'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 06th, 2007 @ 13:47 ( . )

I am now working on the layout of a 6V6 Plexi following Mark Huss's example.
However, I will not exactly follow Mark's layout because I want to adapt it to my chassis,perfboard,caps can....
One question I have right now is about the SS rectification (It is my 1st SS rectified amp).
On Mark's schem/layout, 2 diodes are used to make the full wave rectifier circuit. Looking at a Marshall schem I see they use 4 diodes, simply doubling in serie each of the 2 Mark is using. (hope I make it clear).
What is the difference?
What is the purpose?

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'SS rectification'
Author:Jon Anderson (registered user: 1491 posts )
Date: Wed, Jun 06th, 2007 @ 13:53 ( . )

On 06/06/2007 @ 12:47, Fredaxis wrote :
: On Mark's schem/layout, 2 diodes are used to make the full wave rectifier circuit. Looking at a Marshall schem I see they use 4 diodes, simply doubling in serie each of the 2 Mark is using. (hope I make it clear).
: What is the difference?
: What is the purpose?


The oen with 2 in series is a bridge rectifier; used when a transformer doesn't have a center tap.

[link]

Jon

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'SS rectification'
Author:Zoe N Iain (registered user: 8138 posts )
Date: Wed, Jun 06th, 2007 @ 14:03 ( . )

The diodes are doubled to double the peak inverse voltage rating they have, if it's like the Marshall I'm thinking of.

It's quite common.

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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 06th, 2007 @ 14:18 ( . )

Thanks Jon and Zoe,
Jon, I was not thinking about a bridge rectifier, I link to Mark's layout and Thundertweaks layout. Both use center taped PT as I will do.
[link]
[link]

I'll be using 1N4007 as they both do, follown by a 50/50uf capcan, both section in parallel to reflect 100uF.

Which example should I follow?

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'SS rectification'
Author:Jon Anderson (registered user: 1491 posts )
Date: Wed, Jun 06th, 2007 @ 14:36 ( . )

On 06/06/2007 @ 13:18, Fredaxis wrote :
Thanks Jon and Zoe,
: Jon, I was not thinking about a bridge rectifier,:


Sorry. Most of the schematics I've seen for Marshall plexi's/superleads with ss rectifiers use bridge rectifiers, but it looks like the 50watters used the full wave.

[link]
[link]

Jon

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'SS rectification'
Author:Erik Runeson (registered user: 102 posts )
Date: Thu, Jun 07th, 2007 @ 06:58 ( . )

On 06/06/2007 @ 13:36, Jon Anderson wrote :
Most of the schematics I've seen for Marshall plexi's/superleads with ss rectifiers use bridge rectifiers, but it looks like the 50watters used the full wave.


Both rectification techniques mentioned in this thread are full wave. I.e. both the positive and negative swing of the AC will be converted into positive DC.

The opposite to full wave rectification is half wave, where only the positive swing of the cycle is used while the negative swing is discarded. This is typically used in the bias circuit (a single diode).

Is there a technical term for the "2 diode with centertap" full wave rectification method?

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'SS rectification'
Author:Miles O'Neal (registered user: 13998 posts )
Date: Fri, Jun 08th, 2007 @ 03:49 ( . )

It's called "full wave", "simple full wave" or "full wave center tapped" (or "full wave CT").

Most people just say "full wave" for this, and "bridge" or "full wave bridge" for the 4 diode, non-CT type.

But if you want to be specific, I'd go with full wave center tapped" (or "full wave CT").

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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 06th, 2007 @ 15:03 ( . )

so, if I understand well, nothing hurts doubling the diodes ?
Will that improve reliability or affect the tone?

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'SS rectification'
Author:Doug H (registered user: 5398 posts )
Date: Wed, Jun 06th, 2007 @ 15:25 ( . )

On 06/06/2007 @ 14:03, Fredaxis wrote :
so, if I understand well, nothing hurts doubling the diodes ?
: Will that improve reliability or affect the tone?
--



It will improve reliability- and I would suggest doing it. I've blown the diodes in my amp twice lately so I'm going to double them up.

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'SS rectification'
Author:stevem (guest: search)
Date: Wed, Jun 06th, 2007 @ 15:55 ( . )

You will loose 3/4 of a volt of B+ for every diode you add, but thats nothing.
It also helps the diodes survial to place a .002 at 1000 volt ceraimic disc cap across each one.

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'SS rectification'
Author:Zaphod (guest: search)
Date: Wed, Jun 06th, 2007 @ 16:04 ( . )

An even better idea is to use fast recovery rectifiers (eg UF4007 FREDs) to reduce rectifier switching noise. Then you don't need the snubbing caps.

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'SS rectification'
Author:stevem (guest: search)
Date: Wed, Jun 06th, 2007 @ 16:08 ( . )

True, but some people cant deal with the price, although I have upgraded all my amps with them.

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'SS rectification'
Author:Zaphod (guest: search)
Date: Wed, Jun 06th, 2007 @ 16:14 ( . )

I've found some fast recovery rectifiers (don't remember the exact brand) which only cost very *slightly* more than IN4007s. The cost of adding the 1000V ceramic disc caps would probably have been somewhat more. I think you pay more for Internation Rectifier's FRED brand name.


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'SS rectification'
Author:yecrom (registered user: 1185 posts )
Date: Wed, Jun 06th, 2007 @ 20:42 ( . )

I've been using NTE575's and have had good luck with them. I don't know what noise the fast recovery diodes are supposed to help with, but I put them in my HO in place of the 1n4007's and the hiss is noticeably quieter.

Matt.

