filter cap question

[Randall]

I'm building another Deluxe Reverb from a DRRI platform. The AB763 has two 16uF/450v caps in parallel before the standby switch. Is there an argument for not using a single 47uF/500v in their stead? I am primarily wondering about the way caps see voltage in parallel vs series. I plan on using 22uF in place of the three other 16uF down stream as well.

[Enzo]

The two 16uf they already had in stock were cheaper than the single 32uf or 40uf or whatever they replace. 22uf is perfectly fine.

[bob p]

No problem using a 47/500. For DR builds I typically use a JJ 40/20/20/20 can cap. The reason that you see 16+16 in the schematic is because it was drawn in the 1960s when cap sizes were small due to high cost per uF and low uF density. 16uF was a big cap back then. Today we have high density and low cost per uF, so you don't need to double them up like you used to, you can just buy a bigger cap.

If you're using SS rectification then you don't need to worry about the size of the first filter node as long as you have a rectifier diode that can handle the peak current. This can be a problem with tube diodes, so you have to be sure that the size of the first filter node doesn't exceed the max rating of your rectifier tube. For a GZ34 that would be 60uF for a cap-input filter. So your 47uF would be OK.

I'm serious about being interested in those pulled boards.

[Randall]

They are on eBay. PM me if you'd like to talk.

[bob p]

your own ebay image answers the cap question. Fender uses 220+47/22/22/22 for the PSU rail:
http://www.ebay.com/itm/Fender-Delux...s/282870899630



And the 65 DRRI schematic shows a 100uF bias cap.

65_Deluxe_Reverb_RI.pdf

FWIW Alessandro will sell his pulls over the phone for less than his ebay price, which is only $75.

http://www.ebay.com/itm/Fender-65-De...t/282699850543

[Chuck H]

your own ebay image answers the cap question. Fender uses 100+47/22/22/22 for the PSU rail:

Actually it's a 220, 47, 22, 22, 22

According to the schematic they series the 220uf with the 47uf using a 100k @ 1/2 watt across the 220uf and a 470k @ 1 watt across the 47uf for an approximate current balance and a total of about 38uf. Obviously more of Fenders typical use of the parts they get cheap. Just use a 33uf cap and call it good. You could even use a 47uf cap and it would be fine IMHE, but in keeping with the spirit of the design a 33uf would be near spot on for parallel 16uf caps. And, obviously as Bob has demonstrated, Fender wasn't concerned about the difference between 16uf and 22uf for the preamp filter/decoupler caps. Makes sense because older caps were typically high in value with generous "+" figure for the spec. (80%!)

[bob p]

I had totally forgotten about that oddball totem pole thing on the DRRI. Come to think of it, we had a thread on that odd totem pole configuration. You're right, it's 220uF in series with 47uF.

[Leo_Gnardo]

FWIW Alessandro will sell his pulls over the phone for less than his ebay price, which is only $75.

ONLY $75??? A prince of a man! Anyone who can turn garbage into cash must be a geeeeenius! Ain't that America . . . . ?

[Chuck H]

Not to mention that private selling your *bay contract item is illegal unless you arrange to to pay them the agreed percentage. Which I'm sure he does

[Leo_Gnardo]

Not to mention that private selling your *bay contract item is illegal unless you arrange to to pay them the agreed percentage. Which I'm sure he does

Oh I'm sure he has a barrel full of those boards. Who's to say the one pictured in the ebay ad is exactly the same one he sold to Tommy Tenthumbs. If someone puts up an Ebay ad for a single widget, does Ebay own the rights to profit on ALL the widgets the vendor has for sale? Hmmm, it's Ebay, yes they probably think they do.... good luck collecting on that Ebay!

[bob p]

I only pointed out the "hounddog corp" ebay listings as a price reference. Anything that sells for $75 on ebay should sell for less in a private transaction that isn't subject to their usurious 10% commission plus PayPal fee.

I think it's unfair to assume that anyone is forced to do all his sales through ebay just because he sells some of his stuff on ebay, or that he's cheating if you contact him through his web site and he doesn't kick money back to ebay in that context. Unless that new update to the ebay policy has some ridiculous terms in it, ebay doesn't prohibit people from selling on their own web sites, though it does prohibit using ebay to offer to sell outside of ebay .

You can go to the Alessandro web site, see that he rebuilds modern amps with turret boards, and figure out that he's got to be sitting on piles of those OEM boards. He lists his phone number there, so it's easy to call him. If you work out a deal there's no reason for ebay to get a slice of that transaction as ebay isn't even involved. Especially because you're dealing with a different corporate entity.

Personally, I think $75 is way too high for those boards. I won't pay it. They're not quite junk, but they're not all that valuable either. I wouldn't pay $50 for one, considering that I can buy an AB763 board from Mojo for $15 and populate it with parts on-hand and have something that users will pay more for ... for the same input price.

[Randall]

"I had totally forgotten about that oddball totem pole thing on the DRRI. Come to think of it, we had a thread on that odd totem pole configuration. You're right, it's 220uF in series with 47uF."

Yes, I started that thread I believe.

"Personally, I think $75 is way too high for those boards. I won't pay it."

BobP, when I built my first one, I put the main and panel boards on eBay for $65 in the evening, and they were gone the next morning. So I thought, hmm I guess I could have gotten more. Maybe my $100 asking price is too high, if it is, I will know soon enough, and I will lower it. But I move that someone who is not a builder, who doesn't know about Allesandro, whomever he is, and has a tanked DRRI might think that is a reasonable price to get an amp working. I'm gonna love it if I get to come here and tell you it sold!

[bob p]

Dude, if you can get $100 for it from some numbskull, good for you!

[Pedro Vecino]

I imagine that these boards come from extracting them from the reissues.
I do not find it sense to completely redo a functional amplifier like this with a classic board, new potentiometers, jacks and wiring. Except to get some kind of spiritual relax looking at it.

[Chuck H]

When it comes to the reissue amps my experience has been that they are much more consistent and generally better sounding than originals. They use much tighter spec components and are made on PCB's so there's MUCH less variation amp to amp. And the ground scheme is improved so the new amps are quieter. The "schematic" makes a very good sounding amp so you get that every time with a new one. Originals are all over the map. You can't be sure what speaker is going to be in there, spec on components is wide and lead dress can be better or worse depending on a few things. There are amazing sounding originals to be sure. The very best will be originals, but so will the very worst. And IMHE most of the old ones people sell AREN'T the special ones with the right alchemy in the variables and are either almost bad sounding or, at best, just workman like in tone without much of the special Fender chime that ALL the new amps actually DO have. Rebuilding a reissue with an eyelet board does allow you to "select" components, so there's that. I don't think it makes as much difference as some people think. Same with transformers. Not to mention that an original will have a solid pine cabinet and a reissue, no matter how expensive the iron you put in is, will always be plywood. And if you're in my camp there's absolutely NO advantage to putting a black, pressed paper circuit board in anything unless you like problems.

JM2C on that.