Jump to content

Sign in to follow this  
tromboc

Denon AVC-A1 power capacitors

Recommended Posts

Always learning and won't stop now but the my friend thing was scary. Well outside the range of normal behaviour even for you. Thankfully email notifications still hold the initial pre edit content, I feel all warm and fuzzy.

I miss read your post...silly me!

Share this post


Link to post
Share on other sites

I wouldn't replaced those Panasonic caps from your pics, they look fined. But looking "fine" can be deceiving.

Have a look at this thread:

http://www.stereo.net.au/forums/index.php/topic/48986-stax-srm1-mk2-new-lease-of-life/

One of those CEW 100uf/400 is faulty, from the pics I took, it looks fine. Taking it out of the circuit PCB the vents haven't been effected all look OK, they also measure fine as you can see from the fluke; 99uf. Unfortunately I'm not able to measure the ESR.

One thing that's not clear here is that one of those caps is slightly bulging out and the top plastic cover is Matt finished compared to the other 2 that's gloss finish. edited: if you look it's the cap on the corner, you can see it's not as shinny as the other 2 towards the center.

However, the SQ is effected with a severe hum and slight static of memory. This unit is over 30yrs old! The SS devices and the resistors all look fine. Replacing all the electrolytic caps and the hum cycle and static disappeared, which is what I expected! No big surprise here! Measurable buy ear!

Just because a component looks fine doesn't mean it is fine especially when you have a fault, assuming that it is fine is one big mistake techs make! Yes measurements will determined that, but if you had to remove an electro to measure you might as well replace it.

I've seen failures straight out of the box where series resistors in line with psu go open, and techs wonder why the thing isn't powering up, the resistor looks fine and the components are all brand new so where do you start! I've had solid state devices go open as well, they look fine, and no sign of burn marks but place a meter across it and it's a open circuit.

 

 

I don't disagree with anything that you've said above. In your circumstance where there is a clearly audible fault, find/diagnose the fault, fix the fault, BINGO!

 

The point of my post (and Trevor's post) was that many, many people see a bulging plastic disc atop large snap-in caps and automatically assume the worst, often in gear which performs perfectly well. A bulging plastic disc or deformed heatshrink is not always the sign of a dead or dying cap. One should be careful not to jump to conclusions in these circumstances.. Further investigation is always required.

Share this post


Link to post
Share on other sites

 

see a bulging plastic disc atop large snap-in caps 

 

...love these innuendo's .... :P

Share this post


Link to post
Share on other sites

...love these innuendo's .... :P

 

It's the transition from a bulging cap to an uncontrolled discharge that's usually the concern!!!

Share this post


Link to post
Share on other sites


Do you know what you are doing, and this is an absolute genuine question - please dont take offence. this is a power supply you are working on feeding off AC mains. unless a qualified tech better off left to one.

denon is serviced by qualifi. be no reason they cant sort this out for you. denon are usually quite good with parts and service. they tend to use quite similar as well over the years in their range of gear and to replace mains caps I can imagine a pretty straight forward job.

I agree. Qualifi will replace them with the same Elna caps or better higher temperature rated equivalents. Elna caps are commonly used in premium Denon products. There will be a recommended spare part equivalent.

You probably know what you are doing. Sure It is not a technically difficult job if you have some skill....but....This is a low cost repair and Qualifi will guarantee work for 3 months, plus their repair will be deemed electrically safe. Qualified and certified.

Edited by myPal

Share this post


Link to post
Share on other sites

Wow, didn't expect such a response. I've been quoted $150 minimum plus parts to open the lid, which isn't my idea of "low cost" for an amp that is worth about that much second hand, hence the DIY.

Like has been pointed out, I have no way of testing them really.... but considering they have deformed approx 5mm and are seemingly non-genuine, I can't think of a good reason not to replace them. I spent 4-5 years repairing HF radios and am not afraid of the fairly low tech circuit boards Denon were using 15 years ago. 

