Electret Microphones 101

[@fizzyplazmuh9024]

I found a fun thing about the condenser/FET mics recently. I had a suspicion about how sensitive they might be. I removed the felt cover and wired the mic to one of those little super hearing amplifiers Radio Shack used to sell. I then placed the Am²⁴¹ pellet from a smoke detector face down on the mic. Once you get the mind shattering feedback under control you can hear the gentle patter of raindrops. Those are helium nuclei hitting the mic at about 6% the speed of light. I was amazed the mic was that good and the alpha particles were that heavy. I am hooking it to my oscilloscope to examine the pulses if I get time tonight.

[@alexandrevaliquette1941]

Is it destructive for the mic membrane? Is there a way to make a ultra cheap Geiger counter?

[@codyswanson8481]

What are you hearing? Especially with that high gain. I'd like to know how you know or figure that assumption. Man that could be anything like frequencies from a radio on a ship. You've got to filter that out until you can tell exactly what that is. But would definitely like to hear more back.

[@thisisyourcaptainspeaking2259]

Feedback, as in audio output signal not isolated from electret?

[@TechnologyRules]

3:46 That's a steady hand right there. I could swear it was a picture until you touched the breadboard

[@ahndeux]

His other side job is a hand model for breadboard circuits.

[@rowdyriemer]

That same chip is used in some distortion/overdrive guitar pedals. I've used a couple discreet complementary power mosfets in a midpoint-biased CMOS inverter configuration using a pot with the wiper on the gate, one terminal on the drains, and the other as an input. I could control the volume by turning the pot to vary the feedback, and this setup allowed for much less than unity gain all the way to 0 gain. It was mostly an interesting experiment, but it also made for a nice low-power guitar amp that you could overdrive with nice-enough clipping.

[@donwazu]

This was great, I was fixing an intercom system and wondered how these little guys worked

[@bigbread9000000]

you have some of the most useful and interesting electronic video's on youtube

[@0033mer]

Thanks for the feedback!

[@zachreyhelmberger894]

Nice work! Never heard of using digital logic chips as op-amps! That is pretty cool!

[@0033mer]

When RCA introduced the 4000 series CMOS logic family, using it in linear mode was quite common especially the unbuffered version. kzbin.info/www/bejne/hZCTdICOg82ZgKs

[@9VDC]

Very helpful, thanks for your crystal-clear explanations

[@0033mer]

Glad it was helpful!

[@douglasstrother6584]

Problem 3-13 in "Electromagnetic Fields and Waves" (2nd edition) by Lorrain & Corson deals with a microphone having an electret diaphragm. (The 3rd ed. has a completely different layout.)

[@Electronzap]

Inverters passed the signal a lot better than I thought they would.

[@placedubert]

You explained it very clear. I learned something.

[@mohamedabdalla6479]

Thank you very much for the videos. I appreciate your video and times you spent making these videos. 👍💯

[@0033mer]

So nice of you. Thanks for the feedback.

[@rabbibacongrease88]

How hard is it to identify an Electret characteristics to determine manufacturer and part number?

[@reverend11-dmeow89]

ah, at last, Someone making sense from the 2- vs. 3-pin electret-condenser mic capsule choice decision-making process. it isn't the FET that is inside or not, but the resistor? But where is the resistor in the 3-pin? for current-limiting, is it? Thank You Maestro!

[@ronparker6489]

As good as it gets, me thinks. Thanks for letting us know how these guys work.

[@0033mer]

You're welcome.

[@stevepethel6843]

You are brilliant...God bless you for posting giving.a great video

[@0033mer]

Thank you so much for the feedback.

[@JongyunLeon]

Thanks for your video. Would you help me? What do I need if I put two electric mic? Do I need some resisters in each mic?

[@CrazyCoupleDIY]

Thank you very much for the very detailed explanation

[@0033mer]

You are welcome!

[@bertthefirst26]

How this microphone will sound with tube buffer?

[@JohnDaniels]

Can these be made into stereo and used with USB-C on a android smartphone? I would like to make a mic that looks like the Sony ECMLV1 and Olympus ME-51S but has the EM272 and USB-C connection where you can just plug it onto your phone and then record video with a nice enhanced mic for lots of ambient pickup, is this possible?

