Tube noise, then tick tick tick...

[KeninDC]

Heard what seemed like a rush of wind in the right channel last night. Same volume no matter what I had the gain set at.

This morning, along with the rush, I get a tick tick tick at about 120 bpm out of both channels.

Tried cleaning the tube contacts (5687s in a ModWright tube linestage) and even some tube rolling. Problem persists no matter what set of tubes is in the unit.

Service time? Or am I missing an EZ fix?

Ken

 

[Kegger]

Not sure what that may be, possibly a power supply cap would be where I'd look.

 

[KeninDC]

Thanks.

Since it is still under warranty (5 years), I reckon I'll pack it up and send it to ModWright (Dan Wright).

Ken

 

[chinacave]

For 120hz (BPM) ticking it has to be something sneaking through the power supply - a partially rectified AC at 2 X the line frequency of 60Hz...

I'd be looking at the power supply caps first as candidates to replace, or possibly the rectifier..

Smarter & more experienced folks might soon chime in.

I cut open some old can caps a while ago - the innards were horrifying! Search under FP can caps in this section.

A schematic & underneath photo will help!

 

[KeninDC]

Just got off the phone with the maker, Dan Wright.

Did some due diligence and I will be sending it to him for repair.

Thanks for the input, folks. I'll update the thread after Dan has a look.

 

[GordonW]

Not sure what that may be, possibly a power supply cap would be where I'd look.

This is my guess too. My Heathkit AA100 did something similar to this, and it was a power supply cap arcing!

That was enough to convince me to IMMEDIATELY re-cap the whole thing!

Regards,
Gordon.

 

[gadget73]

experienced that with an old tube radio I was playing with. I was bringing it up slowly to see what worked and what didn't, and the rubber vent plug in the top of the can cap started jumping with each "tick" noise. Shut that off real quickly and stuck new caps in it.

 

[cubby01]

For 120hz (BPM) ticking it has to be something sneaking through the power supply - a partially rectified AC at 2 X the line frequency of 60Hz...

I'm sure you already realized this but the OP said BPM as in beats per minute not per second. I assume thats what you meant Ken, like twice the rate of a wall clock...tick..tick..tick..tick ?

I'm wondering if it's an oscillation hitting a beat frequency. I really have no basis for this, it was just a could it be type question.

 

[KeninDC]

I'm sure you already realized this but the OP said BPM as in beats per minute not per second. I assume thats what you meant Ken, like twice the rate of a wall clock...tick..tick..tick..tick ?

...zactly.

 

[KeninDC]

Talked to Dan Wright this PM. He's going to replace the solid state power supply with a tube-rectified power supply. This is an upgrade and I'm stoked.

Nothing like talking to the cat who both designed and built your kit.

Ken

 

[audiodon]

Nothing like buying from someone who backs up their work and probably learns something in the process either.

 

[Kegger]

Nothing like buying from someone who backs up their work and probably learns something in the process either.

Yep as techs we all learn along the way, and I'd bet down the road we'd all
change a few things on our older designs, nice to see this in a manufacturer.

 

[Kegger]

Thumbs up to the tube power supply update in my book!

 

[KeninDC]

Thumbs up to the tube power supply update in my book!

Dan Wright called it the "heart and soul" of his newer units. The successor to my 9.0 SE tube linestage is the LS 36.5. It uses a 5AR4 rectifier tube (top left in "nudie" picture below:

This power supply update should add some heft to my 9.0's sound. I considered other upgrades (Teflon film and other stuff I will not pretend to understand), but settled on the power supply since that would make the biggest difference.

 

[DanO55]

Generally speaking of course, any amp that uses a 5AR4 is a good amp in my book.

 

[KeninDC]

Generally speaking of course, any amp that uses a 5AR4 is a good amp in my book.

Got it back from ModWright on Thursday. ModWright broke the system in for three days to test it before shipping. Finally had time to open it up and install the tubes yesterday. The 5AR4 is a Sovtek. If anyone has some 5AR4 suggestions that would be better than the Sovtek, I'm all ears.

I'll report back after listening to relay my impressions once I get time to put it back in my kit and have some listening session time.

A new power cord was also part of the deal and Dan at ModWright threw in a pair of 5687 tubes too. Fantastic customer service.

Here are some shots of the insides w/ the new tube-rectified power section:

Power section:

Another shot of the power section:

Input tubes (5687):

 

[KeninDC]

To wrap up this little-read thread, the tube-rectified power really opens up the sound. The top end is clear w/o sounding harsh. I'm pleased as punch.