Help identify glass encapsulated diodes - Page 1
Forum section: electronics / repair

author: 晓看风云
author_rank: Contributor
timestamp: August 24, 2024, 04:31:25 pm
content: 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!

author: fzabkar
author_rank: Super Contributor
timestamp: August 24, 2024, 06:39:40 pm
content: 10V Zener?

author: 晓看风云
author_rank: Contributor
timestamp: August 24, 2024, 07:13:37 pm
content: Quote from: fzabkar on August 24, 2024, 06:39:40 pmI 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!

author: fzabkar
author_rank: Super Contributor
timestamp: August 24, 2024, 08:38:33 pm
content: 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. (?)

author: 晓看风云
author_rank: Contributor
timestamp: August 25, 2024, 01:58:41 am
content: Quote from: fzabkar on August 24, 2024, 08:38:33 pmOkay, 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!

author: 晓看风云
author_rank: Contributor
timestamp: August 25, 2024, 05:48:13 am
content: Quote from: fzabkar on August 24, 2024, 08:38:33 pmI 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.)

author: 晓看风云
author_rank: Contributor
timestamp: August 25, 2024, 05:12:08 pm
content: 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!

author: fzabkar
author_rank: Super Contributor
timestamp: August 25, 2024, 05:46:52 pm
content: 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.

author: 晓看风云
author_rank: Contributor
timestamp: August 25, 2024, 06:08:42 pm
content: Quote from: fzabkar on August 25, 2024, 05:46:52 pmThank 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!

author: MathWizard
author_rank: Super Contributor
timestamp: August 25, 2024, 08:46:20 pm
content: 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

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 25, 2024, 11:31:27 pm
content: Looking at the schematic, it seems like they are some sort of constant current diode.Example attached:

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 02:26:19 am
content: Quote from: MathWizard on August 25, 2024, 08:46:20 pmI 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.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 02:29:18 am
content: Quote from: Kim Christensen on August 25, 2024, 11:31:27 pmI 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?

author: fzabkar
author_rank: Super Contributor
timestamp: August 26, 2024, 04:23:11 am
content: You could replace the diode with an n-channel JFET and series resistor.https://en.wikipedia.org/wiki/Constant-current_diode

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 26, 2024, 04:34:23 am
content: Quote from: 晓看风云 on August 26, 2024, 02:29:18 amI 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 theymightbe.QuoteYou 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.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 04:47:19 am
content: Quote from: fzabkar on August 26, 2024, 04:23:11 amOkay, 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.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 04:52:16 am
content: Quote from: Kim Christensen on August 26, 2024, 04:34:23 amOkay, 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.)

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 06:41:23 am
content: Quote from: Kim Christensen on August 26, 2024, 04:34:23 amBefore 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.

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 26, 2024, 04:57:46 pm
content: Quote from: 晓看风云 on August 26, 2024, 06:41:23 amThough 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:

author: fzabkar
author_rank: Super Contributor
timestamp: August 26, 2024, 05:06:34 pm
content: 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.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 05:34:50 pm
content: Quote from: Kim Christensen on August 26, 2024, 04:57:46 pmI 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?

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 05:45:28 pm
content: Quote from: fzabkar on August 26, 2024, 05:06:34 pmYou 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.

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 26, 2024, 05:58:31 pm
content: Quote from: 晓看风云 on August 26, 2024, 05:45:28 pmR19 (22) 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.Quote from: 晓看风云 on August 26, 2024, 05:34:50 pmIf 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 therelayload directly.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 06:06:20 pm
content: Quote from: Kim Christensen on August 26, 2024, 05:58:31 pmThe 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.

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 26, 2024, 06:12:52 pm
content: That's the problem with surface mount components.XL can mean many things.

author: fzabkar
author_rank: Super Contributor
timestamp: August 26, 2024, 06:19:27 pm
content: You can have some confidence in your decoding of the part markings if the datasheets for Q23 and Q24 indicate that they are complementary PNP and NPN BJTs.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 06:20:30 pm
content: Quote from: Kim Christensen on August 26, 2024, 06:12:52 pm(I'm sorry that the code Q23 misled you, and I sincerely apologize again!) Yes, it's strange that when I removed XL from the circuit board, the diode characteristics between pins 1 and 2 still fluctuated like 0.06-0.08. But when I measured them again after a while, they changed to 0.300-0.500 occasionally, which is a strange phenomenon. I searched everywhere, and only 2SD2704K meets the criteria. I have already ordered it, and I will not rashly install them on the circuit board until I am completely sure that 2SD2704K is the correct model. Acting rashly will only lead to the expansion of the malfunction, which is not what I want to see!

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 06:24:58 pm
content: Quote from: fzabkar on August 26, 2024, 06:19:27 pmYou can take a look at my other latest reply messages. I am very sorry for the inconvenience caused by the code Q23. The component of the silk screen XL is not included in the circuit diagram I provided, it is located elsewhere. I haven't found any problems with the circuit around LT1007 so far. I won't find any problems here for the time being. I will go to other places to seek the fault phenomenon, such as this XL screen printed switch transistor calibrated with Q!

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 26, 2024, 06:29:24 pm
content: Hmmm... It could be a MOSFET. If you leave the gate floating and do a diode check between drain and source, you will get readings that drift. Shorting the gate to the source will make the drain-source measure open, or as a diode if measured in reverse.

author: fzabkar
author_rank: Super Contributor
timestamp: August 26, 2024, 06:40:20 pm
content: The mark might be "KL" ...

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 06:44:35 pm
content: Quote from: fzabkar on August 26, 2024, 06:40:20 pmThere are many components in the circuit that are silk screened as XL. Based on most of the others, I prefer XL. What do you think?