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'SS rectification'
Author:Doug H (registered user: 5398 posts )
Date: Wed, Jun 06th, 2007 @ 17:07 ( . )

On 06/06/2007 @ 15:04, Zaphod wrote :
An even better idea is to use fast recovery rectifiers (eg UF4007 FREDs) to reduce rectifier switching noise. Then you don't need the snubbing caps.
:
--



I've been using the uf4007's (which is what I've been blowing). No rect noise though, but I wouldn't expect it as it's a good layout.

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'SS rectification'
Author:Zaphod (guest: search)
Date: Thu, Jun 07th, 2007 @ 07:13 ( . )

I suspect that these fast recovery rectifiers may be a little more prone to blowing up than regular ones. IMO it's a good idea to use them in series pairs.

On 06/06/2007 @ 16:07, Doug H wrote :
:
: I've been using the uf4007's (which is what I've been blowing). No rect noise though, but I wouldn't expect it as it's a good layout.
:

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'SS rectification'
Author:Doug H (registered user: 5398 posts )
Date: Thu, Jun 07th, 2007 @ 17:11 ( . )

Yes, it started when I started using the EL34 a lot. They run for a while, then get a hot and start stinking, then blow when I switch to standby. I suspect the higher current is "wearing them down" (technical term there...;-) and then switching the load is making them pop. I'm going to beef it up tonight and see what happens.


On 06/07/2007 @ 06:13, Zaphod wrote :
I suspect that these fast recovery rectifiers may be a little more prone to blowing up than regular ones. IMO it's a good idea to use them in series pairs.
:
: On 06/06/2007 @ 16:07, Doug H wrote :
: :
: : I've been using the uf4007's (which is what I've been blowing). No rect noise though, but I wouldn't expect it as it's a good layout.
: :
:
--


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'SS rectification'
Author:Evilchippy (guest: search)
Date: Thu, Jun 07th, 2007 @ 07:19 ( . )

I used UF5408s in my HO at $.53 a pop. .0022uF ceramic caps are $.35 each plus $.04 per 1N4007. So, it's $1.06 for the UF5408 option compared to $.78, which is a $.28 difference. With such a little price difference, it seems to me like the additional reliability offered by the 3A UF5408 is worth it. Plus, a few people have claimed that a simple snubber across the 1N4007 isn't really a 100% perfect fix - a resistor is also needed. In the end, the price is probably much closer to match the performance of the UF5408 with greatly increased complexity.

Mike

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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Thu, Jun 07th, 2007 @ 08:02 ( . )

As I had to order some turrets, I went to the Mouser site and bought some UF4007 that I plan to use in pair.
0.18$ each, 30 for $5.40.

Should I also double the one in the bias circuit?

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'SS rectification'
Author:stringbend (guest: search)
Date: Thu, Jun 07th, 2007 @ 15:43 ( . )

On 06/07/2007 @ 07:02, Fredaxis wrote :
: Should I also double the one in the bias circuit?


No.

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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 20th, 2007 @ 01:02 ( . )

OK, I also got some IXYS FRED 600V 8A 50W DSEI8-06A . same as here [link]
They have a square body, nothing like 1N4007

Should I also double them?
Any recommendation about the way to attach them to the board.
May I simply fit them in the turrets?


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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 20th, 2007 @ 01:51 ( . )

Better link here: [link]

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'SS rectification'
Author:Zaphod (guest: search)
Date: Wed, Jun 20th, 2007 @ 14:33 ( . )

Those are high power versions. You only need 1A rated ones. You should still use them in series pairs for safety against voltage spikes. Yes, just solder them onto some turrets.


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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 20th, 2007 @ 15:12 ( . )

Thanks Phil,
Yes this a bit overrated on term of power, this is what was avialable anyway, will not hurt reliability :)

Which B+ Can I expect with a 300-0-300 PT, using those as rectifier ?

600x0.7 = 420V . What loss factor , 10%, Less?

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'SS rectification'
Author:Zaphod (guest: search)
Date: Wed, Jun 20th, 2007 @ 18:38 ( . )

Very little loss, so expect 420V . Unless your PT is running close to its limits, in which case its voltage will sag a bit.

On 06/20/2007 @ 14:12, Fredaxis wrote :
:
: Which B+ Can I expect with a 300-0-300 PT, using those as rectifier ?
:
: 600x0.7 = 420V . What loss factor , 10%, Less?
:

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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 20th, 2007 @ 18:50 ( . )

OK, I'll be using this PT: [link]
This is the same as I used in the 6V6Lite II.
It actually gave 305-0-305 at the secondaries under load, and 371V on the plates (EZ81 rectified).
A bit high on the heather: 6.8V

All this using the 240V tap with 234V at the plug

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'SS rectification'
Author:Doug H (registered user: 5398 posts )
Date: Wed, Jun 20th, 2007 @ 16:54 ( . )

I've used the DSEI12-12A (1200PIV) before, one on each side, no problems. With a large enough PIV you can get away with that.

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'SS rectification'
Author:Fredaxis (registered user: 117 posts )
Date: Wed, Jun 20th, 2007 @ 19:09 ( . )

Thanks Doug,
For the next SS rectified build I'll have to check for the best source where to buy those Diodes.
One big may be cheaper than 2 smaller ones.

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'SS rectification'
Author:Doug H (registered user: 5398 posts )
Date: Wed, Jun 20th, 2007 @ 19:13 ( . )

I think I got my FREDs at digi-key IIRC. It's been a few years. I believe they were $2 or so a piece.

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'SS rectification'
Author:Strat (guest: search)
Date: Wed, Jun 20th, 2007 @ 20:27 ( . )

I don't think it will matter in your case Fredaxis but the power value will be much reduced if you don't use a heatsink - maybe the spec sheets give a figure?

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