I have to say though I'm fairly surprised at the amount of people who advocate leaving damaged and deformed components because "it still works." You don't wait for the whole engine in your car to seize before replacing the oil that is showing signs of aging just like the main filter capacitors on my Denon amp which are bulging potentially due to released electrolyte should probably be replaced... right?

 

Share this post


Link to post
Share on other sites

I wouldn't advocate leaving damaged or deformed components in a unit that clearly requires repair/restoration. What I think is being advocated is an emphasis on electrical safety, compliance and certification. That is the real agenda.

Why? Because this HiFi industry is about to get cleaned up like it should. On the most part the well known dealers have been doing the right thing but are being dragged down by a few dodgy (non compliant and unqualified) importers and retailers who have been misleading the public. Some of whom are currently running scared, have been doing some quick housekeeping and reassessing their product lines in the hope that past sales will not retrospectively return to haunt them.

Edited by myPal

Share this post


Link to post
Share on other sites

Wow, didn't expect such a response. I've been quoted $150 minimum plus parts to open the lid, which isn't my idea of "low cost" for an amp that is worth about that much second hand, hence the DIY.

Like has been pointed out, I have no way of testing them really.... but considering they have deformed approx 5mm and are seemingly non-genuine, I can't think of a good reason not to replace them. I spent 4-5 years repairing HF radios and am not afraid of the fairly low tech circuit boards Denon were using 15 years ago. 

I have to say though I'm fairly surprised at the amount of people who advocate leaving damaged and deformed components because "it still works." You don't wait for the whole engine in your car to seize before replacing the oil that is showing signs of aging just like the main filter capacitors on my Denon amp which are bulging potentially due to released electrolyte should probably be replaced... right?

Correct. Like I said, I wouldn't let it pass on my watch!!!

In your initial post there was not a lot of detail and there was no pictures to indicate the size of the description " pregnant cap" Even if it wasn't causing any issues it has a potential safety hazard as it indicated the placement near the psu. Without knowing the voltages and tolerances, one should never "assume" and question the clients observations, until they did the measurements and testing. Even though it seems alright you wouldn't refit it back into the circuit, it's actually being brought in for service and restoration. Bulging caps means it's been electrically stress in the circuit. But in any case "the client is always right, even though the client is wrong he/she is right"

Off topic: It depends on what industry you work in and who's willing to pay.

In the reprographics industry you are working against time and cost so you are able to pay the bill at the end of the day. But when this is in a industrial setting operating 24hrs, service inspections will tell you to replace anything that looks odd out of the ordinary. Why because the SLA the client signs off has certain penalties when devices are off line due to issues. Devices that go off line due to issues can cost the service provider $30-50k a day or more! It's the same for the aviation industry, the minute a plane makes an unscheduled stop for repairs it's $1000s every minute that plane remains on the ground.

In the medical field, you will be doing the same, you don't want failures to occur that can cause loss of life or causing professionals to make wrong diagnoses, the same goes to the aviation industry.

Tight tolerances are also required in military, you do not want to pass equipment where it can effect military operations.

Share this post


Link to post
Share on other sites


Wow, didn't expect such a response. I've been quoted $150 minimum plus parts to open the lid, which isn't my idea of "low cost" for an amp that is worth about that much second hand, hence the DIY.

Fair enough.

 

Like has been pointed out, I have no way of testing them really.... but considering they have deformed approx 5mm and are seemingly non-genuine, I can't think of a good reason not to replace them. I spent 4-5 years repairing HF radios and am not afraid of the fairly low tech circuit boards Denon were using 15 years ago.

 

I would bet that the components ARE genuine. Manufacturers commonly change suppliers throughout the manufacturing life of  device. 

 

And I will ask once more:

Have the aluminium cans deformed, or is it just the plastic coatings that have deformed? If just the plastic coating, then it doesn't matter in the slightest.

 

I have to say though I'm fairly surprised at the amount of people who advocate leaving damaged and deformed components because "it still works." You don't wait for the whole engine in your car to seize before replacing the oil that is showing signs of aging just like the main filter capacitors on my Denon amp which are bulging potentially due to released electrolyte should probably be replaced... right?

