President Lincoln/hr-2510 ALC problem

[sp5it]

Hi. A friend of mine brought me his President Lincoln for tune and some mods.
I noticed, that when I set bias currents for driver and final max power I could get on dummy load was 18W AM/FM (nothing strange) and 20W SSB measured on PEP meter I trust. All similar radios I had before could easily go up to 40W SSB.
I noticed also ALC pot is working strange. At the minimum position I have some kind of (how to name it) squealing looks like feedback of the mic with RF with 20W oputput power, after going with the pot clockwise it disapperas, power output is low and moving forward clockwise power is going up to 20W in the middle position of the ALC pot, than to the end output power is not changing.
Anyone has an idea what can be wrong with this radio? 4W/12W is not bad and enough but I want to know what could be the reason that this radio can do only 20W SSB with original driver and final.
Mike

 

[Wire Weasel]

Those rigs are nice but there does seem to be this hard-to-explain difference.

The stock final is rated for 25W. I've heard similar reports about folks routinely getting them to do 40 but I don't see how. The 2510 I had would not do a watt past 25. There is a long standing mod to replace the final and driver with a Motorola MRF 455 I think it is (don't know the # on the driver but should be an easy find on the net) which DOES get 'er up to 40-45 watts or more.

This one you have doing 20w.....maybe it has been talked on a lot over the years and the final is getting weak.

As to the ALC... don't know. What I do know is that the whole line had weak modulation output from stock. They were not loud radios especially on AM....so everyone I ran with back in the day clipped the ALC transistor and added a power mic and then they could get loud on AM.

Good luck. I'm sure others on here can chime something in.

 

[sp5it]

Radio is all stock, no modifications.
I have my own Lincoln on the table doing 40W SSB PEP with the same driver and final transistor. The same type of radio, putput power twice lower.
Almost no diffrente with ALC adjust.
I think the only way is to compare both of them element by element.
Mike

 

[Wire Weasel]

Yeah it's kind of hard to say. Surely there is not that much difference between the manufacturing quality of same-components....but that may be the case. Wait and hear from others. The more heads the merrier

 

[flush]

If radio is stock I don't think you will see to much more than 30w pep. The final is rated at 40w but can do up to 50pep. If the final is tired you could have that output. What was your bias current for the pre, and final? Also sounds like some kind of oscillation or rf feedback problem. Or just wait for rogerbird to chime in..

 

[sp5it]

50mA diriver and 80mA final.
Mike