Quote:
Originally Posted by vortalexfan
Well, this one had a 5U4GB in it in place of the 5Z4 Rectifier tube, and all of the tube substitution books I have show that the 5Y3 and the 5W4 are not substitutes for the 5Z4 tube, and neither is the 5U4.
Is it common for those old flexible resistors to just blow apart? I'm asking because this resistor's outer cloth shell was completely disintigrated and all that was left was the resistor's wire element which then shorted to the chassis and left a burn mark on the chassis where it shorted to the chassis!  
Also as for the replacement resistor I did come across in my parts stash 2 270 Ohm 2 watt flameproof resistors that I tied together in series to make a 540 Ohm 2 watt resistor (the original resistor had no tolerance markings listed so I figured that that would be close enough.
the original 6A8 tube (this radio had all metal cased tubes which were brand new at that time) was completely dead according to my tube testers (I tested it on my Knight Model 600 Tube Tester, my Sencore Mighty Mite VII Tube Tester and on a B & K Model 606/666 Tube Tester and all three of them tested the tube as bad/zero emissions), thankfully I had a NOS 6A8GT tube that I was able to stick in there, hopefully it won't affect the performance of the radio with it not being a metal cased tube like the rest of the tubes.
You said this radio doesn't have AVC or a standard Volume Control configuration, how does this radio perform compared to others in your opinion? I like to use these radios for Night Time DX'ing. |
The 5Z4 is a real odd-ball tube! The first ones looked like a ballast tube, with a perforated metal housing and two sealed capsules in it. They only made it for a short time, as they were failure prone. The newer 5Z4's were like a metal 6F6. As I stated, the 5Y3 has a 5volt 2amp heater and the same pin-out. The 5U4 has a 3amp heater and too much current for the power transformer.
Regarding the flexible resistor, they all crumbled after so many years. I would use two resistors to equal a value closer to 450-470 ohms.
When DXing with a TRF or a non-AVC superhet, you have to have the volume control set to max, to have the sensitivity to seek out distant stations.
If the radio squeals or motorboats, you might have to use a tube shield on the 6A8GT.