Author Topic: Help identify glass encapsulated diodes  (Read 2368 times)

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Offline 晓看风云Topic starter

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Help identify glass encapsulated diodes
« on: August 24, 2024, 04:31:25 pm »
I have a circuit board from Japan produced in 1999, which has two glass encapsulated diodes with silk screen printing of QY10 or QY1O. I didn't understand the alphabetical order of the silk screen printing. The silk screen on the circuit board is labeled as D10 and D11. The multimeter diode cannot conduct in the forward direction when measured in gear, and there is a 0.598V voltage drop in the reverse direction. Both are the same. I need help identifying what kind of diodes they are, whether they are damaged or what I should replace them with. I checked their wiring connections, and one of them provides positive power to lt1007, while the other provides negative power. Once again, I earnestly request everyone's help!
 

Offline fzabkar

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Re: Help identify glass encapsulated diodes
« Reply #1 on: August 24, 2024, 06:39:40 pm »
10V Zener?
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #2 on: August 24, 2024, 07:13:37 pm »
10V Zener?
I don't know, but the silk screen printing on the board is D instead of ZD. I don't know if there will be any difference in the silk screen printing of circuit boards in Japan in 1999. Additionally, one of these two diodes will consistently output -8V steadily. When switching gears, it will change from+8V to+15V. I don't know if this phenomenon is normal. I really want to figure out what type of diode this is now!
 

Offline fzabkar

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Re: Help identify glass encapsulated diodes
« Reply #3 on: August 24, 2024, 08:38:33 pm »
Can you trace the circuit in that area? That will provide a clue. The diodes seem to be behaving as if they are open circuit. The voltage drop in the reverse direction could be due to the associated pass transistor. (?)
« Last Edit: August 24, 2024, 08:45:45 pm by fzabkar »
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #4 on: August 25, 2024, 01:58:41 am »
Can you trace the circuit in that area? That will provide a clue. The diodes seem to be behaving as if they are open circuit. The voltage drop in the reverse direction could be due to the associated pass transistor. (?)
Okay, I will try to draw a simple circuit diagram about diodes to help better identify them. Thank you very much for your help. I will inform you as soon as there is any progress!
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #5 on: August 25, 2024, 05:48:13 am »
Can you trace the circuit in that area? That will provide a clue. The diodes seem to be behaving as if they are open circuit. The voltage drop in the reverse direction could be due to the associated pass transistor. (?)
I am still a novice, and I find it very difficult to draw schematics. There should be some mistakes, but there is probably no problem with the direction. So I want to know, will these two diodes be 10V voltage regulators? I think they must have been damaged and there is no diode voltage drop that they should have. If damaged, could it be caused by overvoltage? (For example, inserted the wrong power voltage? Everything else seems to be working very well.)
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #6 on: August 25, 2024, 05:12:08 pm »
I have updated the circuit diagram, and these two diodes have been removed. The silk screen sequence should be 10QY. Using a multimeter diode to measure the forward direction is OL, and the reverse direction is 0.636V voltage drop. I'm confused, are they damaged? What type of diode is it? Is there anyone here who can help answer this!
 

Offline fzabkar

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Re: Help identify glass encapsulated diodes
« Reply #7 on: August 25, 2024, 05:46:52 pm »
That diode is weird. I can see that Q1 and Q2 are the positive and negative pass transistors in a linear power supply, with Q23 and Q24 enforcing a current limit of 30mA. However, D10 and D11 seem to be reversed, if they were regular diodes. I can't understand their purpose. They appear to be clamps of some kind, but I don't understand why they would be needed. Sorry, I'm totally confused.
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #8 on: August 25, 2024, 06:08:42 pm »
That diode is weird. I can see that Q1 and Q2 are the positive and negative pass transistors in a linear power supply, with Q23 and Q24 enforcing a current limit of 30mA. However, D10 and D11 seem to be reversed, if they were regular diodes. I can't understand their purpose. They appear to be clamps of some kind, but I don't understand why they would be needed. Sorry, I'm totally confused.
Thank you very much for your answer. If there is any progress in the future, I will inform you as soon as possible! I tried to connect these two strange diodes in series with a 10k resistor, which is a common method of testing voltage regulator diodes, but it obviously didn't work. They didn't play according to the script at all. I'm thinking about something. As far as I know, for a normal diode, whether it's a Schottky diode, a voltage regulator diode, or a regular diode, I've never heard of a diode with a forward OL and reverse 0.636V voltage drop. Perhaps I have a misunderstanding??? I will try to replace them with ordinary diodes in the future and see the results!
 

