President Lincoln 1 pill issues

[357]

I picked up a Lincoln with a 455 final in it, looks stock.

I'm wondering what the bias should be, currently its 100ma on the 455.

Also when the top cover is on, it seems to want to go into oscillation on SSB if I whistle or yell into it, I see a carrier that "sticks" there for several seconds while still keyed.
When I take the top lid off, its fine.

I see no signs of abuse or screwdrivering but there is a "grey blob" on the pcb around the area of the final solder points.

Any ideas?

 

[357]

I think I found it.
I broke away some of that stupid frigging glue from this coil and it seems to have cured it.

 

[mechanic]

It is called SONY Bond and when it ages it can become conductive and corrosive. I had a 2510 that lost the B+ to the finals and I found the SONY Bond had made a perfect place to corrode the copper under a wire held down by it.
In certain HAM transceivers it has caused the VCOs to unlock and shorted out switching diodes. Where ever this stuff is found it should be removed.

mechanic

 

[Onelasttime]

I think I found it.
I broke away some of that stupid frigging glue from this coil and it seems to have cured it.

View attachment 22062 View attachment 22063

If u google the data sheet for the MRF455 it will list the bias.

 

[357]

I dont see nothing on the data sheet but it says 80-85 here:
http://195.84.101.101/~goranl/shack/cb_hr2510/output.html

 

[Tallman]

Find the data sheet for the maker of your MRF455 and adjust for the stated quiescent current in the specifications. You read the emitter current keyed but no modulation.
Keep In mind that the MRF455 has two emitter leads and you have to disconnect both of them.

 

[nomadradio]

100 mA is fine. Bias is only critical if you don't have enough, or if you have so much that it causes overheating.

One-tenth of an Amp times 14 Volts is only 1.4 Watts of idle-current heat. Won't create any hazards.

73

 

[357]

100ma it is, thanks