Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

38-116 Code 125 Tube Heater Circuit Issue
#3

I'm glad to hear that the heater circuit is ok.  The socket voltage diagram I have shows 6.3 vac at both heater pins; so, I thought something was amiss.

The plate-to-plate voltage with the rectifier tube (5Y4G) removed measured 723 vac.  I'm using a digital multimeter.  The + side of cap 120 (and 121) is 275 vdc; supposed to be 315 vdc based on the diagram I have.  

I'm wondering if I have misconnected something with the new electrolytic caps.  For cap 123A I had installed a 10 mfd rated at 160 volts (with + side going to chassis ground).  The voltage rating on the original can was labeled as 50 volts.  But after a couple minutes of operation, I heard a small pop and saw a wisp of smoke.  That cap had apparently overheated and discharged a small amount of oily residue.  I've replaced it with a 12 mfd rated at 450 volts (closest one I had at higher voltage rating).  I've attached a couple photos showing how I installed the new caps.  I tried to mark on one photo how I interconnected the - sides of 120, 121, and 123 with the + side of 123A.

I noticed that the socket voltage diagram shows a 60 vdc measurement for the 10 mfd at 50 volts cap.  Seems like that cap's voltage rating is too low.

Thanks for taking the time to help me with this!
Larry


Attached Files Image(s)
       


Messages In This Thread
RE: 38-116 Code 125 Tube Heater Circuit Issue - by LarryFS - 09-21-2019, 10:19 AM



Users browsing this thread: 1 Guest(s)