looking for Q18

[KD2GOE]

i am looking for Q18 on my RCI-2990 so i can install a 2SC2999 where is Q18?

 

[Robb]

After doing a bunch of these mods, I would advise against changing out the transistor. Not all radio models work well with this mod, only a few will. But putting in the four diodes is a real mod and the change is noticeable and useful. I would do just the diodes - IMO . . .

 

[KD2GOE]

After doing a bunch of these mods, I would advise against changing out the transistor. Not all radio models work well with this mod, only a few will. But putting in the four diodes is a real mod and the change is noticeable and useful. I would do just the diodes - IMO . . .

I agree with you I just have the transistor here so I figured what the hell I would put it in.

 

[KD2GOE]

if any one knows where it is on the board I still want to know I have the transistor I mine as well put it in. a few are in wax so it is hard to see what are what...

 

[KD2GOE]

i found it

 

[KG6YGE]

I put a 2sc2999-D in my realistic TRC 458 and it made a definte improvement in SSB receive capability, on weak signals. I didn't retune or anything, just the swap. Carefully ensure your orientation is correct (E-B-C). I compared it to my IC-745 on 11 meter receive and that mod brought it closer to the 745, which sets right on top of it.

Post your results. I'm sure the diode swap is a solid upgrade also, but I haven't done that one.

 

[Robb]

I put a 2sc2999-D in my realistic TRC 458 and it made a definte improvement in SSB receive capability, on weak signals. I didn't retune or anything, just the swap. Carefully ensure your orientation is correct (E-B-C). I compared it to my IC-745 on 11 meter receive and that mod brought it closer to the 745, which sets right on top of it.

Post your results. I'm sure the diode swap is a solid upgrade also, but I haven't done that one.

unit_399 had posted his results with the 858 chassis radios receive mods on this forum. He stated that the 2999 is a downgrade from the original device in this chassis. He did point out that the diodes were an improvement - however.

The main reason for not using a 2999 in most other radios, is that this part of the receive circuit really doesn't need the extra gain. This extra gain - in my own experience as well - has only made the receiver circuit overload the following gains stages; the net result is unwanted distortion. After re-aligning the receive circuit to compensate for this extra gain with a SINAD meter, the only thing you have gotten out of this mod is that the 2999 has a slightly lower noise floor. But AT THE ADDITIONAL COST of having a shop re-align your radio's receiver. If you do that mod w/o re-alignment; then you will have distortion. What gain is that?!? In the end, there is little/nothing gained with the 2999 mod.

G0HZU also contributed a lot to this forum concerning this swap and the misuse of this transistor in circuit. I have found that this mod should NOT be used at all in some radios altogether. Most Galaxy, Ranger, Uniden, and Magnum radios for a start. Some older Cobras may benefit; but not unless the receive re-alignment is done.

Soooo; it is up to you . . .

 

[KD2GOE]

There wont be any results I did it and no I didn't notice anything from the 2999 transistor the guy that had this radio used the golden scrowdriver in it, turned every thing up so The radio needs an major Tunning with a scop and alignment any how.

I was not going to use the 2sc2999 but the main reason I went with the swap was I needed the transistor "2SC945P" from Q16 SSB detection for Q32 "2SC945P". Q32 is the modulation limiter and it was taken out I had a 2SC945Q but it didn't work right.

 

[KD2GOE]

I was talking on 38 low and the guys told be it sounds a lot nicer then when I first got it. I used my bench freq counter and volt/ohm meter. I feal the radio needs a real tech to finish it.

 

[KG6YGE]

unit_399 had posted his results with the 858 chassis radios receive mods on this forum. He stated that the 2999 is a downgrade from the original device in this chassis. He did point out that the diodes were an improvement - however.

The main reason for not using a 2999 in most other radios, is that this part of the receive circuit really doesn't need the extra gain. This extra gain - in my own experience as well - has only made the receiver circuit overload the following gains stages; the net result is unwanted distortion. After re-aligning the receive circuit to compensate for this extra gain with a SINAD meter, the only thing you have gotten out of this mod is that the 2999 has a slightly lower noise floor. But AT THE ADDITIONAL COST of having a shop re-align your radio's receiver. If you do that mod w/o re-alignment; then you will have distortion. What gain is that?!? In the end, there is little/nothing gained with the 2999 mod.

G0HZU also contributed a lot to this forum concerning this swap and the misuse of this transistor in circuit. I have found that this mod should NOT be used at all in some radios altogether. Most Galaxy, Ranger, Uniden, and Magnum radios for a start. Some older Cobras may benefit; but not unless the receive re-alignment is done.

Soooo; it is up to you . . .

I used a 2sc2999-D which has a current gain (beta) similar to the original. The high gain -e is hard to find anyway, and the noise floor reduction was most noticeable in 3KHz wide SSB mode.