'59 Bassman reissue question....

[JSB]

Hello all!
Great place you have here.
I searched before posting and did not find anything significant regarding my question.
My '59 reissue is very, very noisy at idle. It hisses and pops.
It is completely stock except for the jj preamp tubes which are a year old and are going to be replaced soon.
First, I would like to know if the preamp tubes could be responsible for the noise. Secondly, what tubes do you recommend for replacement?
I have read a bit about 1/4 watt resistors needing to be 1/2 watt, would these cause noise?
Thanks in advance for your help.

[JSB]

'59 Bassman Reissue question...

Hello all!
Great place you have here.
I searched before posting and did not find anything significant regarding my question.
My '59 reissue is very, very noisy at idle. It hisses and pops.
It is completely stock except for the jj preamp tubes which are a year old and are going to be replaced soon.
First, I would like to know if the preamp tubes could be responsible for the noise. Secondly, what tubes do you recommend for replacement?
I have read a bit about 1/4 watt resistors needing to be 1/2 watt, would these cause noise?
Thanks in advance for your help.

[Rick Erickson]

First, I would like to know if the preamp tubes could be responsible for the noise.

Yes

Secondly, what tubes do you recommend for replacement?

JJ's - they seem to be the least problematic right out of the box - at the moment.

I have read a bit about 1/4 watt resistors needing to be 1/2 watt, would these cause noise?

They certainly might, especially if 12AT7 or 12AU7 tubes have ever been installed. 1 year is not very old for preamp tubes. I would just locate the noisy one and replace that.

RE

[JSB]

They certainly might, especially if 12AT7 or 12AU7 tubes have ever been installed. 1 year is not very old for preamp tubes. I would just locate the noisy one and replace that.

Thanks for the response.
How quiet should the amp be at idle?
I have never put anything in the tubes sockets but what is listed on the chart.
Is there something about the AT7 or AU7 that is desirable?

Do I need to bias the amp after new power tubes?

[loudthud]

Tubes are always suspect. Do the volume controls have any effect? Have you tried moving the 12AX7's around?

[stokes]

There was a tech advisory from Fender about the 1/4 watt plate load resistors.I have repaired 2 different RI Bassman amps with the same problem by changing them to 1 watt,although 1/2 watt should do it.

[JSB]

Tubes are always suspect. Do the volume controls have any effect? Have you tried moving the 12AX7's around?

No, I haven't tried moving them around yet. I will though......tonite.
It makes the hiss and pop even when the volume is down. When I turn it up, I can hear what I percieve to be a normal, minor increase in hiss....that's it.
Thank you for your thoughtful input.

[JSB]

There was a tech advisory from Fender about the 1/4 watt plate load resistors.I have repaired 2 different RI Bassman amps with the same problem by changing them to 1 watt,although 1/2 watt should do it.

I think I am going to change mine to 1 watt also.
I am not used to finding these things on a circuit board, are they easy to find?

[stokes]

They are the resistors connected to pins 1 and 6 on all your preamp tubes.

[keysersoze808]

hi.. i've repairing few old bassman head..and the most common thing that produce noise was the plate load 100k CC resistor.. maybe its the same issue on your amp..