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 06:59:01 pm
content: Quote from: Kim Christensen on August 26, 2024, 06:29:24 pmBecause I am currently unable to determine the specific pin situation, and I am also unsure if it is functioning properly. Assuming the pin arrangement is as shown in the attached diagram, it will help me explain. When I put the red pen on foot 3 and the black pen on foot 1 or 2, both display a pressure drop of 0.698. Placing the probe in reverse is OL. Another type of measurement is the black probe 1 or 2 and the red probe 1 or 2. The multimeter gave me feedback on a very strange state, constantly flashing, and I couldn't even see its changes, probably flashing back and forth between 2.000-1.9-1.8 and gradually decreasing open.

author: fzabkar
author_rank: Super Contributor
timestamp: August 26, 2024, 07:10:16 pm
content: The stylised "C3" marking appears to be Toshiba's, if this supplier is to be believed:https://www.mscnelectronics.com/home/produto/codigo:12213/smd-di-1ss226-100ma-80v-ultra-high-speed-switching-diodes-diodo-smthttps://www.mscnelectronics.com/upload/Produto12213.grande.71aef49d58c5126b7c1e49ac865f47b1.jpgTherefore, I would look for an "XL" or "KL" part by Toshiba.My advice is to try to view the circuit as functional blocks instead of testing each individual component.For example, the previous circuit could be seen as the following:https://handwiki.org/wiki/images/7/7f/Pushpull_%28English%29.pngAll you would need to do to verify that circuit would be to vary the input to the op-amp above and below ground (by operating the appliance/device), and then observe the output at the junction of the two current sense resistors.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 07:18:57 pm
content: Quote from: fzabkar on August 26, 2024, 07:10:16 pmYou are simply a genius. Based on your ideas, I have retrieved its true model. 2SK209-BL, I will carefully inspect its quality next! Thank you.

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 07:33:56 pm
content: My advice is to try to view the circuit as functional blocks instead of testing each individual component.For example, the previous circuit could be seen as the following:https://handwiki.org/wiki/images/7/7f/Pushpull_%28English%29.pngAll you would need to do to verify that circuit would be to vary the input to the op-amp above and below ground (by operating the appliance/device), and then observe the output at the junction of the two current sense resistors.I cannot distinguish where the frequency comes from with my ability, so I can only search aimlessly. In fact, I found some useful things. The arrow above the figure points to the signal generated by the frequency from the muc, which is exactly the same as the frequency I set. I found the HC4053BF on the back of the line, and it finally went to its 10 legs, but there is only a 0/1 high and low level. I don't know what this means. After entering pin 10 of HC4053BF, the frequency never came out again

author: fzabkar
author_rank: Super Contributor
timestamp: August 26, 2024, 07:46:55 pm
content: U18 consists of 3 SPDT analogue switches. Pin #10 is a control input. A high or low on this pin connects pin #15 to either of pin #1 or pin #2.https://www.mouser.com/datasheet/2/916/74HC_HCT4053-1541743.pdf

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 07:55:35 pm
content: Quote from: fzabkar on August 26, 2024, 07:46:55 pmI understand this, but what I don't understand is that the set frequency is generated by the MCU. Why did it end up here instead of going to the output terminal? If I set the frequency to 100Hz, then this 10 pin will display 100Hz very stably. I am very puzzled about this... and assuming XL is a field effect transistor model 2sk209 bl, what is the purpose of directly short circuiting the source and drain of pin 1 and pin 2?

author: Kim Christensen
author_rank: Super Contributor
timestamp: August 26, 2024, 08:18:06 pm
content: Perhaps they are using it as some sort of crude, or ingenious, DAC.Just a guess and probably not how it's designed:If you wanted to generate a square-wave that swung between 1V and 3.5V you could feed these two DC voltages into pins 1 & 2, and get a square-wave out on pin 15 that toggles between 1V and 3.5V at the same frequency as the logic level signal on pin 10.If the 1V and 4.5V were missing (at zero V) then that would explain why the "signal" at pin 10 seems to go nowhere. Or, if pin 6 (INHibit) is at logic high, then all analog switches would be disabled with the same result.

author: fzabkar
author_rank: Super Contributor
timestamp: August 26, 2024, 08:28:13 pm
content: U15 and U16 (?) appear to be 4053BF ICs. U18 looks different. :-?https://docs.rs-online.com/8004/0900766b8082f4fe.pdf(Toshiba TC4053BP / BF / BFT)

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 08:30:55 pm
content: Quote from: Kim Christensen on August 26, 2024, 08:18:06 pmI have been thinking about whether pin10 can output the correct frequency from pin15, because this signal has no way out unless it encounters an unfortunate disconnection. After listening to your answer, I realized that pin1 and pin2 still need to cooperate, so I will follow them. Don't worry, pin6 is always in a low level state. I vaguely remember testing pin1 and pin2 with a multimeter before, and they both had no voltage, only a weak mv. Also, I just discovered an interesting phenomenon. If I touch both pin1 and pin2 of the LT1012 operational amplifier at the same time, the output port will display the frequency value I set correctly! And both LT1012 can

author: 晓看风云
author_rank: Contributor
timestamp: August 26, 2024, 08:35:10 pm
content: Quote from: fzabkar on August 26, 2024, 08:28:13 pmU18 is CD4052G, analog multiplexer. Please follow my latest reply. An interesting phenomenon... I have already put XL back on the circuit board because I tried another XL and they performed the same. I am a bit reluctant to believe that there may be as many as 8 faults on the circuit board at the same time.