Offline MathWizard

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Re: Help identify glass encapsulated diodes
« Reply #9 on: August 25, 2024, 08:46:20 pm »
So is there a problem with the circuit tho ? If you have a soldering iron and remove them, it should be easy to check if they are zeners, with a 9V battery and some resistor. A current 10mA should be enough to get a small zener fully conducting.

I didn't try the circuit, but for example say they drop 5.1V=Vz, with about 10mA=Iz. Then the resistor size would be R=(Vcc-Vz)/Iz
 

Offline Kim Christensen

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Re: Help identify glass encapsulated diodes
« Reply #10 on: August 25, 2024, 11:31:27 pm »
Looking at the schematic, it seems like they are some sort of constant current diode.
Example attached:
 
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Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #11 on: August 26, 2024, 02:26:19 am »
So is there a problem with the circuit tho ? If you have a soldering iron and remove them, it should be easy to check if they are zeners, with a 9V battery and some resistor. A current 10mA should be enough to get a small zener fully conducting.

I didn't try the circuit, but for example say they drop 5.1V=Vz, with about 10mA=Iz. Then the resistor size would be R=(Vcc-Vz)/Iz
I have tried using a 10k resistor in series, limiting the current to 10ma and setting the power supply to 14v. It did not perform according to the script because it has a forward infinity and a reverse voltage drop of 0.6v. So obviously, when I tested using this method, the voltage between the two segments of the diode remained stable at around 0.6V.
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #12 on: August 26, 2024, 02:29:18 am »
Looking at the schematic, it seems like they are some sort of constant current diode.
Example attached:
I searched and found it very difficult to purchase and the price is expensive. If it is really a current regulator, I would like to know if this type of current regulator would exhibit a forward infinity and a reverse voltage drop under normal circumstances? This is very important, at least I can know if they are normal now. Or are there any commonly used diodes to replace them?
 

Offline fzabkar

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Re: Help identify glass encapsulated diodes
« Reply #13 on: August 26, 2024, 04:23:11 am »
You could replace the diode with an n-channel JFET and series resistor.

https://en.wikipedia.org/wiki/Constant-current_diode
 

Offline Kim Christensen

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Re: Help identify glass encapsulated diodes
« Reply #14 on: August 26, 2024, 04:34:23 am »
I searched and found it very difficult to purchase and the price is expensive.

I wouldn't replace them unless you know they are faulty. Besides, the ones I linked are just an example of the type of device that I think they might be.

Quote
If it is really a current regulator, I would like to know if this type of current regulator would exhibit a forward infinity and a reverse voltage drop under normal circumstances? This is very important, at least I can know if they are normal now. Or are there any commonly used diodes to replace them?

You could try testing them in a circuit like depicted below. The 100 ohm resistor is just for safety to make sure you don't damage the diode or meter. Set the power supply's current limit to 10mA as well.
Slowly adjust the power supply voltage from zero to apx 15V and plot the current at 1V intervals. If it is a constant current diode, the current should hold fairly steady once the power supply voltage reaches 1-3V or so... I suspect the current will be around 1-4mA or so.
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #15 on: August 26, 2024, 04:47:19 am »
You could replace the diode with an n-channel JFET and series resistor.

https://en.wikipedia.org/wiki/Constant-current_diode
Okay, thank you for your suggestion! I will use it as a backup measure. After all, I don't know much, so if I act rashly, I'm worried that I might mess it up. I will first try to understand the model or quality of this electronic component.
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #16 on: August 26, 2024, 04:52:16 am »
I searched and found it very difficult to purchase and the price is expensive.