[@ronhummel9298]

I have a 3 lead electret element that I want to use with a phantom power audio interface. I simply used the center lead on the element to positive, and one of the casing leads to the negative, then plugged the cable into the audio interface? I'm not hearing anything when I did this...what am I doing wrong? Thanks!

[@Raaddller]

Can you make a pressure cooker whistle counter? It would be a hit in India. Better still if you can make an app.

[@0033mer]

You could make this work: kzbin.info/www/bejne/hKjZdoKBqauefK8

[@user-mr3mf8lo7y]

Awesome video. Much appreciated.

[@0033mer]

Glad it was helpful!

[@avp.69]

Hello, thanks for the quality content. I have a question - how does the size effect its performance? Some are thicker than the others and similiarly some larger im diameter. What effect does diameter and thickness have?

[@0033mer]

Electret mics are made in a variety of sizes basically so engineers can find the best one to fit their product. The larger the diameter the more sensitive and broader bandwidth. The thickness depends on the size of the FET that has to fit into the enclosure, so it depends on how small they can make the PCB.

[@roughneckchris]

Could I just wire one of these to a guitar jack, and then run an instrumental cable to a pre amp or direct box that has Phantom Power ?

[@ConorFenlon]

Definitely not. Phantom power is 48V. Electrets only need like 3.3V. Phantom power would absolutely fry one of these things.

[@Cornflakes691]

Do you NEED the 1k resistor? Can you provide the mic with 3v directly without the resistor?

[@lasersbee]

Excellent Tutorial as usual....

[@BADALICE]

That was very helpful, thank you. I like that room monitor.

[@0033mer]

Here is a similar device you can build: kzbin.info/www/bejne/Zquwnmiqm5mYr8U

[@bobvincent5921]

Thanks , I appreciate these Refresher courses you run.

[@HumbleIdeas]

What is the advantage or disadvantages for two pin and three pin ECM?

[@0504328]

This video is timely. I need your input if you don't mind. I have a Chinese copy mic from Icom model HM-36. I need it to sound more natural and with a good gain. Which one should I use the 2 pin or 3 pin or you have a better option. Thanks in advance.

[@0033mer]

The 3 pin version was originally made by Radio Shack as a replacement for their CB radio mics, but are hard to find. If you take apart the HM-36 mic check for a pop filter cloth placed across the electret cartridge and remove it. This will improve your audio.

[@amitghosh6966]

If I use 2 pin mic & opamp like Lm358 or Lm741, why the output is not very strong?

[@factsheet]

Hi. Just a newbie when it comes to electronics. Just want to know if I can improve an existing headset mic by using a max9814. Thank you!

[@reepeez]

My aviation headset has a faulty microphone, its an 80ohm passive speaker (2 terminals), can I straight swap that with a 2 terminal electric mic?

[@wolfgangsnitsar4739]

Can you post or make a video of how to make and hook up a circuit you mentioned that allows you to monitor a room or floor from the telephone system please.

[@0033mer]

This video might help: kzbin.info/www/bejne/qaWodqCJppminKM

[@DrVektor]

ah this is what i was looking for, this video is so helpful

[@0033mer]

Glad it was helpful!

[@jjjames5089]

I have a Roland/boss br600 one of my inter micro condenser mics has failed. I cannot locate any numbers to find a replacement. Roland offered no help. Any ideas on finding a replacement.

[@0033mer]

Check out the selection at Digi-key and match it to the original. www.digikey.ca/en/ptm/c/cui-inc/electret-condenser-microphones

[@gariantroll2975]

Can this setup hear from 1 - 2hz?

[@serdavosseaworth6115]

Hello, is it possible to join a 2 wire electret to a 3 wire electret? I have a 2 wire mic but my headset takes a 3 wire plug. Is this possible? My understanding of this isn’t that great, thanks.

[@0033mer]

The headset is also wired to the 3 wire plug.

[@Rivecha]

Hey man. How were you able to connect the oscilloscope to the microphone circuit? Sorry if this is a bad question but I'm a total beginner at this and I'm actually doing something similar for a project, so any help would be appreciated!

[@0033mer]

The scope is connected between the "output" point and ground. Ground on the amplifier circuit is pin 7 on the CD4069. You can also use an opAmp circuit. Check out this video: kzbin.info/www/bejne/h5TCmaGdmNakbaM

[@Rivecha]

Thank You! My project is on generating electricity from sound. In short, I am not attempting to conserve the information in the energy from the mic, I just want the energy. Is there a way to power a small condenser mic without external power, and if so, have the output of power greater than the input?

