Icom IC-R9000 power unit

[Khitry Lis]

Good day everyone

This weekend I bought a broken Icom IC-R9000 receiver. quickly I located the problem to be in the power unit.
The capacitors C5 and C6 were totally dried out and therefore I replaced those.
After replacing those I had still no success in getting the receiver to work again. Therefore I continued measuring for broken components. I found out that after Q2 I measure 0 Volt so I suppose that Q2 is broken also.

Does anyone know how I can be sure if Q2 is broken or could the problem be in Q1 (the base voltage of Q2 seems to be rather low to me) or with any of the zener diodes?

And if Q2 is broken with what kind of transistor can I replace this 2SD797 transistor? I've been searching online for this transistor and it looks to me that this transistor is out of production. To which values do you have to look to find a equivalent?

[PA0PBZ]

You have 2 arrows pointing to the same wire, one with 17V and one with 21V ??

What do you measure on Q2 if you pull P5 from the back?

[Khitry Lis]

I have made a mistake in drawing the arrow, the 17v arrow is wrong but I am not sure now anymore where I measured the 17v.
Unfortunately I'm not able to look at the receiver again before this Friday. By this time I will write here again with my new findings.

[coromonadalix]

I would try an 2n3055, they are easily found, you have 2N3772, 2N5686, 2N6338, 2N6339, 2N6340, 2N6341  ... any TO-3 case  NPN who has 20 amps collector current.

You have an 4 amp fuse in the line, it would help start the radio.

Do you have an beefy 13.8v 20 amps  power supply around, fixed or variable current limited just in case     you could try to put an supply on p4 pin 1 (DCI) once p5 is removed.

Q2 is not necessarily broken, it is an powerful transistor, 100v at 30 amps, normally they wont go up easily, unless a thermal breakdown, badly dissipated heat ... killed it.

You have Q1 and Q3 to check, all the zenners, electrolytics ... low values ceramic or mica capacitors.

The 2 zenners in serial give 10.2 volts (5.1v each)

All this circuit to make an 13.8v regulator ...  no current limitation.

[PA0PBZ]

A battery would be a very bad idea if there is a short in the radio, unless you want to smoke the pcb traces. That is why I asked to remove P5 and measure again to find out if the problem is in the power supply or in the radio.