DENON and the irreparable failure. 

I want to try something new. Something more live. So I’m running a 3-part live workshop that takes us on… A Time Travel Through Vintage Electronics. We’ll rewind the clock, dive into the tech of the times… (and study the very history of how things were broken and repaired has evolved) From the 1950s all the way to 2020s. It's still just an idea. The dates and times are to be confirmed. But if you're reading this, then the workshop hasn't yet taken place. So if you're interested and don't want to miss out, you can sign up here: menditmarkk.ck.page/6e8fbd9521

That ending with the red led dimming, definitely like the death of the Terminator in the first film!

Best tech repair channel on the tube.

While I enjoy a successful repair as much as anyone else, what I most enjoy is the process of trying to find the fault in the first place. In that regard, this video did not disappoint.

Cutting your losses with a smile, thats a great attitude. Thanks for uploading the dead ends too.

Great detective work Mark! At least there was a datasheet and schematic for you to use to try to fix this. (Unlike so many computers I try to fix)

That receiver may be repairable. The RESET MCU line is two-way. It can be a watch-dog timer output if the MCU is stuck in a loop. According to the MCU TMP87CM71 datasheet section 1.11 "Reset circuit", in watch-dog activation mode the RESET line can be a pulsed output with a period of 2^20 / Fc [s] = 131ms at Fc = 8Mhz. In this unit the crystal gives Fc = 4MHz. Thus the watch-dog output period here is 262ms which gives 3.8146 Hz, which is virtually exactly what you are seeing at 9:32. Therefore the MCU may be stuck, glitched. This can be a classic case of supercap holding up the stuck MCU. I recommend you gently fully discharge the memory supercap which seems to be C401. Don't bother with reset procedures, the supercap is THE reset procedure. Simply pressing power a few times is NOT the official reset procedure. And check for shorted outputs. That (protection mode) and other reasons may also be why the MCU does not come up. Please keep trying. It is highly probable that the unit can be fixed. It is highly unlikely that the MCU is bad. Good luck. Let me know if I can be of further assistance. [ Edit ] One more thing: Please be aware that for complete grounding often the complete back panel must be attached or jumper wires connected to fully connect all grounds. Failure to do so can often lead one down the wrong path. Perhaps not in this unit, but still good practice.

I like that you don't faff about unnecessarily testing unrelated stuff to find the fault, you get right to the issue. Excellent work, as always.

Be like telling someone a Family member has died. You can't win them all Mark. Keep 'Em Coming.

I've never seen anyone proceed with electronics disassembley with such evil delight. Charming!

I have this excat denon amp from over 20 years ago it's my baby I actually cleaned it out recently and it's still alive after all this time I'm sad to see this one has died this was my first ever Amp it has a special place in my heart ♥ After watching this video I pray it's got many more yrs to live

What a knowledgeable and friendly man! I just found your channel and been bingeing on your content lately!

You are one of the best electronic repair channel on RU-vid. I definitely learned more about electronics with you than in school. Thank you for sharing your passion with us.

Iam so glad your Channel came up on my RU-vid. It was great to see you go through diagnosing the fault .I Have Subscribed and will be checking some other videos of yours, Great work Mark.

One of my favourites from you Mark this one! Love the detective work more than anything. Fix or not, it's always an education.

Your opening sequence is such a joy. The subsequent repair etc is the icing on the cake.

Recently found your channel Mark and love it. A true engineer at work. Keep up the amazing work. Cheers. Matt

Thank you for this educational video, very nice to learn more about electronics.

Excellent video, I love the ‘Hal 9000’ quote at the end. I’ve been repairing vintage and modern electronics for a long time now and I find your videos extremely informative.

"That 80-pin rectangular bastard has all the answers" LOL

Back in the 80s, when these computer controlled audio receivers became popular, we had a lot of success "discharging" the MOSFET inputs by power off, connecting a jumper to ground and swiping it across all the legs of the MCU. Not exactly sure, really didn't care since it worked, this worked, and I hadn't thought of it in 30 years. It might be worth a try, if you haven't trashed the Denon yet. I enjoy watching you work. I've been away from component level repair for more than 20 years, having gotten into IT when I saw the repair business disappearing, with "swap while in warrantee, and trash when out" manufacturer philosophy. Thanks for sharing.

Worlds, happiest component level, electronics repair person.

