Schottky rectifier improvisation

[Pimpom]

A Schottky diode in the standby power supply of a Panasonic
TH-P42X30T plasma TV failed short but I don't have a spare or any
close substitute. It's a B3100 (3A, 100V) used in a single-diode
half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage
and frequency unknown. I have some 1N5822s which have a Vr rating
of only 40V.

Ordering parts from here takes a month or more. I'd like to do at
least a temporary replacement of the diode and see if there's
anything else wrong.

I'm thinking of using two 1N5822s in series and parallel each
with a resistor to help distribute the reverse voltage evenly.
Choosing a suitable resistor value wouldn't be a problem with
low-leakage Si PN diodes but the 1N5822 has a published max
leakage of 2mA (0.12mA typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?

 

[Look165]

Why changing ?

B3100 can be found at Farnell or RS for some .7€ pce

SO just replace !

idem for the transistors (it dimishes the unit shipment cost).



Pimpom a ĂŠcrit :

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?

 

[N_Cook]

On 04/12/2017 10:29, Pimpom wrote:

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?

It is the recovery time, ie frequency that is important, surely you
could rob a shottky package from some SMPS somewhere?

 

On Monday, 4 December 2017 11:28:22 UTC, Look165 wrote:

Pimpom a ĂŠcrit :

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close substitute..
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?

Why changing ?

B3100 can be found at Farnell or RS for some .7€ pce

SO just replace !

idem for the transistors (it dimishes the unit shipment cost).

presumably they don't ship to india or are prohibitively expensive

I'd just try one diode, accepting it might or might not work temporarily. I'd test its Vr max first, it's regularly well above rating. But I'd not want to leave it in there even if it works, there's some reason the OEM paid extra for a shottky.


NT

 

[Pimpom]

On 12/4/2017 7:08 PM, tabbypurr@gmail.com wrote:

On Monday, 4 December 2017 11:28:22 UTC, Look165 wrote:
Pimpom a ĂŠcrit :

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?


Why changing ?

B3100 can be found at Farnell or RS for some .7€ pce

SO just replace !

idem for the transistors (it dimishes the unit shipment cost).

presumably they don't ship to india or are prohibitively expensive

That and more. Farnell and RS both have branches in India but
they cater only to OEMs. I can get almost anything from
AliExpress (China) and they ship quickly but transit time with
free or nominal shipping charge is anywhere from 1 to 3 months.

> I'd just try one diode, accepting it might or might not work temporarily. I'd test its Vr max first, it's regularly well above rating.

I'm worried that it might cause further damage if the diode fails.

But I'd not want to leave it in there even if it works, there's
some reason the OEM paid extra for a shottky.
>

The 1N5822 *is* a Schottky.

 

[bitrex]

On 12/04/2017 12:06 PM, Pimpom wrote:

On 12/4/2017 7:08 PM, tabbypurr@gmail.com wrote:
On Monday, 4 December 2017 11:28:22 UTC, Look165  wrote:
Pimpom a ĂŠcrit :

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close
substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of
only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?


Why changing ?

B3100 can be found at Farnell or RS for some .7€ pce

SO just replace !

idem for the transistors (it dimishes the unit shipment cost).

presumably they don't ship to india or are prohibitively expensive


That and more. Farnell and RS both have branches in India but they cater
only to OEMs. I can get almost anything from AliExpress (China) and they
ship quickly but transit time with free or nominal shipping charge is
anywhere from 1 to 3 months.

I'd just try one diode, accepting it might or might not work
temporarily. I'd test its Vr max first, it's regularly well above rating.

I'm worried that it might cause further damage if the diode fails.

But I'd not want to leave it in there even if it works, there's some
reason the OEM paid extra for a shottky.


The 1N5822 *is* a Schottky.

Do you have a schematic available you can post? Is the "standby supply"
a linear PSU? Could be that they just used the B3100 because that's what
they had on hand in quantity and the faster recovery time is immaterial

 

[Pimpom]

On 12/4/2017 5:40 PM, N_Cook wrote:

On 04/12/2017 10:29, Pimpom wrote:
A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?

It is the recovery time, ie frequency that is important, surely you
could rob a shottky package from some SMPS somewhere?

