Phono II looses right channel

[Greg.]

Hi Nick,

Absolutely no complaint and very happy with the mutation of this thread. Hell, I can't stay on focus when I'm obstructed in doing the things that are important.....well for me anyway.

I'll bring it back later. In the meantime, get those dud valves to me.

Oh, and I'm jealous. Why can't I be staring at Victorian floural patterns on the ceiling as melody surrounds my head and ears?

Best wishes,

Greg

[MMike]

If you don't have a second turntable set up to plug in and try, you could build an inverse RIAA circult, Hagerman has a kit at http://www.hagtech.com/iriaa.html and the pdf manual has sufficent detail to cobble a circuit together, would also be useful for running in phono units off a white noise radio signal, while saving your stylus

[Darren D]

Originally Posted by NickG

No. the normal voltage drop is of the order of 15v, without much difference over a wide range of current. It may vary a little, but not so I notice out of 1300v.

Ok, maybe the reference was made to when they are used at several Kv and it's not an issue at our level?

Good to hear anyway.

I really must do some more building soon.

[Greg.]

I did my decorating and when the light failed, returned to Phono II. This is turning out to be a nightmare problem with no obvious solution. I've messed around a bit and now have no sound on the right channel although at high volume, I do have phono roar. This indicates that signal coupling is good. I've also established that my cartridge is good and signal transfers all the way on both channels from needle/cartridge/connectors/phono wires onto output phon plugs. Thereafter I'm satisfied the signal goes through the phono sockets onto the steppers and comes out the other end.

My current situation is that with normal use, there is no music on the right channel. However, If I push down hard on the right channel input valve, the sound kicks in appropriately balanced. In fact, if I press down on the PCB next to this valve, likewise, the right channel correctly sounds as it should.

This suggests either a dry joint somewhere, a broken track or a faulty valve base socket. For the life of me I can't find a broken track with plenty of good continuity and I've been running the iron over most of the solder joints. I've not completed this process yet and anyway at this moment I can't test as the good lady is once again back infront of the box. Remember, my voltage readings were fine. I've checked all pin sockets on the valve base which seem fine. Whatever ECC83 valve I use makes no difference. I'm running out of patience.

Any suggestions?

Best wishes,

Greg

[Tony Moore]

Hi Greg,

Hairline fracture in a track perhaps? Could you measure continuity of all the tracks around the problem area? Maybe an eyelet for one of the valve base pins come adrift from the adjacent track?

If you can find it you can easily bridge it with wire.

Cheers,
Tony

[colin.hepburn]

Hi Greg
I had a similar problem on my CD output which Iwas unable to find I think you have looked at this but I used a good magnifying glass and strong light to check the tracks if there’s a crack in the track it will show up as a black circle round the component legs and the valve base pins
Hope this helps
Good luck

[NickG]

Well, normally with test kit I would inject a signal and see where it stops, but without kit its not so simple.

Are you getting the same amount of noise from both chans with no source plugged it? If so, I would guess all the valves are amplifying. If a lot less, that would indicate the first stage isn't amplifying or isn't connected.

As the voltages are all correct, I would guess the valves are ok, and so the signal path must be disconnected or shorted to ground.

How about having it connected to the amp when measuring voltages. The meter probe should inject a litle noise into the thing when you apply it to the points, see if that gives any hints.

[Greg.]

Hi Tony,

I've exactly done what you suggest. Continuity is fine on all local tracks. I don't see any dry joints and I'm gradually working over them all anyway. I've not completed this although I've done all the critical ones. That just leaves the valve socket where I've already re-soldered the connectors anyway. I'm at a loss now. I have to say that the original WAD Phono II PCB is a very low quality product and this may be much to do with my problem. Oh how I love the alternative of a hard wired system or, as with my 300B PP clone, a very high quality circuit board.

Best wishes,

Greg

[Tony Moore]

Hi Greg,

I can only suggest hardwiring each of the valve pins, following the normal tracks onto a suitable next component and thereby eliminating any hairline fractures that may have occurred on the valve base pins. They get hot and cold and are prime candidates for fracture at the point where the through plate meets surface track. (I'm assuming this board was the same as the one I had which was through plated)

Best wishes,
Tony

[KennyK]

Greg, although I'm a novice at this, I'm going to have a stab at suggesting something.

have you tried swapping C10/11 to rule out one of them going intermittently open circuit? (they're those Russian PIOs, IIRC, aren't they, in which case they're off the pcb and attached with flying leads - possibly a failed joint here? )

failing that, a dodgy valve base would indeed seem to be likely.