Ranger blowing meter shunt

[kA5WHO]

 My Ranger keeps blowing the plate meter shunt when switched to the plate position on SW4,big bang,I think it happens in any position of the Function switch,phone ,standby,cw.I did solid state the rectifiers,has any one had this problem before.
thanks,dale

[WD5JKO]

Dale, I presume you refer to shunt SH4 (.51 ohm). I'd start by looking at that mode switch carefully and clean away any carbon from the contacts, and ascertain the extent of metal contact damage from the sudden discharges. The switch might be toast already, possibly repairable.

Looking at the schematic at amforever, the HV B+ path for SH4 goes through the mod transformer secondary on the way to the 6146 plate circuit. Anything on that line could be shorting to ground including the mod transformer secondary, the mode switch, the Octal accessory socket, any of the three bypass caps, and even the 6146 tube if it is gassy.

Maybe make an adapter cable with a 100 watt incandescent light bulb in series with one side, and bring the Ranger up in "phone" mode with a variac. Don't dump the high voltage any more with the mode switch. A discharge on the way up should light up the bulb brightly and do so suddenly. Maybe you will see or hear something.

Hope this helps,
Jim
WD5JKO

[WA5VGO]

Check the connections at the meter. I'll bet you'll find one of the terminals shorted to the can that shields it.

Darrell, WA5VGO

[kA5WHO]

thanks for the replys,no Darrell that was the 1st thing I checked.  Jim the ranger works fine 45 watts out nice audio as long as I don,t put the meter in plate position,so It wouldn,t be the 6146 or mod transformer ,I allready had checked those bypass caps they are ok,however I will check the mode switch and accessory socket closely.
thanks agn/dale/ka5who