I have several different Schottky diodes besides the 1N5822
including types with much higher current ratings, but none with a
Vr rating more than 45V. And that includes those from SMPSes.

I stock one 3A ultra-fast PN type but it's the 1000V version
(UF5408) and has a high forward drop. I also have some
fast-recovery types but they're probably too slow.

 

On Monday, 4 December 2017 17:06:29 UTC, Pimpom wrote:

On 12/4/2017 7:08 PM, tabbypurr wrote:
On Monday, 4 December 2017 11:28:22 UTC, Look165 wrote:
Pimpom a ĂŠcrit :

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?


Why changing ?

B3100 can be found at Farnell or RS for some .7€ pce

SO just replace !

idem for the transistors (it dimishes the unit shipment cost).

presumably they don't ship to india or are prohibitively expensive


That and more. Farnell and RS both have branches in India but
they cater only to OEMs. I can get almost anything from
AliExpress (China) and they ship quickly but transit time with
free or nominal shipping charge is anywhere from 1 to 3 months.

I'd just try one diode, accepting it might or might not work temporarily. I'd test its Vr max first, it's regularly well above rating.

I'm worried that it might cause further damage if the diode fails.

hence test its V_r first. It's often way higher than the specs claim. Just use diode, capacitor & resistor from the mains to apply a tiny reverse current, measuring the voltage at which it conducts. Following safe practice etc.

But I'd not want to leave it in there even if it works, there's
some reason the OEM paid extra for a shottky.


The 1N5822 *is* a Schottky.

my bad. It might be perfect for the job then, depending on V_r.


NT

NT

 

[Look165]

NO !

I am a lambda person.

And I am a customer of both RS and Farnell.

And yes, they do ship in India (just a question of delivery delay).




Pimpom a ĂŠcrit :

On 12/4/2017 7:08 PM, tabbypurr@gmail.com wrote:
On Monday, 4 December 2017 11:28:22 UTC, Look165 wrote:
Pimpom a ĂŠcrit :

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close
substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of
only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?

 

On Monday, 4 December 2017 18:19:21 UTC, Look165 wrote:

NO !

I am a lambda person.

And I am a customer of both RS and Farnell.

And yes, they do ship in India (just a question of delivery delay).

Maybe visit India some time


NT

 

[Pimpom]

On 12/4/2017 11:05 PM, bitrex wrote:

On 12/04/2017 12:06 PM, Pimpom wrote:

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close
substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of
only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C.

What value of resistors do you suggest? Is my idea at all feasible?




Do you have a schematic available you can post? Is the "standby supply"
a linear PSU? Could be that they just used the B3100 because that's what
they had on hand in quantity and the faster recovery time is immaterial

No schematic. I downloaded the service manual but they omitted
the power supply - deliberately it seems. They note in one place
that the PSU is not serviceable and must be replaced as a unit.

The standby supply is definitely a switching type. It is only one
section of the whole power supply system which is on one large
single-sided board.

 

[amdx]

On 12/4/2017 4:29 AM, Pimpom wrote:

A Schottky diode in the standby power supply of a Panasonic TH-P42X30T
plasma TV failed short but I don't have a spare or any close substitute.
It's a B3100 (3A, 100V) used in a single-diode half-wave configuration.

The DC output seems to be 15V. Load current, peak reverse voltage and
frequency unknown. I have some 1N5822s which have a Vr rating of only 40V.

Ordering parts from here takes a month or more. I'd like to do at least
a temporary replacement of the diode and see if there's anything else
wrong.

I'm thinking of using two 1N5822s in series and parallel each with a
resistor to help distribute the reverse voltage evenly. Choosing a
suitable resistor value wouldn't be a problem with low-leakage Si PN
diodes but the 1N5822 has a published max leakage of 2mA (0.12mA
typical) at Vr(max) at 25°C, 20mA at 100°C. you

What value of resistors do you suggest? Is my idea at all feasible?

Since you want an answer about function before ordering parts,
Can you supply an external 15V to the driven circuit?
Then put the best solution for the diode replacement you come up with
and verify the switcher is functioning using an external load.
A little convoluted but reasonable to save a month wait for a second
order of parts.
Mikek