I wouldn't replace them unless you know they are faulty. Besides, the ones I linked are just an example of the type of device that I think they might be.

Quote
If it is really a current regulator, I would like to know if this type of current regulator would exhibit a forward infinity and a reverse voltage drop under normal circumstances? This is very important, at least I can know if they are normal now. Or are there any commonly used diodes to replace them?

You could try testing them in a circuit like depicted below. The 100 ohm resistor is just for safety to make sure you don't damage the diode or meter. Set the power supply's current limit to 10mA as well.
Slowly adjust the power supply voltage from zero to apx 15V and plot the current at 1V intervals. If it is a constant current diode, the current should hold fairly steady once the power supply voltage reaches 1-3V or so... I suspect the current will be around 1-4mA or so.
Okay, thank you for your suggestion! I will try to set up a testing environment and observe the results, and then provide feedback! (As for whether they have faults, I can only compare them with other things within my knowledge, such as voltage regulators and rectifiers: they all have the characteristics of forward voltage drop and reverse infinity.)
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #17 on: August 26, 2024, 06:41:23 am »
I searched and found it very difficult to purchase and the price is expensive.

I wouldn't replace them unless you know they are faulty. Besides, the ones I linked are just an example of the type of device that I think they might be.

Quote
If it is really a current regulator, I would like to know if this type of current regulator would exhibit a forward infinity and a reverse voltage drop under normal circumstances? This is very important, at least I can know if they are normal now. Or are there any commonly used diodes to replace them?

You could try testing them in a circuit like depicted below. The 100 ohm resistor is just for safety to make sure you don't damage the diode or meter. Set the power supply's current limit to 10mA as well.
Slowly adjust the power supply voltage from zero to apx 15V and plot the current at 1V intervals. If it is a constant current diode, the current should hold fairly steady once the power supply voltage reaches 1-3V or so... I suspect the current will be around 1-4mA or so.
Before using your testing method, I searched everywhere and found that the model should be CRD E-102 produced by SEMITEC in Japan, with a current of 1mA. After using your testing method, I further validated this result. When the voltage is 1V, my power supply displays 0.000A, and the current remains at 0.001A at any stage between 2-15V. I think this should indicate that it is a 1mA current limiting diode and is working completely normally! I am very glad that your answer has enabled me to reach the current level, and I will continue to try to find other possible faults! This instrument is Yokogawa CA100, which is a process calibrator. The other gears are very good, but the frequency gear cannot work properly. No information was found on the forum, so I had to face it myself! If there are any new developments in the future, I will publish a new repair post about the frequency of maintenance faults.
 

Offline Kim Christensen

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Re: Help identify glass encapsulated diodes
« Reply #18 on: August 26, 2024, 04:57:46 pm »
After using your testing method, I further validated this result. When the voltage is 1V, my power supply displays 0.000A, and the current remains at 0.001A at any stage between 2-15V. I think this should indicate that it is a 1mA current limiting diode and is working completely normally!

Though the current meter on your power supply doesn't have enough resolution, it appears to be working as expected. If both diodes check out the same, you can put them back in circuit if you haven't done so already.

Looking at your circuit again, it looks like the transistor circuit is a current buffer for the LT1007 Op-Amp. I assume the output load is connected at the junction of R19 & R22. If the circuit is operating properly, the voltage at R19 & R22 should follow the voltage at the output of LT1007 (pin 6), within a slight error, while connected to an appropriate load:

 

Offline fzabkar

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Re: Help identify glass encapsulated diodes
« Reply #19 on: August 26, 2024, 05:06:34 pm »
I expect that the junction of R19 and R22 would be connected to pin #2 of the op-amp, possibly via a potential divider. The output would then follow the input at pin #3, scaled down by the divider.
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #20 on: August 26, 2024, 05:34:50 pm »
After using your testing method, I further validated this result. When the voltage is 1V, my power supply displays 0.000A, and the current remains at 0.001A at any stage between 2-15V. I think this should indicate that it is a 1mA current limiting diode and is working completely normally!