[@0033mer]

No, electret and condenser mics need an external power source. Dynamic mics produce their own output signal which is very low.

[@Rivecha]

Yeah. I've been thinking of using Piezoelectric buzzers instead, which produce electrical energy from vibrations of sound and don't require external power. Thank you for the help!

[@ExcelComputerInstitute]

to the point explanation ... really appreciate your effort. Thanks

[@0033mer]

You are most welcome

[@johnmacleanmotorcycling9795]

Great video. Thanks for your help.

[@0033mer]

You're welcome

[@mickeymouse5267]

How small can electret microphones be constructed? Who makes them?

[@ghanshyamkashivale2019]

What will be the output current from an electret microphone ? If we give in 0.5mA?

[@haujetzhao225]

Another question: I have a recorder which provides 1.5V on it's 3.5mm jack, and then I have a ECM capsule which require 5V to get the optimum performance, how could I change the 3.5mm wire to power the ECM with 5V with an external battery? Would you mind giving a suggestion?

[@toileon]

I have a 3.7 battery case with a negative and positive wire how do I make mine work ?

[@DuroLabs85]

Hi Nice project loved the idea of logic gate amplifier !! I've one question how to calculate the Load resistor for a 2 pin Electret Microphone like I've couple of those which I bought from an Offline store so I dont have a datasheet for them

[@0033mer]

If you are powering the mic from 3 to 10 volts a 2.2k resistor should work. Generally the operating voltage is around 3 volts with a current draw of .5 mA. If you know the specs RL = VCC - Operating voltage / .5 mA

[@DuroLabs85]

@@0033mer Oh Thank You :D

[@terykwan]

I want to buy this, electret consider

[@percetakaneduartdesign3209]

please help me sir .. im from Indonesia if mic condenser mark toa zm 360 replace condenser panasonic wm 61a is according to specs whether or can't function

[@jonahvimeo4276]

thanks, very goooooood explained

[@0033mer]

You are welcome!

[@grantcreasey8003]

Hi, great video, really helpful. I wonder if you could help further with a modification I am trying to make. I have a pcb which is a dmx controller for dmx lights. The pcb has a two wire ecm mounted directly on the board, such that the controller can detect sound and sequence the lights to the music. I would like to improve this: A- relocated the ecm via wires off the board such that the ecm can be placed in front of the speakers for a more direct sound recognition. B- replace the ecm with a jack plug such that I can connect a line out from the sound mixer directly to the pcb of the dmx controller. Option A is obvious but messy (though may have issues with the extra impedance of the wires?) Option B is preferred but I don’t know/understand if you can directly replace the ecm with a line out signal? Perhaps a resistor would be needed? Would I use a true line out, or a head phones output from the sound mixer? Does it make a difference? Can I mod the circuit such that it could take any kind of 3.5mm jack signal?!? Given I’m just looking to detect the beat, the actual quality of the measured sound signal is not that important. I’d love your thoughts/help on this? Thanks GC Ps I note that you gave an answer to anon yomous ten months ago on option A and suggested coax (great idea as I was worried about interference), but still wonder if option b could be achieved?

[@0033mer]

You need a line to mic interface which is an audio attenuator with DC blocking capacitor. Check out this video for construction details. You might have to change the 330 ohm resistor to a higher value for your optimum desired level. kzbin.info/www/bejne/l6DZpXqrlNV6atk

[@grantcreasey8003]

@@0033mer thank you ever so much, I’ll give it a go and see how I get on. People like me (ie the people on these comments) are very grateful that you take the time to help us out. Thanks very much, it’s really appreciated!

[@0033mer]

@@grantcreasey8003 You're welcome!

[@sunilamin3031]

@@0033mer can i use this microphone as a replacement of shure beta 98h /c saxophone mic replacement part"superdiode condenser rpm 110

[@sunilamin3031]

@@0033mer shure beta 98h/c saxophone mic not working condenser problem can you please give me a solution on this can i replace it with electret microphone with some modifications will it work please reply Waiting for your reply Thanks

[@mumbaichaking3192]

Can u help me customised 1 spk and 1 mic headphone.