Amazing, I got a Denon AVR receiver just last week with the exact same issue -- only the standby light on, no other display and no reaction from the power switch or any other switches no matter what -- AND all of the output voltages were there so it acted like it was on. I came to the same conclusion -- dead CPU. I learned a lot in the troubleshooting though, and also learned never to bother with a Denon showing only a standby light again. Thanks for the video, now at least I have some confirmation I wasn't way off base!

really enjoy learning from you, Thanks

This is why I steer clear of all Denon receivers. I've seen way too many broken ones and I'm not a skilled enough technician to keep them alive. Thanks for sharing this video Mark!

I have a similar era Denon receiver, an AVR 2500 that I bought new in 1996 or so. I've used it heavily and it's my favorite receiver ever. It has the ability to make any set of speakers you hook up to it sound fantastic. It ran a pair of Klipsch Chorus IIs for about a decade, it lived through 8 years on a modified sine wave power inverter in my cabin, now it runs a sub/satellite Bose speaker system in my office. It was my 2nd "big" audio purchase ever and I hope it lives another 27 years. Only quirk it has is sometimes the buttons on the unit will act like you pressed a totally different button.

I have a Denon 35 watt am fm receiver I bought in the eighties. It's class A and can be cranked up to maximum volume with little distortion. Great video on this one Mark............

only came across this channel, absolutely brilliant!!!!

Great to see, hopefully further advice from comments will see this working. I used to work at Marshall Amplification in test & service (88-93), then Alpine Car Audio (93-97), before the days of in-circuit firmware upgrades so regularly replaced similar controllers.

Thanks for showing us the ones that got away!

I enjoy so much your very interested channel. Thank you so much, please never stop to make fantastic videos. Thanks so lot !!!

Hi! I recently found your channel. I really enjoy your videos and your knowledge. You troubleshoot and fix the problem without going on a tangent. Great job!

Really enjoy the logical approach and tips.

well tried I forgotten a lot I learned since my stroke so admire you and being a radio ham i need to repair things but often i just leave them , thanks for the video

As usual excellent video. Thanks 👍

Ho letto i messaggi di alcuni utenti su queste discussioni per il raggiungimento della riparazione finale, per far tornare in vita l'apparecchio. E sono sempre più convinto che 40anni fà ho fatto la scelta giusta, per aver deciso di studiare l'elettronica. Il mio indirizzo di studio era radio e tv. Grazie a Mark e a TUTTI QUANTI VOI, per aver conosciuto anche soltanto leggendo, le vostre assolute grandi capacità di arrivare fino in fondo alla riparazione. Mark è assolutamente eccezionale nel riparare di tutto, ma leggo con mia grande gioia che ci sono altrettanti Mark a cui poter tranquillamente affidare in riparazione i propri gioelli elettronici. GRAZIE A TUTTI VOI ❤

electrical appliance repair It's a stressful job. But you're playing for fun. ..extremely appreciated

Ohh I love a quick troubleshot without 5 min watching how you unscrew a box, I love it. You have a new subscriber!

Very interesting video. Thank you very much.

Great analysis of the problem. I would never have found it.

Hi Mark I stumbled on your videos, I must admit I really enjoy the videos, how you're repairing equipment. Very impressed with your test gear. Keep up the good work. One day I may need you to fix some of equipment. Brian

Thanks Mark, lovin' the content of your videos.

Great video - I worked in a Hifi shop at weekends 30 years ago when I became interested in electronics and building amps and active crossovers. I was horrified at the amount of nasty cheap components in the signal path - stuff I would never put in my own builds - carbon film resistors in the signal path - even in the NFB in amps costing a months wages! Marketing, Gimmickry, proprietary protectionism and planned obsolescence, not much has changed.

Absolutely fascinating. I detest the way we have to throw away stuff now. I recently repaired my 1994 akai integrated amp. Cost 17p for a couple of capacitors and resistors . Sadly went again 6 months later so beyond my skill to fix. I then wnet for a marantz costing over a grand. Sadly I know some day maybe ten years from now something will go and it will be another bin job. It is crazy. Thanks for the video, I am subscribing.

You poor little Denon, I will always carry you in my heart 😞

Just love the time lapse repair thanks to editing. That was some good troubleshooting, your eyes are doing better than mine. Would have a difficult time counting the leads on that controller, yikes.

thank you again keep on with awsome good channel.

What a shame !! I love your channel-and your good and cheery humour,I’ve watched you successfully fix quite a number of products-but sadly ‘you can’t win ‘em all’ !!