Though the current meter on your power supply doesn't have enough resolution, it appears to be working as expected. If both diodes check out the same, you can put them back in circuit if you haven't done so already.

Looking at your circuit again, it looks like the transistor circuit is a current buffer for the LT1007 Op-Amp. I assume the output load is connected at the junction of R19 & R22. If the circuit is operating properly, the voltage at R19 & R22 should follow the voltage at the output of LT1007 (pin 6), within a slight error, while connected to an appropriate load:


I have tested both and the results are the same. They work normally. So I have already put them back into the circuit board. As you said, the point between R19 and R22 is the output point, which ultimately reaches the relay contact and then the output terminal. Is the function of this current buffer to increase the current load?
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #21 on: August 26, 2024, 05:45:28 pm »
I expect that the junction of R19 and R22 would be connected to pin #2 of the op-amp, possibly via a potential divider. The output would then follow the input at pin #3, scaled down by the divider.
You are right, I roughly remember that the input was a signal from the MCU! Now I have encountered a new problem. The Q23 component with XL silk screen printing does not measure properly, and the voltage drop between pin 1 and pin 2 of the diode is 0.060V. I found an NPN transistor with the model number 2SD2704K on my search, but I'm not sure if it's correct. I noticed that there are several XL screen printed components on the circuit board, and they measure the 1st and 2nd pins online to be 0.060-0.070V. Even a few have pins 1 and 2 directly connected together on the circuit board. I am very confused, this is completely different from the NPN transistor I know.
 

Offline Kim Christensen

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Re: Help identify glass encapsulated diodes
« Reply #22 on: August 26, 2024, 05:58:31 pm »
The Q23 component with XL silk screen printing does not measure properly, and the voltage drop between pin 1 and pin 2 of the diode is 0.060V.

R19 (22 \$\Omega\$) is across Q23's pins 1 & 2 (b-e junction) and therefore will make Q23 appear to be faulty when doing a diode check in circuit.

R22 will do that same for a diode check on Q24's b-e junction.

You have to interpret in-circuit measurements of components with caution. Other components connected to them can give false results, making you chase ghosts.


As you said, the point between R19 and R22 is the output point, which ultimately reaches the relay contact and then the output terminal. Is the function of this current buffer to increase the current load?

If it's driving a relay, I suspect it's one of those single coil, set/reset, relays that require a bipolar pulse to turn off and on. Yes, the transistors increase the current capability of the LT1007 because it can't drive the relay load directly.
« Last Edit: August 26, 2024, 06:15:51 pm by Kim Christensen »
 

Offline 晓看风云Topic starter

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Re: Help identify glass encapsulated diodes
« Reply #23 on: August 26, 2024, 06:06:20 pm »
The Q23 component with XL silk screen printing does not measure properly, and the voltage drop between pin 1 and pin 2 of the diode is 0.060V.

R19 (22 \$\Omega\$) is across Q23's pins 1 & 2 (b-e junction) and therefore will make Q23 appear to be faulty when doing a diode check in circuit.

R22 will do that same for a diode check on Q24's b-e junction.

You have to interpret in-circuit measurements of components with caution. Other components connected to them can give false results, making you chase ghosts.


As you said, the point between R19 and R22 is the output point, which ultimately reaches the relay contact and then the output terminal. Is the function of this current buffer to increase the current load?

If it's driving a relay, I suspect it's one of those single coil, set/reset, relays that require a bipolar pulse to turn off and on. Yes, the transistors increase the current capability of the LT1007 because it can't drive the relay directly.
The Q23 here is not on the circuit board I provided, I just wanted to facilitate understanding and let you know that it is a switch tube starting with Q. In fact, it is a silk screen printed XL component, and the measurement is also very outrageous when removed, which is completely different from the diode characteristics of ordinary NPN transistors such as BE or BC. So I don't know if the 2SD2704K I found is correct.
 

Offline Kim Christensen

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Re: Help identify glass encapsulated diodes
« Reply #24 on: August 26, 2024, 06:12:52 pm »
That's the problem with surface mount components. XL can mean many things.
 


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