# 6G2 (brown) Fender Princeton: OK to use 5881s & "plug in" SS rectifier?



## StevieMac (Mar 4, 2006)

Generally speaking, is it OK to substitute 5881s & a plug-in SS rectifier for the existing 6V6s & 5Y3? I read something some time ago by Gerald Weber indicating it was OK to do this in early (i.e. tweed/brown) Princetons & Deluxes as plate voltages were considerably lower (by approx 50-100 volts) than later versions of those amps.

Complete disclosure...I already tried it and LOVED what I heard. Noticeably more volume, headroom, and overall clarity. Not sure if it matters but both the 6V6 (JJ) and 5881 (Tung-Sol RI) tubes I used in the amp were rated @ "21" by the supplier (thetubestore).


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## loudtubeamps (Feb 2, 2012)

No standby switch on that one, is there?

Thump-whack!
Cheers, d


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## StevieMac (Mar 4, 2006)

loudtubeamps said:


> No standby switch on that one, is there?
> 
> Thump-whack!
> Cheers, d


No standby...so I assume you're referring to the output tubes getting "hit" with full voltage from the SS recto. That'll happen regardless of which tubes are chosen however. Anyway, I thought I might get one wired in where the (now defunct) ground switch sits, to help extend tube life. 

Other than that though, are there any other concerns I should have?


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## nonreverb (Sep 19, 2006)

The biasing will be off a bit but due to low plate voltage as stated, it shouldn't be a huge problem. Might be a tad harder on the power transformer due to increased filament load. 
One word of caution is that you will be applying more power to the output transformer and a higher plate voltage....ever seen how many brown amps have changed output trannies?...just sayin'


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## StevieMac (Mar 4, 2006)

nonreverb said:


> ...ever seen how many brown amps have changed output trannies?...just sayin'


Good point. Now that you've mentioned it, all but a couple of the brownies I've owned came to me with replacement OTs!


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## Wild Bill (May 3, 2006)

After checking the schematic you should be fine! The extra filament draw is a small worry - wouldn't hurt if after the amp has been on for an hour or two you could put your fingers on the power transformer to see if it seems to be running hot. The old tech rule of thumb is that you should be able to keep your finger on it for at least 20 seconds. If you can't then its running too hot!

The lower plate voltage inherent to the design eliminated my worry about the SS rectifier replacement. There are two different kinds. The "Copper Cap" models don't just use solid state diodes. They also have a similar voltage drop to the tube rectifier they are replacing. The 5Y3 in a 6G2 will drop maybe 40 volts or more under heavy load. There are other models of SS tube rectifier replacements that do NOT have any voltage drop. This means the plate voltage for your output tubes will be over 40 volts higher!

This won't be a problem with the 6G2. it is designed for a much lower plate voltage - the tubes are closer to class A which means less power and a more vintage tone. Running with a higher plate voltage will not hurt 5881s and they will be closer to class AB1, which would sound louder and more "blackface".

If you like it then go for it!

Wild Bill/Busen Amps


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## nonreverb (Sep 19, 2006)

With all due respect Bill, the output transformers on those amps were fragile even when they were new. Altering the output tube complement and/or plate voltage is simply asking for trouble. I would suggest replacing the output transformer with something a little more reliable and puttng away the original. Steve quite rightly stated most of the Brown amps he's seen, have had them replaced. Apart from the Bandmaster and Bassman which had more robust trannies, I have found the same problem with many Brown Fenders as well. Caveat emptor!



Wild Bill said:


> After checking the schematic you should be fine! The extra filament draw is a small worry - wouldn't hurt if after the amp has been on for an hour or two you could put your fingers on the power transformer to see if it seems to be running hot. The old tech rule of thumb is that you should be able to keep your finger on it for at least 20 seconds. If you can't then its running too hot!
> 
> The lower plate voltage inherent to the design eliminated my worry about the SS rectifier replacement. There are two different kinds. The "Copper Cap" models don't just use solid state diodes. They also have a similar voltage drop to the tube rectifier they are replacing. The 5Y3 in a 6G2 will drop maybe 40 volts or more under heavy load. There are other models of SS tube rectifier replacements that do NOT have any voltage drop. This means the plate voltage for your output tubes will be over 40 volts higher!
> 
> ...


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## StevieMac (Mar 4, 2006)

Thanks for all of these thoughtful responses. I am concerned about the added power from the 5881s stressing the output tranny BUT it also got me thinking...the SS recto and JJ 6V6s should be fine yes/no? They're very robust tubes and, presumably, the OT would have no problem handling more output from a 6V6 (i.e. if they run "hotter" with SS rectification).


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## Cups (Jan 5, 2010)

A 6v6 takes 450ma of heater current. A 5881 takes 900ma. Fenders are great amps but they're not known to be built "overspec". 

The 6v6 shouldn't be bothered by the extra voltage of ss rect. Wild Bills suggestion of the ss replacement with the voltage drop is a good one because the tone may change with higher voltage. You may like the sound (more the feel of the amp then the tone probably) so experiment but be careful and check voltages and temperature as you go along

(unless you've never checked voltages before - not a good idea for the inexperienced.)


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## nonreverb (Sep 19, 2006)

The JJ 6V6 is still a 6V6. It's plate impedance is basically the same and it's operating spec, although more robust, will work just fine in that amp. Where you can run into trouble is when as stated earlier, you install a SS rectifier with no drop resistor in series with it. The Weber Copper top type use a large dropping resistor after the diodes to mimic the drop from a tube rectifier. 
As I stated before, my concern wouldn't be the power tranny but the output tranny. Those old schumacher open ended transformers sound great but are fragile and prone to arcing. Any increase in voltage or altering the design is just playing with fire. (no pun intended) 
I suppose it could be rewound if the unthinkable were to happen...




