Zener vs. High speed Diode designs? Technical & audio/sound related advantages?

undertow · « **on:** 16 Mar 2016, 02:18 pm »

I am just curious about both technical, and audio/sound quality enhancements if any replacing all Zener Diodes with the High speed types?

I have done some in the past with perfectly fine results just because well it was cheap to do so when messing with other upgrades, but are these substantial improvements in doing so for power supplies, power regulators in audio applications? Normally I have just taken an old amp or preamp deciding to update/upgrade the power supply caps, and since I was in there might as well pull the zener diodes out, but honestly I have never taken a component to just stand alone replace $5 bucks worth of diodes to listen to any differences.

I noticed even a lot of higher end gear still seems to skimp on putting better high speed diode packages in their power supplies, and instead opt to your basic 10 cent a piece Zener's. So to me either they don't see the benefits, or hear the benefits, or simply is it that much of a cost restriction having to pay a buck or 2 a piece when manufacturing with these things?

HAL · « **Reply #1 on:** 16 Mar 2016, 02:37 pm »

Typically Zener diodes are used in regulator circuits. Are you referring to Schottky Diodes vs standard rectifier diodes in a AC-DC power supply?

undertow · « **Reply #2 on:** 16 Mar 2016, 02:40 pm »

Yes Zener vs. Schottky style in a power regulator or supply. I assume in any application where there is a zener is there benefits to upgrading it?

HAL · « **Reply #3 on:** 16 Mar 2016, 02:45 pm »

Zener diodes are designed to work at a specific DC voltage as a regulator typically at low currents.

A Schottky or Fast Recovery diode will not work properly in a Zener diode application.

You can use Schottky or Fast Recovery instead of rectifier diodes if they have the correct specifications in an AC rectifier application.

undertow · « **Reply #4 on:** 16 Mar 2016, 02:48 pm »

Actually only because you mention it I have an application I am considering replacing them all right now where its an AC/DC power regulator. Its fed by the transformer and has some higher amperage Zener Diodes right at the input taps, and then the power regulators on the board are surrounded by 2 Zeners each. Actually I have a photo here for that specific case... The Zeners are all highlighted in red boxes, and this regulator simply takes AC in from a toroid, and converts to +18 / -18 volt DC.

HAL · « **Reply #5 on:** 16 Mar 2016, 03:36 pm »

The 4 diodes at the bottom of the picture are rectifier diodes. If you replace them with Zener diodes, they will not work and probably explode. They are usually rated in mA of current, where rectifier diodes are rated in amps of current for AC to DC conversion. Look at Schottky or Ultra Fast Soft recovery diodes to replace them of equal current rating or higher.

The other diodes in the upper part of the picture look to be reverse current protection diodes for the regulator IC's. Not sure of the specifics, but you will need the specs for the specific units to see what possible. If they are Zeners, there are possible ways to improve the circuit with capacitor bypass caps on the Zeners.

Look for old articles in Audio Amateur magazine online for information on the G-5 (KG-5) regulator design by Gary Galo.

Replacing diodes needs to be done for specific applications with knowledge of the use to select the correct ones. If not, usually circuit failure follows.

undertow · « **Reply #6 on:** 16 Mar 2016, 03:59 pm »

Hello,

Those larger diodes are HER303 seen here:

http://pdf.datasheetcatalog.com/datasheet/good-ark/HER305.pdf

Can I go ahead, and use these "Stealth" Diodes since I have them to replace the HER303 seen here:

https://www.fairchildsemi.com/datasheets/IS/ISL9R1560P2.pdf

Do you see an issue with this?
_______________________________________ _______________________________________ ______________________________

However, the smaller Zeners by the regulators are standard 1N4007 parts. These are the exact ones here:

http://www.parts-express.com/1n4007-1a-1000v-general-purpose-rectifier-diode--1n4007

Could I just replace with these 1N4007 zeners with these below since I have them in the smaller than above Fairchild Stealth series as well?

https://www.fairchildsemi.com/datasheets/IS/ISL9R460PF2.pdf

Thanks

randytsuch · « **Reply #7 on:** 16 Mar 2016, 04:02 pm »

Undertow
I think you are creating confusion with the term zener diode, because you are not using it correctly.

