HarryA

At 3 seconds pulsing you could see that with a multimeter. I would start at the output of U2 looking for pulses; if so look at its input and likewise back to U1 and U2 outputs and inputs. The op amps U1 - U3 (TL081) are short circuit protected. "When shutdown occurs and less power is dissipated, the circuit cools as desired. The shutdown circuit is then disengaged and the circuit heats up. Again shutdown occurs and so forth."

Do you have a better schematic? It's hard to read this one. Can you reference where you got the schematic or the kit?

Q: Can the module amplify square wave or pulse? What is the module bandwidth? A: The module can amplify low-frequency square waves or pulses. Because it is an audio amplifier, the total bandwidth is not high. Signals within 100K can be amplified. The module is compatible with DC input. This is the over priced one with best Q/A https://www.amazon.com/operational-amplifier-current-continuous-voltage/dp/B07D8V1YBG/ref=sr_1_18?dchild=1&keywords=opa548&link_code=qs&qid=1605968887&sourceid=Mozilla-search&sr=8-18&tag=mozilla-20 The best price is 57.80$ Amazon.com - actually it's 35.60$ plus 5$ s/h on Ebay

The OPA548 op amp looks promising. It has up to 5 amperes output into 4 ohms or better. It can be bought in a complete amplifier see OPA348 on Ebay or Amazon.com just search for OPA548. The data sheet is here: https://www.ti.com/lit/ds/symlink/opa548.pdf As the amp can be used in a dc pwoer supply makes it look useful. If you have an Amazon account you can ask about the complete amplifier low frequency range else I can.

See the LM3886T at: https://www.alldatasheet.com/datasheet-pdf/pdf/8893/NSC/LM3886T.html?link=https%3A%2F%2Fwww.alldatasheet.com%2Fdatasheet-pdf%2Fpdf%2F8893%2FNSC%2FLM3886T.html It has a sample circuit with no capacitors in the pdf file. Also this amp board maybe useful, what ever "Pure DC Mono Power AMP Amplifier Board" means. It uses the LM3886T chip also: https://www.ebay.com/itm/LM3886T-x3-Parallel-150W-4-8-Assembly-Pure-DC-Mono-Power-AMP-Amplifier-Board/113895598886?_trkparms=aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D225086%26meid%3D999c10d87a084a45a12ccb2f6e019c74%26pid%3D100005%26rk%3D2%26rkt%3D12%26mehot%3Dco%26sd%3D113918167015%26itm%3D113895598886%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv5PairwiseWebWithBBEV2bDemotionHighArwV3%26brand%3DUnbranded&_trksid=p2047675.c100005.m1851

I am not to sure what your question is. Are you asking can IC by its self, not in a package, be connected to a circuit on a PCB? Yes but it would need power and ground, etc connections also. An IC in a package like a DIP can. For example in the CDI (capacitor discharge ignition) circuit,that I am currently working on, the optoisolator (yellow) has the transistor directly connected to another device (MOSFET) on a another PCB.

Also sounding proofing outside going doors and windows with heavy fabric is said to help. Plus having sound absorbing rugs and wall hangs reduces the unwelcomed sounds. I see one cannot edit previous postings.

Some years ago there was research on noise suppression by picking up a noise and playing it back 180 degrees out of phase. If you played a sound through two speakers connected out of phase, that is so when one cone came out while the other went in, would they tend to cancel? Thus creating a small cone of silence.

My guess would be that D!! and C7 are to suppress superfluous outputs on at the power outputs. D10 is part of the biasing for Q2 transistor? Member audioguru is far more knowledgeable of this circuit than I; hopefully he will come by and give an expert input.

I see little or no difference using Firefox, Opera, or Edge. I am thinking that it is my monitor. Watching to many "Extra History" videos on YouTube.com is wearing out the pixels 📺 Thanks for trying.

The font: "The font:" above is much lighter than the uploaded example. I could not see how to continue with the next image so I am here. I am using an HP x20LED; I can not get to the model number. Lets see what others say. For login one does not see the "Display Name" nor the "password" text. Perhaps removing the dead space above it would help?

