Has this Maggie bought the farm? (sorry, Bob)

[Moonwatcher]

Hey, tube guys . . . so my Magnavox 9304 console pull was severely jarred during a move. After just a few seconds of being powered on, it made a loud, scary rattle and the tubes sparked (see below). I quickly pulled the plug. One modification that was made was adding Edcor output transformers--but they have been working fine for years.

I took it to a local guy who repairs vintage solid state and occasional tube units. But after looking at it, he felt he was out of his depth (and doesn't want to be electrocuted).

Does anyone have any idea where such a problem could start? The big can capacitor on top? I have changed out all the tubes--el84s (7189) and 6eu7s. Thanks in advance for any suggestions!

 

[Jalousie]

Hehe. I can't help with your question, but I heard Maggie's Farm on Underground Garage in the car this afternoon. Love that song.

 

[Jalousie]

I don't think severely jarred would cause a can cap to go bad. Maybe some wires touching together from the jarring?

 

[gadget73]

Pics please? If the transformers haven't failed everything else can be fixed easily

 

[FB night]

Did you change out your rectifier tube?

 

[Lavane]

Look underneath for any wires or leads that got shortedd to each other.
If the noise is in both channels, look real close at the power supply area.

 

[mrwood200]

my Magnavox ...... was severely jarred during a move.

DOH! Sorry to hear.
Any additional details on 'jarred'? Sometimes details help point towards solutions.

Pics please?

Yes, bottom cover removed, and any specific damaged area.
Was it just the one tube that 'sparked'? (FYI - never seen that before....). If no other clues, I am starting at the one tube & tracing the path.

 

[Moonwatcher]

Me too. And pretty much anything he ever did.

Hehe. I can't help with your question, but I heard Maggie's Farm on Underground Garage in the car this afternoon. Love that song.

e

 

[Moonwatcher]

I don't think severely jarred would cause a can cap to go bad. Maybe some wires touching together from the jarring?

Thanks, I will look again, but the amp was worked on by a competent tech about five years ago and seems pretty clean underneath. Some solder joints could probably be cleaned up.

Look underneath for any wires or leads that got shortedd to each other.
If the noise is in both channels, look real close at the power supply area.

Believe it or not, the noise is not coming from one channel or another, because the speakers are not even hooked up. It's the amp itself that makes that rattling sound you can hear in the video.

You have to watch for it, but you can also see a brief spark in the third el84 tube on the right channel. Changing out all the tubes made zero difference.

Did you change out your rectifier tube?

Look underneath for any wires or leads that got shortedd to each other.
If the noise is in both channels, look real close at the power supply area.

Pics please? If the transformers haven't failed everything else can be fixed easily

More pics coming tomorrow, Gadget. Thanks!

I don't think severely jarred would cause a can cap to go bad. Maybe some wires touching together from the jarring?

DOH! Sorry to hear.
Any additional details on 'jarred'? Sometimes details help point towards solutions.

Yes, bottom cover removed, and any specific damaged area.
Was it just the one tube that 'sparked'? (FYI - never seen that before....). If no other clues, I am starting at the one tube & tracing the path.

Several years ago I changed out the rectifier tube. But that's a thought: the rectifier was bent way over after the amp slid off a shelf and hit the floor hard. Maybe something underneath was damaged in that incident. (It's extremely heavy because of those Edcor transformers.)

DOH! Sorry to hear.
Any additional details on 'jarred'? Sometimes details help point towards solutions.

Yes, bottom cover removed, and any specific damaged area.
Was it just the one tube that 'sparked'? (FYI - never seen that before....). If no other clues, I am starting at the one tube & tracing the path.

 

[Moonwatcher]

I don't think severely jarred would cause a can cap to go bad. Maybe some wires touching together from the jarring?

Thanks, Mssr. Jalousie. I will look again when I get the amp back, but things look pretty clean under the hood. Some soldered joints could probably be improved on.

 

[Moonwatcher]

I don't think severely jarred would cause a can cap to go bad. Maybe some wires touching together from the jarring?

Thanks, I will go through it again, but I checked pretty closely for that.

 

[Moonwatcher]

Did you change out your rectifier tube?

I did a few years ago, but it did get bent in the accident, so replacing it might be a good idea. (I am having a hard time with these replies--I write them but then they disappear . . .)

 

[Moonwatcher]

Hehe. I can't help with your question, but I heard Maggie's Farm on Underground Garage in the car this afternoon. Love that song.

Me too--and pretty much everything else he ever did.

 

[Moonwatcher]

Me too--and pretty much everything else he ever did. (Did they change something about replying to posts? It keeps

Hehe. I can't help with your question, but I heard Maggie's Farm on Underground Garage in the car this afternoon. Love that song.

Hehe. I can't help with your question, but I heard Maggie's Farm on Underground Garage in the car this afternoon. Love that song.

 

[Moonwatcher]

I don't seem to have the hang of the new way these chats work--my replies keep disappearing ... and then duplicating. Sorry.

 

[gadget73]

a shorted rectifier could be causing this, luckily 5U4's are pretty cheap. Still some pics to rule out obvious damage would be good, then test it with the rectifier out.

also you really shouldn't run amps with no speakers connected. It can cause the tubes to arc or damage to the output transformers if something is trying to make sound and the amp is not loaded. It should be connected to a dummy load if you don't want to risk speakers.

 

[Lavane]

Maybe that's what caused the problem to begin with. Never turn the amp on without speakers or load resistors connected!! And especially when feeding it a signal. The screeching was most likely the output transformers singing. They don't like that.

 

[century tek]

Let's see the bottom side. It could be that feedback was reversed on one channel but holy cow, if that sound is coming from the output transformers themselves, do not turn it on again until the problem has been resolved.

 

[gadget73]

if it worked before they didn't suddenly reverse. I'd buy a shorted rectifier or broken loose filter cap though.

 

[Gigantic]

apples and oranges, but recently, my kitten "jarred" one of the EL-84s loose on my amp, causing almost exactly what you described. in my case, since my amp is ss rectified, it took out a couple resistors in the rectifier circuit, which were easily replaced. I suspect that the recommendations to replace the rectifier tubes or the associated filter caps to be not far off the mark. take off the bottom cover of your amp and let's see the innards. Those Maggies are dead simple and it shouldn't be too hard to spot any singed resistors or caps.