StevieMac said:


> Thanks for all of these thoughtful responses. I am concerned about the added power from the 5881s stressing the output tranny BUT it also got me thinking...the SS recto and JJ 6V6s should be fine yes/no? They're very robust tubes and, presumably, the OT would have no problem handling more output from a 6V6 (i.e. if they run "hotter" with SS rectification).


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## StevieMac (Mar 4, 2006)

Well, I know I have a Weber CC somewhere around the shop so perhaps I'll replace the SS plug-in I tried with it and then see if I still like it. If not, I have a few candidates in mind for a replacement OT (see below). Any thoughts about going with a 20 or so watt vs the larger 40 watt (for 5881/6L6 use)? 

ClassicTone # 40-18002 Fender Deluxe Style 20W Output Transformer 8 Ohm

ClassicTone # 40-18087, Fender Deluxe Style, 20W Upgrade Output Transformer, 4/8/16 Ohms

ClassicTone # 40-18088, Fender Tweed / Brownface Super, Tweed Bandmaster, Tweed Pro, 40W Output Transformer, 2.67 / 4 / 8 Ohms


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## loudtubeamps (Feb 2, 2012)

As well: maybe ask WCGILL re: Mercury O/P tranny? He seems to be a big fan of the MM.
Cheers, d.


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## nonreverb (Sep 19, 2006)

Classic Tone, Heyboer or Mercury are all good. Hammond makes some good ones as well. I've done a lot of business with MM and have been happy with the results.
I believe Classic Tone and MM have drop in replacements. No chassis modding required. 
As for power, the 20W will probably do. The bigger tranny will require modification and there will be far less saturation with something that size. The tone will be different and not necessarily in a good way. It might clean it up a little too much.


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## StevieMac (Mar 4, 2006)

nonreverb said:


> The bigger tranny will require modification and there will be far less saturation with something that size. The tone will be different and not necessarily in a good way. It might clean it up a little too much.


THAT was really the info I was after. I'd like to leave the amp stock and the tone and "saturation" characteristics largely intact, but have a bit more overall volume available. Maybe I'll go with the first one then since, @ just $27, it strikes me as "good value". Thanks!


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## WCGill (Mar 27, 2009)

I have a Hammond here that I use in my Gibson Falcon which I converted to 5881's. If you're interested I'll send one your way for an audition for the cost of postage and if you like it we'll work something out. It's not a very big transformer but can handle all the current the Princeton can dish out. I'd sooner see someone use one of these instead of ClassicTone.


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## StevieMac (Mar 4, 2006)

Sounds like a good match for what I'm hoping to achieve with the Princeton. My only concern would be having to drill new mount holes however and I'm skeptical about the Hammond bolting right up with existing holes...


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## loudtubeamps (Feb 2, 2012)

If the footprint of the replacement is not the same as the original re: mounting holes, you can fasten an aluminum base plate to the new trannie and bolt the plate to the existing chasssis holes.
3/16" pop rivets ,face up of course for attaching the base plate to the tranny.
A couple of lengths of foam adhesive weatherstripping between the plate and chassis to eliminate possible vibration.
Just a thought.
Cheers, d


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## WCGill (Mar 27, 2009)

Mounting holes are 2 7/8". Primary is 6k, secondary, 8 ohms.


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## Wild Bill (May 3, 2006)

Forgot about that, NR! Most Fenders are reasonably rugged but the 6G2 was indeed a bit lame in ratings. Isn't it great to get old and foggy? lofu

Actually, I find the OTs in the newer Pro Jr.s and such to be rather puny. I replace a couple every year. I used to use exact 3rd party replacements like MM and such but I tried a few of Hammond's exact replacements and they sound great! Their OTs for classic guitar amps saturate just like the old ones, with the low end cutoff starting around 70 hz. For the Pro Jr types with a pair of EL84s I use the 1750F. Haven't had one even get warm, let alone fail.

I suspect that since Fender moved all production to China they are using lame ass spec OTs in the newer series of amps. That may just be my own prejudice.

Wild Bill/Busen Amps

PS - After being away from the board for a while I have to say that the increased level of technical help from guys across the country has exceeded my wildest hopes! Years ago when I stumbled into here there was no help happening, as far as I could see. I jumped in and Scott added some tech forums. Soon other techs began to show up and pitch in. Now, we have got some of the best tech advice and help happening of any such board, anywhere! Not just in Canada!

I think I'll crack a beer, put on my vinyl LP of Jerry Doucette and feel all warm and fuzzy for a while! sdsre


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## Printer2 (Apr 8, 2012)

If it were me I would use a replacement OT if I were concerned about the original. Mind you maybe a couple of flyback diodes, catch diodes (whatever people are used to calling them) might be in order on the old OT.


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## dtsaudio (Apr 15, 2009)

> Hammond's exact replacements and they sound great!


Most under rated (for sound quality) transformers made. I hear people knock Hammond all the time. I've been using them for a long time, and no complaints



> I think I'll crack a beer, put on my vinyl LP of Jerry Doucette and feel all warm and fuzzy for a while!


Best idea I've heard all week.


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## nonreverb (Sep 19, 2006)

+1...Hammond makes excellent transformers. 
Beer is pretty excellent too ;P



dtsaudio said:


> Most under rated (for sound quality) transformers made. I hear people knock Hammond all the time. I've been using them for a long time, and no complaints
> 
> 
> Best idea I've heard all week.


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