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Author Topic: RF Concepts RFC 2-117 help  (Read 989 times)
KC8PCL
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Posts: 35




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« on: November 12, 2012, 06:17:08 AM »

Hello All,
    I have an RFC 2-117 that I bought used. the previous owner replaced the 2 output transistors in this unit. but now, with 15 watts drive, the power output is only 55 watts max. and the ceramic trimmers are all screwed down tight to even get 55 watts. I am not sure if any other component were changed out. it looks like he changed the value on the base bias resistors to 10 ohm. I think that the are supposed to be 22 ohms. the schematic I have seems different than what is installed in the amp. can anyone help me fix this amp, any suggestions will be welcome, other than send it back to Alpha / RF Concepts. I am on social security, not much money for that. Thank for reading my post, Hope to hear from someone on this problem, 73.
                                     Dave
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KA5IPF
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« Reply #1 on: November 12, 2012, 06:31:14 PM »

What transistors are in it? RF Parts shows the MRF248 as a sub but at $105/pair not cheap.

Clif
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KC8PCL
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Posts: 35




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« Reply #2 on: November 13, 2012, 05:22:49 AM »

Hi Cliff,
   The output transistors are MRF 248's, the driver is the same number that was installed when built, but even that one has been replaced with a new one. what concerns me is that all of the rf chokes have been replaced with wire wound ones, no markings on them anywhere. the base bias resistors have all been changed out, not sure if they are the right value, they are all 10 Ohm film resistors. I have another RFC amp that has the same output as this one and the base bias resistors are 20 Ohm resistors. I have tested the driver transistor out of circuit, and it is good. there are no signs of any component running hot, all looks good. I am stumped on this one.
                              Dave
   
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