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Are these valves dead?
Old 23rd August 2019
  #1
Gear Nut
 
compo's Avatar
 

Are these valves dead?

Hello,

I'm getting a very strange intermittent problem with my TLA "Ivory 2" 5051, which is ruining some recordings (example audio attached).

If I record for more than 10 or 20 minutes, there's a decent chance that the volume of the recorded signal will drop by half over time, and the noise floor will increase to an unusable level. I occasionally get the squeaking sounds which you can hear in the attached recording around the time that the signal and noise really get worse.

Is this a common problem with dying valves, or has something else gone awry in my lovely 5051? It's unpredictable and intermittent, so I guessed it was due to valve heat or something.

Please help if you have experience of this kind of thing

Thank you so much!

Compo
Attached Files

WTF.wav (1.36 MB, 562 views)


Last edited by compo; 24th August 2019 at 12:30 AM..
Old 23rd August 2019
  #2

It sounds more like a cap or a digital artifact... doesn't sound like a tube dying. Have you replaced the tube?

Is that a condenser mic? How is it with a dynamic?

maybe it's time to get it to a service shop....




-tINY

Old 23rd August 2019
  #3
Gear Nut
 
compo's Avatar
 

Hi tINY,

Thanks for reaching out dude.

The mic is a Neumann TLM-103. I've tried it with my Rode NT1, and AKG condensor mics, and it does the same intermittently. I sold all my Shure's, so I can't test that theory, but I doubt it's a condensor/dynamic issue.

I've swapped in one other valve (also used) from another piece of kit. They are all ECC83/12AX7 type valves, so they are interchangeable. Since there are three in the various stages of the 5051, I swapped them around to see if I could isolate the problem, but to no avail.

I've just heard various words like "microphonic" when referring to valves, and wondered if I was experiencing something like that for the first time.

Thanks again,
Compo
Old 24th August 2019
  #4
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emrr's Avatar
That’s what would happen with leaky caps, re-biasing the tubes until they shut down. I’ve seen it in many old amps.
Old 24th August 2019
  #5
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Radardoug's Avatar
 

Actually switches and pots could be the problem, TL used cheap crappy parts.
Old 24th August 2019
  #6
Gear Nut
 
compo's Avatar
 

Quote:
Originally Posted by emrr View Post
That’s what would happen with leaky caps, re-biasing the tubes until they shut down. I’ve seen it in many old amps.
You sound super confident, so I'm really grateful for your experience and help.

I'll whip the case off, and check the "+" on top of the caps for upward movement (if they are that type).

Cheers!
Old 24th August 2019
  #7
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emrr's Avatar
Quote:
Originally Posted by compo View Post
You sound super confident, so I'm really grateful for your experience and help.

I'll whip the case off, and check the "+" on top of the caps for upward movement (if they are that type).

Cheers!
Leaky meaning leaking DC voltage to the next stage. Many old amps will fire up with minimal leakage at first, and that leakage will rise over time as you are experiencing, slowly reducing gain and increasing noise. Sometimes going all the way to shutoff. You can usually turn the amp off, then turn it back on with short-term full gain again.
Old 24th August 2019
  #8
Lives for gear
Swelling on the top of a cap CAN indicate a leaky cap, there was a bad batch in the late 90s I think that took out tonnes of motherboards in the 2000s. HOWEVER, swelling does not always indicate a bad cap and a bad cap does not always swell.

So, if you think it’s a bad cap, pull em and test em. Or just pull em and replace them, cuz they’re already out. Don’t forget to watch out for charge, caps in tube gear can retain enough kick to kill you (this is not a joke!)
Old 24th August 2019
  #9
Gear Nut
Might be caused by a bad solder joint. When the device is warmed you have thermal expansion and your bad solder give you problems. May not be the valve but a solder joint in a warm spot.

Dan
Old 24th August 2019
  #10
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GYMusic's Avatar
It does sound like a component, maybe a capacitor going out of tolerance and causing a circuit to go into oscillation.
Old 25th August 2019
  #11
Those things have 4 tube stages and those are simple. It's all the opamps and power supplies you need to check out.
Old 26th August 2019
  #12
Quote:
Originally Posted by compo View Post

I've just heard various words like "microphonic" when referring to valves, and wondered if I was experiencing something like that for the first time.

Microphonic tubes will make a sound at their output when you tap on them with a pencil....



-tINY

Old 9th October 2019
  #13
Gear Nut
 
compo's Avatar
 

Here are some internal photos of the TL Audio 5051 Ivory 2, just in case it can help anyone else in the future, either for part numbers or to act as a schematic check.

I can't see anything obvious myself, that would be causing the issue I'm having with the drop in recording level, and level increase in the noise floor, as well as the artefacts which I originally posted. It looks like a repair shop job.

Photos attached.

Cheers.
Attached Thumbnails
Are these valves dead?-recording-level-dip.jpg   Are these valves dead?-tlaudio-5051-ivory-2-above.jpg   Are these valves dead?-tlaudio-5051-ivory-2-left-half-1.jpg   Are these valves dead?-tlaudio-5051-ivory-2-left-half-2.jpg   Are these valves dead?-tlaudio-5051-ivory-2-left-side.jpg  

Are these valves dead?-tlaudio-5051-ivory-2-right-half-1.jpg   Are these valves dead?-tlaudio-5051-ivory-2-right-half-2.jpg   Are these valves dead?-tlaudio-5051-ivory-2-right-side.jpg  
Old 9th October 2019
  #14
Gear Nut
 
compo's Avatar
 

TL Audio 5051 Ivory 2 Schematics and manual also attached for reference.
Attached Files
Old 10th October 2019
  #15
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Radardoug's Avatar
 

I've just done one of these, it was the pots and switches causing all the problems. You can drill a little hole in the switches and put some contact cleaner in. The pts you need new.
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