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Old 27th April 2011, 03:40 PM   #1
sbelyo is offline sbelyo  United States
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Default I put a bad ouput tube in my amp, did I hurt it?

I did a dumb thing...

I got a 6AS7 off of ebay, tested it and it only posted like 10 on a scale of 0-120. I wanted to see if I could hear anything out of it anyway so I put it in my Van Waarde design headphone amp flicked the power switch and plugged in my good headphones like an idiot.

I got a load hum out of the left channel and nothing out of the right.

I unplugged the headphone and checked the output with a meter just to make sure that I didn't send a stupid amount of DC to the phones, nope just 20 mV I think

It was at that time that I noticed some noise coming from the choke in the PSU. One side of it was hot to the touch and the other side was cold. I cut the power and pulled the tube.

I put the good tube back in and everything sounds normal but I only listened for 10 minutes so I don't think it had much time to warm up yet.

Do you guys think I hurt anything?
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Old 27th April 2011, 04:09 PM   #2
Cassiel is offline Cassiel  Libya
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Quote:
I put the good tube back in and everything sounds normal

Most likely just a little stress, nothing to worry about.
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Old 27th April 2011, 04:28 PM   #3
sbelyo is offline sbelyo  United States
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Quote:
Originally Posted by Cassiel View Post
Most likely just a little stress, nothing to worry about.
That's what I was hoping. I didn't see any smoke or smell anything odd with my nose to the choke.

I'm always warning other's not to do stupid stuff like this, but I forget to listen to myself
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Old 27th April 2011, 07:08 PM   #4
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Here's something I've always wanted to know - how do you know when a choke is faulty? I hear of chokes becoming 'oversaturated', what happens then?
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Old 27th April 2011, 07:18 PM   #5
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If none of the tube elements were shorted and it just tested weak, that shouldn't cause any harm.
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Old 27th April 2011, 07:27 PM   #6
sbelyo is offline sbelyo  United States
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Originally Posted by boywonder View Post
If none of the tube elements were shorted and it just tested weak, that shouldn't cause any harm.
good, there were no shorts
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Old 27th April 2011, 07:32 PM   #7
M Gregg is offline M Gregg  United Kingdom
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Originally Posted by carbondated View Post
Here's something I've always wanted to know - how do you know when a choke is faulty? I hear of chokes becoming 'oversaturated', what happens then?
depends on the fault!

If the choke overheats or the back EMF is very high you can get shorted turns this means your power supply will become noisy due to lower henrys. (Hum). If you get a short to Gnd then the B+ will either blow a fuse or if no fuse then rectifier or HT winding on power Tx will fail.


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Old 27th April 2011, 08:38 PM   #8
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@M Gregg Thanks, that helps!
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Old 27th April 2011, 08:44 PM   #9
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If a saturated choke sits around for a long time the magnetic field will diminish. It also drops a bit just about every time you power it up. So if you don't notice any hum, you got an almost free lesson.

Now you can place the same tube back on eBay and honestly say you tried it and did not like it!
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Old 27th April 2011, 08:45 PM   #10
sbelyo is offline sbelyo  United States
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the amp was dead silent before and still dead silent after, so I don't think I shorted any turns
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