Hardware

• Pi Model 3B  V1.2
• Raspberry Pi 4 Model B Dual Fans CNC Aluminum Alloy Case Metal 4 Color Armor Shell with Heat Sinks for Raspberry Pi 4B/3B+/3B
  
• T9 Fan Control Module / TCFan Raspberry Pi 4B 5V PWM Temperature Control Speed Contro
  

Python3 program

I have red a lot of pages how to control a fan using PWM signal.
Some of them:

• Raspberry Pi Frequency management and thermal control
• PWM Regulated Fan Based on CPU Temperature for Raspberry Pi : 4 Steps (with Pictures) - Instructables
• Smart Raspberry Pi CPU fan - Hackster.io
• Variable Speed Cooling Fan for Raspberry Pi using PWM (video#138) – SensorsIOT
• Fan Control for Raspberry Pi

Finally, it seems my fans don't have much effect on the temperature. About 5°C. So I decided to set an hysteresis:

• Switch ON fans if temperature > 75°C
• Switch OFF fans if temperature < 60°C
• Do nothing if 60°C <= temperature <= 75°C

Set linux service

Zacapa 23

Containing a blend of rums from 6 to 23 years old.

Keynote
Wonderfully intricate with honeyed butterscotch, spiced oak and raisined fruit, showcasing the complexity of the sistema solera ageing process.

Appearance
Light mahogany, with the tones of long barrel ageing at the rim and long, slow legs clinging to the glass.

Bolívar

The Cuban-produced Bolívar cigars are very full-bodied, with considerable ligero in the blend and have traditionally been some of the strongest and most full-bodied Havana cigars.

I have tried to use Wireguard following two guides :

1. From this forum thread, without succes: Guide: Install Wireguard On Raspberry latest releases
2. From this blog article, without succes as well: Installing and Configuring WireGuard on Raspberry Pi OS (August 2020)
   Updated (last with iptables): Installing and Configuring WireGuard on Raspberry Pi OS (September 2021)

This can be used as well to generate wireguard peers configurations + QR codes: Wireguard Tools

=> no successfull handshake between server (raspberry) and peers (Android and Windows 10).

Configuration

Server:

Peer 1:

Peer 2:

Troubleshooting

12/10/2020

UDP correctly forwarded

I verified UDP port was correctly forwarded by my ISP modem/router, following Test whether UDP port is open: simple UDP server and client

Server side:

Client side:

Checking if packets arrive to server

Listening on specific interface and on precise port of the server:

Here I tried two times to connect a peer to the server while pinging Wireguard server IP (192.168.99.1) from peer.

17/10/2020

Recording packets using tcpdump on both client and server sides

CLIENT: in a country potentially blocking VPN stuff
SERVER: in France, probably not blocking anything

I have generated another peer configuration. This time it is not a windows, not an android, but an openwrt router using same .
I have fixed the port in use for the wireguard client on openwrt in order to listen WAN interface on 51820.

What is observed on CLIENT openwrt side:

• Only first two captured packets were seen by SERVER side.
• These two captured packets are enough to declare successful handshake on CLIENT side.

What is observed on SERVER raspberry pi side:

• Only first two packets captured by CLIENT are seen as well on SERVER side.
• Handshake is not declared successful on SERVER side.
• Why SERVER is not seeing following packets ??? If I restart CLIENT, SERVER does not see packets for new handshake unless port used by CLIENT changes.
• Why SERVER is not seeing anything from this CLIENT packet: " 14:37:46.038821 IP 192.168.1.102.51820 > raspberry.abo.wanadoo.fr.58280: UDP, length 32 "

Trying to connect from local country

CLIENT: in a country potentially blocking VPN stuff Computer using Windows in France, probably not blocking anything
SERVER: in France, probably not blocking anything

=> It worked ! I conclude that wireguard is blocked in the country where the client is.

Interesting to read about how easy it is to block wireguard: Let's talk about obfuscation again

Try to simply update

It says the package is already at the newer version 0.11, but on github.com/matplotlib/mplfinance there is even newer.

Alternative that worked

Download the sources :

Unzip :

Go in unziped folder :

Install :

Done, should be good.

