Yamaha RX-V2500 buzzing bad power board / rectifier heats up and buzz's / caps ? - AVS Forum
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post #1 of 8 Old 05-27-2013, 08:05 PM - Thread Starter
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I have noticed allot of people who report on threads, the models such as RX-V1500 and RX-2500, excessive heat, the 24v internal fan does not come on, the unit resets after 2 or 3 seconds...
Not all of those at the sametime of course.

It is amazing that many of these people actually state inside the thread that they cant even unhook ALL the various RCA's and speaker wires from their own AVR system...whatever it maybe... because they are afraid, because they paid some "professional" to do the initial install.

I have experience using car amps inside the house. I love them. They get power from a switched DC source , mainly Gel batteries that are fed by a solar array. So actually allot of components
in my system run isolated and on DC. Its really cool. However my old 1987..Dobly Prologic "Processor" unit (yeah i was rocking that), My prized possession.. had truely had it. After what ...25 years.
Previously in that unit, for academic purposes... i re soldered the timing crystal (cold solder joint)...fixed it for a few years. Resoldered a cap (cold solder joint)...fixed it a few years.....


Today, i got a Yamaha RX-V2500 for $40 bucks. It works too. However the tall tale signs it requires repair very soon...are there. So far the only warning sign is a buzzing sound from the unit itself.
It is infact NOT coming from speakers, but the unit itself. I also noticed it gets very hot where the transformer is located. the most heat is from the transformer.

Now i know what you are thinking... No, it is not the transformer. That transformer is connected to a small board directly in front of it, mounted vertical. This board is filled with capacitors... 16v at 10,000uf..
and 25v at 3300uf. More importantly, TWO (2) RECTIFIERS.... and guess what... one of those rectifiers is getting really **** HOT.... and the circuit board around where the rectifier is soldered to, has changed color to indicate allot of heat comes from that rectifier.... Now an identical rectifier sits in a seemlessly identical spot with no heat damage on the board...no evidence of heat at all and feels only luke warm to touch after operating the unit for 30 minutes, while the other is so hot it would burn you, and did so to my finger.


The whole power setup..... makes me feel that yamaha knowingly and intentionally built the power portion to fail. Owners do not ever suspect that it is defective design, they always suspect they did it, or that the problem is only localized to their own unit, like some bad part. NO.. this is very much incorrect way to go about this. Yamaha put sensor wires.... basically monitoring wires on everything in there....you may not notice, but if any of the power portion does fail,, the unit has at least the ability to know, what it does with that info i do not know yet. However, assuming that this company built the unit correctly, is absurd. I tested the caps... and they are not just caps OK.... the affected Rectifier has the following caps across its DC output +/and/- terminals , they are 2 caps soldered on parallel rails...followed by the PLUS rail hooking to the negative side of another set of 2 caps... so this is "SERIES" now... ok... parallel for 2 ... series ...and parallel for another 2.... so ....then there is another set
of caps grouped lower on the board... which is parallel on the rails of the 2nd set... so 3 Sets....

this mix and match capacitor ....parallel and series and parallel again..... is amazing to track down. It has 2 tracers which goto a pair of wires called (B+) (B-). This circuit must be 24 Volts DC.

I will post my results soon, but anyone who has no fan working,... and it heats up on one side...we will be in for a surprise when i tell you the REAL problem of this unit.

Not like you dont already know, many of you i have read have sent your unit back ... to get the "caps" replaced. Yeah, that board.... right there.... is what they are working on, and they simply desolder
1 bad cap....not all of them, but 1, and replace it. Worthless. I wish more consumers knew how to solder and how to do things. I am out in Portland, Oregon.

I wanted to write this because, people seem to assume, that the overall design is correct and that they are in good hands with any company, and that they assume the company they deal with is honest.
Just like cancer and products.... it takes time... 30 years from now... is hard to prove that happy meal toy you ate as a kid...lol didnt have lead in it.

Same as the capacitors...i know where they come from... and they are not always the best quality. Caps fail when the company purposely chooses a 3rd world factory to produce
electronic parts for them the way they want it... Now here is speculation... we dont know. However it makes sense, that since they are corrupted anyway out in that 3rd world country....
that quality and accountability etc is not an issue. clearly. But most importantly, Yamaha knows exactly what parts fail.

They did it so, rich people are sort of well,,...forced to upgrade. When the caps go out, or short the rectifier, or whatever... Its a time bomb.
They make more money this way, considering the price of these units. Basically the caps are designed to last with a spec that put its out of its useful service life of what yamaha determines to be.

