Realistic TRC 474 seeking advice on irf520/schematic

[Uncle Ronnie 336]

One of these came into my hands with a blown final and I got the 520 mod mostly done but something isn't right when I try to key it down. I can tell there's some signal getting through but it is not putting out enough power to wake up any meter. I feel like this has to do with some capacitors somewhere.

 

[nomadradio]

Ahh, you didn't happen to test the old final when you removed it did you?

If it tests good, this means there is another fault that kept it from transmitting.

The fault that's keeping it from transmitting now, maybe?

73

 

[Uncle Ronnie 336]

The final was bad and there is a signal coming from the driver. It is passing signal just not very much of it

 

[nomadradio]

What are you using for DC gate bias voltage on the MOSFET?

73

 

[Uncle Ronnie 336]

I'm using the 3.3k, 470, diode setup. The voltage step down regulator is roughly 6 volts and I did put a resistor between tx point and the bias area on the gate but I'm still not getting anything. I think I have to alter something in the output area of the whole final but that's just my general hunch

 

[LeapFrog]

Perhaps that bias voltage is too high, should be about 3.7 V for the irf520.

 

[Uncle Ronnie 336]

This is a uniden pa-206ac chassis. What is an equivalent to this? CB tricks doesn't list the 474

 

[Handy Andy]

Can you post a pic of the board?

Might be able to cross-reference from that...

 

[Uncle Ronnie 336]

10-4

 

[Uncle Ronnie 336]

Last night while burning the midnight oil I realized a trace between the driver and final was broken. So everything is gravy now and I get about a 6 watt dead key and about 28 watts of peak. I didn't use the en 1230 and opted to make my own set of biasing resistors and diodes and instead of 3.3 k I used 4.7 which bumps the biasing voltage up a little bit because the driver is not the strongest thing in the world

 

[Handy Andy]

because the driver is not the strongest thing in the world

Glad you got it working.

It has the 9106 PLL - does it use the 2086 Driver and 2029 Final?

Similar to the PC-33/PC-55.

Just much more compact

 

[Uncle Ronnie 336]

Idk what the driver is because I never took the heat sink off of it. This was part of a teenage years throwback radio with one of my friends that goes way back so he just got it. I used 120 PF shunted after that first tuning coil on the final and I threw in 100 PF in parallel to the series bypass cap between the driver and final gate. It definitely talks way bigger than the one my friend had when we were younger