[@ska757]

Would you know if it is necessary to replace one of these electret microphones with the same exact type or will any type perform equally well. Why I ask is because the replacement I am looking for is CZ034 and I am not getting much luck finding that type. It is for an analog guitar tuner that I am trying to fix. Any suggestions would be appreciated . Thanks.

[@0033mer]

Electret mic specifications are pretty similar unless it is for a specific custom application. Any general purpose mic that fits your enclosure should work. Here is the spec for your mic: www.goodsourcing.com/main/exec/more/mod/pdts/pid/b153025ea1dzuzq4 Search for electret mics online at Digikey.

[@ska757]

@@0033mer Thanks for the information and your swift reply. Is there a test that can be done using a multimeter to test these microphones. I have another electret mic that I have but it has no written information on it and I cannot remember what I removed it from. Prior to this , I never worked with these before. If not I will do as you suggested in your response.

[@0033mer]

The best way to test the mic is to build the simple circuit shown in the video and hook it up to a scope to monitor the output signal.

[@Gadgetronicx]

Great explanation :)

[@saloom_5622]

explain how op-amp amplifies information signal and cancels noise.???

[@JeanIbarz]

Hi, I'm trying to use a 2pin electret microphone to make audio measurements. I directly connected it to the mic sound card, but I get 50hz power supply noise. I also tried to power it with circuit like the one shown in your video (one resistor + one capacitor), but I get the same 50hz noise coming from the power supply or the ground. Is there an easy way to get rid of it ? like buying a pcb board already made by some experts ? I am not able to find any... Thank you !

[@0033mer]

Sounds like you have a ground problem. Easiest solution would be an USB mic. www.banggood.com/1_5m-USB-Lapel-Collar-Microphone-Omnidirectional-Mic-with-Sound-Card-for-PC-Computer-Mobile-Phones-for-KZbin-Live-Broadcast-p-1605071.html?rmmds=search&cur_warehouse=CN

[@crostofor]

cool stuff:)

[@zainmubarak8679]

Thank you sir .... i really needed this

[@nabilrise1551]

I see that you're active in the comments, so I'll ask you here: I'm looking for an analog circuit like this to use to activate a microcontroller from deep sleep mode. The thing is, the activation circuit needs to consume little power when idle as it will be on all the time(the whole system is battery operated). So my question is: do you think this circuit is the best way to accomplish the task I described above or do you think there is a better way to do that? If you have any ideas that may help, please just give me keywords and I can look them up. Thanks

[@0033mer]

There are a few ways to bring a microcontroller out of deep sleep. You can use an internal interrupt like a timer overflow or with a watchdog timer. An external interrupt can also be used by simply pulling a GPIO pin low. A mosfet transistor like a 2n7000 can be used to pull a GPIO pin low when a wakeup trigger voltage appears on the gate. kzbin.info/www/bejne/iJ6XoYSQgqeIjaM

[@juanmanrique4395]

Hello sir, do you know where I can find that exact 3 pin microphone. I’m Looking for that model for a project. I can’t find it on the internet and that ECM is very useful for what I need it to do.

[@0033mer]

They were made for Radio Shack as the mic replacement for their CB radio handsets so they are hard to find. Check Ebay. www.ebay.ca/itm/3-NOS-Archer-Radio-Shack-Microphone-Electret-Condenser-Elements-600-ohms-CB-Ham/362937629741?epid=1023837363&hash=item5480c4bc2d:g:1IcAAOSwu1deZABk

[@juanmanrique4395]

Ty, another question. If you add an extra inverter to the circuit, would the output be more amplified or is it too much. To detect a medium to low sound when other sounds are happening as well

[@0033mer]

More gain stages will mean more noise in the output signal. An increase in sensitivity not gain is needed. Check mic specs for best sensitivity.