Source

Shell script that will check if there is connectivity to a defined website every 60 seconds and switch ON/OFF the led :

• /usr/bin/WANLED :

Check which LEDs are available and modify in above script if necessary:

If --tries option is not recognized, you may need to install proper wget. Check like this:

Schell script to autostart the above script :

• /etc/init.d/WANLED :

Now let's make these script executable and started at startup:

Now the orange LED should be ON when there is no connectivity to Google.

LEDs may be driven by other component. To be sure it is not, go to System > LED Configuration.
In my case it looks like this:

FYI OpenWRT in use was : OpenWrt 22.03.5, r20134-5f15225c1e

Source: LED, Start script at startup, LED on when Internet is available

Autoscroll every ms

Source 1, 2, 2

Autoscroll every ms

Si tu es né dans une cité HLM
Je te dédicace ce poème
En espérant qu'au fond de tes yeux ternes
Tu puisses y voir un petit brin d'herbe

Et les mans faut faire la part des choses
Il est grand temps de faire une pause
De troquer cette vie morose
Contre le parfum d'une rose

C'est l'hymne de nos campagnes
De nos rivières, de nos montagnes
De la vie man, du monde animal
Crie-le bien fort, use tes cordes vocales!

Pas de boulot, pas de diplômes
Partout la même odeur de zone
Plus rien n'agite tes neurones
Pas même le shit que tu mets dans tes cônes
Va voir ailleurs, rien ne te retient
Va vite faire quelque chose de tes mains
Ne te retourne pas ici tu n'as rien
Et sois le premier à chanter ce refrain

C'est l'hymne de nos campagnes
De nos rivières, de nos montagnes
De la vie man, du monde animal
Crie-le bien fort, use tes cordes vocales!

Assieds-toi près d'une rivière
Écoute le coulis de l'eau sur la terre
Dis-toi qu'au bout, hé! il y a la mer
Et que ça, ça n'a rien d'éphémère
Tu comprendras alors que tu n'es rien
Comme celui avant toi, comme celui qui vient
Que le liquide qui coule dans tes mains
Te servira à vivre jusqu'à demain matin!

C'est l'hymne de nos campagnes
De nos rivières, de nos montagnes
De la vie man, du monde animal
Crie-le bien fort, use tes cordes vocales!
Assieds-toi près d'un vieux chêne
Et compare le à la race humaine
L'oxygène et l'ombre qu'il t'amène
Mérite-t-il les coups de hache qui le saigne?
Lève la tête, regarde ces feuilles
Tu verras peut-être un écureuil
Qui te regarde de tout son orgueil
Sa maison est là, tu es sur le seuil

C'est l'hymne de nos campagnes
De nos rivières, de nos montagnes
De la vie man, du monde animal
Crie-le bien fort, use tes cordes vocales!
Crie-le bien fort, use tes cordes vocales!

Peut-être que je parle pour ne rien dire
Que quand tu m'écoutes tu as envie de rire
Mais si le béton est ton avenir
Dis-toi que c'est la forêt qui fait que tu respires
J'aimerais pour tous les animaux
Que tu captes le message de mes mots
Car un lopin de terre, une tige de roseau
Servira la croissance de tes marmots!
Servira la croissance de tes marmots!

C'est l'hymne de nos campagnes
De nos rivières, de nos montagnes
De la vie man, du monde animal
Crie-le bien fort, use tes cordes vocales!

C'est l'hymne de nos campagnes
De nos rivières, de nos montagnes
De la vie man, du monde animal
Crie-le bien fort, use tes cordes vocales, hey!

