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Old 10th February 2019, 11:45 PM
bikerhifinut bikerhifinut is offline
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Join Date: Jan 2006
Location: Penrith, Cumbria
Posts: 1,093
Default Re: New build WDPhono 3 Questions; heater voltage/LED

Ok first things first,
remove the PCB in Phono3 and examine your wiring against the images in the instructions, the heaters should be wired in parallel i.e all pin 9 wires connected together and all pin 4+5 wires connected together and thence the heater wires from LH Valve back to the correct pins on the socket i.e pins 1 and 4, polarity is important here to ensure the LED lights up when power applied. Check the dropper resistor and wiring to the indicator LED is correctly wired to the heater pins on V4. It may be theres a short circuit or dry joint here. If all checks out against the diagrams then proceed to the next stage. It doesnt hurt at this point to check continuity with your multimeter.
I don't need to remind you thatthe above checks should be done with the unit disconnected from pSu and mains.

Now then if all checks out visually:

First measure the voltage available at the output of the PSU3, don't worry that the HT will be high without any load on it. Also measure the voltage between the heater - and ground, this should be in the 50V ball park, as per the instructions. the + obviously will be 6.3V higher and 6.3V across pins 1 and 4 of the power plugs. Depending on your home mains voltage it can vary a bit which is why you allow 15% either way. The 6.3V DC will not as its regulated in PSU3.
Assuming that all checks out then plug the umbilical cable into PSU3, then measure the voltages again at the pins of the female plug without having it plugged in to PHono3, this will eleiminate any possibility of a wiring fault in the power cable.
Then plug it in to Phono3 if all measures ok.
WITHOUT any valves plugged in, measure the voltages at the 4 pin socket. We are interested in the voltages around the heaters for now. so you should get 6.3V give or take (you measured 6.5, thats fine) across pin 9 and 4+5 on each valve base.
its worth checking the voltage from heater- to earth but that shouldnt change.
If you are getting this voltage drop without valves plugged in, theres still a wiring fault. My instinct would be to disconnect the LED wiring from the baord and see if that makes a difference.
then plug the valves in, I'd do it one at a time, you won't harm them doing this, and measure the heater volts each time in case its a valve with an internal short pulling the voltage down.

get back to us after these tests, and if you can supply some photos of your build showing how you have wired it up they will be a great help.

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