Looking for someone with a Firebird F-500 WITH the preamp...

[ExitThirteen]

I have a Firebird F-500 linear in good shape I got from a buddy, and it has the optional preamp built in. However the preamp does not work, and I'm needing to know the transistor (or FET) that is used to amplify the RX signal. I need the actual number off that part. If anyone has one of these linears (I think a Kicker K-500 is the same thing) that has a working preamp in it could get me the number of that transistor (FET), or can take a good up close picture of the preamp board so I can read it, that would be great. I can't find a schematic of that preamp board anywhere! Thanks in advance!


~Cheers~

 

[ExitThirteen]

Up to the top. Still looking.





~Cheers~

 

[Atlasta]

I've seen a lot of K/ F 500s- but one with a preamp? That's got to be a rare bird.

Since most of these old sweep tubers used more or less the same design, perhaps looking to an old Palomar, D&A or Eagle amp (just to name a few) might put you in the ballpark for the value that you need.

 

[ExitThirteen]

Yeah, I'm finding out that these aren't very common. Reason I don't think it's a transistor is that the original one has 4 legs, and all 4 have "circuits" going to easch leg. Makes me think it's a FET of some type. Unfortunately, the schematic of the linear does not have the schematic of the preamp board. Has everything else, including the RF "sniffer" circuit to key the relays, but all it shows on the schematic is "Pre-amp Board". Almost makes me believe that the preamp was a bit of an afterthought, and not something that was originally designed with the amplifier itself.




~Cheers~

 

[V8Vega]

Here's a schematic of a Thunderbolt 305 which seems like a very similar amp. Do you see it on here?... I don't.THUNDERBOLT 305 KW Amp picture by foxfire55_photos - Photobucket
The instuction sheet lists one transistor as 12N5401

 

[Atlasta]

Yeah, I'm finding out that these aren't very common. Reason I don't think it's a transistor is that the original one has 4 legs, and all 4 have "circuits" going to easch leg. Makes me think it's a FET of some type. Unfortunately, the schematic of the linear does not have the schematic of the preamp board. Has everything else, including the RF "sniffer" circuit to key the relays, but all it shows on the schematic is "Pre-amp Board". Almost makes me believe that the preamp was a bit of an afterthought, and not something that was originally designed with the amplifier itself.




~Cheers~

Interesting. Could you post a pic of the thing? I'm curious as to where the switch for the preamp was placed.

 

[ExitThirteen]

Got it fixed... did some research, it takes a dual gate FET. Ironically, the 3SK45 that is common in all the old Uniden D858 AM and D858 AM/SSB boards worked perfectly. Now, I need to get rid of the astronomical SWR I have when the amp is inline but turned off, and I'll be good to go.


~Cheers~