8719 Washington

[redlght]

Have a washington that may have took a lightning strike replaced some blown out caps shorted diodes the predriver driver and final and such it is working rx and tx but ssb audio is choppy and the TP7 wil not adjust or read any ma the TP8 will it is set to 35ma. Any ideas what to check on why it wont bias? VR9 is good in that section.

 

[redlght]

~Fixed~ TR40 Was bad radio works perfect again

 

[tinkerer973WI]

another 8719 washington

Been stumped by this thing for days, bought used non-working, needed quite a few parts including AM reg, predriver, driver, final, thermal diode on both final and driver(not new salvaged from 148), and a couple solder joints that weren't suppose to be. Replaced parts, full alignment. Here's were I'm stumped, Voltage at the predriver is a little high on xmit, I'm getting .34 v at the collector of the predriver on rx almost 9v on tx, driver and final bias are 35ma and 50ma , base on final and driver are close to normal on tx. collector of driver shows 2.6v on tx AM, Final collector shows 2.6 as well. I've double checked alighnment of the tx cans and all the soldering, I'm only getting 1 watt AM 3.5 SSB. Anyone got any ideas

 

[loosecannon]

in AM mode, the voltage on the collectors of the driver and final transistors will vary with the setting of the AM POWER pot.
they are normally about 6 volts.

on SSB you should have full supply voltage on the collectors. (13.8 volts or so)

you need to find out if you have a shorted component that is in parallel with the voltage line to the collectors that is pulling the voltage down.

or, you may have a problem with the proper voltage not being available to that line.

the fact that you are getting some voltage on that line means that if there is a part that has shorted, it must have some resistance to ground otherwise you would get nothing.

hope this helps
LC

 

[tinkerer973WI]

I do have 13+ volts in rx, during tx it drops to 2.5-2.6 volts. I'll check through some of the caps in the area, especially the ones going to ground. If it means anything, I can adjust the bias trimmers with almost no change in the output, it seemed a little odd , but not knowing why my new tranny weren't putting out was more concerning at the time...
Thanks I'll report back tomorrow.

Tinkerer973wi out