I can not stop watching your videos! I have no words! Just brilliant! Perfect! I am not sure about your background. Priest? School teacher? Bilioner hobbiest? All together?

My compliments for your endurance anf skills. A pitty to waste a Denon. I still have an AVR 1000 pro logic recoevet with excellent audio quality. Build around 1992 and still going strong. Greetz from 🇳🇱

your excellent video, along with the incredible insight from the commenters, has earned you a subscription! looking forward to binging more of your videos.

Age-wise, according to HiFi Wiki, the manufacturing years for that Denon receiver was from 1996 - '98. I have a 'DRA 425-R' receiver that's older, but still runs fine. Maybe one aspect that has kept it in shape was using a power-strip as a power-on/power-off switch; as I am suspect of push-button on/off switch's lifespan.

Hey Mark, I have one of the same model that is also dead. I hope you can solve this. I look forward to seeing your second episode. I get motivation from your smile. Go ahead.

What a lovely and educational video! You´ve got yourself another keen subscriber :)

I had a Denon receiver around that time. It didn't have an issue removing from standby mode into playing mode. Mine also had an enhanced bass button near bottom right next to the variable loudness. It worked very well, I added a graphic equalizer to it using the first cassette player input which gave more control and doubled the volume.

Great video, enjoyed watching that, have subscribed and will be watching more of you! Excellent work!! Thank you!

Found this channel at random. Very interesting and more views to you, very educational.

Bummer... Nice job chasing it though. Your logic is sound, it was interesting following along and you're tenatious.

Showing things that can't be rejuvenated is assume. Most tubers don't do this.great job sir

If I still may suggest, provided it is not yet scrapped, I would suggest you to check main Vcc pins on MCU on an (fast DSO) scope during power on. If some capacitor on power rail is dead, which I can imagine there may well be some, the inrush current to MCU will cause a voltage drop, simply causing MCU to reset. All I am saying this could be as simple as power supply issue.

Mark is like the Bob Ross of electronics.

Excellent work, the fading of the LED at the end really made me sad tho hahaha

Well done Mark, I enjoyed this vid. Thank you.

Love your video Mark.

Have repaired thousand of thousands of Denon Hi-Fi between late 80's to early 2000. Do even have a DRA-275 for my pc.. :P It's was a very very reliable receiver. Most common thing was blown inputs (due to user connecting/disconnecting stuff with all stuff turned on) or a cooked mains transformer because of stacking things on top and drive it hard. The transformer has a temp fuse you can locate and wiggle out and replace with some handywork. Your thing is rare and seems more of just get the remote and turn it on or manual reset by first discharge all caps completely then use a solderwick and ground all legs on the mc by drag the grounded wick over the legs of the mc. Feel free to holler if you need Denon tips.

Nice to see the use of an Aldi screwdriver, I must have missed when that was for sale! I have a Lidl one, branded 'Parkside' - bloody brilliant, has survived use and abuse over several years. Lithium Battery is getting a bit weak now, but only to be expected after all this use. As a hobby user, I wouldn't spend the money on 'De Wilt - sic' etc...

Soooo much screws, you definitely need a DeWalt DCF680. I enjoy your videos very much. I am a hobbyist from Vienna Austria. I try my best an learn from you. Rock on and best regards.

I had this exact amplifier, I'm fairly sure from memory that you need it's remote control to bring it out of standby and that was the only way you could do it. I assume the processor is generating it's own reset cycle. Thanks for the excellent continue, reminds me of my TV and audio repair days.

First time I see this channel. IT IS GREAT. Love the old HiFi stuff.

Every identifiable date code in that is from 1996. That’s way before the transition to lead-free. But cracked joints (not “dry joints” - dry joints are a specific type of soldering error, which does not include thermal cycling induced fracture) happen to thermally cycled joints with leaded solder.

I repair electronic equipment for a hobby (self taught) and I usually get everything working, but when I start to open some device to repair, I always dread that an unobtainable IC has failed in it. For example, in this video, where you will have to bin the Denon. That's why I enjoy working on pre-IC equipment like old Dansette record players, where the parts are still easily available.

This is pure mastery!

Excellent work. The comment, "That's weird?" .........is something I have muttered a hundred times when trying to debug a circuit. I know the unit is old, but to be unable to fix a receiver because of software in a discontinued chip is very disappointing. That software/chip is just an unnecessary (control) wart in the circuitry: I am old school....all you need is: input jacks, selector switches, preamp, amp, speaker jacks. Leave the software to iPads.

