Any disadvantage to a higher rated bridge rectifier ?

[jnashguitar]

I've got a fried bridge rectifier in my Soundcraft power supply. The schematic calls for a KBL02 (200V), but I'm noticing at Digikey the higher-rated rectifiers in the same line (KBL04, KBL06, KBL08, KBL10) are exactly the same price. Is there any reason not to go with a 400V rectifier (or 1000V for that matter) ?

Thanks!

-James

[brianroth]

No

Bri

[Matt Syson]

Hi
Higher ratings on a 'bridge' are sometimes beneficial as for a 'one off' the extra insurance against high voltage 'spikes' outweighs the hassle of changing it.
Obviously if you are building thousands of units the 'per item' cost is significant, assembly cost being the same.
Matt S

[memphisindie]

Make sure that you change both of them if there are two.

[jnashguitar]

Great--thanks for the advice!

So, it sounds like higher-rated is always better for a rectifier ? Makes it doubly-weird that they're all the same price at DigiKey... some kind of temporary pricing quirk, I guess--not sure how they ever expect to sell the lower-rated ones ?

I'll go ahead and order the best in the line, then--thanks!

-James

[LeeYoo]

Rated voltage is just one of the specs.
What about lowest forward voltage at a certain current.
Maybe the lower voltage rectifiers are selected for lower forward voltage.
This makes the rectifier run less hot, and live longer.
Double sided sword, because a hot rectifier has less forward voltage loss.
Voltage spikes are more of a problem in (direct) mains applications.
Maybe less important on the secondary side of a transformer.
Why did this rectifier fail. Current, heat, or voltage.
Leo..

[The Real MC]

Reverse voltage is not likely why the original bridge rectifier got fried. Its current handling (1A, 2A, etc) was probably too low. If it is too low then the rectifier gets hotter and too much heat will destroy any component. If you want better reliability, then select a rectifier with higher current capability.

[memphisindie]

Originally Posted by LeeYoo

Rated voltage is just one of the specs.
What about lowest forward voltage at a certain current.
Maybe the lower voltage rectifiers are selected for lower forward voltage.
This makes the rectifier run less hot, and live longer.
Double sided sword, because a hot rectifier has less forward voltage loss.
Voltage spikes are more of a problem in (direct) mains applications.
Maybe less important on the secondary side of a transformer.
Why did this rectifier fail. Current, heat, or voltage.
Leo..

It failed because it was rated for 1/2 what spec was for the stock part.
Someone did a lame repair. Probably a field repair when the original part failed and that part is what was in their box.

[jnashguitar]

Originally Posted by memphisindie

It failed because it was rated for 1/2 what spec was for the stock part.
Someone did a lame repair.

Agreed, and that's not the half of it--the soldering was abysmal, resulting in a half dozen lifted/missing traces, poorly patched. Made my job way more tedious, since I went through and tried to attach the parts securely and patch everything neatly with wires... then, I plug it in and immediately smell burning... thought I must have made a mistake. Carefully traced through the whole circuit, ultimately finding the problem was a poorly-chosen replacement part... ARGH!

The fun of repairing a poorly-maintained hacked-up power supply

The good news is at least the modules in the console are all original, untouched by the blowtorch soldering iron used on the power supply.

Thanks for the advice!

-James

[jnashguitar]

Originally Posted by LeeYoo

Rated voltage is just one of the specs.
What about lowest forward voltage at a certain current.
Maybe the lower voltage rectifiers are selected for lower forward voltage.
This makes the rectifier run less hot, and live longer.
Double sided sword, because a hot rectifier has less forward voltage loss.

These are the kind of trade-offs I was wondering about. Thinking there might be some inherent advantage to a lower voltage design, that going with something way overrated might have a downside ?

Looking at the spec sheet, though, it appears performance is identical except for the voltage rating. So there's really no downside to using the higher rated components (especially given the identical price) ?

-James

[Matt Syson]

Hi
In many cases the parts for a particular 'series' are identical and are merely 'selected' for a given characteristic. The rectifiers will all be 'designed' for a certain current and for a voltage 'aspiration'. At the testing stage those that cannot withstand the 1000 Volts (or whatever the maximum was) get graded to what they will be reliable working at, I believe it is the point where 'leakage' gets more than a certain amount but not necessarily the 'catastrophic failure' point.
Many factors like availability, brand loyalty and stock requirements all have an impact on which particular unit a manufacturer choses. If a high current unit is required for other products there is a chance that over rated parts will get used on the 'smaller' units as the price per rectifier (or whatever) falls with quantity.
I usually carry 1000 or 800 Volt 35 Amp rectifiers in my toolbox. Not easy to fit on a SMD board though!
Matt S

[Ike Zimbel]

Originally Posted by jnashguitar

Agreed, and that's not the half of it--the soldering was abysmal, resulting in a half dozen lifted/missing traces, poorly patched. Made my job way more tedious, since I went through and tried to attach the parts securely and patch everything neatly with wires... then, I plug it in and immediately smell burning... thought I must have made a mistake. Carefully traced through the whole circuit, ultimately finding the problem was a poorly-chosen replacement part... ARGH!

The fun of repairing a poorly-maintained hacked-up power supply

The good news is at least the modules in the console are all original, untouched by the blowtorch soldering iron used on the power supply.

Thanks for the advice!

-James

Welcome to the glamorous world of audio repair!
Cheers,
Ike

[jnashguitar]

That makes a ton of sense--thanks, Matt!

I really appreciate all the advice, you guys!

-James