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Post subject: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 7:01 pm
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I bought this fender bassman used a couple months ago and I realized that the previous owner put 6v6 power tubes in instead of 6l6 tubes. I was never able to get a lot of volume out of the amp. Even when putting the amp on volume 10 (both master and channel) I would barely be louder than the drums.

I decided that I was going to try to see if I could some how get this amp to be louder. I figured I would start with the suspected 6v6 tubes. I only had a set of these vintage Ken-Rad 6l6 metal tubes lying around so I figured they couldn't be any worse than the 6v6 tubes that were currently in the amp.

I stuck them in and let the amp warm up for a few minutes. I made sure all the volumes were set at 0 before turning it off standby. After turning it off standby there was a loud hum followed by silence. I quickly turned the amp off and let it cool down.

I put the 6v6 tubes back in and tried turning the amp on but there wasn't any power going through the amp. Neither the tubes nor the red power light in the front lit up. I remembered I had some 6l6 tubes in my fender blues deville so I stuck those in the bassman, but still there isn't any power.

Any ideas? I thought I might have blown the power transformer but from what I have read, most cases with a blown PT result in black smoke coming out of the amp and a burnt electronics smell. My amp didn't have any smoke come out and it does not smell...

Here's some pictures of the amp and the 6l6 tubes:

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Any help would be much appreciated!
Thank you!


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Post subject: Re: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 7:30 pm
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Not trying to be a wise guy but......
Did ya check the fuse ? :mrgreen:

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Post subject: Re: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 7:36 pm
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Ya I checked the fuse it doesn't look blown. There isn't any discoloration in the glass and there aren't any breaks inside. That was my first thought too and I really hoped it was just the fuse...


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Post subject: Re: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 7:44 pm
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Use Caution !!!

Pull the chassis and look for burnt stuff.

Check that fuse on an ohm meter just in case, slow blow fuses can hide the trouble some times, see if its an open circuit between the caps before you go too far in another direction.

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Keepn' the Blues Alive

2004 50th Ann. Limited edition AMSE Stratocaster
2017 50's Baja Telecaster BSB

1968 Bandmaster with 2X12 cab C-rex speakers
VHT Special 6 Ultra combo

Visual Sound Route 66
Cmatmods Signa Drive


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Post subject: Re: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 7:52 pm
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Thank you I'll buy a new fuse tomorrow just in case it is the problem (hopefully it is). If not I'll open up the chassis and see if I can find any problems.


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Post subject: Re: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 8:19 pm
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The Ken-Rad's are likely toast -- those metal-cased 6L6's are only good for about 350VDC and when you took the amp from "standby" to "play", you hit them with close to 470VDC. And judging from the JAN "Signal Corps" designation, they probably date to the 1950's -- pretty old. If the pilot lamp still lights when you switch the amp on, the PT may be alright but maybe not. You may also have a dead rectifier tube. A thorough examination of the power supply is in order before proceeding with any further troubleshooting.

Arjay

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Post subject: Re: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 10:25 pm
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blues bondsman wrote:
Use Caution !!!

Pull the chassis and look for burnt stuff.

Check that fuse on an ohm meter just in case, slow blow fuses can hide the trouble some times, see if its an open circuit between the caps before you go too far in another direction.


Good advice ; just by looking a fuse could look good , an ohmmeter check is a must . Be sure to put the fuse with same power than write on back panel, Don't trust the old fuse


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Post subject: Re: NEED HELP 1978 FENDER BASSMAN TEN NO POWER
Posted: Wed Mar 28, 2012 10:32 pm
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Also, pin 1 of the metal case tube is connected to the tube case. Since pin 1 of glass 6L6 is not used, that socket pin is sometimes used as a tie point for other components. If there are metal tube retainers, or if the metal tube case contacts the chassis in any way, whatever is tied to pin 1 of the tube socket becomes grounded.

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