Diode Replacement

[1beertap]

I need help in a replacement diode for the one shown in the attached photo. It has the numbers 676 printed on it as well as arrows. The first number six could actually be a nine as it's laying on its side. Any help would be appreciated...thanks.

[1beertap]

Re: Diode Replacement

I have uploaded photos of the power supply. It came out of a slot machine.

[Jack Crow]

Re: Diode Replacement

Mr Beer Tap
Greetings on the day.
Item one, great board name.

Item two
Ran into these things in two way radio.

It's a kind of varistor / zener combination.
If the voltage goes too high across the terminals, it starts to conduct.

Some things for you to try.

Will the PSU power up on it's own now?
What is the voltage across the point where the device was removed.

These parts die for only one reason.

They can't over dissipate for long.

In Yeasu radios the part was rated for 16 volts.
Seems transiant voltages in cars will spike the line over 16, the thing conducts, and after a while, pow, short city. The client is stuck with a radio that blows fuses. And I get to track down a mystery.

If you can. Catch me off list, thinking of moving to Reno and fixing PSU's in games is a line of side work Im thinking about.

Thanks in advance
Jack Crow

[Toasty]

Re: Diode Replacement

What makes you believe it is bad?

[1beertap]

Re: Diode Replacement

Will the PSU power up on it's own now?
What is the voltage across the point where the device was removed.
Jack Crow

Jack,
With the part in question removed, it will power up with no problems. Also, the reading I get across the point of where the device was is 38.7Vdc.

This unit died because of a person plugging in 110vac into the back of the supply not realizing it works on 24vac. Also, when they plugged it in, they pushed the connector in so hard that it bent the case thus shorting it out against an internal heat sink.

[1beertap]

Re: Diode Replacement

What makes you believe it is bad?

It's shorted and will blow the fuse when it's in circuit. The unit works fine without it.

[Jack Crow]

Re: Diode Replacement

Mr Tap,
Yupp, that is a standard symptom.
Pull the offending part and the voltage comes up.

Everything seems to work fine. (Assuming that 37.5 volts is what you expect.)

What I do when a weird part comes across my desk.
I look at it under a microscope, get all the numbers off it, then do a google search with the numbers I find. Most times that is enough to find the part I want.

If that won't do the trick, find a Zener about five volts over your target voltage and call it a day.

Much luck.
Jack Crow

[Jack Crow]

Re: Diode Replacement

BT,
Found the parts I was telling you about.

This one is used on a 12 volt ham radio.

From the spec sheet on Mouser.com
http://www.mouser.com/ProductDetail/...AkAmo4UA%3d%3d


Manufacturer: Vishay
Product Category: TVS Diodes - Transient Voltage Suppressors
RoHS: No

RoHS Version Available


Polarity: Unidirectional
Clamping Voltage: 16.7 V
Operating Voltage: 10.2 V
Package / Case: DO-204AC
Breakdown Voltage: 11.4 V
Peak Surge Current: 75 A
Peak Pulse Power Dissipation: 600 W
Maximum Operating Temperature: + 185 C
Minimum Operating Temperature: - 65 C
Packaging: Reel
Dimensions: 3.6 (Max) mm W x 7.6 (Max) mm L
Factory Pack Quantity: 4000


Went back to the web site and looked up a similar part for above 37.5, and found this.

http://www.mouser.com/ProductDetail/...kCPHn4jNdW8%3d

See an Error?
[Vishay Semiconductors 1.5KE47C-E3/54]
Mouser Part #: 625-1.5KE47C-E3
Manufacturer Part #:
1.5KE47C-E3/54
Manufacturer:
Vishay Semiconductors
Description: TVS Diodes - Transient Voltage Suppressors 1500W 47V Bidirect

PDF Data Sheet
Order quantities greater than 1,390 may be subject to a minimum order quantity. If a minimum applies, Mouser will contact you.
Images are for reference only
See Product Specifications
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Specifications
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My Notes

Manufacturer: Vishay
Product Category: TVS Diodes - Transient Voltage Suppressors
RoHS: RoHS Compliant By Exemption Details
Polarity: Unidirectional
Clamping Voltage: 67.8 V
Operating Voltage: 38.1 V
Package / Case: Case 1.5KE
Breakdown Voltage: 42.3 V
Peak Surge Current: 22.1 A
Peak Pulse Power Dissipation: 1500 W
Maximum Operating Temperature: + 175 C
Minimum Operating Temperature: - 55 C
Packaging: Reel
Dimensions: 5.3 (Max) mm W x 9.5 (Max) mm L

Hope this helps.
Jack Crow
Herndon VA

[1beertap]

Re: Diode Replacement

Jack,

Sorry it took so long to respond. I've been away from the computer for a few days. Anyway, thank you for looking the part up for me. I ordered the part just shortly before I posted here. Thanks again.

[Jack Crow]

Re: Diode Replacement

BT,
This is how we operate here. May not be the fastest but eventually we get around to it.

Much luck on the project.

Jack Crow in the less than free world.

[1beertap]

Re: Diode Replacement

Jack,
Will unidirectional polarity matter using the TVS diode? I have a working diode with the same part number that I located on another area of the board. The TVS diode and the 676 diode I found do not test the same.

[Jack Crow]

Re: Diode Replacement

BT,
A moment of truth here.
Have not had much time to play with them.

Suppose the OEM might have data sheets and test circuits that will explain how they work and are to be used.

I found one bad in a two way ham radio.
Seems start up surge in the vehicle wiped the part out.

It's been happening across the country.

You know how it works, fine one bad one, and then hear about four more.

Keep us in the loop. This is good education.

Jack Crow