metal mica cap. Has longer leads than the one Texas Star used, but will do the job.

https://www.icamanufacturing.com/shop/capacitors

73

<blockquote data-quote="nomadradio" data-source="post: 855062" data-attributes="member: 22">Yep. Both of the two-transistor push-pull circuits have to deliver the same power to the output combiner. Leaving off that capacitor guarantees that one half the amplifier is putting out less than the other half. That imbalance tends to totally toast the resistor inside the output combiner toroid, and eventually the wires on the combiner as well. The combiner only sees the difference in wattage between one pair and the other. If they&#039;re equal, the difference is zero and the combiner runs cool. But the bigger the difference, the hotter the combiner resistor will get. Very first item offered on this web page is a 1000pf Semco-style metal mica cap. Has longer leads than the one Texas Star used, but will do the job.<a href="https://www.icamanufacturing.com/shop/capacitors" target="_blank">https://www.icamanufacturing.com/shop/capacitors</a>73</blockquote>

[QUOTE="nomadradio, post: 855062, member: 22"] Yep. Both of the two-transistor push-pull circuits have to deliver the same power to the output combiner. Leaving off that capacitor guarantees that one half the amplifier is putting out less than the other half. That imbalance tends to totally toast the resistor inside the output combiner toroid, and eventually the wires on the combiner as well. The combiner only sees the difference in wattage between one pair and the other. If they're equal, the difference is zero and the combiner runs cool. But the bigger the difference, the hotter the combiner resistor will get. Very first item offered on this web page is a 1000pf Semco-style metal mica cap. Has longer leads than the one Texas Star used, but will do the job. [URL]https://www.icamanufacturing.com/shop/capacitors[/URL] 73 [/QUOTE]

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