I hope this helps a fellow electronics oriented person repair some "RICH" guys garbage....high end equipment, which part ?

biggrin.gif

At least, I took the thing apart... have not broken it yet.. and are making an effort to tell everyone who may find this, that yes..you can fix this, and it is not complex.
They even arranged the little board...to swing out and has enough wire so that presumably a serviceman can replace the caps or rectifier, whichever dies...probably both die...considering
what i see in there.... first the caps go...then it forces the rectifier to die...? plausible. We will see...

Even if i dont find the problem...the fact this is happening to others ...means that overall they intentionally designed a product to crap out on you. By using "timed" components.

ANOTHER THOUGHT : For anyone out there...... use external amps.... Use them and hack this or other units... take the whole garbage .. rectified transformer power supply out of there...
and solder underpowered supplies in there. Maybe use the surround only...definitely not the mains... I wonder if tiny switching power supplies can be clean enough these days... to mimic
the original stock power circuits.... Just feed the rectifiers DC.... it will pass the DC through i promiss. Tests are your friend. make this 100W oven .... into a 10 or 20 watt "switcher/processor" and move the power amps over to "REAL AMPS". Saves power...and wont put load on your AC unit in the summer.

We can always think about it.... smile.gif
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post #2 of 8 Old 05-27-2013, 09:28 PM - Thread Starter
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Okay, so far my tests continue... I have removed a few caps... i left the minimum .... 2 caps on that rectifier.... so electrically they are in series... 16v+16v caps = 32v . Now it is unknown by me what voltage to expect on this circuit. However i powered the unit up with the caps removed except the minimum... 2x 16v 10,000uf... and measured at (-B5) and (+B5) for a whopping 23.91 Volts.....

This explains why the buzzing noise... the transformer is being pulled down.... basically a load or short or partial short is pulling on the transformer output on that specific winding/ac output / secondary , which i think maybe considered abnormal. Now i am going to suspect where (-B5) and (+B5) goes... which is what i perceive as all the little power fets ...on the heat sink that is closest to the front panel... so facing you.... that heat sink gets hot . Perhaps, the presence .... which is the only terminals i have yet to get sound out of... the fets for those are gone.... or partially shorted. Now i dont know .... we are merely analyzing . Im going in Doctor.... With my MetCal soldering iron... and my Solderwick.. and My flux pen. I am also going to check the regulator.. I wonder if half its internal diodes are fused together,.,LOL .

I am going to try to track down the load to see if i can eliminate it. Chances are, its not a vital part that i even use and can infact be replaced. If it is a cap... the load measured at (+B) should be way less.... like 500ma... guessing. However... If its 2 A or more... okay buddy, imma hafto operate on your parts.


So this is a sign so far... there could be for this unit.... something farther from the caps on that little board in front of the transformer... We will see.

Time to do exploratory surgery.
biggrin.gif Anne will be disappointed if i break my find.

TERMINALS B5
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post #3 of 8 Old 05-27-2013, 10:53 PM - Thread Starter
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Okay, Terminals +B5 measure 1.52 amps. I put a digital ammeter in between to measure this wire. im going back to continue the repair. +B5 is the terminal that goes to the "appearance" overheating rectifier... i am making sure to cover most things practical as this moves forward.
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post #4 of 8 Old 05-27-2013, 11:37 PM - Thread Starter
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Okay, update... i swapped out the rectifier with one i found in a computer power supply. It gets warm, but not hot. I can hold it in my hand while the unit is powered... between my thumb and finger.

Even more interestingly, the transformer does indeed make noise, however, i have a feeling it is not as loud ..so maybe a warmup time of 10 minutes "might" produce the slightly louder...like a florescent ballast... buzz... Meantime... 1.52 Amps on that +B circuit. hmm... at 24 volts basically..hmm.

Without any rectifier connected, the transformer still makes noise, so that does make sense. However, the stock rectifier having burnt the circuit board from its radiant heater element....ahem sorry, its heat, still is not acceptable to me. So perhaps indeed the load is questionable Whats more remarkable is that, If the unit was hooked up and playing music, what load would then be at +B5..... and if it feeds surround speakers.... such as center....surround R and L.... presence... surround back.... Thats allot of little amps ... combined it may overload an already loaded rectifier.

Recap... I replaced 1 rectifier... Result... less heat... Im actually going to mount this rectifier to the case to dissipate warm heat... thinking maybe it will get warmer when i use the system.,
Hmm... well it sure feels like one of those mosfets must be shorted.

Whatever it maybe.. i hope it is going to be an easy fix once i do find the phantom problem. Then again.. i maybe chasing a phantom problem.

I am going to put a 12 volt fan in there ... none of this.... " leave it upto yamaha " .