Source

Links

English

https://jestineyong.com/how-to-repair-amplifier-no-sound/
https://jestineyong.com/about-shorted-transistor/
https://audiokarma.org/forums/index.php?threads/blowing-a-power-transistor-root-cause.196876/
https://www.thegearpage.net/board/index.php?threads/what-causes-power-transistors-to-fail-solid-state-amps.945586/

French

https://www.pascalchour.fr/ressources/repar_ampli/repar_ampli.htm
http://jeanluc.rigal.free.fr/reparer_un_ampli_hi-fi.html
http://www.bedwani.ch/electro/ch14/index.htm
Réparation canal droit РОМАНТИКА 15у-120

Russian

https://forum.cxem.net/index.php?/topic/74746-романтика-15-120-с-hi-fi/
https://forum.cxem.net/index.php?/topic/117997-романтика-15-120-с-hi-fi-не-работает/
http://radiostorage.net/3225-usilitel-romantika-15u-120-50u-220-stereo.html
Методика ремонта транзисторного УМЗЧ - Аудиоаппаратура - Форум по радиоэлектронике
Files: Original RU or automatic translation EN

What happened

The amplifier is a Романтика 15-120С. It sounds quiet nice but sometime the sound gets no so clear either on right or left speaker.
To fast improve sound quality, I unpluged and replugged AUX input 3.5 jack. Dumb but done. One day it resulted on no more sound at all.

I quickly found dead fuse F3. I took one of the fuse of the other channel and F3 died again. Dumb but done.

I put 2 working fuse on left channel, and 2 dead fuse on right channel. Switched on the amplifier. Left channel is working. Good.

After reading internet, I quickly suspected that power transistor of the right channel were shorted. It was the case.

Test a transistor

How to test a TRANSISTOR with a multimeter PNP or NPN
How to check fuses, diodes, transistors, voltage regulators
3 Ways to Check Capacitors in Circuit with Meters & Testers

Troubleshooting (eyes+multimeter)

Le fusible FU3 de l'alim +27V cramé.
Les deux transistors de puissance VT3 et VT4 en cours-circuit.
 => +27V s'est vidé en quasi direct dans le -27V (R23 et R24 de 0.22ohm sur le chemin)
R15 et R20 cramées sur la carte principale.
R17 et R23 cramées sur la carte module de la voie droite.

Power transistors that were in service before the problem

Left channel (working), original ones:

• PNP: KT818BM
• NPN: KT819BM

Right channel (not working), not original ones:

• PNP: Toshiba A1941 (second link)
• NPN: Toshiba C5198 (second link)

Intervention

Remplacement des transistors
PNP A1941 => A1943
NPN C5198 => C5200
Les nouveaux sont un peu plus gros. Il me reste à les coller sur le radiateur (je n'ai pas pu reprendre les anciens mica).

Remplacement des résistances sur la carte principale
R15 et R20. J'ai mis des 1/4W en comparant visuellement...
Ces résistances servent à prévenir l'utilisateur qu'un certain niveau de puissance a été atteint à travers l'alimentation d'une LED.

Remplacement des résistance sur la carte module
R17 100 ohm je voulais mettre 1/4W mais le vendeur n'avait plus que du 2W.
R23 0.22 ohm. A la base la résistance avait une forme de ressort (j'imagine que ces résistance doivent avoir une petit propriété inductive ?). Le vendeur n'en avait pas. J'ai hésité entre 2W et 5W. J'ai mis une 2W de forme classique.

Power transistor replacing broken ones

• PNP: Toshiba A1943
• NPN: Toshiba C5200

Fixed!

Intervention 2 - January 2024

After first intervention the amplifier worked well for a while and then start to be unstable, with too much cracks on the right channel
It was then replaced by a small chinese amplifier. Романтика 15-120С  remained unused for about 3 years.
Then troubleshooting occured again in December 2023:

1. By swapping the the amplifier module boards, it was identified that the defective(s) componant(s) where on the module board.
2. Using multi-meter, VD1 was found faulty and replaced (but installed in the wrong way!).

Amplifier worked well for a day then started again to crack and even relay protection was triggered every few seconds due to this same right canal.

1. Comparing right and left modules using multimeter to measure each resistance and diode showed something different around VD1 VD2.
2. VD1 was put in the right way.

So far so good.

Intervention 3 - March 2024

Online Tone Generator - Free, Simple and Easy to Use.

The right speaker is working always good after intervention 2. But sometimes, the left channel is obvioulsy producing a lighter sound. I would say it is the case since I bought it.
By swapping the channels output from preamplifier, problem did not moved to the other side.
But for some reasons I checked preamplifier voltages vs. what is written on the schema:

I then swapped VT1 and VT2. The voltage values from left channel (top on the schema) exchanged with right chanel (bottom).
It didn't solve the problem but I will try to find a КП303Е transistor to get voltage in line with schematic (or not because sound is good anyway).