A 1n4007 is a standard, run of the mill diode, it is NOT a zener diode.

As far as replacing, you need to worry about the voltage and current rating of the parts.
A 1n4007 is rated a 1A current, and 700Vr (RMS), and 1000Vr peak.

Quick check shows current is fine, but it appears the ones you want to use are lower voltage. However, I doubt you're anywhere close to the 600V rating of the replacement diodes, unless this is tube gear.

Randy

undertow · « **Reply #8 on:** 16 Mar 2016, 04:09 pm »

Please see above with the specific part #'s I just took off the board, and the considered replacements which I happen to have from some other project long ago. It seems these are suitable or beyond from the specs. and design that I can tell.

However, what is confusing me is they put the Diode rectifiers than in the same style 2 lead package as the Zener diodes in the middle of the board.

So now I am asking for verification. If I need to order something else so be it... Not a big deal.

Thanks

undertow · « **Reply #9 on:** 16 Mar 2016, 04:13 pm »

Quote from: randytsuch on 16 Mar 2016, 04:02 pm

Undertow
I think you are creating confusion with the term zener diode, because you are not using it correctly.

A 1n4007 is a standard, run of the mill diode, it is NOT a zener diode.

As far as replacing, you need to worry about the voltage and current rating of the parts.
A 1n4007 is rated a 1A current, and 700Vr (RMS), and 1000Vr peak.

Quick check shows current is fine, but it appears the ones you want to use are lower voltage. However, I doubt you're anywhere close to the 600V rating of the replacement diodes, unless this is tube gear.

Randy

Randy yes...

I appreciate your input... I was thinking a Zener Diode was in fact the 1N4007. But its not a zener from what you point out sorry about that.

Basically we have ZERO Zener diodes in this power regulator from what we are talking about then?

Also, you are correct that 1N4007 does seem to peak out at 1000 volts, but this board is only putting out 18 volt DC... So I think we are going to be VERY far from any issues with that.

Now I am more concerned about the fact the HER303 parts coming directly in off the AC/Transformer is being considered a rectifier directly, maybe the above fairchild is not like a Schottky etc...? I thought it was?

Any verification if my above replacements are correct would be highly appreciated.

By the way I am very aware of importance to the "Cathode" direction of installation as we lose the stripe indicators etc...

I just now need to verify the above 2 fairchild parts, will in fact work in these 8 locations on the board as pointed out as direct replacements. I have stuff like this before without issue, I just did not realize all this time I thought the reference of Zener diode was related to these types. I am wrong obviously.

HAL · « **Reply #10 on:** 16 Mar 2016, 04:20 pm »

The HER303 Stealth diode is a fast recovery rectifier like the ones I mentioned earlier. These are already very good for AC rectifiers and much ahead of a standard rectifier diode in performance. They should already sound very good compared to a normal 3Amp rectifier for AC-DC conversion. Since they are low forward voltage units, they are harder to find replacements for in that same package. Possibly the TO220 Schottky diodes from ON Semi will replace them but the sound quality will depend on the circuit.

The 1N4007 diodes in the circuit are reverse protection diodes and normally do nothing in the circuit. They are only there to protect the IC regulator during turn off transient situations. There will be no change in sound quality replacing them and they need to be 1000VDC rated to protect from transients.

undertow · « **Reply #11 on:** 16 Mar 2016, 04:27 pm »

Hal,

By the way I am not fighting you on this at all.. It was my mistake bringing the Zener term into this! Now I just gotta make sure I am on track to install this stupid thing with parts I have.

The "HER303 Stealth diode" does not exist

The HER303 rectifier does which you are correct. I want to replace the HER303 with Fairchild Stealth seen here -

https://www.fairchildsemi.com/datasheets/IS/ISL9R1560P2.pdf

Why? Because I only have these Fairchilds right now, the HER303's are not on the board anymore.

