I have a Lincoln 2 plus with blown final MOSFETS. After replacing the finals, the RF Power knob has no effect. The AM carrier is close to 50 Watts. I believe Q55, a series pass transistor that feeds the finals is shorted. Is this something that happens often?
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President Lincoln II Plus blown finals and regulator
- Thread starter aeromojito
- Start date
It can happen because when MOSFETS go they almost always fail with a drain to source short (at least temporarily until they explode). This of course shorts the regulator to ground taking it out as well.
It's not actually the regulator but a series pass transistor. It is shorted base to collector causing it to be fully on. The good news is that the base voltage changes like it should with that transistor removed. Got the TIP36C on order. We wait.
Irf520 9Amps and 13n10 12Amps both
MOSFET, my CB friend here has them in stock
MOSFET, my CB friend here has them in stock
My Lincoln 2 plus good again, with 2 MOSFET 13n10 and one PNP 2SB827 25amp 60volt transistor, did not have the tip36c which is 25 amp 100 volt. It works excellent again
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The 60v vs 100v is irrelevent, the 25 amp current passthrough is.
You do not need to up grade it it is fine as it is. The problem is the mosfet finals. This is not a 1990's design were the voltage regulator was barley up to requirements. In this case the voltage regulator was taken out when the mosfet finals failed. Nothing to due witht he voltage regulator not being up to scratch. Save the voltage regulator upgrade for old Connex, Galaxys, RCI2950's and such from the 1980's and 1990's and such!
I know it is hard to break old ways of thinking.
Either radio could have 520's or 13n10's. Seems the more current ones have 520's. You'd just have to pop the hood and look!
