Big trouble with Pre Phono 2

[LSfarzo]

Hello...
it's a lot of time I do not write on the forum. Hope you all are doing fine!

I'm in big trouble with my (old) WAD Pre Phono 2. The Pre has 2 sowter 9570 step-up, PIO and jensen caps, as can be seen in the photo.

It souded really great (but really !) coupled with a Benz Ace L.
I also matched the load for this cartridge.

Some time ago the sound chnaged suddenly. It is like there is a sort of "cut" to some mid and low frequencies. It has suddenly turned harsh and bad, like if the cartridge is not able to track the LPs. The sound is definitely "packed" and unpleasant... it is bad, like something is not working anymore.

I sent the cartiridge for a complete check and it was cleaned and tested by a very well kown and good cartridge master (i do not write the name to avoid unwanted advertisitng...).

The cartridge has come back and the things are getting only very slightly better.

I think that the problem is with the phono preamp.
The WAD Pre works fine.

Now the point is: do someone has some smart idea about what I could do? I do not want to start changing things .. I could end up losing a lot of time and money !

The strangest thing is that this behavior affect both channels !

Every idea is very very well welcomed !

Regards
Luca
Italy

[Richard]

Hi Luca,


First thing is to check the HT voltage and the Heater voltage coming in to Phono2 and, if not correct, back in PSU2.

[bob orbell]

Yes, I would agree with Richard, it could be a HT voltage problem, now I know I am going to sound a bit aggressive here but, the build construction looks appalling, pictures of the PSU may help. Bob

[Greg.]

Originally Posted by bob orbell

Yes, I would agree with Richard, it could be a HT voltage problem, now I know I am going to sound a bit aggressive here but, the build construction looks appalling, pictures of the PSU may help. Bob

Clearly Luca’s Phono II has worked satisfactorily for a long time. You, like Richard, is of the view this is likely to be a PSU II issue. Is a derogatory comment on Phono II build quality necessary?

Luca, is the poor sound quality on vinyl replay only or is there also poor sound on line level sources straight into Pre II, such as CDP, Tuner etc?

[bob orbell]

Is a derogatory comment on Phono II build quality necessary? In a word Greg, YES, of course, I will help Luca all I can with his problem, the comment was made because this hobby can be very dangerous to a novice builder, and this construction looks dangerous and very poor to me, also, how do you think other potential would be customers thinking of buying a kit from Matthew would react if this is what his finished kit is going to look like ? , I rest my case, if the moderators think my comments are inappropriate, them please remove. Bob

[Richard]

If the HT and Heater voltages are correct go on to check the circuit running voltages around the valves using the build instructions.

When it's powered off, check around for dry/poor solder joints and bad earth connections. Check the umbilical lead connections.

Then change valves etc, but now we are into an area which is more likely to affect just one channel.

[John Caswell]

As V3, the cathode follower valve, affects both channels I would suggest swapping it over for either V1 or V2 to see if the poor sound follows it.

John

[LSfarzo]

Dear all,
first, let me thank you all for your first suggestions and help.
In the very next post I'll try to let you know which the results are of the first checks I'm going to make now.

Second, concerning the builidng quality. I accept any comment and I do not pretend to be a pro. I have several electronic engineers who works in the electronic dept. of my Company and I want them to make a pro work !
But I did this kit by myself, in my house, and I am not a pro. Especially wen modding them, I ended up using big caps, hard to install and so the final work is not so wonderful.
Anyway, if there are any suggestion, I'll be pleased to learn and apply them.

As it has been said before, please know that I've been very happy with this WAD trio (and KAT 6550) for several years.
With other friends we made many comparisons with other HiFi systems pricing many more bucks than my WAD trio and WAD power amp... and the WAD equipmet had always appeared as a wonderful equipment even when compared to them.

With that said, I am not so concerned about any possible reaction of any potential customer of WAD kits when looking to my poor construction quality. Anyway, in case there is a given minimum construction standard to adhere to send pictures of a WAD kit, please, let me kow, I will delete all the photos I posted on many BB, forum and so on till now, where I supported the WAD kit good features and souding.

