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Post subject: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Fri Aug 15, 2014 1:35 pm
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Need some advise/suggestions. I'm going to be replacing the 13 year old filter caps on my drri real soon and I was debating over what cap values to use. DRRI schematic calls for 22uf x3, 47uf, and 220uf. Original AB763 calls for 16uf x4. Has anyone ever tried the original AB763 cap values on a DRRI? If so, what are the results? Or should I stick with the original DRRI values?

Research indicates that converting just the 22uf to 16uf probably won't hurt anything, but is it worth it? Also, it's the other two values that concern me(the 47uf and the 220uf).
Thanks.

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 2:16 am
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13 years old caps are not old , It is a 2001 caps !

How many electronic stuff you have in your home and older than 13 years ? They have all filter caps .

If they are defective it is another story and I see some DDRI using cheap IC ( illinois ) caps . If you want to replace them don't use cheap caps.

But check before if you have enough room in your printed circuit for the new caps.

F & T make very good caps , all the values you need .

http://www.thetubestore.com/Capacitors/F-T_3


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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 8:45 am
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They are the Illinois caps that are standard in these amps. I figured I would at least upgrade them with F&T's.

Everything I've read indicates a ten to fifteen year life expectancy from electrolytics so why wait till they leak/blow. A little preventive maintenance in this section of the amp is a good thing, right?

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 12:27 pm
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Especially when you consider the quality of the original caps

I'm in the F&T camp also (gleaned from info gotten here Roger & Steve) 8)

The only issue with the F&T I ran into was the shorter leads than that other cap company

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 4:06 pm
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socal323 wrote:
Should I stick with the original DRRI values?

Research indicates that converting just the 22uf to 16uf probably won't hurt anything, but is it worth it? Also, it's the other two values that concern me(the 47uf and the 220uf).
Thanks.




Art,

The first filter stage of the DRRI (and newer '68 CDR) is a 220mfd/100VDC + 47mFd/500VDC caps in series. With 100k-ohm, 1/2-watt resistor across the 220mfd cap. And 470k-ohm, 1-watt across the 47mfd cap. This setup is one of the main differences between the Reissued Deluxes and the original BF/SF DR.

I've replaced several DRRI main filter caps and was kinda puzzled by this choice. I believe that it was done mostly because if the availability of caps (from IC, at the time of the DRRI initial design) and as a space constraint issue. Two ~70mfd/350VDC caps with 220k-ohm, 1-watt resistor across each cap would be better.

Dunno real reasons for this asymmetric arrangement. No one at Fender, at the time, had the motive for the setup.

Final filtered value for the first stage = 38.7mfd (~40mfd) rated at ~600VDC. I replaced the OEM caps with as close to nominal valued Sprague ATOMS, at the time (last one done was about 10 years ago). I replaced the voltage leveling resistors, too. As, these are critical for this stage. Used metal oxide.

Today, I'd use two 80mfd/450VDC F&T and replace R65 & 66 with 220-k-ohm, 1-watt, 5% tolerance metal oxide resistors. I believe that the 80/450 will fit under the doghouse. Symmetric balance across two equal caps is better than two unequal values caps that use unequal valued resistors to compensate. Final filtering = 40mfd/700VDC. Watch the polarity of each cap!

http://www.tubesandmore.com/products/C-ET80-450-FT

For the other main caps use the F&T 22mfd/500VDC caps. Don't forget the 100mfd/100VDC cap for the bias supply.

http://www.tubesandmore.com/products/C-ET100-100-FT

Good luck with the fix! :mrgreen:


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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 5:12 pm
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Steve,

For that 100uf 100v cap, it's gonna have to be mounted off the pcb, right? The current cap is a radial type and the f&t is axial. Is this how you've done it? Or once the radial cap is removed will there be enough space left to finagle it into place? I'm open to suggestions.

As for the dual 80uf caps, I just pulled the trigger on the original value caps so I'm a buck short and a day late for that move. I Couldn't find a 220uf 100v cap that I could rely on so I went with the f&t 220uf 350v cap. Looks like its gonna be a tight squeeze in that dog house.

I'll make sure to upgrade r65 and r66 with 1w 5% metal oxides, original values.

Thanks for the info.

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 5:26 pm
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Art,

You can't use the 220mfd/350VDC cap for the OEM 220mfd/100VDC. You run the risk of damaging the GZ34 rectifier. Fender kinda half-@ss this first stage by putting a low voltage value, high mfd cap to compensate for the lack of a good 70mfd/350VDC cap (seen in nearly all BF and SF Fender amps that use this setup). Remember, it's the energy stored by a cap (or wattage = voltage X current) which is important. In general, low mfd cap with high voltage rating stores similar energy as high mfd, low voltage rated cap. Albeit, proper capacitance, high voltage rated caps tend to last longer in PSU's.

