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ICOM IC-V8000 Repair [message #1833] Sat, 26 January 2013 16:15 Go to next message
root is currently offline  root
Messages: 207
Registered: December 2004
Senior Member
Icom IC V8000 is a power house with 75W RF power from a Base station equipment. In the earlier days to pump this much power we have to use external amplifiers, like the Daiwa VHF Linear(mentioned as 'Brick' in the bands!)

But unfortunately, on regular full power blast the V8000 go dump very fast! No TX out put. It is due to a design failure.

Open up the back cover. Check the PCB. You can easily identify the RD70HVF1-the 75watt Giant- transistor as a white block mounted directly to the aluminum chassis using two screws. On the left side of this there is a small black square, the driver transistor-2SK 3075 mounted on the PCB. Data sheet will tell you this little brother of the giant will provide 7.5watts of RF power!

Remove the PCB and see the other side, a small heat sink is provided for the driver, with two small projections goes to the other side of the PCB, where we solder the driver transistor. On screw down of the PCB it mates with the aluminum chassis to transfer the heat generated.

The surface area for the heat transfer is very less and in between the PCB is sandwiched. On regular use the driver gets heated up and the thermal contact with the two pegs of the Heat sink below the PCB goes into a dry joint, unnoticed. On the next press of the PTT, with full power, it gets barbequed!

Check the web for a replacement, Last week I got a quote from EU! Euro102! It is really big amount for us to do a replacement into a after market rig.

The suggestion already available in the mods.dk gave me more light. But the mentioned transistor 2SC 1971 is now obsolete and not available with any mail order services.

My search end up in Motorola MRF 237-the 7watt driver for the Moto GM300. This one have the outer casing connected to the Emitter, hence can be mounted directly to the Chassis, which is at negative potential, providing good thermal dissipation.

Removal of the defective 2SK 3075 from the PCB is tricky and need good amount of heat from a heavy Iron or hot air blast. It also takes away the tracks of the PCB. All because of the Heat sink on the other side!

To test, mounted the MRF 237 with a small heat sink clipped on it, selected the low power. PTT-it works, gave 5 watt into the power meter- dummy config connected to the antenna socket.

See the Pictures in the "Picture Section" for details on how I gave permanent life back to the V8000. Use Heat sink thermal conducting paste in all joints.

It is simple and with little care all can do the work- 65Watts of RF power. Many V8000-from the marine junk still available in the after markets.

Good luck.






Peter VU2PJP

[Updated on: Sat, 26 January 2013 16:17]

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Re: ICOM IC-V8000 Repair [message #3045 is a reply to message #1833] Wed, 27 August 2014 11:36 Go to previous message
1966lincoln
Messages: 1
Registered: August 2014
Junior Member
This repair only worked for about 5 activations of the transmitter before failing. I checked low power through high power without problem. Then tried a contact through the repeater and it went dead. Oddly, on the first test, it took the transmitter about 4 seconds to activate after key down on the hand mike. The next couple of times were instant until failure. Total transmit time before failure was only about 10 seconds. Any suggestions? Thanks, Paul AE7VA

[Updated on: Mon, 15 September 2014 21:54]

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