[TenTec] Model 315 Receiver

[gunnerjuulnyholm at me.com]

Hello again, Byron,

I have run through the received 315 schematics in order to evaluate the robustness of the circuits in detail against variation on receiver performance due to chance in component values . I find that the engineers at Ten-Tec were indeed very clever people, as negative feedback is used in numerous places to stabilize functionality. I think that there are less than 10 components, where a change in value of 20% would change anything in the performance of the receiver. Wide differences in transistor parameters can therefore be tolerated. An exact transistor substitution is not important.

In short: All the “A…” transistors of NPN type can be substituted by a mature Si-type, such as the 2N2222, and all the PNP types including the BC418B can be substituted by for example the 2N2907. If any of them gets a little hot, then change to 2N2219 or 2N2905, respectively, but I doubt it. These types are well known and rather robust, and should be easily available and cheap as they have been industry standards for 50 years. More recent and cheaper types are available in plastic houses from the entertainment industry, but not my choice!

Good luck with the renovation. Let me hear if you run into trouble in finding the transistors.
73
OZ6NF-Gunner

> Den 15. mar. 2022 kl. 03.09 skrev Byron Tatum <bjtatum1 at att.net>:
> 
> I received no replies to my post regarding the transistors in the Model 315 receiver. I am speaking of the A138, A154, A2739 and BC418B devices. In trying to find data on them it appeared some were germanium devices. I looked at the Argonaut #505 schematics and found some identical circuits (exact same resistor and capacitor values) as used in the Model 315.         An example is the IF Amplifier, the model 315 Q-1 uses a A154 as IF amp and the model 505 uses a 2N5134 (silicon device). The dual transistor Q4-A,B in model 315 is an A2739 however in the model 505 each corresponding transistor is a 2N5133 (silicon device).        This continues throughout the comparisons of model 315 identical circuits to model 505 ones, in general the A138 was replaced by the 2N5133 or 2N5134. The A154 was replaced by the 2N5128 and the A2739 by a pair of 2N5133.
>         I would surely like to hear from someone who has knowledge of these transistor types and what the ones in the model 315 are. I have gone into my model 315 and sure enough the devices are all just as shown on the schematics. I am curious about the logo on these transistors, all three part numbers have the same logo stamped on them. It is the capital letter A inside of a diamond. The A138 is a black epoxy appearing case (gold leads), the A154 is a white ceramic appearing case and the dual unit A2739 appears as a metal can TO-39 size case.
>         Thank you,
> Byron W5FH
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