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Smelly preamp


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One of my Tram 2 preamps (yes, I am a masochist, I have two of them) puts out a strange odour when it has warmed up.

 

The smell is hard to describe.  It's definitely nothing burning - more like the vaguely antiseptic smell that comes from medical equipment.  To be honest I have been aware of the odour since I got the preamp from the UK, but up now it has always been in a largish room and so was only barely discernible. Now it's in a much smaller room.

 

I've only just got the preamp from Decky, who replaced the volume control boards, so it is in perfect electrical condition.

 

Would anyone have an idea of the possible culprit - perhaps a component that could smell like this when warmed up?

 

Here is a photo of the insides.

Tram_1.jpg

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Could be a leaking electrolytic capacitor, they make a nasty smell. Can't tell by your pic.

 

If fully regulated for every stage, it should not be a problem.

 

If some stages are not regulated these are the ones to look at to see if those caps in that stage are leaking, due to over voltage.

Being made in Asia, there voltage can be just under the max for the caps, which is fine, but not great practice if shipping to other countries. 

But the voltage here can be 10-20v higher than there, and push the max volts of the caps over the edge, which can slowly kill them.

 

Cheers George

Edited by georgehifi
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9 hours ago, Decky said:

do not spread the panic for no reason. :)

 

I'm not, I'm giving facts as many techs will back me on quite a few Asian products.

 

Cheers George 

14 hours ago, georgehifi said:

Could be

 

And I did say "could be" 

 

Cheers George

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Here's what you do: (Make certain you know what you are doing!)

 

* Remove all the screws securing the top cover.'

* Have a multimeter ready to check stuff.

* Locate a 100 Ohm/10 Watt resistor, terminated in alligator clips (or something similar).

* Switch the preamp on for (say) 30 mins (enough time for the smell to become obvious.

* Find the high Voltage parts of the power supply (you want the main filter caps, not the ones after the regulators)

* UNPLUG the preamp from mains power.

* Connect the 100 Ohm resistor across the main filter caps for a few seconds.

* Use the multimeter to ensure any high Voltage sections are now as a suitably low Voltage (say: < 30 Volts).

* VERY CAREFULLY, touch all the components that typically run hot. That would include power resistors, heat sinks and power transformer. Even better, would be to use a thermometer. Anything hotter than around 70 degrees C is cause for concern. 

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Trevor (Zaph) probably also means the transformer top cover to see how hot the transformers are getting, as they can smell also if overly hot.

 

Cheers George 

Edited by georgehifi
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4 hours ago, Tony M said:

Infra-red (no-touch) thermometers with laser targeting are available from Jaycar and seem ideal for this purpose.  You can get an instant spot reading of the temp of almost anything.:thumb: 

 

Yes, total isolation. The best solution in tracing and tracking heat source.  I have an infrared Fluke that does the job and gives you a digital temp reading.

 We have the brightest techs here and I'm at a lost why anyone would recommend a possible non technical person to put a 100 ohm resistor connected via alligator clips across a potentially high voltage point on a cap that may take 30-60min to fully discharge.    Even if the mains is disconnected some caps take a long time to discharge.  If you wanna risk coping an electrical shock from  a high voltage electric discharge, be my guest.

Edited by Addicted to music
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7 hours ago, Addicted to music said:

 

Yes, total isolation. The best solution in tracing and tracking heat source.  I have an infrared Fluke that does the job and gives you a digital temp reading.

 We have the brightest techs here and I'm at a lost why anyone would recommend a possible non technical person to put a 100 ohm resistor connected via alligator clips across a potentially high voltage point on a cap that may take 30-60min to fully discharge.    Even if the mains is disconnected some caps take a long time to discharge.  If you wanna risk coping an electrical shock from  a high voltage electric discharge, be my guest.

 

My initial words:

 

Here's what you do: (Make certain you know what you are doing!)

 

Emphasis added. That said, yes, a no-contact thermometer is the best way to go. 

 

However, these are the words that should send big alarm bells ringing:

 

Tram does not have a top cover

 

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13 hours ago, Tony M said:

Infra-red (no-touch) thermometers with laser targeting are available from Jaycar and seem ideal for this purpose.  You can get an instant spot reading of the temp of almost anything.:thumb: 

 

Great idea.