[@juanmanrique4395]

Do you think this microphone has a vdd a ground and an output pin like the one in your example. It’s listed on eBay but it does not contain a pin-out guide or any type of guide and it’s terminals look so different www.ebay.com/itm/Electret-Condenser-Microphone-with-Dustscreen-and-3-Pins-10-mm-3-to-15-V-DC-/271353125841

[@juanmanrique4395]

It’s terrible because with no guide on how to use, I was hoping someone is familiar with this specific element

[@solotudemusic6337]

Howsit bud, I wanted to make a mic to connect to phone to produce much better audio quality for my scratch track videos/song writing and had infact a few weeks ago bought the exact same looking mic as your 2 pin one in the video a few weeks back, only now had time to get into sourcing info and amping circuits etc, j don't know much at all about the inner workings of different mics to be honest but being a multi instrumentalist and having studied electrical and having done electrical sorts of hobbies turned profession as I own and operate a electrical (residential & commercial) installation and maintenance business I thought I'd give it a go, just one question though, will this mic render a much better audio quality than a regular cellphone or cellphone headset microphone? I will reply again with the model number of the one I have, I'm sure it's exactly the same as the 2 pin, quite a bit larger than that of a regular ear phone headset microphone, I want to "condense" the sound more, eliminate ambient sounds and just regular likely sounds that would disturb a recording.. obviously I am aware I am not going to get nearly the same effect as being in a glass booth at a music studio, just want better clarity than the phones mic itself.. you recon it's the one to do the job yeah?

[@zofmod]

hi buddy nice project, this is along the lines of what i need to do or what i need for my project as i'm using speech rec and want to be able to hear my voice anywhere acrossmy house, i want to use multiple micro phones as well, would it be possible to shrink the project and maintain the high sensitivity pick up from the mic ? im new to mic but want to fast track on my project would you be interested in building what i need if i pay for it ? as it will save me time, let me know either way buddy thanks again and nice work

[@0033mer]

It would be faster and cheaper to get off the shelf mic amp modules. Check out these sites: www.canakit.com/electret-microphone-pre-amp-kit-ck495-uk495.html www.banggood.com/CJMCU-4466-MAX4466-Electret-Microphone-Adjustable-Amplifier-CMA-4544PF-W-For-Arduino-p-1101527.html?rmmds=search&cur_warehouse=CN

[@dianace2000]

which is the maximum output voltage?

[@leacender]

can you tell me what different when different capacitances have the same capacitance?im wondering why you using different kind of capacitances.

[@0033mer]

The capacitors determine the frequency response of the circuit. The source impedance driving the input and the output load impedance work with the capacitors to form RC filters.

[@awesome7732]

Earned a subscriber

[@JaysonReis]

Does anyone know some content that explains why you need a load resistor and the capacitor on the output?

[@macgyver5108]

From what I understand... The mic pickup element is a type of capacitor, one of the capacitor plates is a flexible diaphragm that holds a permanent charge. When it flexes from sounds it causes a voltage change in the capacitance as a voltage signal. That signal then goes into the transistor gate and out one leg to the resistor and capacitor, but the transistor acts as a transducer turning that "voltage" impulse into a "current" signal at a fixed voltage. The resistor turns that current signal back to a voltage signal (and I believe it also acts as a high pass filter) to turn into sound, the capacitor is used for both AC coupling and to block DC current, also acting as a filter. Also the industry standard for the resistor is typically 2k Ohm, if you increase that resistance to say 4k-20k Ohms with either a higher value resistor or even add a variable resistor in series it increases the audio gain too.

[@JaysonReis]

@@macgyver5108 and when you say signal, is it the frequency in which the voltage alternates between positive and negative? I think that there is still a lot for me to unwrap from your answer, but many thanks!

[@macgyver5108]

@@JaysonReis there is a change in the amount of voltage. So the nominal voltage of 5.0v without any sound input will bounce higher or lower than that fixed voltage according to the frequency.

[@inconspicuous-nobody]

Is there any easy way to get a PCB mounted mic out of the PCB and on a long wire that's mobile? I wanted to move it closer to the sound source, but results were disappointingly bad instead of better. (My entire knowledge of mics is this video, and I'd be lying if I said it all makes sense to me. If anybody here has a spare moment, I'd be very thankful.)

[@0033mer]

Using wires to connect the mic will act as an antenna and pick up a lot of noise. Use shielded coax cable like RG174. Hook up is polarity sensitive as power is also fed down the coax cable. Ensure the shield is connected to the ground of the mic.

[@inconspicuous-nobody]

@@0033mer Wow, thank you so much! That's brilliant!

[@lowellcamp3267]

Where can one find 3-pin condensers? I've been searching all over, but haven't found any.