Also, the 1N4007's were removed so I happen to have these Fairchild stealths (below in a lower amp version) already which seemed to be a good choice... Maybe not? I can order what I need if this is not suggested.

https://www.fairchildsemi.com/datasheets/IS/ISL9R460PF2.pdf

I just hate to have to order .09 cent PARTS if I can get away with something better on hand!

I very much appreciate your efforts and time... I was on a different page originally, but I might still be right in what I was trying to do once we verify this.

HAL · « **Reply #12 on:** 16 Mar 2016, 04:36 pm »

The original AC rectifier parts were HER303 are rated at 200V PIV and 3 Amp current.

The Fairchild units are rated at 600V PIV and 3 Amps and should work fine. Make sure you have them installed properly for direction.

Speedskater · « **Reply #13 on:** 16 Mar 2016, 04:42 pm »

Skilled power supply designer's place a Resistor/Capacitor snubber network across the rectifier bridge diodes. This is reduce high frequency switching noise. The values of the resistor and the capacitor depend on the transformer and diode models.

undertow · « **Reply #14 on:** 16 Mar 2016, 04:52 pm »

Quote from: HAL on 16 Mar 2016, 04:36 pm

The original AC rectifier parts were HER303 are rated at 200V PIV and 3 Amp current.

The Fairchild units are rated at 600V PIV and 3 Amps and should work fine. Make sure you have them installed properly for direction.

Hal,

Yes I am not too overly concerned about the HER303 replacement with the Stealth from Fairchild as you state, but I am slightly concerned using the stealth units in the "1N4007" position... Is it a correct type Diode replacement for those, or do you really believe in this circuit that 1000 volt peak will be important, and I should just stick with ordering the generic 1N4007 replacements?

I mean it's only a 16 volt AC transformer feeding it, and 18 volt DC outputs... I assume the Regulators on the board would not even take a 1000 volt spike anyway in this case?

By the way I am 100% aware of the importance of the "Cathode" direction of these units, and they get tricky as they are not marked with silver bands like the parts we are replacing.

Thanks

undertow · « **Reply #15 on:** 16 Mar 2016, 04:54 pm »

Quote from: Speedskater on 16 Mar 2016, 04:42 pm

Skilled power supply designer's place a Resistor/Capacitor snubber network across the rectifier bridge diodes. This is reduce high frequency switching noise. The values of the resistor and the capacitor depend on the transformer and diode models.

Appreciate your input. Unfortunately in this case I am just trying to get back a good operational circuit. I would delve further into more complications with adding parts, I just don't think it's necessary here, also not so sure the space, and setup will work out well trying to add any snubber circuits.

HAL · « **Reply #16 on:** 16 Mar 2016, 05:04 pm »

The transient suppression application is not one that effects sound quality. You can use the 600VDC rated unit instead of the 1N4007 for the transient suppression. Those diodes are not in operation when listening.

undertow · « **Reply #17 on:** 16 Mar 2016, 05:10 pm »

Understood... Not worried about sound, yes they are wasting away using "Stealth" Fairchilds in that position sonically vs. generic 1N4007. But luckily either way they are only about a buck each... I have no other need for them so might as well toss them in there is all I am thinking at this point as long as technically there would be no problems with using them.

I realize you say the HER303's are good enough, but hopefully putting the 15 amp / 600 volt fairchilds in there will give us something? Oh well total of about $5 bucks so not gonna break the bank if there is no results.

Thanks for your time glad I asked because honestly I would have thought nothing of it till the zener controversy!

Speedskater · « **Reply #18 on:** 16 Mar 2016, 08:01 pm »

Quote from: undertow on 16 Mar 2016, 04:54 pm

Appreciate your input. Unfortunately in this case I am just trying to get back a good operational circuit. I would delve further into more complications with adding parts, I just don't think it's necessary here, also not so sure the space, and setup will work out well trying to add any snubber circuits.

So the unit is broken and you are trying to find replacement parts?

undertow · « **Reply #19 on:** 16 Mar 2016, 08:11 pm »

Quote from: Speedskater on 16 Mar 2016, 08:01 pm

So the unit is broken and you are trying to find replacement parts?

Not broken... Just a plain board missing the parts. Same as above, but that photo is of a "Populated" board.