Well, the idea was to preserve the method used - nowadays they use those 7530 MOSFETs that pretty much put out the same power levels.
The rest of this you can read at your leisure --- was done for a previous site but I sent this as a series of Emails PM'd from me to another that wanted to install such a kit - these things don't exist anymore but were from CBC Intl amongst others and several variants were done/sold back then for those that wanted a boost but also a way to keep their radios from blowing up in heavy use and mobile environments. It's condensed and reworded so if you feel inclined to use it - give credit where credit is due...
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But the 2290 I had one myself that used a daughter card like the one shown above, only it was packed with discretes - which included an RF sense for auto TX so I wanted to help some one keep theirs going on an older SS3900. It was a kit
So this was a "training manual" for someone they wanted to install this in their AM/SSB radio...it had limitations - setup was for Class C and mostly driven by Final with it's power backed way down. 2 watts or less.
You got the board, a relay - a series of "stand - off" tabs - the daughtercard and several (12 discretes) parts and wire...you soldered the kit together placing the 2290 in the middle. Its lot like what is shown above - only the above is the SMD version with a lot of extra space...the standoff was used for with the filter network for TX relay or for point to point wiring of the TX sense using 8V+ or Ground (TX pin 3 ground and the needed support filtering and steering diode to prevent voltage from damaging the board).
The real purpose of this "method" was to make a modulator - you had two choices with the kit, replace the final and drive direct (using an NTE-37 PNP for AM Regulator) or piggyback on the rear panel as separate "bolt on" like the RFX75 kits and run power straight rom the power cord - no modulation added...Class C
But if you had the time - you can take the parts on the daughtercard and make up a Class AB bias scheme - you had the 150 ohm resistor on the main board (or whatever was used for Bias feed). And they supplied a 4004 and 914 diode for the TX or Bias - you picked. You soldered those for your choice of operation, one went for relay "Sense" and the other was used (if you needed SSB) for the Class of operation - the coil for the base bias side (in the instructions posted earlier, it's this coil you wound, in the photos above, it's a molded choke and you soldered the diode in series with it for SSB) - you used a 47 ohm 1W or 2W resistor ACROSS these two for the AB biasing (non adjust - you had to determine it by mA back at the test point in idle and used a fixed - I just dropped in a 47 ohm 1W carbon comp for this as default. - about 25~35mA - OR used the built in resistor and mount the choke on the main board's BASE lead - like shown in the photos above (Across Base to Ground) gave you Class C.
The wattage problem was the Final it replaced - you got more capacity but limitations were the drivers own ability to have enough power to fully drive the 2290 as a final - but SSB it was great and the NTE-37 seemed to handle it well enough. The other methods of external relay drive was more for their likening drive power for High-Drive amps - gave you 20~30 watts carrier but kept the final from being the last point on the chain and suffer the higher SWR fail rate - the 2290 was built more for high-SWR applications but was not indestructible - so if you used it to replace the final - it made it nearly bulletproof - but as an external driver - it still left the final vulnerable.
Bill Either did one for HR2510's to replace the MRF477 - seems the Class AB bias scheme worked well for the HR2510's.
The unique thing about this kit was it's width and height. As in the heat sink itself - oriented one way - the "height" gave you the vertical fins, and two holes to mount over the driver and final section (side to side top to bottom) - oriented another 90 degree way, the WIDTH of the heat sink was enough to mount it flush to the rear panel you just removed the daughtercard - slid out from the grooves. It had a cover bracket that was "U shaped" those holes were tapped to screw thru the rear panel from the inside into that U-bracket cover - you used the card as the template to drill two holes for the flange mounts - and used the U-bracket for the external rear panel mount of that driver amp.
IF you wanted to replace the final - The Pill itself mounted flush to the rear panel on the INSIDE - the rear heat sink sandwiched the rear panel to it using the threaded part thru the rear panel from the 2290. You also can, as I found out later, it wasn't necessary - the other two holes above and below the flange for the bracket - you didn't need it - you took off the 2290 from the heat sink and the flange mount itself was strong enough - since you sandwiched it all thru the rear-panel. The only thing I could think of when it came to the U bracket install was to keep the heat sink flat against the rear panel and add more metal to dissipate the heat - there were only two "fins" per side. but it was deep - about 4" so you needed clearance to use this setup. (The rear panel coax connector - well it was a tight fit but it worked...removing the U-bracket cover at least let you gain access to turn the knurl of the coax connector.)
The heat sink's Flange mounting was tapped all the way thru - so once the holes spaced for the 2290 got drilled - you turned it - the heatsink fins were horizontal - you mounted the card INSIDE the radio THRU the rear panel and into the heat sink flush and there were "tangs" set up that you could solder directly to the main PCB and another set to wire in the relay's TX voltage "lead" - you had two Disc caps 0.01 and 0.1uF and a RF choke to keep RF out and that is what you used to filter the Relay's coil power. So essentially this kit was a modulator or a driver amp setup...you sandwiched the 2290 to t rear panel - and the heat sink kept it flush and provided the surface area to take away the heat.
Now, to answer the 30 watt versus the 50~60 watt question was how you set up the kit
Using it for class AB - you kept the radios bias setup and removed parts from the daughtercard (actually just one and a jumper on the main PCB took it's place - you soldered in a hairpin - and installed / relocated a jumper (the relay is used but you had to obtain the NTE-37 to make this work (upgrade the AM Regulator)) and soldered in place - for Class C you kept the original too but moved the jumper so the relay would work with TX and power was sent direct from power connector thru relay as DC no audio.- so you could use it in Class C or Class AB - but whether two stage (as a final replacement) or the tri-stage (modulator or driver) gave you the various configs to make the wattage needs work for your setup.
Replacing the final gave you 15~20 watts carrier at the most - add to the radio gave you 25 ~30 watts seems like small potatoes these days, but back then it was the cats meow and novel use.
The major selling point was the bigger final - to replace the "smaller more limited" ones in the day.
It was more of a learning tool - you needed a lot of tooling, time and patience but what you got in return was some great experience.
:+> Andy <+: