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Author Topic: Ameritron AL-572 Burning Smell  (Read 8512 times)
K4HYZ
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Posts: 14




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« on: October 26, 2012, 09:48:00 AM »

My al-572 has a burning smell when tuning on cw. The amp still functions but i need to address the issue. I can see some possible arcing on the bottom of the tube sockets but am not sure if this is the culprit.  R27/R127 10ohm looks to be deformed compared to similar PS resistors although it meters ok...please look at the photo links and feel free to input your knowledge.

http://i254.photobucket.com/albums/hh88/funbiz99/al572%20eham/P1040135.jpg

http://i254.photobucket.com/albums/hh88/funbiz99/al572%20eham/P1040134.jpg

http://i254.photobucket.com/albums/hh88/funbiz99/al572%20eham/P1040133.jpg

73 marc k4hyz/hs0zju
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K3STX
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« Reply #1 on: October 26, 2012, 11:24:09 AM »

That choke does not look too good. And it looks like the PIN of the tube is cooked, not the socket. Have you switched tubes?

paul
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W8JI
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« Reply #2 on: October 26, 2012, 11:30:37 AM »

If you look at the relay near the resistor, it looks like the armature has slipped out of place. This happens if there is a really hard drop on the amplifier. What happens is the G-force of the sudden stop overpowers the relay spring, and unseats the armature. This picture seems to show the armature as not seated flat in the relay frame:

http://i254.photobucket.com/albums/hh88/funbiz99/al572%20eham/P1040135.jpg

That could be an illusion, but it looks skewed.


Further along that line, it looks like the physical hit was hard enough the transformer under the tubes hit the chassis and chipped. I can see a definite chip in the core right where it would hit the chassis, and other signs of a pretty hard drop. (Actually the drop doesn't matter, the stop does.)

UNPLUG the amplifier, be SURE you unplug it, and you should be able to grab the relay armature and slip it back into place.

I would also IMMEDIATELY call the shipper and say it appears to have concealed damage, and be sure to save the boxes. I would carefully and closely inspect the amplifier for bent metal, like the chassis below the transformer where the G-force of the transformer might bend the steel bottom.

What shape are the boxes in, and where was it shipped from? You can tell a hard drop by the cardboard being crushed either inside or outside.

It should have been double boxed with foam supports on the amplifier. Were the inner foam cushions in place? Look at the packing closely.

« Last Edit: October 26, 2012, 11:34:45 AM by W8JI » Logged
HS0ZJU
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Posts: 163




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« Reply #3 on: October 26, 2012, 11:46:42 AM »

That choke does not look too good. And it looks like the PIN of the tube is cooked, not the socket. Have you switched tubes?

paul

the tube pin looked bad so i installed another tube. Although it didnt seem to look bad where it contacts the socket. Only above the socket and it looks oxidized not burnt.

73 marc k4 hyz/hs0zju
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W8JI
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« Reply #4 on: October 26, 2012, 11:57:57 AM »

Marc,

Read my previous post before you do or try anything else.

Tom

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HS0ZJU
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« Reply #5 on: October 26, 2012, 11:59:51 AM »

@w8ji

The relay is working fine i am just a poor photographer. The tranformer under the tube sockets has no chips. I rotated the one on the left just now and it is also discolored at the but less then the right one.

The amp has been in service for over a year and perfomed excellent. The amp still works great except the odor when tuning it.

73 marc k4hyz/hs0zju
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HS0ZJU
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« Reply #6 on: October 26, 2012, 12:01:15 PM »

Tom

i am not doing anything without your blessing ;]

73 marc k4hyz/hs0zju
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W8JI
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« Reply #7 on: October 26, 2012, 12:12:27 PM »

@w8ji

The relay is working fine i am just a poor photographer. The tranformer under the tube sockets has no chips. I rotated the one on the left just now and it is also discolored at the but less then the right one.

The amp has been in service for over a year and perfomed excellent. The amp still works great except the odor when tuning it.

