Is DENON AVR Model X-500 Prone To Fungus Attacks And Rusting?

Those of you who have read my previous articles on servicing same model might know the reason for my question. For those who have not, here are the links, Case 1, Case 2 and Case 3:

Case (1) https://jestineyong.com/protection-mode-in-denon-avr-x500-solved/

Case (2) https://jestineyong.com/return-of-denon-avr-x500-in-dead-condition/

Case (3) https://jestineyong.com/third-visit-of-complaint-monger-denon-avr-x500/

I received the same model from a different customer living in my home town with the complaint that it just blinks after switching on, which the customer also knew was a protection mode.

I am only giving the image of the model number plate, to show that it is a different set with a different serial number. I am skipping insertion of other images of inside as it will be a repetition.

After dismantling the whole set and subjecting it to thorough cleaning of every part, I took up the remote control for rectification, as it had rusted battery contact springs:

I had to clean the area thoroughly and literally dig out the rusted broken spring from its groove. After replacing the spring and putting the battery, and also replacing the capacitor on it, the remote did not work, even though I had cleaned all the contacts too using IPA. Then I replaced the crystal, upon which the remote started working very well.

Why did I take up this first? Because, controlling the system through manual mode was very difficult, when sets are dismantled and connected externally for check-up. As the display was dim, I dismantled the front panel and was not surprised to see the condition inside:

I cleaned the board thoroughly using IPA. Removed the display and cleaned the legs carefully, as the pins were very thin and likely to break, and replaced all the electrolytic capacitors on this board. Then when I tested, the display was found very healthy and responded to dim commands.

After providing extension wires and connecting the amplifier board externally like how I did in the case (3) link given above, I applied power and saw the serial bulb lighting up indicating high current drawn. I switched off and discharged the tank capacitors and looked for the trouble maker. When I checked the output transistors of the amplifier one by one, I saw two transistors short in one channel. So, I removed them. Still the short was present. (Short between ground and + rail) Then traced it to its speaker protection relay, which was dead short between one pole and one way! I have never seen a relay shorting like this before in my whole years’ experience!

Replaced the transistors and relay after checking every part in that area for any short or open and reconnected the board externally and applied power. This time there was no problem and it worked well. The probable cause for failure was leaky transistor which might have drawn high current shorting the relay. That’s how we also got a thermal error, as the transistor might have been exceeding the temperature limit. Anyhow, I let the set run for several hours before closing it.

You can have a look at the number of pages printed to study the circuit diagrams for easy trouble shooting and the number of minimum components that were replaced in the set, due to the fact that the customer did not have a large budget for the service.

Anyhow, I fit the set back and delivered it to the customer, after he saw its full functions at my home.

He was so happy to get the set back to working condition. Mission accomplished with great satisfaction getting added to the collection!

This article was prepared for you by Parasuraman Subramanian from India. He is 74 years old and has more than 30 years’ experience in handling antique equipment like Valve Radio, Amps, Reel Tape Recorders and currently studying latest tech-classes conducted by Kerala State Electronics Technicians’ Association. He has done graduation in BBA degree, private diploma in Radio Engineering and retired as MD of a USA company. Presently working as Consultant to Hospital and other institutions.

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You may check on his previous article on Intermittent On/Off Problem Solved In YAMAHA RX-V485 Receiver Amplifier

10 Comments

1. 

   Waleed Rishmawi

   December 9, 2023 at 2:14 pm

   you are a device reviving expert and I salute you my dear friend. I like the way you start the repair by clearning and then you start to do the repair. I admire that since without cleaning the faulty part are seen. good job on the repair success.
   keep up the good work and have a blessed day

   Likes(2)Dislikes(0)

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   • 

     Parasuraman S

     December 9, 2023 at 10:43 pm

     Many thanks dear! I normally do not like to put my hand on anything that is not clean! So, I keep top priority for cleaning!

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2. 

   Albert van Bemmelen

   December 9, 2023 at 4:30 pm

   It was no doubt another time-consuming repair that took a lot of study of the printed out circuit diagrams before any action could be taken. Your pre-caution in these circumstances is again admirable including the way in how you add external cables to be able to test any device safely and to easily always be in control!

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   • 

     Parasuraman S

     December 9, 2023 at 10:45 pm

     Many thanks dear! I do such extra work only to ease out the troubleshooting process! Otherwise looking at the condition of a board underneath another one is almost impossible!

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3. 

   Babu MS

   December 10, 2023 at 1:17 am

   Sir, It is really great repair work. Your way of approaching the fault is fantastic.May I know how to check display board alone.

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   • 

     Parasuraman S

     December 12, 2023 at 12:33 am

     Just do a cold check with analogue multimeter and digital for any shorts or value change of restances, diodes and caps. The display won't get on without a command from the uController IC. After doing all that, you need to connect it to the mother board and check. Many thanks for your question and comments!

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4. 

   Imoudu.O

   December 10, 2023 at 2:52 am

   You are a genus in e-repair works,hope you are mentoring someone to replace you when the time comes.Thanks friend.

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   • 

     Parasuraman S

     December 12, 2023 at 12:37 am

     Unfortunately, I don't have anyone in my house who would take over. Nor do I have anyone under training. After my time, in all probability, all my things would go to a scrap dealer or technicians who might buy some or both. As the position stands today, this work will cease on my departure! We did not bring anything when we came and might not take also anything with us! So, why worry? Many thanks for your comments and concern.

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5. 

   Yogesh Panchal

   December 11, 2023 at 11:28 pm

   Good Job! Sir

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   • 

     Parasuraman S

     December 12, 2023 at 11:31 am

     Many thanks!

     Likes(0)Dislikes(0)

     Reply

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