36 coupe filament problem

[jeffsjazz]

This is the first time I've ever posted on a forum of any kind. I have been reading some of the troubleshooting help here and thought that someone might have advice for my problem. I am very new to amp repair and am working on a Kustom 36 coupe that has no filaments heating up on v1, v2, v3. these are DC filaments in this amp I have replaced the components in the dc filament circuit,but still not working. Have tested the 12ax7's in a different amp and all three tubes worked fine. The circuit runs off a 28v center tapped secondary which all reads fine. The plate voltages for the 12ax7's are supposed to be 300 to 320 but they all read around 410. Any thoughts would be greatly appreciated. There is nobody in this area that does work like this at all that I can pick their brain.

[Alex R]

If you're checking the plate voltages with the tubes out that's why they're high.

Is the heater voltage there on the sockets? If not, trace back towards the components you replaced and see where it stops.

Do you have a schematic?

[jeffsjazz]

I tested the plate voltages with the tubes in the sockets. I do have a schematic. I just traced the voltage to a 5 ohm 2 watt resistor that reads 15.8 vdc on the transformer side of the resistor and only reads .03 vdc on the tube side of the resistor. I put in a brand new resistor of the same type and value, but I still got the same results. that seems like quite a drop across one resistor.

[Enzo]

If the heaters are not running, it would be the same as if the tubes were removed.

Until you get the heaters going, none of the other stuff matters.

Post the schematic?

[jeffsjazz]

I thought that that might be why the voltages were off but wasn't sure. I might have found the problem. When I ordered the 5 ohm 2 watt resistor, They sent me 5k ohm instead but the package is marked 5 ohm. The original resistor faded to a point that the bands were not very visible, I guess you learn the hard way not to assume that the part is what it says on the package. I had to order the correct resistor since there are no electronics stores in the area (except Radio Shack and they don't have anything anymore). The local music store got the schematic for me (he is a Kustom dealer), I don't have a scanner at home but I'll try and scan it so I can post it. Thanks for the help, I'll be back if that doesn't fix it.

[jeffsjazz]

Got the right resistors today, I put it in and tested the voltages and everything was where it was supposed to be. Plugged in and finally I had sound! Works fine now, thanks for the help.