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Post subject: Fender Super 6 Helpy! (Red Plating)
Posted: Wed Jun 20, 2018 8:43 pm
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I have not seen many of these around but we all know there are plenty. Fuses blew after 45 seconds.

Installed "new" tubes and replaced fuse and amp still blows fuse after 45 seconds and TUBES ARE STILL RED PLATING.

Pulled tubes out and no blowing fuses.

Pulled chassis and found one of the 80uf caps (white ones) was dead so i replaced it with a quick replacement (electrolytic type just to test) you can see it on the lower side of the photo...... still red plating.

Tested the 470 Ohms resistors on all the sockets and they are all good, Tested the smaller 1.5 (or as schematic reads 1500) and they all test good.

Tested all the caps in the dog house and they all test within spec and there are no leaks, bulges or anything close to looking bad and my meter sees them within spec.

What am I missing here? Resistor on the Bias (really balance pot) ? Below are photo links

https://500px.com/photo/262998131/image ... 753251/url

https://500px.com/photo/262998131/image ... 753251/img


Last edited by Ryan41018 on Thu Jun 21, 2018 7:15 am, edited 1 time in total.

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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Wed Jun 20, 2018 11:41 pm
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How about the bias-supply cap -- did you replace it?

If so, is it correctly polarized?

(the "+" lead should be connected to ground)

Arjay

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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Thu Jun 21, 2018 5:55 am
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Retroverbial wrote:
How about the bias-supply cap -- did you replace it?

If so, is it correctly polarized?

(the "+" lead should be connected to ground)

Arjay


Kinda hard to tell from the picture, but it looks like it might be backward.
Image

FWIW I don't find a capacitance test with a multimeter to be a good indicator that a capacitor is viable or not. Yes they will measure capacitance. But they don't measure ESR, they can't test a capacitor at working voltage.

What sort of voltages are you getting at the power tube sockets? Bias voltage?

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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Thu Jun 21, 2018 7:57 am
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That's the correct orientation. (+) end of cap to ground, for bias supply. However, the cap maybe dried out --- replace the two 80mfd/75VDC caps with two 100mfd/100VDC F&T or Sprague Atoms. The (C-) should be rock steady (-52VDC +/- 10%) after the 3.3K-ohm dropping resistor, in the bias supply. See schemo.

http://ampwares.com/schematics/Super-Six-Schematic.jpg


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Thu Jun 21, 2018 8:48 am
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Yes, the white Mallory cap is correct, but I was referring to the radial lead cap circled in red towards the bottom right of the photo.

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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Thu Jun 21, 2018 9:45 am
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Vinyl, Whoa! Didn't even see that cap. What a crazy way to add a cap! You maybe correct. Need to see the side of the radial cap.

I'd replace it with proper axial cap.


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Thu Jun 21, 2018 1:16 pm
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I recently got new glasses. :lol:

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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Thu Jun 21, 2018 3:58 pm
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The side of the radial cap is in FACT ground to chassis. The other white one (check with my Fluke capacitance meter) reads good and if I jumper / piggyback another will that be dropping the uf spec?


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Thu Jun 21, 2018 5:51 pm
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So the (+) side of that radial cap is to ground? Needs to be this orientation --- for the bias power supply.
:?: :mrgreen:


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Fri Jun 22, 2018 3:22 am
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Remove your power tubes from the amp.
Power amp ON and read how many négative volts you have on both 6L6's pins 5

You must read at least - 30 volts DC ( minus 30 )
If not adjust bias pot

Don't put power tubes unless you fix bias circuit to read -30 vDC and more.
It is safe to operate the amp with no tubes.

Be carefull; lethal voltage on tubes amps


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Fri Jun 22, 2018 3:46 am
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Statele, just to be sure... the Super 6 does not have a bias pot, per se. It is a balance pot. So, only one pair of 6L6GC tubes affected by the balance pot.

:)


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Fri Jun 22, 2018 3:46 am
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Boo-Boo.


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Fri Jun 22, 2018 3:52 am
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BMW2002Ti wrote:
Statele, just to be sure... the Super 6 does not have a bias pot, per se. It is a balance pot. So, only one pair of 6L6GC tubes affected by the balance pot.

:)


Thank's ,
This make bias adjustment more difficult for a beginner in electronic.


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Fri Jun 22, 2018 8:01 am
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I will pick up 2 new axial caps today install and then read voltages on tubes pin 5 and report my findings back.


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Post subject: Re: Fender Super 6 Helpy! (Red Plating)
Posted: Sat Jun 23, 2018 5:11 am
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[quote="Ryan41018"

Pulled chassis and found one of the 80uf caps (white ones) was dead.

How do you test it to tell it is dead ?




Tested all the caps in the dog house and they all test within spec and there are no leaks, bulges or anything close to looking bad and my meter sees them within spec. [/quote]

Only a Heatkit IT-28 Capacitor Checker ( or similar ) can check.
Filter caps in dog house have nothing to do with red plating

Report.


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