• КП303Е: аналог
  D - drain (сток)
  S - source (исток)
  G - gate (затвор)
• Транзистор полевой КП303 - DataSheet
• 2П303А, 2П303Б, 2П303В, 2П303Г, 2П303Д, 2П303Е, 2П303И, КП303А, КП303Б, КП303В, КП303Г, КП303Д, КП303Е, кКП303Ж, КП303И - Транзисторы кремниевые эпитаксиально-планарные полевые с затвором на основе p-n перехода и каналом n-тила - 2p303_kp303.pdf
• 2N5459R Datasheet Search

Sumup of operations:

• I swapped right and left chanel at several location:
  • Before the preamplifier
  • After the preamplifier / Before the amplifier
• I swapped КП303Е transistor (VT1 and VT2 on preamplifier board)
• I swapped right and left channel модуль ОУНЧ
• I swapped speakers

Problem always remained on the left channel.

Conclusion: it is due to some component on the last stage. Obvious old component : two power amplifier transistors and on old capacitor which is not on the way of the sound signals. Replaced.

Now need to listen music!

Intervention 4 - July 2024

So, intervention 3 didn't solve the issue with left channel to sometimes loosing sounds and strange noise when playing very low frequencies.
My conclusion above was : it is due to some component on the last stage.

So studying the schematics again I checked what it could be:

• Relay
• C1 capacitor
• Resistor R21 and R22

I changed the relay. Not better.
I swapped C1 with C4 of the right channel. Not better.

I was disapointed and checked again the schematic. Then I saw the signal was going to the headphones plug before going to speakers. I decided it won't go there anymore.

So far so good. One bonus difference I noticed, phones frequency are not audible anymore (before a call or when receiving a SMS). Now need to listen music!

Futur intervention : fixing balance potentiometer СП3-33-22 68к

• СП3 33 конструкция ремонт восстановление
• СП3-33-22 М1ОМ Разбор Чистка Сбор
• Резисторы СП3-33-23 33кОм, 47кОм в Вега 10У120С и не только. И была ли смазка в резисторах на контактах изначально? — Сообщество «Клуб Почитателей Кассетных Магнитофонов» на DRIVE2

In the futur : to make new PCB or use chinese made amplifier boards

https://www.pcbway.com/
Maybe i could use stuff like this to repair last stage: Amplifier Board - AIYIMA A2D847

Install Munin

https://angristan.fr/monitorer-serveur-linux-munin/

Make a new pluggin

Then need to make it execuable :

Test it as munin user :

If you get that :

Somehow you will need to add munin user in the video group :

Or maybe that was that helped :

Then it will work :

Restart what is necessary :

Source : http://guide.munin-monitoring.org/en/latest/develop/plugins/howto-write-plugins.html

Préparer la pâte à crêpes : basé sur cette recette

Pour 15 crêpes :

• 300g de farine (=714mL mais j'ai mis seulement 600mL)
• 3 oeufs entiers
• 3 cuillères à soupe de sucre
• 2 cuillères à soupe d'huile
• 50g de beurre fondu
• 60cl de lait
• 5cl de rhum

Recettes :

1. Mettre la farine dans une terrine et former un puits.
2. Y déposer les oeufs entiers, le sucre, l'huile et le beurre.
3. Mélanger délicatement avec un fouet en ajoutant au fur et à mesure le lait. La pâte ainsi obtenue doit avoir une consistance d'un liquide légèrement épais.
4. Parfumer de rhum.
5. Faire chauffer une poêle antiadhésive et la huiler très légèrement. Y verser une louche de pâte, la répartir dans la poêle puis attendre qu'elle soit cuite d'un côté avant de la retourner. Cuire ainsi toutes les crêpes à feu doux.

Alternative :

• 250g de farine
• 500mL de lait
• 3 oeufs

1. Mélanger les oeufs
2. Rajouter la farine
3. Puis le lait  petit à petit