Is it me or is the forum running out of toner? The font seems to be getting lighter over time. I can not adjust the browser to improve it. Also at login there is no physical response; the login area is down below the screen so one thinks nothing happened. Just trying to be helpful 😀

Although it is for the Arduino there is a library plus others here that maybe helpful for you to look over: https://github.com/deskwizard/TDA7418_arduino scroll down to see the implemented functions.

What are you connecting the PCF8575 to? You most likely need to include some type of library.

You can find some information on the sleeve balum that maybe helpful here: https://en.wikipedia.org/wiki/Dipole_antenna

I would think you need a power supply that is USB C compatible and supplies 15 volts like this one perhaps: https://www.amazon.com/ZMI-zPower-Turbo-Power-Adapter/dp/B07D64QLQ1/ref=sxin_10?ascsubtag=amzn1.osa.36fe220c-4964-4c9f-ae33-99b6c0c7c1df.ATVPDKIKX0DER.en_US&creativeASIN=B07D64QLQ1&crid=22R39DEACHL6V&cv_ct_cx=usb+c+wall+charger&cv_ct_id=amzn1.osa.36fe220c-4964-4c9f-ae33-99b6c0c7c1df.ATVPDKIKX0DER.en_US&cv_ct_pg=search&cv_ct_wn=osp-single-source-gl-ranking&dchild=1&keywords=usb+c+wall+charger&linkCode=oas&pd_rd_i=B07D64QLQ1&pd_rd_r=469feb9c-4fd4-4a62-9cee-bd7d3d9bc4b1&pd_rd_w=XpVfQ&pd_rd_wg=6mOQo&pf_rd_p=26c7e498-3189-4918-a321-ec25e32964ce&pf_rd_r=M6B5K23BD7AP9JZRKZ2Q&qid=1602096804&sprefix=USB+-C+charger%2Caps%2C234&sr=1-1-d9dc7690-f7e1-44eb-ad06-aebbef559a37&tag=thewire06oa-20 Plus a charger that has connections for balenced charging: https://www.amazon.com/11-1V-Balance-Lithium-Battery-Protection/dp/B07JMY631D/ref=sr_1_27?dchild=1&keywords=balanced+li+ion+3s+charger&qid=1602101378&sr=8-27 You can program the ZY12PDN to default to 15 volts instead of 5 volts. https://www.youtube.com/watch?v=aIHj3qMRqqE I never found a ZY12PDN datasheet.

I would disconnect one end of R35 and see if that fixes the problem or just replace it. It maybe breaking down under the higher voltage?

https://www.manualslib.com/manual/119606/Panasonic-Sc-Dm3.html#manual

If you compare your board with the one on Ebay that one looks like the better board. You may gain some insight by comparing the P6? on your board with the three in the schematic and see if it connects the same as one of them. This is the schematic of the Viber12a in a battery charger.

There are used Cherokee International power supplies on ebay.com if that is any help.

Yes, you are not the only one with that problem! See the circuit here: https://www.ebay.com/itm/Polk-Audio-DSW-PRO-500-Subwoofer-Amp-Plate-Not-Working-For-Parts-Repair/184441091699?hash=item2af18bb673:g:2~QAAOSwEkxfWY2A I was thinking you could get the correct parts from that one but no such good luck.

The eight leaded DIP is a " Low power offline switched-mode power supply primary switcher" see: file:///C:/Users/harry/AppData/Local/Temp/viper12a-e.pdf The larger diode P6? maybe a protection diode to protect from over-voltage. The two smaller diodes most likely are rectifiers used as part of the power supply. The question is what caused the fault that damaged the components. You need to investigate that before replacing the components else they may just blowout again. Try drawing out that part of the circuit to get insight into the circuit.

see: https://www.nteinc.com/semiconductors/ComplPr.php They list matched complementary pairs that maybe helpful like the NTE128/NTE129 at 80 volts and 1 ampere. And many others as well.

There is an article "Design Project2 - BCD Calculator" that maybe helpful. http://homepages.cae.wisc.edu/~ece352/fall02/old_project/p2.pdf

Hunter College has a course in electronics that is online. That maybe helpful: Lessons are ElectronicsLab1.pdf through ElectronicsLab15.pdf http://www.hunter.cuny.edu/physics/courses/physics222/repository/files/pdf/ "Practical Electronics for Inventors" by Scherz and Monk is a very good book by not cheap.