This really bothers me... but chances are.... if you are one of those people that have a unit that will not turn on... check the rectifiers for fun. Specifically the one i have been messing with.... since i did spot
thermal stress on the board.... i conclude that part may fail or be underrated...since its out.. i will lookup the datasheet pdf on that rectifier to see if it can even handle high currents at 24 volts.
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post #5 of 8 Old 05-28-2013, 01:29 AM - Thread Starter
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Update.....I discovered what the front mosfets do... they are attached to the big giant fan cooled heat sink. The half that is facing the front. Thats actually power regulators. These make +5 volts and +12 volts
and stuff like that... This makes sense.

Now i mounted the replacement rectifier remote from the capacitor board. It is mounted to the chassis. It is doing well.

The 24 volt fan that i tested does not seem to work when i apply 24 volts to it. This is not a surprise since it never worked since i got the RX-V2500.

I put a 12 volt fan in place of it. I did something different for 12 volt power....but if you think you can tap a line somewhere...they are there but i think they are weak like 15ma or something. It will make it shut down.

However a simple linksys 12 volt power supply from a wireless N router...plugged into the switched port on the back could work for those people who put a computer power supply fan in there... It doesnt make much noise at all and the linksys switching adapter is about the size of a cellphone charger. I put a 300ma fan in there. I could have put a 150ma likely.


So recap... it is not the surround mosfets like my previous posts suggest. Those are Various voltage regulators. I am not even going to explore that area, for now.


If your RX-2500 is not working, which i confirm by removing that rectifier..it does indeed shutoff after a second... (2 sec for people who have an inability to judge passage of time) One - Thousand-One.....
The rectifier maybe toast. Replace the one that looks like Toast literally, and see if that does anything.

If your RX-2500 does not turn on, and all other options have been exhausted... check the rectifier... or replace blindly... it is on the board with all the 10000uf 16v caps all over it....
smile.gif good luck

This may apply to many models that are similar to this one...

Yamaha, your high end AVR department.... what is that ? imagine people who made these decisions...living the high life... your purchase contributed into their yacht or a BONUS, or went into
a investment account overseas, who knows. I wonder what others have experienced.
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post #6 of 8 Old 05-29-2013, 12:08 AM - Thread Starter
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post #7 of 8 Old 05-29-2013, 06:31 AM
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So did you find something else wrong besides the rectifier? Was the excessive current draw normal? If you don't think anything else is broken and causing excessive current draw, you may consider buying a rectifier that can more easily handle that load. I don't believe these things are engineered to fail, but they are engineered to be cost-competitive. Unfortunately, that sometimes means buying the cheaper part that is rated just to do the job, but not overrated to do the job easily. We've seen this type of thing happen across all types of modern electronics. Capacitors especially are sized to just handle the types of voltages they'll be seeing, no longer having the 2X safety margins of yesteryear. Plus, considering how much hotter these things run due to increased complexity, that's a combo that's bad for electronics components longevity.

bg
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post #8 of 8 Old 05-30-2013, 03:47 AM - Thread Starter
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I agree with that statement. I have not found anything else wrong so far. So far the heat from the front most heat sink i can only speculate is from the voltage regulators that supply the various smaller parts of the unit. These could be rated just to slip by since they only provide power to the "administrative" portion of the unit, such as controls and the GUI... the chips etc.. so a constant load rather than a varying, however i have not measured that load while under moderate use at all. By looking at it, it seems strange so much heat from those regulators, i have modern regs that do not produce that much heat, however they too may be cheaper and cheaper equates to more heat ? interesting. since replacing the rectifier alone... The unit has worked very good, I will need to re-open it soon to swap the fan out with yet another. The one i put in it., is okay, but ive got a better sounding one for it. at which i will definately snap a photo of the finished rectifier.


amazing some sound equipment from the 60s and up... still work. yet modern tech..have the best of the worst power supply area and other strange things. The simple transformer/rectifier/cap/regulator combo's are easy and can be less noisy for an ac powered item...desirable as i understand... being a hifi. Switching powersupplies , cheap built ones could introduce harmonic RF noise onto everything... a high frequency whine... perhaps.. rf chokes and caps could attenuate/filter it .

I did not have a remote for this unit... so i manually programmed a comcast remote... every key manually using the Extended IR codes. There is about 30 comcast remotes behind my chair... i asked for one everytime i payed my bill at their service center. It comes with 2 free AA batteries . i'm relentless.


I should test the 24 volt fan socket...where it used to get fan power from... I know the fan was dead in mine. I wonder if the socket works, not that i would use the socket.

I cant think of anything else to test . When i looked up this info before i took mine apart.... i could not find a thread about it. i hope at least in some way this thread will help someone .
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