[@0033mer]

They are hard to find. Radio Shack original sold them as a replacement part for CB radio hand microphones. A quick solution is the mic from Adafruit with an onboard amplifier. www.adafruit.com/product/1063?gclid=EAIaIQobChMIt56Nlb_u3wIVlh-tBh3OXgqzEAAYAiAAEgKs6fD_BwE

[@yatharthacademy1920]

Brother, what is the table on which you have laid something like a graph?

[@0033mer]

It is a cutting mat. www.staples.com/Olfa-Gridded-Cutting-Mat-18-X24/product_291995

[@yatharthacademy1920]

0033mer thanks brother

[@admniyeokuyorsun...3044]

Can we use a 2 pin electret microphone as a speaker ?

[@0033mer]

No.

[@ChrisLBradly]

if you cannot identify the polarity on the two wire mic and wire it up in reverse what will happen ?

[@RXSVN_2]

You'll get electrocuted.

[@TheRandomINFJ]

Thank you. I found one inside my vape. Weird!

[@Akari-rn7pk]

Please build a low noise opamp for this or link me up to a resource with circuit diagram for opamp with a 3.5mm female output

[@0033mer]

Check out the MAX9814 from Maxim. Adafruit has a breakout board. www.adafruit.com/product/1713

[@bambang8060]

can we just line the mic and 1.5v battery in series? will it work?

[@Miles-co5xm]

Yes but will not amplify

[@drdra]

Hello! Is there a possibility to make this circuit work on 12V?

[@0033mer]

Yes, change the external load resistor for the electret mic ( pull up ) to 8.2k ohms.

[@sukshithshetty4847]

0033mer how did you calculate thr required sensitivity resistance for the supply . I am using 9v so what must be the pull up resistance??

[@stolevole]

@@0033mer Thanks! I'm trying to light up 3W led diode with this, I have connected IRLZ24N mosfet to your circuit (and a simple diode before it) and it works really nice, but sometimes it powers up with diode lit up to the max. Everything is battery powered. Can you help me with this?

[@0033mer]

Try putting a 10k resistor from gate to ground (source).

[@stolevole]

ok, I'll try!@@0033mer

[@vishnueroor]

Can you provide complete circuit of room monitor

[@0033mer]

This video should give you enough information to build your own room monitor. kzbin.info/www/bejne/qaWodqCJppminKM

[@sirthatisoneverylongname]

Maybe it's cuz I'm new to all this but I'm even more confused

[@taboosaboo]

There should only be one cord. #StaticVoltage #Electret

[@saloom_5622]

In some electret condenser microphone, amplifier is not included. [ True /False ]

[@enzocalzone5298]

False, the signal would be way too weak for your standard device to be able to use it without amplification

[@hubercats]

Thank you!

[@0033mer]

You're welcome!

[@asilva781]

Thanks a lot.

[@Ramon-ei5bc]

so basically you can use an inverter as an amp

[@0033mer]

Yes .. when configured in linear mode.

[@phasorsystems6873]

Hello could you test this software? inspect androidcircuitsolver on google!

[@SureshSuresh-ii5mp]

Many times i make this mic but not work so pls kindly send me exact materials and material names sa soon sa possible

[@0033mer]

You can always resort to the common op Amp driven microphone preamplifier. Here is a complete document that can help you out. www.ti.com/lit/ug/tidu765/tidu765.pdf

[@sukshithshetty4847]

Should the ac coupling capacitor be only from 3 uf to 10uf or can it be more

[@0033mer]

It can be more. The value of capacitance and the impedance of the circuit you are driving form an RC filter which will determine your frequency response.

[@sukshithshetty4847]

0033mer i am designing a electronic stethescope and taking the input of heartbeats through a electret mic and passing it on to a preamplifier made of TL072 opamp. In between TL072 and mic i have a resistor of 2.2 k nd capacitor ( value not decided). The heart beat frequency ranges from 20 to 300 Hz . The input resistance of TL072 is 10^12 ohms. Now how should i decided the value of capacitor. ???

[@0033mer]

You can use an RC filter calculator. www.v-cap.com/coupling-capacitor-calculator.php

[@sukshithshetty4847]

0033mer should i design a filter for 3 db cutoff or optimized frequency ?? I am confused

[@michaelberna987]

Bugged his own phone line. Putting some poor NSA worker out of a job.

[@stanTrX]

Pro!

[@Ruben.11113]

Styx

[@N5LRZ]

On the schematic section please remove that d*** pencil so we can see all the details.