What Ken think About the Flyback Diode's

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DaveWell
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What Ken think About the Flyback Diode's

Post by DaveWell »

OUTPUT SPIKE PROTECTION
This modification involves taking three 1N4007 silicon diodes in series with the banded end connecting to pin three
of your output tubes and the other end to ground. You use one on each side of a push-pull output. So for example,
on a 100 watt Marshall the two tubes on the left, either pin three of either one of those tubes can connect to this
diode to ground. And on the other side either pin three can connect to the other set of diodes to ground, as the
tubes on either side are in parallel.
We use 1N4007 silicon power diodes which are effective in suppressing spikes at certain frequencies. These will
not necessarily prevent spiking on all amps! There is a fast recovery or high speed diode which will suppress higher
frequency arcing however these diodes have a very distinct disadvantage as they alter the tone of the amp! They
make the amp sound muddy as they bleed off high frequencies from the output transformer! Trainwreck does not
use these kinds of diodes because of their effect on the tone.
While the Trainwreck method does not eliminate spiking in every amp, it does not effect the tone at all. Every other
method which will totally eliminate spiking will have a negative effect on the tone of your amp.
Another point to remember concerning spiking is that hot biased amps tend to generate more high voltage spiking
than properly biased amps.


This Information Was Find On : https://robrobinette.com/The_Trainwreck_Pages.htm

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ArnyLogan
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Re: What Ken think About the Flyback Diode's

Post by ArnyLogan »

Hi...I have question regarding using flyback diode for 12/24 VDC motor. The motor will be selected to run on 12VDC or 24VDC via mechanical toggle switch. The motor current will very depends on the load from 2A up to 40A. The switch is rated for 80A. The motor will be running in one direction only.I want to install a flyback diode parallel to the motor to protect the switch contacts. I have FR307 diodes, reading the FR307 datasheet shows to be OK as flyback for my project? 3A continuous current, 150 peak current, 1000V and fast switching Trr 500nS.
Did I make a good choice on the flyback diode? or should I using something else?

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Last edited by ArnyLogan on Tue Sep 11, 2018 4:49 pm, edited 1 time in total.
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pompeiisneaks
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Re: What Ken think About the Flyback Diode's

Post by pompeiisneaks »

ArnyLogan wrote: Wed Aug 15, 2018 4:45 pm Hi...I have question regarding using flyback diode for 12/24 VDC motor. The motor will be selected to run on 12VDC or 24VDC via mechanical toggle switch. The motor current will very depends on the load from 2A up to 40A. The switch is rated for 80A. The motor will be running in one direction only.I want to install a flyback diode parallel to the motor to protect the switch contacts. I have FR307 diodes, reading the FR307 datasheet shows to be OK as flyback for my project? 3A continuous current, 150 peak current, 1000V and fast switching Trr 500nS.
Did I make a good choice on the flyback diode? or should I using something else?
First off, this is a forum about building tube guitar amplifiers, so not really focused on motors. I don't know if anyone here has much expertise there, but you may do better finding a forum more focused on that area.

That being said, my more general understanding of electronics tells me that the diode would burn up with 40A of current since it's rated for 3A. You'd need a diode rated for the expected current maximum, unless the diode has some allowance for extremely short bursts and lists that on the datasheet, and your expected 40A load would be the max and only for extreme circumstances. Since I'm no expert about that level of specifics, though I wouldn't count on me being right. You'd be 100% sure to handle the 40A current with a diode that can handle 40A. (if such a diode existed, if not you'd need to setup some way of sharing the current over multiple diodes. I believe in parallel? to add up to the max expected current)

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pdf64
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Re: What Ken think About the Flyback Diode's

Post by pdf64 »

Flyback diodes don't pass regular load current, so they may work ok. It would be better to ask on a forum where folks are likely to have experience of this type of application.
DaveWell wrote: Sun Jun 18, 2017 2:47 pm OUTPUT SPIKE PROTECTION
This modification involves taking three 1N4007 silicon diodes in series with the banded end connecting to pin three
of your output tubes and the other end to ground. You use one on each side of a push-pull output... it does not effect the tone at all. Every other
method which will totally eliminate spiking will have a negative effect on the tone of your amp.
Another point to remember concerning spiking is that hot biased amps tend to generate more high voltage spiking
than properly biased amps...
I question the above. I can't hear the difference between different types/brands of functional film caps, or between wiring with differing colour insulation, but to me, the above method of spike mitigation makes a noticeable tonal change to an overdriven amp (smooths it out a bit); the change is also apparent on a scope wave.
The spikes occur when the (inductively loaded) output tubes are flipped rapidly into cut off, by being overdriven with high slew rate signals to their control grids; dunno that the 'hotness' of the operating point has a significant effect on that.
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