If the component is damaged, then it needs to be replaced. If the component is just cosmetically affected, leave it be.

If it ain't broke, don't fix it!

Share this post


Link to post
Share on other sites

Yes, more info is required! Can you take photos of the capacitor in question? It is still not clear whether the cap is faulty or not.

Edited by pete_mac

Share this post


Link to post
Share on other sites

I agree with Zaphod ,that the caps are almost certainly genuine .Capacitor manufacturers have their retail line , but huge amounts of caps are custom manufactured for end users who can ask for any specification they wish .You can open up top end amps from Sansui ,Marantz , Pioneer and Yamaha and you will often find parts with odd sizes and ratings made by Nippon Chemicon ,Nichicon and Elna.

Parts from left over runs will find their way onto the market .

One of the most likely reasons a cap can fail is if the equipment has been sitting idle for 10 or 15 years ,the insulating oxide layer on the aluminium in the cap breaks down so far that on powering up ,the cap begins to short out and will heat up and boil the electrolyte ,causing it to swell.When this happens its is not the cap manufacturers fault .Caps that havent been used for a long time can in most cases have the oxide layer reformed by applying the rated voltage at a very low current to avoid heating .

Many of the cases of dried up electrolyte in caps are probably heat related either internally by damaged oxide layer or in very hot valve amps etc .

The 105 degree rated caps use a solvent electolyte whereas the 85 degree caps use a water based electrolyte.

Most audio types are 85.

Heat is the real killer of electrolytics . A good designer will over rate the cap with voltage and ripple current to keep internal heat low and keep external heat sources well away.Its probably good practise to periodically give electronics stashed away in the cupboard a power up ,just to keep the oxide layer formed on the caps .If it is kept well formed they wont have to endure the bursts of heat which lead to premature failure .Large caps will tolerate heating better than small caps simply because of the surface area .multiple smaller caps will also allow better heat dissipation .I prefer bigger caps . Installing a soft start to a big power amp will likely extend the life of big caps by avoiding internal heat inthe caps on amps that havent been used for longer periods .

Audio caps generally sound better as thats what the designers designed them for . If it was all smoke and mirrors ,companies like Sansui and Marantz would not be fooled into forking out the premium. If u listen you can hear it .,but thats not to say an industrial cap like a panasonic FC cant sound good .Its just that a Silmic 2 sounds superior to most peoples ears.

Share this post


Link to post
Share on other sites

I agree with Zaphod ,that the caps are almost certainly genuine .Capacitor manufacturers have their retail line , but huge amounts of caps are custom manufactured for end users who can ask for any specification they wish .You can open up top end amps from Sansui ,Marantz , Pioneer and Yamaha and you will often find parts with odd sizes and ratings made by Nippon Chemicon ,Nichicon and Elna.

Parts from left over runs will find their way onto the market .

 

Hey Brenden,

Cheers for your response, and the others, some good information in here! Your information regarding capacitor types is really what I was looking for with my OP. In regards to the above comment, the original service manual does definitely call for a different spec to what was installed, and I can find literally zero reference to capacitors of this spec by the manufacturer or anywhere else online, I would have thought someone would have asked around at some point as they surely sold more than a couple of these units. I've ordered genuine replacements (of a slightly higher spec) than the originals in any case, and eagerly awaiting their arrival!

EDIT: In response to the number of posts regarding "why bother" or "they are probably fine" or "you aren't a technician how can you test them" etc, I have a unit that's barely worth spending the quote fee, with a fault somewhere in the power supply, and bulging caps of non-original spec. I'm happy to take the gamble replacing them, and worst comes to worst I can still take it in for a quote in the future, knowing that I've got brand new filter caps which I didn't have to pay someone $150 to install... Best case scenario it's problem solved.

