Resurrection of my WD88A XL

[NickW]

Hi Guys,

Been working on the rebuild all weekend and have just finished. It works again.

I have measured all the voltages inside again, and the only one that worries me is the DC Heater supply. For the XL kit, the original instructions and test procedure call for the voltage across C14 to be 5.9V to 6.3V.

Now WD have changed the diode type to UF5408, and I measure 5.64V across C14, and 4.80V across C17. The 0.84V drop occurs across the 0.47 ohm filter resistor of course. So the small signal valves actually see 4.8V across their heaters - which sounds a little on the low side to me.

I've wired the amp for 240V mains, and most of the other voltages are on the high side. For example:

The AC output of the Mains Tx (pink wires) measures at 332V as opposed to the test spec of 325V.

The DC HT measures at 425V as opposed to the test spec of 410V to 420V.

The anode voltages and cathode voltages all lie within spec.

So its only the DC Heater supply that seems low.

So my question is - is 4.80V acceptable?

Many thanks, Nick