Thanks Mark for a great video

I'm new, I like, I subscribed. Cheers from Canada!

I repaired a similar vintage receiver the other week. What was odd is that the reset was not clean / fast enough with the "dim lamp" in series with the mains and the micro failed to start. As soon as I went back to straight mains the unit it worked fine. It had me flummoxed for a minute!

I knew it would be a micom failure. It's the only thing that will stop my shop from fixing one of these too. Micom failures are rare and so disappointing when they're encountered.

That pulse looks quite digital (timing etc.). So I expect the CPU still runs fine. It's probably the program running on the MCU trying to initialize some peripheral, then gets stuck waiting for it to respond. The watchdog unit then attempts to reset the MCU hoping that the next boot will be successful. Maybe there is some i2c bus you can monitor. But it's a lot of work :)

It might just be the watchdog timer resetting the processor, so it might still be caused by some other external circuit.

Great video I really enjoyed it!

Bless you, RU-vid algorithm 🎉. Subscribed

Excellent channel on the topic of repairing electronics, on par with NorthridgeFix, which is based exclusively on microsoldering. Mark seems to be much more versatile and modest than NorthridgeFix guy. At the same time Mark shows his work very entertaininly...

i picked up the same reciever about 9 years ago for 30$cad at a yard sale. It's been my bedroom radio for quite some time. I always thought there was more on the inside. So far i been lucky no issues yet

Yes when AV Receivers and the like are controlled by a Microprocessor it's a ticking bomb. Onkyo AV receivers are also notorious with similar problem in their Syscon boards. With this Denon you may succeed in fidling for the On/Off control to power up but other function like source selection, etc. may not work either so yeah it's parts out unit then. I love watching videos on this channel which give good information. Mark is really patient at work and always smile.

I admire your patience! You are well equipped. If there was some form of backup there was a possibility to restart the processor. Now how much time is it worth?

The microcontroller is reprogrammable, and still available. The Denon allows for DFU ( direct firmware update ) using a DOS/Windows program to perform the first update. It is an older Denon ( being 20 years old indeed ) which doesn't support many modern features that are needed for HDTV's ... but it is a pity that it's for the bin.

The good old days when you got a circuit board diagram with high end hifi equipment.

10 out of 10 for determination Mark, Thanks for that , interesting job.😉😉

Great vid and channel.

Love your channel Mark, keep em coming.

My 40 year old Sansui Amp is still working with the only issue is scratchy pot’s. Some of the good stuff are still Made in Japan!

I always put these machines on the floor outside and give them a good blasting with the hosepipe, then leave them to dry, they look like new afterwards. They are always fixable afterwards :)

I own a DRA 45 that was dead after power switch cycle! The only repair shop wanted more in a bench check charge than what the receiver was worth ! I decided to at least try resetting board connections , and clean internal power switch ! The receiver powered on with no other apparent issues !😁

Happens more and more, ending up with a factory programmed chip making repair completely impossible, absolutely frustrating !!!

looks exactly like my Kenwood here in the States from around the same year, mine has optical, and Dolby 5.1 also, Works almost like new to this day.

Can't win them all. But this video is a great example of investigating and finding the source of the problem. I have a Denon DRA-325R from 1989. Was given to me. Lightly used in an office (they guy listened to AM radio through some fairly expensive speakers).. I got it some years ago and just started using it again when my NAD C368 failed. Died in 3 years yet the old Denon still works. Go figure!

Onkyo TX84. I have a similar-era setup I love. I live on a half an acre, and out in my shop I have my shop-laptop that I download Pandora Music from the internet, and send it into the Onkyo for the amp, into some rather large (very) JBL speakers. Even tho my property is larger (as are all my neighbors), I dare not turn the volume much past half. Beyond that I DO get a little distortion (and it is LOUD --- my neighbors are accommodating, but I don't want to push my luck with them). I do have one question for the electronics-savy: I have to turn the Bass all the way down, otherwise the bass gets overwhelming. Could that be the amp, or is it more likely the speakers?

I'm sorry mark i'm afraid i can't do that. Could it sometimes be the coupling cap for that leg of the chip or is this more of a short in the chip pulling the voltage down?

Ive actually seen a number of amplifiers where the only thing that was wrong was the microcontroller and maybe the 5 volt supply for it. Depends on design mostly.

just great to see,,,excellent work,, greatings from germany Mike😂