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Fender Bassman - Bad Hum

kbakerde

kbakerde

Supporting Member
Jan 24, 2012
3,013
4,695
#1
It looks like I may have to get my Bassman out to the tech for a look-through. Background, about two years ago I went out and bought myself a 78-79 Bassman 135 amp. Best sounding amp I've ever played and it's kind of what my tone is now. I took it in and it got all new power tubes, a filter cap job, and a few other misc resistors and caps that were old.

Got a new bass, wanted to put it through the paces the other day. Amp is kept in the basement, and it hasn't seen a show since late September. At that time it worked completely fine, but the other day I plugged it up and turned it on to warm up. Speaker wire was connected, nothing was in the input jack either. I was bringing my new bass into the room to plug it in when I noticed a pretty loud hum that wasn't there before. I turned off the amp and there was a pretty loud pop, I turned on the amp to try again, but there was still a hum and now there was an oder to go with it. I flipped the ground switch which didn't do anything. I turned it off and put it away.

One thing is that I hadn't used the amp in that part of the house, so the outlet could possible have something to do with it? I will try it in a different part of the house, but it seems like there might be a problem with the amp. I know there are some pretty knowledgeable guys here, so I am just looking to see how bad this might be for the amp. Could I just have bad tubes, or does this sound like a big problem?
 
#3
Check your house outlets with a receptacle tester just to be sure your outlet is wired properly. Normally there shouldn't be a loud popping when the amp is turned off. Once you find a proper working outlet, try using a extension cord with a power switch between your amp and the power. Then, after warming up the amp and using it:
1) turn on the stand by, wait 3 to 5 min,
2) next, turn OFF the power switch on the extension cable,
3) then wait another 3-5 min and turn OFF the amp's power switch.

This may eliminate the pop. But you should get the amp checked out to see what the cause of the pop is, and have it fixed. The amp should not pop when turning off.
 
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#8
Some old tube amps smell. Tube sniffers like amps that do this. The smell could be a brew of accumulated dust, absorbed humidity, and solder flux. It might need a cleaning.

Sounds like you have funky wiring in the basement. Maybe the outlet doesn’t have a third prong safety ground connected. A $5 hardware store outlet tester will indicate if there is a wiring issue.

I used to have a Fender 135W amp that I bought new. I always regret selling that one.
 
#10
beans-on-toast said:
Some old tube amps smell. Tube sniffers like amps that do this. The smell could be a brew of accumulated dust, absorbed humidity, and solder flux. It might need a cleaning.

Sounds like you have funky wiring in the basement. Maybe the outlet doesn’t have a third prong safety ground connected. A $5 hardware store outlet tester will indicate if there is a wiring issue.

I used to have a Fender 135W amp that I bought new. I always regret selling that one.
Click to expand...

I just moved into the house but almost nothing would surprise me. There are a lot of weird little things we’ve had to fix up after the move. I have an outlet tester but it only shows hot or not. Can you send a link of what you’re referring to? Thanks.

This is my second 135. I know most players think the 100 is superior but I’ve always disagreed. I think having a 3 Band EQ instead of the 2 Band makes a difference.
 
#11
kbakerde said:
I just moved into the house but almost nothing would surprise me. There are a lot of weird little things we’ve had to fix up after the move. I have an outlet tester but it only shows hot or not. Can you send a link of what you’re referring to? Thanks.

This is my second 135. I know most players think the 100 is superior but I’ve always disagreed. I think having a 3 Band EQ instead of the 2 Band makes a difference.
Click to expand...

Here is an example of the type of three prong outlet tester that I was thinking of:
Commercial Electric Tools Outlet Tester, Green-MS112H - The Home Depot

The 135W has output transformer primary taps for the tube screens, some call this ultra-linear taps, this lowers distortion. The amp is cleaner. Guitar players like amps that don’t have this type of transformer because they distort.
 
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