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Post subject: NAD - 1962 Fender Super Amp
Posted: Fri Oct 09, 2015 2:59 pm
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http://1drv.ms/1ZmlA0b

Arrived just in time for Thanksgiving. I will post some more pics in the next couple of days when I get a chance to take the chassis out. Has had a good looking cap job (bias caps and filter caps) with Sprague Atoms, and a 3 prong plug at some point in her life. Original iron, 2 x 10" Oxfords. Tubes are a giant mish mash of old and new but she still sounds fantastic as is. The tremolo is bonkers.

Now I have one question for the wonderful people on this forum. The last owner was running JJ 6V6s for the power tubes to keep the volume down a bit, and to add some extra sparkle. I need to double check the values on the new bias caps, but does this seem like a workable option? Or should I get out some decent 6L6s or 5881s?

Happy Thanksgiving weekend to one and all!


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Fri Oct 09, 2015 3:19 pm
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Very cool amp! Run good quality 6L6GC (6G4) or 5881 (6G4-A).

The amp has no bias adjustment pot --- so look to see if the fixed resistors in the bias supply have been changed to suit the JJ 6V6S. Replace the bias supply caps, too. I'd go to 33mfd/160VDC (F&T) in place of the 8mfd/150VDC. Better long-term filtering. Be sure bias is checked on the new tubes.


Good luck! I love brownface era Fenders.


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Fri Oct 09, 2015 3:53 pm
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BMW2002Ti wrote:
Very cool amp! Run good quality 6L6GC (6G4) or 5881 (6G4-A).

The amp has no bias adjustment pot --- so look to see if the fixed resistors in the bias supply have been changed to suit the JJ 6V6S. Replace the bias supply caps, too. I'd go to 33mfd/160VDC (F&T) in place of the 8mfd/150VDC. Better long-term filtering. Be sure bias is checked on the new tubes.


+1

Nice score!

That 3-tube harmonic tremolo circuit was the best that Leo ever designed. Add a 6G15 reverb tank and you're all set.

8)

Arjay

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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Fri Oct 09, 2015 5:47 pm
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Nice clean score! Those brownface Supers are the one amp that could make me give up my '65 Super Reverb.

Enjoy that puppy!

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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sat Oct 10, 2015 2:26 pm
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Hi guys,
Thanks for the info! I had a bit of time today to check some bias readings, and the 6v6 in the amp were very well matched and biased for the extra voltage in the amp. I did try some Tung Sol RI 5881s for a moment, and the one redplated after a few minutes of being ok. I tried the old Tung Sol tubes above, and the bias is still very uneven but they seem to be able to handle the voltages much better as there has been no issue with overheating or redplating so far. When I have time I will get the chassis out and confirm the new cap values in the bias section. Tone is unbelievable with the Tung Sols in it right now. Those old Oxfords have quite a bassy punch to them as well.

Thanks again!


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sat Oct 10, 2015 4:24 pm
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Original OEM Fender Oxfords from the pre-1965 era were sonically quite articulate -- perhaps not as bright and glassy as vintage ceramic Jensens but very soulful nonetheless. Oxford's status as a Jensen protégé began to erode only after the production surge created by the demands of CBS after they purchased FEIC and it became FMI.

Arjay

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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sat Oct 10, 2015 5:45 pm
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Hokusai22 wrote:
http://1drv.ms/1WTRTBC

Hi guys,
Thanks for the info! I had a bit of time today to check some bias readings, and the 6v6 in the amp were very well matched and biased for the extra voltage in the amp. I did try some Tung Sol RI 5881s for a moment, and the one redplated after a few minutes of being ok. I tried the old Tung Sol tubes above, and the bias is still very uneven but they seem to be able to handle the voltages much better as there has been no issue with overheating or redplating so far. When I have time I will get the chassis out and confirm the new cap values in the bias section. Tone is unbelievable with the Tung Sols in it right now. Those old Oxfords have quite a bassy punch to them as well.

Thanks again!


Do you mean that the 6V6 are old-school USA made Tungsol tubes? Or are these also Russian re-issued, like the 5881 tubes? I would not run TSRI 6V6GT in this amp, unless you have the plate voltages dropped to less than 450VDC and run around 20mA idle current per tube.

Use 6L6GC, like EH for modern issues. You may want to have a bias pot installed into the amp, so that you can adjust the idle bias --- for various 6L6 or 5881 tubes.


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sat Oct 10, 2015 8:03 pm
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Hey BMW,
Sorry that last post was a bit rambling. The amp came with a matched set of Groove Tube 6V6s that tested on my bias probe to be around 20MA per tube. I then tried in order:
New Tung Sol Reissue 5881s (redplated)
NOS Tung Sol JAN 6L6WGB
NOS Jan Phillips 6L6WGB

I haven't had a chance to check the plate voltages, but the 6v6s seem to run fine, and the JAN Phillips seem to be running about 45-48 MA each, so I have left them in for now. And no redplating in sight.
I also looked at a photo the seller sent of the guts and it looks like the bias caps are Sprague 8mfd/150. Would the ones you suggested instead smooth out the bias a bit?

So far, between this and the Blackface Deluxe Reverb I'm in some kind of tonal heaven over here. : )


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sun Oct 11, 2015 1:47 am
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Leave the vintage US made 6L6WGB in the amp. These are mil spec 5881s, relabeled "WGB" for consumer use.

They will last forever, under sane idle bias conditions.

As for the bias supply filter caps, 33/160 will filter better. Since the circuit is rectified with a solid-state diode, no worries about the extra capacitance (compared to cap specs with tube rectifiers).


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sun Oct 11, 2015 7:54 am
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Actually, it is tube rectified. It has a GZ34 in it. I had a chance to get in a few minutes more with the Philips tubes and it seems to be running fine. No signs or sounds of distress. The sound with the 5881s and the 6L6s is fantastic. I'm not sure why the last owner thought the 6V6s would sound better


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sun Oct 11, 2015 9:45 am
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Hokusai22 wrote:
Actually, it is tube rectified. It has a GZ34 in it. I had a chance to get in a few minutes more with the Philips tubes and it seems to be running fine. No signs or sounds of distress. The sound with the 5881s and the 6L6s is fantastic. I'm not sure why the last owner thought the 6V6s would sound better


In that case, leave well enough alone. Replace any marginal electrolytic caps as necessary (F&T's are preferred), optimize the bias for whichever output tubes you decide on, upgrade the power cord to modern safety protocols, then enjoy the amp for the next ten or fifteen years.

Arjay

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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sun Oct 11, 2015 11:16 am
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Only 10 to 15 years? Hopefully the amp and I last longer than that! I need to have a look at the chassis still. The pics I got were good enough to see how original it was and that the cap job looked good. The 3 prong plug was done previously, and I believe the death cap is still in there.

A quick shot of the happy family. : ) 1961 to 1964.

Image[/url][/img]


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Post subject: Re: NAD - 1962 Fender Super Amp
Posted: Sun Oct 11, 2015 12:19 pm
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Hokusai22 wrote:
Only 10 to 15 years? Hopefully the amp and I last longer than that!


Oh it will, trust me.

But there are certain "consumables" that will require periodic attention......tubes, electrolytics, carbon-comp resistors, etc.

But once attended to, the amp will continue to soldier on for decades to come.

I cannot predict the same for you though (or me).

:mrgreen:

Arjay

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