PH-16 Issues

Long story short, I was listening to my PH-16 when one day one channel exhibited lots of crackle and noise while the other channel exhibited lots of hum and buzz. Then only one channel seemed to work while the other cut other. I swapped the tube positions but the problems remained in their respective channels, so I decided to send it in to Roy. He repaired the unit and reported back that it tested good with the tubes that I had sent him. After reciving the unit, the same crackle and hum still remained, although both channels where now playing music. I know Roy isn’t available for the next few weeks while he moves but I’m hoping someone on the forums can help me out.

thermionicvinyl wrote:Long story short, I was listening to my PH-16 when one day one channel exhibited lots of crackle and noise while the other channel exhibited lots of hum and buzz. Then only one channel seemed to work while the other cut other. I swapped the tube positions but the problems remained in their respective channels, so I decided to send it in to Roy. He repaired the unit and reported back that it tested good with the tubes that I had sent him. After reciving the unit, the same crackle and hum still remained, although both channels where now playing music. I know Roy isn’t available for the next few weeks while he moves but I’m hoping someone on the forums can help me out.

I would start by testing all the tubes on a good tester, leaving each one in place for at least 10 minutes to check for any warm-up degradation. That is a LOT of testing on the dual-triodes - if you even have such a tester.

OK, I must preface these remarks to state that I am NOT familiar with the PH16. But I am familiar with the symptoms you describe. I also need to remember that I have a bunch of diagnostic tools acquired over the years that would help me eliminate a lot of issues with components in-situ.

Typically, the symptoms you describe are indicative of a bad semi-conductor (crackle and noise) and a bad filter cap (Buzz/Hum). Now, near as I can *see* from the PH-16 pictoral (http://tubes4hifi.com/PH16-am.htm  ), it Looks like there are separate B+ (1 & 2) for each channel. If this is true, try switching the two blue wires and the two red wires (separately by color, not blue-to-red) and see if the problems switch places. Or, if you get _all_ the problems on the one channel. If this _is_ the outcome, you will need to diagnose the power-supply board relative to which of the two switched made the difference.

If all the problems move to one channel, you have a power-supply issue separate to the mother-board issue. If you identify the hiss/crackle channel, go to the transistor for that channel, and replace it. It might pay to upgrade that transistor as well. There are substitution guides that will help you through that. But, here is a good one:

https://alltransistors.com/crsearch.php?mat=Si&struct=NPN&pc=200&ucb=120&uce=120&ueb=7&ic=20&tj=200&ft=1&cc=500&hfe=20&caps=TO3  
 
That happens to show my latest search for an obsolete power-transistor. This is hard, as you are diagnosing-by-substitution, just not a good procedure. And without an ESR meter, you are almost forced into shotgunning the electrolytic caps.

Mpffff.... Where are you? If you are near-enough 19027, I could have a look. No, I do not do repairs without the owner of the piece at the bench, full-stop. Nor do I charge when I do them as-described. Keeps it a hobby. OR, you could bring the beast to Kutztown in September as I run a diagnostic clinic for vintage radios and such there.

See what you can find under the hood, and if you are willing, try switching the B+ wires. Clearly it does not matter which goes where as they are a twisted pair. Nor am I sure they are actually separate or not. Worth a shot.

so this crackle hum you are still experiencing, is this on both channels or just one. Did you build the PH16 or did someone else built it.
Either way, do a good visual on both the preamp and power supply pcb's and check that all solder joints are good and none look dry or different to the others in any way.

So it was previously working fine.  Then you sent it to Roy who pronounced it to be good...  Are you sure it's a problem with the PH-16?  Maybe your amp?

Dave

Peter, thank you very much for such a comprehensive reply. I’ve tried swapping the tubes one more time and...the noise remains in the same channel. I will continue my diagnosis. Sorry, I’m nowhere near there (Calgary, Canada) but hopefully I will contact Roy once he is available again.

I’m utterly convinced it’s something with the circuit now.

This maybe too simple, but I just finished a PH16 build. It was working fine, then it began to get some random noise in the right channel. After eliminating everything but the PH16, I discovered that the right channel output cable was too close to the power supply board. I rerouted it over the center of the audio board and the problem went away.

Is this internally? Or do you mean the RCA cables?

thermionicvinyl wrote:Is this internally? Or do you mean the RCA cables?

There is considerable virtue in trying non-invasive fixes first, and Itusler's suggestion is a good one. I believe he means the internal jumper-cables from the jacks to the board - although they are already pretty far from the P/S board. If he means the external RCA cords - then they are of poor quality if they are not shielded from something as basic as a pre-amp power-supply.
Keep trying additional routes if you are not successful at first.

If that does not work, try switching B+1 & B+2 (one at a time) as previously suggested. This will, at least confirm or eliminate the power-supply as a potential culprit, and it is simple enough to do without a lot of risk.

Above all, TAKE YOUR TIME. And give it a rest every so often.

As Peter said, I meant internally. It may be running under the board, if so it should be good.

I've decided to make a recording of the noise using my ADC plugging into the outputs of my PH16. I'm hoping that maybe by hearing the noise/hum directly, someone might be able to pinpoint the problem. (Just keep in mind the recording is of the right channel only, so that's why it's in mono)

https://drive.google.com/file/d/176bFJhGoA7lTwcImCSmhI0c8IWFXv87Y/view?usp=sharing

Sounds like a 60Hz hum to me.

https://mynoise.net/NoiseMachines/60HzHumNoiseGenerator.php

You may need to turn up your computer speakers.

Aguaazul

I had to use a "cheater plug" (2 for $1.99 harbor freight), to lift the GRN on the PWR-IN of my solid state amp for my surround speakers today, to get rid of exactly that same sound. I put everything (HT stuff) on an APC line conditioner and that noise started after that. Weird, but that was the sound and the solution. Most likely no help to you though, sorry.

thermionicvinyl wrote:I've decided to make a recording of the noise using my ADC plugging into the outputs of my PH16. I'm hoping that maybe by hearing the noise/hum directly, someone might be able to pinpoint the problem. (Just keep in mind the recording is of the right channel only, so that's why it's in mono)

https://drive.google.com/file/d/176bFJhGoA7lTwcImCSmhI0c8IWFXv87Y/view?usp=sharing

Yes, it does sound like 60 Hz hum. Suggesting that either it is being induced from some external line-source, or from the onboard transformer, or one/more of the diodes is bad, or the rectifier tube is bad, pretty much in reverse order.  

Critical question: is the hum now on _BOTH_ channels or only ONE channel? IF both, start with the rectifier tube. if only one, on the SS Diodes dedicated to that channel.

It just struck me - do you have an auto-ranging VOM, and are you comfortable using it inside your preamp? If so, set it for AC and measure for AC at all the tie-points where DC goes into the main board - from the board to the chassis. Please report your findings. So, 12 V DC x 2. B+ 1 x 2 & B+ 2 x 2.

If you have any sort of AC spike anywhere, you have your problem.