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Post subject: bassman 59 ri rattles
Posted: Mon Jul 02, 2012 3:46 pm
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my bassman rattles, especially at high frequencies. :roll:

i already checked the speakers, loose screws and the cabinet, they don't produce the noise. you only hear the rattle when the amp is turned on, not in standby.
i suspected the tubes so i put on some tube silicon tube dampers. they didn't help, either.
i checked the chassis and i found that the first preamp tube seems to be involved in this:

it is somewhat microphonic!

when you touch the wired attached to its socket or the tube itself you can hear it.
is a preamp tube meant to be like that?
i was putting in a new tube, but with the same result. after that i put about 6 tube dampers on it to prevent rattling. now it's a lot quiter, but still present.

what the heck am i supposed to do?

thanks in advance!

t.


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Post subject: Re: bassman 59 ri rattles
Posted: Mon Jul 02, 2012 3:56 pm
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I had a bad rattle on the 59 Bassman clone that I built. Turned out it was a bad solder joint on the 68K Ohm grid stopper resistor for the hi-level bright channel input. I resoldered it and the noise went away.

Yours being the Reissue is not wired like mine is, but you said you noticed the noise while tapping the wire going to the V1 socket. I would try resoldering each wire at the socket and at the PCB if possible and see if that helps. Just heat each connection up until the solder reflows. You may not even have to add any solder. I didn't.

Make sure you discharge the power supply caps before going into the amp. If you are not comfortable doing this, take it to a good amp tech.

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Post subject: Re: bassman 59 ri rattles
Posted: Mon Jul 02, 2012 7:06 pm
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timohohoh wrote:
my bassman rattles, especially at high frequencies...i checked the chassis and i found that the first preamp tube seems to be involved in this:

it is somewhat microphonic!

when you touch the wired attached to its socket or the tube itself you can hear it.
is a preamp tube meant to be like that?...


First, could you explain what you mean by "rattle"? And does the noise happen all the time, or only on certain notes? Does it sound like a feedback or howl or squeal? The latter being microphonic.

I think that you are looking at two separate issues, one of which probably has nothing to do with the problem.

All tubes are "somewhat microphonic", and the V1 position of many amps usually being the most sensitive. If you simply touch the wires near V1, the sound can be like interference/humming and is normal. If you tap on the wires near V1 you would expect to hear the tapping, as the tube will amplify the sound naturally, and is normal. If the tube produces too much sound with only a little tapping, that tube could be too sensitive (microphonic) and might need to be replaced (you already tried replacing, indicating that it isn't the tube).

"Microphonic" and "rattle" are two different things, and mostly not related to one another. If you tried a new tube in V1 with the same results, I'd say that tube is not your problem, and maybe you're wrongly attributing the tube's natural microphonics to the "rattle" noise.

Have you tried replacing the other tubes besides V1? You can try the same new tube in the other two positions also. If not any preamp tubes, it could be an output tube. Try some dampers on the other tubes. If it is tube rattle, you can grasp the tube and feel the rattling while someone else plays. Tubes are hot, you might need to use a pot holder to grasp the output tubes

In a 50 watt amp with 4x10s, I would expect the possibility of tube rattle, you have to use very good tubes, and dampers would be a good idea in such a large combo as a preventative measure.

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Post subject: Re: bassman 59 ri rattles
Posted: Mon Jul 02, 2012 8:53 pm
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Keep in mind that the 59 Bassman Reissue uses a 12AX7 in V1 while I use a 12AY7 in my clone.

When I tapped on the solder joint at the input jack, it almost sent V1 into oscillation. A slight tweek of the resistor and a resolder cured the probelm, so I thought that would be worth mentioning as a possible similar problem/solution.

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Post subject: Re: bassman 59 ri rattles
Posted: Tue Jul 03, 2012 2:18 am
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shimmilou wrote:
timohohoh wrote:
I think that you are looking at two separate issues, one of which probably has nothing to do with the problem.


yeah, you're right, 'kind of'. :wink:
v1 is just so sensitive that it amplifies something resonating on the chassis, either the wires at the socket or some sort of screw somewhere around the chassis.
i will resolder the socket and see what it turns out.
thank you so much,guys!


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Post subject: Re: bassman 59 ri rattles
Posted: Tue Jul 03, 2012 7:05 am
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timohohoh wrote:
shimmilou wrote:
timohohoh wrote:
I think that you are looking at two separate issues, one of which probably has nothing to do with the problem.


yeah, you're right, 'kind of'. :wink:
v1 is just so sensitive that it amplifies something resonating on the chassis, either the wires at the socket or some sort of screw somewhere around the chassis.
i will resolder the socket and see what it turns out.
thank you so much,guys!


You might want to consider replacing V1 with a 12AY7 like the originals. It will drop the gain somewhat and give the amp a slightly warmer sound. The one I favor is this:

http://www.kcanostubes.com/content/nos-jan-ge-12ay7

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Post subject: Re: bassman 59 ri rattles
Posted: Tue Jul 03, 2012 1:20 pm
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crazy, i resoldered it and the noise is gone...


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Post subject: Re: bassman 59 ri rattles
Posted: Tue Jul 03, 2012 1:24 pm
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timohohoh wrote:
crazy, i resoldered it and the noise is gone...


What did I tell ya. :wink:

Now, yank out that 12AX7 and stuff a 12AY7 into V1. :D

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Post subject: Re: bassman 59 ri rattles
Posted: Tue Jul 03, 2012 2:09 pm
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:mrgreen:

Arjay

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Post subject: Re: bassman 59 ri rattles
Posted: Tue Jul 03, 2012 2:44 pm
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Well, a swing and a miss for me. Good catch bluesky636!

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Post subject: Re: bassman 59 ri rattles
Posted: Tue Jul 03, 2012 3:24 pm
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shimmilou wrote:
Well, a swing and a miss for me. Good catch bluesky636!


Well, I hope it is the final solution for timohohoh. I think I posted about this problem in my 5F6A build up thread. It drove me nuts for several days.

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