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Had one of the very-earliest production samples of this model come in the door about ten years ago. The report was that it showed good power for the first ten keys of the mike, or so.

Then nothing.

Here's what one 2SC2290 looked like when pulled from the pc board.

They had not yet begun to overtorque the mount screws. The layer of white compound NEVER TOUCHED the heat sink surface. Not one trace of white smear is visible. The pc board was mounted on spacers so thick that there was a total air gap beneath each RF transistor. Kinda surprising it lasted more then the first key of the mike like this.

A wider shot showing that none of the compound ever touched the surface of the heat sink.

We gouged out the opening in the pc board enough to bend the new transistors' leads upwards, and bolt the flanges firmly to the heat sink.

Once this was done, the radio performed okay. Lasted a lot longer this way.

73

<blockquote data-quote="nomadradio" data-source="post: 633774" data-attributes="member: 22">Had one of the very-earliest production samples of this model come in the door about ten years ago. The report was that it showed good power for the first ten keys of the mike, or so. Then nothing. Here&#039;s what one 2SC2290 looked like when pulled from the pc board. <img src="https://imageshack.com/a/img922/2209/rXxzOy.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" />They had not yet begun to overtorque the mount screws. The layer of white compound NEVER TOUCHED the heat sink surface. Not one trace of white smear is visible.&nbsp; The pc board was mounted on spacers so thick that there was a total air gap beneath each RF transistor. Kinda surprising it lasted more then the first key of the mike like this. <img src="https://imageshack.com/a/img923/3227/CaAQ21.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" />A wider shot showing that none of the compound ever touched the surface of the heat sink. <img src="https://imageshack.com/a/img921/8516/gGppDd.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" />We gouged out the opening in the pc board enough to bend the new transistors&#039; leads upwards, and bolt the flanges firmly to the heat sink. <img src="https://imageshack.com/a/img921/2972/hvFILl.jpg" alt="" class="fr-fic fr-dii fr-draggable " data-size="" style="" />Once this was done, the radio performed okay. Lasted a lot longer this way. 73</blockquote>

[QUOTE="nomadradio, post: 633774, member: 22"] Had one of the very-earliest production samples of this model come in the door about ten years ago. The report was that it showed good power for the first ten keys of the mike, or so. Then nothing. Here's what one 2SC2290 looked like when pulled from the pc board. [img]https://imageshack.com/a/img922/2209/rXxzOy.jpg[/img] They had not yet begun to overtorque the mount screws. The layer of white compound NEVER TOUCHED the heat sink surface. Not one trace of white smear is visible. The pc board was mounted on spacers so thick that there was a total air gap beneath each RF transistor. Kinda surprising it lasted more then the first key of the mike like this. [img]https://imageshack.com/a/img923/3227/CaAQ21.jpg[/img] A wider shot showing that none of the compound ever touched the surface of the heat sink. [img]https://imageshack.com/a/img921/8516/gGppDd.jpg[/img] We gouged out the opening in the pc board enough to bend the new transistors' leads upwards, and bolt the flanges firmly to the heat sink. [img]https://imageshack.com/a/img921/2972/hvFILl.jpg[/img] Once this was done, the radio performed okay. Lasted a lot longer this way. 73 [/QUOTE]

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