President Lincoln 2+ V3 blown regulator AND....L14.....

[Lkaskel]

Hi Everyone,
I was asked to see if I could get this Lincoln 2+ transmitting again as I have sucess with these and some of the RCI boards with a similar regulator setup. The operator said that he did the 11 meter mod (but used a 10K resistor istead of a 1K) and then cranked up the SSB power, AM power, AMANL and SSBANL. Then poof..... I have seen this blown the regulator and sometimes the regulator driver but never this L14. The regulator is a TIP36 and now shows as a capacitor on my component tester. I'm a little nervous to replace the regulator and the inductor unless I can figure out why the inductor blew in half. Could it be that the regulator shorted and took the inductor out? The radio does power up and receive.

Please no comments on the operator. Just any thoughts on the blown inductor.



Thanks!!

 

[BayouRadioAmplifier]

I just downloaded the schematic. L14 would burn up due to high
current through it. If one or more of the RF amp MOSFETS Q45/46/47
got destroyed, and a short from source to drain, this would cause this.
also maybe burning up Q55 TIP36 and/or Q54 also? ?

So first test at TP9 AM MOD. test for MOSFETS Q45/46/47
measure to circuit board ground, the resistance.
if it is low, a few ohms, then a problem.

if it is OK, then put your DMM in diode test mode. the black lead to TP9,
red lead to board ground. see if you can read about .6 volts, the diode
structure on the MOSFETs. then reverse the leads, and see that this
volatage is out of range.

also do all this same testing on each MOSFET Q45/46/47 from the drain,
to chassis ground. to double check all these tests.

 

[Lkaskel]

I just downloaded the schematic. L14 would burn up due to high
current through it. If one or more of the RF amp MOSFETS Q45/46/47
got destroyed, and a short from source to drain, this would cause this.
also maybe burning up Q55 TIP36 and/or Q54 also? ?

So first test at TP9 AM MOD. test for MOSFETS Q45/46/47
measure to circuit board ground, the resistance.
if it is low, a few ohms, then a problem.

if it is OK, then put your DMM in diode test mode. the black lead to TP9,
red lead to board ground. see if you can read about .6 volts, the diode
structure on the MOSFETs. then reverse the leads, and see that this
volatage is out of range.

also do all this same testing on each MOSFET Q45/46/47 from the drain,
to chassis ground. to double check all these tests.

Thanks so much for your direction here. The radio had a bad FET and regulator. It's back to transmitting again.

Thanks again!!