| Author |
Message |
    
Thunderbolt
| | Posted on Monday, September 02, 2002 - 11:43 am: | 
|
The radio wotks fine on AM,deadkey 5 watts ,swing 11 watts or so. On SSB it starts out swinging to around 15 watts then after a few seconds it drops lower and lower to finally close to nothing. The 2SC1306 final gets extreamly hot even with the mic keyed and no modulation. The 1969 doesnt seem to get hot. I switch back to AM and it still is swinging fine and the 1306 cools back down. Can I put a 2166 in place of the 1306 without any modification? |
Thunderbolt
| | Posted on Monday, September 02, 2002 - 12:56 pm: |
|
Well,solved my own question. I did replace the 1306 with a 2166 and the radio works fine now. The final stays cool also. Now all I need is to find out how to get a lower dead key with the same swing. Dont really want to cut mod limiter. I would like to see a 2 or 3 watt dead key and swing to 10 0r 12 watts. May run an amp with it. Any sugestions? |
Thunderbolt
| | Posted on Monday, September 02, 2002 - 2:13 pm: |
|
I am back again. I am still getting alot of heat build up at the 2166 driver when on SSB,mic keyed and no modulation. Goes away when back on AM |
307
| | Posted on Tuesday, September 03, 2002 - 7:32 am: |
|
It almost sounds like a few shorted capacitors in the tank (matching) circuit (after the Final , before the SO-239). This will do the exact same thing you are talking about...
307 |
2600
| | Posted on Friday, September 06, 2002 - 2:07 am: |
|
Ummm, and no one has suggested a bias check on the driver? A blown bias diode and/or bias pot can do this to a driver. Just turning the pot too high can do it, too. Folks who set it for "Max Swing" cook a lot of driver transistors. Pull the test wire for the driver, insert your current meter, and set the little trimpot next to the driver for 40 mA. with 1) the radio on SSB (upper, lower doesn't matter) 2) The mike gain all the way down 3) Keyed. (Will show no wattmeter power like this, just "idle current" on the ammeter)
Ahhh, just peeked inside a 148. The driver bias trimpot is VR8. The one next to it, VR9, gets set with the meter feeding the final wire. If the radio has been 'power jumped', this means unsoldering it to put the ammeter in line with it. Always leave the driver test wire unplugged while measuring the current on the final wire. This shuts down the driver while reading the final current, improves accuracy. VR9 is set for 60mA. on the final test wire.
If either one won't set, suspect damage to the bias diode bolted to that transistor's mounting screw, or alongside it on the rear panel. If it is bad, the trimpot VR8 is suspect as well.
Oh, and not to put too fine a point on it, but did you apply heat-sink compound when you changed the driver? It makes a difference to this exact problem. Really.
73 |
|
