Author Topic: Advice needed - Identify a diode  (Read 21793 times)

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Offline CariboTopic starter

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Advice needed - Identify a diode
« on: April 10, 2024, 06:56:42 pm »
Hello everyone,

I need your enlightened help to identify a diode to replace.

Here's the context:

I have a monitoring active speaker, model PM5 from brand E-MU, which suddenly failed on me. I opened it up to see if I could find any clues to the malfunction, and came across components that seemed burnt. I cleaned up as best as I could. The capacitors are easily identifiable for replacement, but I have absolutely no idea how to find the reference of the diode to change, D105. This one is probably the same as D106. The regulator behind it is an LM337SP.

As I'm writing this message, I thought I'd take a look at the LM337SP datasheet, to see if there were any examples of setups involving diodes. There's one with 1N4002 and 1N4148. Given the package, I don't think it's a 1N4002.

Could it be a 1N4148? If someone could enlighten me, I would be greatly appreciative!

Thanks in advance!

 

Offline fzabkar

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Re: Advice needed - Identify a diode
« Reply #1 on: April 10, 2024, 08:07:04 pm »
It would help to know where the diode connects. Is one end grounded? Does it connect to any of the regulator's pins?
 

Online isometrik

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Re: Advice needed - Identify a diode
« Reply #2 on: April 10, 2024, 08:21:11 pm »
Based on the symmetry of the components in that area of the PCB, I suspect D105 is identical to D106, as you suggested in your initial post.

I suggest you desolder D106 to read its part number.
 
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Offline Haenk

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Re: Advice needed - Identify a diode
« Reply #3 on: April 11, 2024, 06:52:11 am »
The package and size would match a 1N4148.
It is certainly not a 1N400x - these are all plastic packages.
Unfortunately, this only helps to rule out things, but is no confirmation. In my opinion, a 1N4148 will do.
 

Offline CariboTopic starter

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Re: Advice needed - Identify a diode
« Reply #4 on: April 11, 2024, 01:14:34 pm »
A big thank you for your initial responses.

I found a way to read what's written on the package: 1N4 and below it, a 5.

Could this help someone?

Thank you




 

Offline fzabkar

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Re: Advice needed - Identify a diode
« Reply #5 on: April 11, 2024, 05:21:32 pm »
1N45 is a germanium diode, which is a relic from the past. It would help if you identified the connection points. Does it connect between Vin and Vout, or between Adj and Vout, or between Adj and Ground?

A germanium diode would make some sense if it were connected between Vout and ground, reverse biased.

From National Semiconductor's handbook:

Quote
Figure 4-2 is an example of a typical connection for obtaining a positive and negative power supply. The diodes between output and GND are for preventing latchdown at startup and are absolutely necessary in the case of loads shown by solid lines. Without the diodes, current flows in the separation regions between elements as described in Figure 4-2 is an example of a typical connection for obtaining a positive and negative power supply. The diodes between output and GND are for preventing latchdown at startup and are absolutely necessary in the case of loads shown by solid lines. Without the diodes, current flows in the separation regions between elements as described in chapter 2 and the output voltage does not rise (refer to Figure 4-3).
« Last Edit: April 11, 2024, 08:15:12 pm by fzabkar »
 


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