A 220mfd/350VDC will draw a lot of current on initial startup. Notice how this cap is the first one that the GZ34 "sees" in the filter supply. I don't recommend that you use this cap. If you are going to stay with the OEM setup, you need ~200-300mfd, but low voltage rated (100VDC) 'lytic.

If you have already bought a 47mfd/500VDC cap, get another one. Replace both R65 & R66 with 220k-ohm, 1-watt resistors (use metal oxide). Replace C31 and C32 with the 47mfd/500VDC cap in both positions. Then, the first cap seen by the GZ34 is the 47mfd. And the overall first stage filtering equals a balanced 23.5mfd/1000VDC stage. Very hefty, nice stage.

To fit the caps... put heat shrink insulation on the leads. And bend them to fit over the leads of the original caps. Cut the old cap to leave its lead on the board. Then you can wrap the new cap's leads around the old ones. Solder the leads together. This way you aren't pulling leads out of the circuit board. The boards on these amps are a bit delicate. Preserve the board, its pads and tracings... at all costs!

http://support.fender.com/schematics/gu ... ematic.pdf


Last edited by BMW2002Ti on Sat Aug 16, 2014 5:39 pm, edited 2 times in total.

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 5:37 pm
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Oh boy, thanks for the heads up. I will go ahead and order another 47uf and the two 220k 1w mox resistors.

Thanks.

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sat Aug 16, 2014 5:45 pm
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Art,

Good luck with the fix. Be sure to rebias the amp, check changes in B+ on the plates. Tell us how it sounds (Should be stiffer, better bass). F&T put a lot of muscle into the amp's PSU. Esp compared to the original IC's.


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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sun Aug 17, 2014 1:16 am
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socal323 wrote:
T

Everything I've read indicates a ten to fifteen year life expectancy from electrolytics so why wait till they leak/blow. A little preventive maintenance in this section of the amp is a good thing, right?


Any link ?

10 to 15 years !!! This is no sense to me .

My newer amp ,a Princeton Chorus has more than 15 years.

I have few amp made in 1964 all original caps . For giging I may replace their filter caps ,not for home use .


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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sun Aug 17, 2014 1:18 am
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blues bondsman wrote:
E

The only issue with the F&T I ran into was the shorter leads than that other cap company



1 3/8 inches long each side . Why need more ?


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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sun Aug 17, 2014 6:45 am
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The short leads were a pain when changing out caps on the silverface bassman amps, the old caps had enough lead to run the underwire routing right off the cap.

The shorter F&T's leads meant you had to add solder joints, no biggie really

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sun Aug 17, 2014 7:23 am
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I alway solder caps on the eyelet only . Shorter than Fender do .


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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sun Aug 17, 2014 9:02 am
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stratele52 wrote:
socal323 wrote:
T

Everything I've read indicates a ten to fifteen year life expectancy from electrolytics so why wait till they leak/blow. A little preventive maintenance in this section of the amp is a good thing, right?


Any link ?

10 to 15 years !!! This is no sense to me .

My newer amp ,a Princeton Chorus has more than 15 years.

I have few amp made in 1964 all original caps . For giging I may replace their filter caps ,not for home use .



No problem, I did the math using capacitors ratings and specifications. Illinois capacitors are rated for 2000 hrs @ 85C. If I play the amp at least 4 hours a week that comes to a life span of approximately 9.6 years for this particular brand of cap. I play my amps a minimum of 4 hours a week, more if gigging. (2000/4hrs a week)/52 weeks a year

Since I bought this amp used, there's no telling how many hours have been put in this amp in thirteen years. So I want to do preventive maintenance in this section before it goes ca put. :D

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Post subject: Re: Deluxe Reverb Reissue Filter Cap Replacements
Posted: Sun Aug 17, 2014 9:31 am
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BMW2002Ti wrote:
Art,

You can't use the 220mfd/350VDC cap for the OEM 220mfd/100VDC. You run the risk of damaging the GZ34 rectifier...


This is simply not true. Using a cap with a higher voltage rating will not damage anything. The voltage rating on a cap simply means that it can handle up to its rated voltage and has nothing to do with how much current it will draw. The higher the voltage rating on a cap, the better, it means that the cap with a higher voltage rating is beefier/stronger/more durable. A cap with a voltage rating of 350 VDC can be used on any lower voltage application with no problem whatsoever. It is always OK to use a higher voltage rating for a cap replacement, the capacitance value is what should usually not be increased very much.

It would be the same as increasing the weight rating on your amp carrying strap. If the strap was rated to handle up to 100 pounds and you changed it to a strap that was rated to handle up to 350 pounds, the amp wouldn't be any heavier, you would just have a more durable strap.

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