 

One thing to be aware of is that at close range such as would be used here, there will be effectively a parallax error or offset in distance between the laser and the actual centre of the measurement area - the laser is sent out in parallel to the measurement field of view. It may be displaced by 20mm or so.

The individual components would best be tested at close range, directly in front of the IR sensor, not the laser.

 

Regards,

 

SS

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10 minutes ago, bronal said:

It's like ozone,

 

Ammonia maybe??

 

From BadCaps.net

"In some cases, you may also catch a whiff of a strange odour. Some people say it smells like ammonia"

 

Cheers George

Edited by georgehifi
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10 minutes ago, bronal said:

I've just thought of how to describe the odour.

 

It's like ozone,

Had to look up what ozone smells like.

"It smells like electrical arcing. Under "incidental production" Wikipedia lists ionic air purifiers, laser printers, photocopiers, tasers, arc welders and electric motors as possibly producing ozone."

 

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Reminds me of one time we were trying to solve a problem with a natural rubber perishing in a NIR spectrometer at work. One of the things we found was that a Xenon discharge lamp used for wavelength calibration created ozone when in an atmosphere containing oxygen. I'm not familiar with "vacuum" tubes as such, but could a tube/valve give a similar effect?

 

SS

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38 minutes ago, Sub Sonic said:

Reminds me of one time we were trying to solve a problem with a natural rubber perishing in a NIR spectrometer at work. One of the things we found was that a Xenon discharge lamp used for wavelength calibration created ozone when in an atmosphere containing oxygen. I'm not familiar with "vacuum" tubes as such, but could a tube/valve give a similar effect?

 

SS

 

Only if there is some kind of arc or discharge around the HV circuits. I have seen it, but it is very rare with properly designed and constructed equipment. Even laser printers, with their (typically) 5kV discharge systems, ozone production is kept to a minimum and they always employ a system to 'soak up' any remaining ozone. 

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7 minutes ago, Zaphod Beeblebrox said:

 

Only if there is some kind of arc or discharge around the HV circuits. I have seen it, but it is very rare with properly designed and constructed equipment. Even laser printers, with their (typically) 5kV discharge systems, ozone production is kept to a minimum and they always employ a system to 'soak up' any remaining ozone. 

 

In the instance I referred to, the discharge was inside a quartz envelope (xenon gas) and ionised the air outside, due to the UV produced by the arc. The quartz did not block UV.

 

Cheers,

 

SS

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50 minutes ago, Zaphod Beeblebrox said:

 

Even laser printers, with their (typically) 5kV discharge systems, ozone production is kept to a minimum and they always employ a system to 'soak up' any remaining ozone. 

 

That depends whether a corotron charge wire is in use or a charge roller.   

They are steering away from corotron charge wires due to the high ozone levels being discharged.  However corotron charge wires are more reliable than charge rollers.  The remaining ozone produced is suck into a duct directed into a carbonised filter and it is pushed out into the environment.  In theory the carbonise filter should absorbed all the ozone and the voltage can be anywhere up to 8kv depending on design.

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11 minutes ago, Addicted to music said:

 

That depends whether a corotron charge wire is in use or a charge roller.   

They are steering away from corotron charge wires due to the high ozone levels being discharged.  However corotron charge wires are more reliable than charge rollers.  The remaining ozone produced is suck into a duct directed into a carbonised filter and it is pushed out into the environment.  In theory the carbonise filter should absorbed all the ozone and the voltage can be anywhere up to 8kv depending on design.

 

Thanks for the clarification.

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A few years ago I purchased a Yaqin MC-13S, a Chinese built EL34 integrated, for the first few months of operation it would emit a very similar smell, difficult to describe, chemical - medical with a hint of heated metal, certainly not an electrical smell nor burning though
I put it down to the various soft plastics used in the wiring, plus there was some still quite soft glues used to keep wiring in place, along with the heat of the transformers.
Over time the wiring started to firm up as did the glues and the smell eventually went away.
I wouldn't say the internals of your Tram 2 resemble the Yaqin though.

In contrast, I recently picked up a new PrimaLuna Dialogue HP integrated and it has never produced any kind of smell.

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