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Transistor help

KJ4BAE

Member
Aug 14, 2008
50
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A friend of mine has a palomar tx100 with bad pills. The problem is i cant find any info on thees pills or a cross reference. They have printed on them CTC TX100 G648. What can we put in this amp to make it useful again? Thanks in advance for any help..
 

If it's the stud mount devices, tell your friend to buy another amplifier... Seriously, those things are SPENSIVE when ya can find them.

If it's standard flange mount, then call RF Parts. RF Parts Company™ Amateur Radio Catalog They can tell you which devices from their SRF line will cross reference. Typically you see 10-25 percent more Pout with the RF Parts devices. If it has no negative feedback, I'd order their kit as well, to prevent the new high gain devices from launching into oscillation.

--Toll_Free
 
I think that CTC transistor has the larger of the two flange mount cases. Most of the transistors that have the closest specs to the original part have been discontinued and their price is well beyond their value. The reason behind this is that those transistors are obsolete. I believe one of the closest common transistors available today would be the 2SC2290. This transistor will have a lower input and output impedance then the original.

This means to get the full power from the transistor one would have to make slight modifications to the wraps on the transformers or change the values of the caps used on them. The good news is even without any modification the amp will work well just installing the 2SC2290 transistors. It will most likely make more power then stock but with slightly less efficiency. The larger transistors will handle the dissipation so long as you don't go crazy with the drive.
 

HG makes a replacement version of the 2290 that is much lower in price. I would still try to double check what the closest final would be to that original part.


Here is a nice video on this amp.

 

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