Edited by tromboc

Share this post


Link to post
Share on other sites


Hey Brenden,

Cheers for your response, and the others, some good information in here! Your information regarding capacitor types is really what I was looking for with my OP. In regards to the above comment, the original service manual does definitely call for a different spec to what was installed, and I can find literally zero reference to capacitors of this spec by the manufacturer or anywhere else online, I would have thought someone would have asked around at some point as they surely sold more than a couple of these units. I've ordered genuine replacements (of a slightly higher spec) than the originals in any case, and eagerly awaiting their arrival!

The capacitors fitted are very likely originals. Manufacturers regularly change suppliers over the life of a product.

EDIT: In response to the number of posts regarding "why bother" or "they are probably fine" or "you aren't a technician how can you test them" etc, I have a unit that's barely worth spending the quote fee, with a fault somewhere in the power supply, and bulging caps of non-original spec. I'm happy to take the gamble replacing them, and worst comes to worst I can still take it in for a quote in the future, knowing that I've got brand new filter caps which I didn't have to pay someone $150 to install... Best case scenario it's problem solved.

Are the capacitors ACTUALLY bulging? Or is it just the plastic coating?

Share this post


Link to post
Share on other sites

The capacitors fitted are very likely originals. Manufacturers regularly change suppliers over the life of a product.

Are the capacitors ACTUALLY bulging? Or is it just the plastic coating?

Does it really matter at this point?

Share this post


Link to post
Share on other sites

Yes. VERY important.

Alright :) I'll post a photo of the originals when i pull them out for group judgement.

Share this post


Link to post
Share on other sites


Alright :) I'll post a photo of the originals when i pull them out for group judgement.

No need. Just cut the plastic away. You'll be replacing them anyway. If the aluminium can is not bulging, then they do not require replacement (probably). You should be looking for leakage at the base of the cap. If you purchased new caps from an unknown source (ie: eBay), rather than a proper ISO9000 accredited one, then you are quite possibly wasting your time an money on a needless exercise. You might even make things worse. There's a reason why professional repair people don't buy spare parts from eBay, unless there is no other option. 

 

http://www.eevblog.com/forum/projects/warning-fake-large-electrolytic-on-ebay-!!/

 

http://www.eevblog.com/forum/reviews/fake-nippon-chemi-con-capacitors-at-ebay/

 

My oft-cited adage STILL applies:

If it ain't broke, don't fix it.

Extending that adage, should also:

Fix what is actually wrong.

Edited by Zaphod Beeblebrox

Share this post


Link to post
Share on other sites

@@tromboc I know it doesn't seem like it, but I and the other experienced techs are trying to help you. You appear to be bent on ignoring that advice. I find this mystifying and slightly frustrating. 

 

Here's how it works in the service business:

 

1) Establish the symptoms. Describe in full.

2) Trace the fault to the part/s that require replacement/repair. 

3) Replace the parts with the correct parts, sourced from a reputable supplier.

 

Using a 'scattergun' approach to servicing is expensive, wasteful and often ineffective.  

 

The caps in your amp may be faulty, but you have not established this as a fact yet. FWIW, those types of caps tend to last a long time. Failure, whilst possible, is unlikely. 

Share this post


Link to post
Share on other sites

@tromboc

 

 

Anything to report? Have you examined the caps yet? Are they bulging, or is it just the plastic?

Edited by Zaphod Beeblebrox

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By zakblue
      Price: $1300 Item Condition: Excellent Shipping Options: Pickup is available Suburb or Town: Balwyn State: Victoria Payment Method: Paypal, EFT, Cash on Pickup Reason for selling: NLR  
      These were purchased from this SnA member here:
       
      75W per channel with 4xEL34 tubes on each amp. 
      Lightly used to power my left and right mains for HT duties.
      Happy to demo for serious buyers. Weight is 30kg each.


    • By MFidelity
      Item: schematic for Electrocompaniet ECI 5 (not ECI5 MKII)
      Price Range: $20 or ONO
      Item Condition: New or Used
      Extra Info:
       
      If you can help to find a full schematic, I need to know R620 R621 resistors value. 
       