73 marc k4hyz/hs0zju

OK. Those pictures sure fooled me. The picture of the transformer really looks like chips, and the relay armature looks skewed!!!

 What band are you on when it smells, and what does it smell like, if it is any smell you recognize?

Did you look close for something that looks hot? Maybe unplug it and sniff around to see what area smells?

Does the HV stay up within normal range when you tune??

 

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K4HYZ
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Posts: 14




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« Reply #8 on: October 27, 2012, 03:43:43 AM »

@w8ji

The relay is working fine i am just a poor photographer. The tranformer under the tube sockets has no chips. I rotated the one on the left just now and it is also discolored at the but less then the right one.

The amp has been in service for over a year and perfomed excellent. The amp still works great except the odor when tuning it.

73 marc k4hyz/hs0zju

OK. Those pictures sure fooled me. The picture of the transformer really looks like chips, and the relay armature looks skewed!!!

 What band are you on when it smells, and what does it smell like, if it is any smell you recognize?

Did you look close for something that looks hot? Maybe unplug it and sniff around to see what area smells?

Does the HV stay up within normal range when you tune??

 



The only components that looked like they have/had issues were r27/r127 and the transformer underneath. The problem occurs on all bands 10-40 meters. I assume 80 too but can not check it.  The HV is 2700 at idle with 70 watts drive on cw it drops to 2250 with 900 watts output. GRID 80 and Plate 750

 It smells like burning components. The smell is not there in ssb or rtty.

fyi the amp is running 240v

73 marc k4hyz/hs0zju
« Last Edit: October 27, 2012, 04:04:26 AM by K4HYZ » Logged
W8JI
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« Reply #9 on: October 27, 2012, 05:07:50 AM »

R127 is only in the circuit while the relay RL101 is not closed. As soon as RL101 closes, the resistor is shorted. If RL101 does not close, it is very evident. R127 will smoke.

R127 or F101 can fail on start up, with bad tubes or a bad transformer.

What is the history of the amp? Has the transformer been replaced?
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HS0ZJU
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« Reply #10 on: October 27, 2012, 05:16:42 AM »

hi tom

the only thing that has been done have been replacement tubes and repair of a bad solder joint when the amp would not load on 40meters

73 marc k4hyz/hs0zju
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K8AXW
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« Reply #11 on: October 27, 2012, 08:36:20 AM »

Quote
That choke does not look too good. And it looks like the PIN of the tube is cooked, not the socket. Have you switched tubes?

paul

While I don't think for a second the burnt tube pin is your problem, I think that socket needs attention.  It been my experience that a pin discolorization is caused by heat caused by poor pin contact/pressure.  I'd clean that pin up inside and gently squeeze the pin and then reinsert the tube.  I also suggest you check that pin occasionally.

Tom:  If the relay is hanging.....not shorting out the dropping resistor it will get very hot and give off an odor.  The point he makes about working OK on SSB and RTTY might be throwing him off because of the relay "hang" being intermittent. 

If the thing is going to smoke or smell, it certainly should be doing it on RTTY!
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W8JI
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« Reply #12 on: October 27, 2012, 09:02:09 AM »

I wouldn't worry about anything at this point. It doesn't sound like a problem.




 
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WB2WIK
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« Reply #13 on: October 27, 2012, 09:08:42 AM »

Last Thanksgiving my amp smelled like turkey for hours, but then I found so did the whole house. Wink
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K4HYZ
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Posts: 14




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« Reply #14 on: October 31, 2012, 01:58:28 AM »

I have located the problem please see photos. I re-soldered and tightened the connection but the pillar is still heating up at bottom connection. What would be a better approach to repair?

http://i254.photobucket.com/albums/hh88/funbiz99/al572%20eham/P1040136.jpg

Another problem i discovered and repaired

http://i254.photobucket.com/albums/hh88/funbiz99/al572%20eham/P1040139.jpg
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