New build WDPhono 3 Questions; heater voltage/LED

[G Willis]

Hi,

I have just completed a new build of the PSU3 and WDPhono3. This is my first build so I am new to this.

In testing the voltages are all measuring within the stated 15% except the heater voltages which seem off.

I measure a healthy 6.5v across the heater pins (1&4) on the power cable from the PSU. However when plugged into to the phono stage the voltage across HTR+ and HTR- is a fairly anaemic 4,9v. More, the HTR+ to ground reads 54v rather than the specified 49v, and for HTR-/Gnd measures 49v rather than 43v.

Does this indicate a problem?

Also the L.E.D does not light. The instructions say to wire between LED1 and LED2 but LED1 does not seem to go anywhere. I would like to get some confirmation of where the L.E.D should go as its not shown on the circuit diagram. As the LED uses the heater circuit maybe my problems are connected.

Any help gratefully appreciated.

Graham

[bikerhifinut]

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.

Andy.

[bikerhifinut]

Originally Posted by G Willis

Hi,



Also the L.E.D does not light. The instructions say to wire between LED1 and LED2 but LED1 does not seem to go anywhere. I would like to get some confirmation of where the L.E.D should go as its not shown on the circuit diagram. As the LED uses the heater circuit maybe my problems are connected.

Any help gratefully appreciated.

Graham

My copy of the instructions tells me to wire the LED directly to the base of the output valve under the PCB, maybe you've got it connected across some other part of the circuit causing issues. I'd disconnect the LED wiring altogether at the PCB and measure again. As in the previous post, photos would be a big help.

[G Willis]

Hi Bikerhifinut,

Thanks for responding.

I followed your instructions and the first thing I found was that I had neglected to fit the LED resistor - R34. This immediately fixed my LED problem.

I proceeded to run the tests with the valves out as you described and I found the heater circuit to be correctly wired using a continuity test and I measure 6.5 volts on all the bases between 4/5 and 9 as expected.

However on fitting the valves I have exactly the same wrong readings in the heater circuit. You suggested this was indicative of a wiring error and I will check through the entire build again. In the meantime I will post some pictures in case there is anything standing out.

Regards, Graham

[G Willis]

Another picture...

[bob orbell]

My only comment Graham is, are one of your LED tails contacting the chassis, they need to come out straight, and please solder both sides of the valve bases for mechanical strength. Bob

[bikerhifinut]

is it a Phono 3S? if so theres bits you haven't fitted. Like the rest of the interstage coupling capacitors that form the LF filter before the first RIAA correction network.
Those heater connections don't look right to me, I didnt build mine so I've never looked underneath it. However what you could do is solder the heater wiring DIRECTLY to the relevant solder pin pads i.e. pin9 fpr - and pins 4/5 for + to save confusion.
Or take valves out of sockets and with the unit unplugged from power, use a meter on resistance range and check the continuity from the actual valve base pins to all the heater solder points, all should measure zero ohms between their relevant pins and back to the powersocket. That is all pin 9 should measure zero ohms between each other and back to the plug and likewise all pin 4/5 zero and back to the plug. With the LED disconnected the meter should show no circuit between pins 9 and pins 4/5 as the valve heater filament completes the circuit.
I think theres something not right with your heater wiring.
Theres a few others have actually built this circuit who can shed more light on it. My eyes were spinning trying to follow the board tracks. at these times I would have been metering to see where the solder pads were connected.

Andy.

[bikerhifinut]

Originally Posted by bob orbell

My only comment Graham is, are one of your LED tails contacting the chassis, they need to come out straight, and please solder both sides of the valve bases for mechanical strength. Bob

Aha! Bob do you think because its a double sided board and it looks like the heater tracks cross on both sides of the board maybe theres a dry or solderless joint where a base pin goes through? I realise I was looking at a phono3 not 3S board and now I see the difference. I think you may have spotted the elephant in the room Bob?
Do I take it Mr Willis that you havent bothered with the rest of the LF warp filter capacitors for a reason? or the pics show the board incomplete but screwed down in position?

A.

[G Willis]

Its a WDPhono3 XL. The instructions state explicitly that C3,4,5 & 6 are not fitted, nor or are they supplied. They do not appear in the circuit diagram or the parts list.

I was aware that the LED was contacting the chassis and have removed it, I will insulate both legs. I intend to go through the whole heater circuit again later in the week but as I say I am measuring 6.5v with no valves in between 4/5 and 9 on all three bases whereas when the valves are in I am only seeing a 4.9v differential. Doubtless I have missed something or made a soldering error but I am curious about these 'missing' capacitors.

Graham

[bikerhifinut]

It must be an update.
I take it you don't have the rotary switch on the LHS of the front panel to switch in the LF filters? They are a decoration anyway in my opinion, mine stays on the 10hz setting permanently.
No matter it wont affect the heaters.
Have you considered the possibility of a duff valve?
Also try checking the voltages with just 1 valve in and swap it round the sockets, if theres a wiring fault it might show up?
It'll be something fundamental it usually is.

A