I will let you know the results of the tests asap.

Regards
Luca

[LSfarzo]

Hi all,
I made tests on the PSU 2 and Pre Phono 2.

Tests on PRE PHONO 2

Tests made on the pins of the cliffcon socket of the Pre Phono.
Pin 1 (heater): read 37.5Vdc
Pin 2 (H.T.): read 229Vdc
Pin 3 (H.T.): read 0.13Vdc
Pin 4 (heater): read 44Vdc

Results of the test points in the PSU:
Test Pt.1. Expected 120Vdc. Read: 100.1Vdc (TOO LOW?)
Test Pt.2. Expected 95Vdc. Read: 97.8Vdc
Test Pt.3. Expected 250Vdc. Read: 231Vdc
Test Pt.4. Expected 120Vdc. Read: 92Vdc (TOO LOW?)
Test Pt.5. Expected 95Vdc. Read: 89.3Vdc
Test Pt.6. Expected 250Vdc. Read: 231Vdc
Test Pt.7. Expected 1Vdc. Read: 0.873Vdc (TOO LOW?)
Test Pt.8. Expected 1.1Vdc. Read: 1.019Vdc
Test Pt.9. Expected 150Vdc. Read: 143.3Vdc
Test Pt.10. Expected 1Vdc. Read: 0.918Vdc
Test Pt.11. Expected 1.1Vdc. Read: 1.117Vdc
Test Pt.12. Expected 150Vdc. Read: 135.2Vdc (TOO LOW?)

Tests on PSU

Measuring the voltage at the pins of the Cliffcon socket of the PRE II in the PSU, I measure.
Pin 1 (heater): read 38Vdc
Pin 2 (H.T.): read 105Vdc
Pin 3 (H.T.): read 0.12Vdc
Pin 4 (heater): read 43.6Vdc

Results of the test points in the PSU:
Test Pt.1. Expected 338Vdcunder load, 363Vdcunder no load. Read: 300Vdcunder load (TOO LOW?), 320Vdcunder no load
Test Pt.2. Expected 327Vdcunder load, 353Vdcunder no load. Read: 291Vdcunder load (TOO LOW?), 314Vdcunder no load
Test Pt.3. Expected 250Vdcunder load, 345Vdcunder no load. Read: 232Vdcunder load, 313Vdcunder no load
Test Pt.4. Expected 106Vdcunder load, 110Vdcunder no load. Read: 105Vdcunder load, 108Vdcunder no load
Test Pt.5 (2 pts). Expected 41Vdc under load, 44Vdcunder no load. Read: 37.5Vdcunder load (2 pts.), 41Vdc both pts. under no load
Test Pt.6 Expected 50.5Vdcunder load, 56Vdcunder no load. Read: 46.3Vdcunder load, 51.9Vdcunder no load
Test Pt.7. (2 pts.) Expected 47.3Vdcunder load, 50.3Vdcunder no load. Read: 44Vdcand 43.9Vd cunder load (TOO LOW?), 47.2 both pts. under load
Test Pt.8. Expected 41.6Vdcunder load, 44.6Vdcunder no load. Read: 38.5Vdcunder load, 41.6Vdcunder no load
Test Pt.9. Expected 42.2Vdcunder load, 45.2Vdcunder no load. Read: 39.1Vdcunder load, 42.3Vdcunder no load

I marked with "TOO LOW" the measured voltages under 10% of expected value. Am I too strict?

Do you have any hint on this? I have not spotted any significant problem. At least in my opinion, though the "TOO LOW" markings.

Many thanks for your help. I woudl really solve, instead of buying a new COTS pre phono !

Regards
Luca

[bob orbell]

Hello Luca, first, thank you for your honesty with regard to your build capabilities, my second post was / is posted to respond to Greg, not you. All your voltages are in no way responsible for the problem, yes, the HT voltage is down aprox. 20 volts, but that would be your mains voltage, but as said the phono will run OK at that, over here in the UK most of us have a problem of too high mains voltage, mine is almost 253 . and after rectification is almost 400. I would now read John Caswell's post and proceed with his advice and report back. Bob