It is currently Tue Mar 17, 2020 12:08 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 9 posts ] 
Author Message
Post subject: Bassman 410 LTD RI low end hum problem
Posted: Wed Mar 20, 2013 12:44 pm
Offline
Hobbyist
Hobbyist

Joined: Wed Mar 20, 2013 12:41 pm
Posts: 5
Having an unexpected problem with my Fender Bassman 410 LTD reissue. Was used pretty heavy during the past week at SXSW, hoping someone can shed some light on the issue.

When I flip it off standby a low, machine like low end hum begins and builds until it's fairly loud. No signal is plugged in and all the pots are at 0. Have tried different power sources, wall, surge protector, etc.

Uploaded a video of the issue, please watch

Thanks!



Top
Profile
Fender Play Winter Sale 2020
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Wed Mar 20, 2013 1:25 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Hi gibstone,

Sounds like either a bad tube or a bad coupling cap or a bad power supply cap. You might try pulling each preamp tube, one at a time and then replacing, to see if the noise stops when any particular one is pulled. If the noise stops when any one is pulled, the problem might be that tube or the tube before it, or the coupling cap for that tube, or the coupling cap for the tube before it. Substitution of a known good tube in each position, one at a time, is also another method.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Wed Mar 20, 2013 1:42 pm
Offline
Rock Star
Rock Star

Joined: Mon Apr 05, 2010 2:37 pm
Posts: 8708
Location: Natural Bridge, Virginia
+1

Given the fact that you have both volume controls zeroed, I think that would eliminate the problem being in the preamp stage (V1) of the amp. The cathode follower (V2) is a possibility as is the PI and power tubes.

Image

_________________
Bill

Image


Top
Profile
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Fri Mar 29, 2013 2:33 pm
Offline
Hobbyist
Hobbyist

Joined: Wed Mar 20, 2013 12:41 pm
Posts: 5
I'm also thinking it's a tube issue. I'll give your methods a shot and let you know what happens.

The fuse has been periodically blowing, if that helps.

Anyone know of a good amp guy in Austin, TX? You'd think we'd have a glut, but everyone that I've gone to has sucked.

Thanks everyone!


Top
Profile
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Fri Mar 29, 2013 2:57 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Wed Mar 31, 2010 12:48 am
Posts: 26417
Location: Tombstone Territory
If the amp has fuse issues I'd start by replacing the rectifier with a known good GZ34/5AR4.

HTH

Arjay

_________________
"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


Top
Profile
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Sat Mar 30, 2013 7:36 am
Offline
Rock Star
Rock Star

Joined: Mon Apr 05, 2010 2:37 pm
Posts: 8708
Location: Natural Bridge, Virginia
Retroverbial wrote:
If the amp has fuse issues I'd start by replacing the rectifier with a known good GZ34/5AR4.

HTH

Arjay


Definitely get the power supply stable before any serious testing. Power supplies are the cause of many problems that can look like something else.

_________________
Bill

Image


Top
Profile
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Tue Apr 02, 2013 7:33 pm
Offline
Hobbyist
Hobbyist

Joined: Wed Mar 20, 2013 12:41 pm
Posts: 5
bluesky636 wrote:
Retroverbial wrote:
If the amp has fuse issues I'd start by replacing the rectifier with a known good GZ34/5AR4.

HTH

Arjay


Definitely get the power supply stable before any serious testing. Power supplies are the cause of many problems that can look like something else.


Very engaging gentlemen, thank you. Bill do you mean the power cable, power tubes, or ?

Thanks again.


Top
Profile
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Tue Apr 02, 2013 7:44 pm
Offline
Rock Icon
Rock Icon
User avatar

Joined: Tue Jun 29, 2010 1:20 pm
Posts: 9640
Location: Indiana
Power supply ---> rectifier tube.

_________________
---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


Top
Profile
Post subject: Re: Bassman 410 LTD RI low end hum problem
Posted: Tue Apr 02, 2013 9:01 pm
Offline
Rock Star
Rock Star

Joined: Mon Apr 05, 2010 2:37 pm
Posts: 8708
Location: Natural Bridge, Virginia
shimmilou wrote:
Power supply ---> rectifier tube.


And caps if necessary.

_________________
Bill

Image


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: