Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Big chief on December 10, 2015, 08:53:21 am

Title: Super Reverb
Post by: Big chief on December 10, 2015, 08:53:21 am

Fender super reverb keeps blowing resistor at tube 8 I use 470 2 watt. This is a solid state rectifier with 6l6 tubes
With master volume. I'm trying to help some one with little money and this amp is over 35 years old
Please help

Thank you
If any one has a layout of this amp it sure would help

Title: Re: Super Reverb
Post by: shooter on December 10, 2015, 10:10:54 am

couple ideas, what's the bias reading for each tube?, check the plate diode (d5) verify its not shorted. 
If bias and diode looks good, mark V8,  put in a spare if you have one, otherwise swap with V7

Title: Re: Super Reverb
Post by: Willabe on December 10, 2015, 10:52:52 am

Which SR? Is it a real Fender? Please post Fender model number.

Title: Re: Super Reverb
Post by: sluckey on December 10, 2015, 11:07:26 am

Here's the schematic...

  http://el34world.com/charts/Schematics/files/fender/Fender_cbs_70w_mstrvol_pullsw_super-pro-bmstr_rev.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_cbs_70w_mstrvol_pullsw_super-pro-bmstr_rev.pdf)

Title: Re: Super Reverb
Post by: PRR on December 10, 2015, 12:59:29 pm

> resistor at tube 8 I use 470 2 watt

*Which* resistor?

I would guess (from size and power) this is the Screen resistor. That resistor at that power rating won't blow unless the tube is sick. Just to be sure, swap the two 6L6. If now you smoke the resistor on the other socket, toss the tube.

Title: Re: Super Reverb
Post by: shooter on December 10, 2015, 09:27:56 pm

Sluckey, what was the give-away for the schematic you referenced over this one? 


http://el34world.com/charts/Schematics/files/fender/Fender_65_super_reverb.pdf (http://el34world.com/charts/Schematics/files/fender/Fender_65_super_reverb.pdf)

Title: Re: Super Reverb
Post by: sluckey on December 10, 2015, 10:39:34 pm

He said it had a solid state rectifier and a master volume and was 35 years old. There's only one SR that fits that description. It also helps that I've had to chase that same schematic recently.  :wink:

The schematic you posted is for a Reissue SR and is dated 10/27/2000. It has a 5U4 5AR4 tube rectifier and no MV.

Title: Re: Super Reverb
Post by: Big chief on December 11, 2015, 07:09:38 am

Thanks a bunch power tubes are ok now. Now I have another problem I have no power at the pre amp tubes.
Checked all preamp tube and all tested ok changed the inverter tube twice to make sure it was ok.

Any help as I amworking on this free do help a friend.

Thanks

Title: Re: Super Reverb
Post by: sluckey on December 11, 2015, 07:47:31 am

Quote

I have no power at the pre amp tubes.

What does that mean? Can you be more specific? What are the symptoms? How did you determine you "have no power at the pre amp tubes"? Are you saying the tubes don't light up? Have no B+? Have you measured anything with a meter?

Title: Re: Super Reverb
Post by: shooter on December 11, 2015, 08:18:42 am

Thanks Sluckey, I keep thinking 35yrs ago was 1965 :icon_biggrin:

Title: Re: Super Reverb
Post by: sluckey on December 11, 2015, 08:23:33 am

Quote from: shooter on December 11, 2015, 08:18:42 am

Thanks Sluckey, I keep thinking 35yrs ago was 1965 :icon_biggrin:

I do that too! Then I see all the white hair and come to my senses!

Title: Re: Super Reverb
Post by: Big chief on December 11, 2015, 01:21:04 pm

The tubes do not light up and when I plugg guitar in no sound
Please understand I can install caps and little things as I have played music for 65 years and worked on my own tube amps many times this one has been difficult.  Any help would be great.
I do get a hum when turned on.

Thanks

Title: Re: Super Reverb
Post by: Big chief on December 12, 2015, 07:49:10 am

Have power on pin 1 no power on pin 6 phase invertor tube.
Appears no power on grid pins on all other preamp tubes
Thanks

Title: Re: Super Reverb
Post by: sluckey on December 12, 2015, 09:31:11 am

If the big tubes light up but the little tubes do not light up, then the filament string is broken between the big tubes and the little tubes. The filament string is two twisted wires (probably green) that starts at the first 6L6 and runs across the top of every tube and ends at the small tube at the opposite end of the chassis. These two twisted wires connect all those tubes together kinda like a 'chain gang'. One of those two green wires is probably not making a good connection at a socket. Or the wire may actually be broken (not likely). I would first look at the connections of the last big tube that's lit and the first little tube that's not lit. Probably just needs resoldering.

Title: Re: Super Reverb
Post by: Big chief on December 13, 2015, 04:54:09 am

Thanks for the help. It works

Title: Re: Super Reverb
Post by: sluckey on December 13, 2015, 05:35:46 am

What did you find?

Title: Re: Super Reverb
Post by: Big chief on December 13, 2015, 10:58:08 am

Found loose wire on big tube going to the first small tube re- soudered as you stated

Thank you and Happy Holidays to you

Title: Re: Super Reverb
Post by: eleventeen on December 13, 2015, 01:28:52 pm

Another success story from the annals of El34world! Good work!

Title: Re: Super Reverb
Post by: Big chief on December 18, 2015, 09:46:26 am

Have a hum in the out put section in the amp when I use my bias probe the hum goes away. The hum balance has been removed from amp. Volume control has no effect on hum have tried different 6l6 tubes no change
Any help would be great
Thanks.  Super reverb silver face

Title: Re: Super Reverb
Post by: HotBluePlates on December 18, 2015, 01:01:17 pm

Quote from: Big chief on December 18, 2015, 09:46:26 am

Have a hum in the out put section in the amp when I use my bias probe the hum goes away.

Try removing the phase inverter tube, then listening to the amp. If the hum is still there, try replacing the bias filter cap (on the small bias board under the pilot light).