      (thanks Rockeater. That is the first thing I did but they direct me a local dealer in Melbourne that never reply any email. 
       
      thanks Aab. I will Geiger a try. Will let you know the result.  Will contact you. 
       
      sorry I am new here don’t know how to PM and reply....)
    • By afie
      Hi,
       
      So currently I have nothing setup, but have narrowed down on speakers and am looking for what avr/power amp/dac are required to make work everything I desire.
       
      Id like to be able to have a 2ch setup for a main tv/kitchen/living area, with speakers to play:
      - music currently on a hard drive (internal and external);
      - tv/movies through streaming apps like Netflix through a Fetch box or a Xbox1 or a Chromecast;
      - streaming apps/Youtube through casting from an iphone.
       
      Sound quality of music is the priority, but I do find it much easier to hear spoken words on tv with separate speakers.
       
      I have been looking at Ascension speakers from Adelaide and talked to the guy there last year.  The likely model will be around 150 wrms at 8 ohms. I will call him again to discuss, but if I remember correctly from what he recommended last time, an AVR to drive such speakers is expensive relative to the speakers just to offer extra channels that I don't need. Would a suitable alternative be a 2ch power amp plus a second device to hand all the digital inputs?
       
      Emotiva BASX A-300 or AMC: 2N100MKII-2 are both 150w 8ohm power amps for about $800, but an AVR that can do 150w at 8 ohms are about $5k - what am I missing here? Ive looked into this several times over the last year and I feel like I am just going round in circles.
       
      Any help would be appreciated. Cheers.
       
    • By olegau
      Price: $350 Item Condition: good working order Shipping Options: Pickup is available,Audition is not available, but in-person pickup can be arranged with limited personal contact Suburb or Town: Melbourne State: Victoria Payment Method: Cash on Pickup Reason for selling: too many amps Further information: 
       
      The amp was checked and serviced recently. 
       
      Power output: 100 watts per channel into 8Ω (stereo)
      Frequency response: 4Hz to 100kHz
      Total harmonic distortion: 0.03%
      Damping factor: 1000
      Input sensitivity: 0.25mV (MC), 2.5mV (MM), 150mV (line)
      Signal to noise ratio: 70dB (MC), 75dB (MM), 97dB (line)
      Speaker load impedance: 4Ω (minimum)
      Dimensions: 440 x 121 x 347mm
      Weight: 10.1kg
      Year: 1991
      Price: GBP £400 (1991)
      https://www.hifiengine.com/manual_library/rotel/ra-980.shtml
      Photos: Advertisements without photos of the actual item will not be approved.




    • By Alpine Electrocats
      Price: $220 Item Condition: Very good plus Shipping Options: Pickup is available,Audition is not available, but in-person pickup can be arranged with limited personal contact Suburb or Town: Canberra State: Australian Capital Territory Payment Method: Paypal, EFT, cash on pickup Reason for selling: no longer needed Further information: 
       
      This magnificent Sansui receiver came from the ANU school of music recording studio, where it was used to drive altec monitors.(note the sticker from Canberra institute of the arts- one of many names covering the school of music over the years) It works fine- as a pro use studio amp it was very well maintained.
      One curious feature is that the tuner is AM and Short Wave (MW ).
      They are photos of the actual receiver below.
       
      I am in Canberra and can post anywhere. 
      Postage should be between $25- $45 depending on distance
      OneBay these go for about $280 so this is a steal
       
       
       
       
      From the HIFI Engine:
      Power output: 30 watts per channel into 8Ω (stereo)
      Frequency response: 20Hz to 20kHz
      Total harmonic distortion: 0.05%
      Input sensitivity: 3.5mV (MM), 200mV (line)
      Signal to noise ratio: 75dB (MM), 105dB (line)
      Output: 200mV (line)
      Speaker load impedance: 4Ω to 16Ω
      Dimensions: 430 x 136 x 311mm
      Weight: 7kg
      Photos: Advertisements without photos of the actual item will not be approved.
       


×
×
  • Create New...