I'm having a very strange issue with an old National amp I picked up. It's an old Westwood model, with 2 12ax7's, a 5y3, and a 6v6. When I got it I opened it up and noticed one of the coupling caps leaking so I went ahead and replaced it, along with another coupling cap and the filter caps. It used one of those old Mallory can caps so I found a suitable replacement from tube depot. I also went ahead and added a 3 prong cord. I grounded it to a power tranny lug.
I also got new preamp tubes and a new 6v6. I purchased the vintage 6v6 used off eBay from a reputable seller who claims it tested strong.
Now, when I turn the amp on, it plays ok, but with an annoying buzz. It does get louder when I turn the amp up, and I'm thinking this is just typical dirty power, etc?
What really concerns me is the fact that when I put the amp on standby the power tube starts squeeling. Not through the speaker, but noise emitting from the actual tube. I looked at it and it was emitting a bluish slightly flickering light like it was shorting or something? I have no idea. Any ideas?
I also got new preamp tubes and a new 6v6. I purchased the vintage 6v6 used off eBay from a reputable seller who claims it tested strong.
Now, when I turn the amp on, it plays ok, but with an annoying buzz. It does get louder when I turn the amp up, and I'm thinking this is just typical dirty power, etc?
What really concerns me is the fact that when I put the amp on standby the power tube starts squeeling. Not through the speaker, but noise emitting from the actual tube. I looked at it and it was emitting a bluish slightly flickering light like it was shorting or something? I have no idea. Any ideas?
Thanks alot for taking the time to respond. I'm not exactly sure how to go about determining how it acts. How would I go about doing that?
pics
If it helps, here is a picture of the inside of the amp:
And here is one of the exterior configuration:
If it helps, here is a picture of the inside of the amp:
And here is one of the exterior configuration:
Squealing what? Power transformer, speaker, output transformer?
I ask the way the stand by switch is wired, because in this manner it is easiest to identify where is the issue, after or before that switching.
I ask the way the stand by switch is wired, because in this manner it is easiest to identify where is the issue, after or before that switching.
Its literally the power tube that is squealing. Its a terrible noise. Not extremely loud or anything, about the decibel lever of a meowing cat... Strange comparison, but it's the first thing that came to mind...
How do I tell which way it is wired?
How do I tell which way it is wired?
How many time does the tube do it sound. Some tubes, and any other stuff makes noise when heating (because of dilatation of materials), and when cold (by contraction), like a rain noise on a steel sheet. but for few seconds.
You can see from the picture that there is no switch between the transformer, rectifier and output transformer. Is there a model number anywhere? I can not find a reference to a "National Westwood" in any of my usual sources.
How are you putting it on standby? I don't see a standby switch.
If the output tube is squealing, it seems to indicate that the loudspeakers may not be connected and the stage is oscillating.
We really need more information.
If the output tube is squealing, it seems to indicate that the loudspeakers may not be connected and the stage is oscillating.
We really need more information.
Well, Im certainly learning a little about this amp through the process. First off, my apologies. They amp was already put back together when I initially posted and I just grabbed a picture of the inside of this amp off the internet. Upon close inspection, I realized mine has has some modification and apparently someone installed a standby switch of some sort. I took my amp back apart and took some pictures. I hope I didn't wasted to much of anyones time the first go around! Again, my sincerest apologies.
What I would really appreciate your opinions on at this point is:
1. Being that this amp didn't even come with a standby switch,should I just disconnect it altogether and fix this problem that way? If so, and idea which wires I connect when I remove them from the switch terminals?
2. Also, any idea what the hum/buzz might be caused by?
Here is my actual amp. Its a National Westwood Model N 6416 T by the way.
Thanks a lot for any additional help on this guys.
What I would really appreciate your opinions on at this point is:
1. Being that this amp didn't even come with a standby switch,should I just disconnect it altogether and fix this problem that way? If so, and idea which wires I connect when I remove them from the switch terminals?
2. Also, any idea what the hum/buzz might be caused by?
Here is my actual amp. Its a National Westwood Model N 6416 T by the way.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Thanks a lot for any additional help on this guys.
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