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• 
  @mdzacharias2 күн бұрын

  Wow! That thing is a Marantz inside! '90s Marantz Japan. (MJI) Basically an SR-63 with the added Carver board.

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  @danhorton61822 күн бұрын

  I really appreciate you posting the part replacements. Hope you’re busy, I’m booked out about 8 months at the moment. Would you mind in the future posting the device number pulled along with the replacement? The outputs can be read in the video, but I was curious what the TO92 package was. Thank you.

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  @dualityrepair47702 күн бұрын

  Ah good call. Will do Dan.

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  @bpalpha2 күн бұрын

  Nice to see a great unit like this given more life. Thanks.

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  @midmodaudio65762 күн бұрын

  Really well presented video, a joy to watch. Thank you

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  @dualityrepair47702 күн бұрын

  Thanks midmod

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  @davidrippy16052 күн бұрын

  Outstanding informative video and a Great job!!!

• 
  @johnbravo75422 күн бұрын

  Nice job Nick, as always.

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  @FrankieZR3 күн бұрын

  That was awesome. The explanation and commentary made all the difference. Great job on the repair.

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  @dualityrepair47703 күн бұрын

  Thanks Frankie

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  @TravelOutlook3 күн бұрын

  Thanks Nick! Wonderful to see you at work and staying busy.

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  @dualityrepair47703 күн бұрын

  Thanks John. This one was a battle. Probably 10 hours of work for a 10 minute video. I learned a few things along the way.

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  @davidrippy16055 күн бұрын

  Well done Sir...

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  @tenminutetokyo26436 күн бұрын

  Do a Carver m-400t cube amp.

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  @dualityrepair47706 күн бұрын

  I did the plain M-400. DR #37.

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  @SSD996 күн бұрын

  Replacing those single-turn quiescent current- and DC offset pots with multi-turn ones would let you dial in the precise numbers called for.

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  @nitishshiboo51308 күн бұрын

  Helo i have changed the two 6.8 ohm resistors still short again why??

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  @michaeln238610 күн бұрын

  I knew all this stuff 30 years ago when I graduated from NEI. Thanks to your videos I want to learn it all over again. We have a throw away society, nobody wants to fix anything any longer but I'm going to give it shot on my 8060 that doesn't work any longer. Thanks!

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  @dualityrepair477010 күн бұрын

  Glad to hear it and good luck!

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  @user-oe1jk2ro4o13 күн бұрын

  One of the things that I think technicians like you don't take into account is that a manufacturer will use certain capacitors to get a certain sound that he is aiming for. That means he may have tried many types of capacitors with many hours of listening until he decided what to put. And just because you put something with the same values ​​and the wave looks good on the oscilloscope doesn't mean it sounds the same. This is audio equipment not a TV or a refrigerator. Therefore, when you decide to put something that has the same similar values ​​but is produced by a different manufacturer, you should understand that it can affect the character of the sound.

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  @dualityrepair477013 күн бұрын

  That may be true, but 45 year old caps should be replaced if you want a piece of equipment to last another 45 years. And I can only use the components I have available to me.

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  @user-oe1jk2ro4o13 күн бұрын

  @@dualityrepair4770 It is okay to make the equipment more stable and durable for years to come But if a certain component such as a capacitor or diode is measured properly I think it's better to leave them as they are. Especially if they are related to the audio signal. Because if you start replacing everything like this, you might change the original design of the device. And it can damage the magic of the sound that the designer aimed for. Even if from an electronic point of view everything is measured according to the electircal schem. In terms of sound, this could be a change for the worse.

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  @RennieAsh14 күн бұрын

  KZread shoved this video in my face but i didn't want to look at amp videos yet Next minute, i end up with an amp with no bass. Had to try and remember the name lol

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  @dualityrepair477014 күн бұрын

  Wow what timing

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  @bobmulhiemer756414 күн бұрын

  I have the other two amps one is failed I am interested in having You repair them.

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  @simont368615 күн бұрын

  Hi, I've got a similar issue on my Mission Cyrus one. Did you measure the output voltage under a resistive load?

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  @dualityrepair477015 күн бұрын

  Yes, the amp was connected to 8 ohm - 500 watt resistors.

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  @simont368615 күн бұрын

  @@dualityrepair4770 Thanks!

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  @johnsnowlow188316 күн бұрын

  Your video is very useful and gave me the notion that the ayre mxr i owned has a similar issue. I always felt that the ayre lacks bass weight and resembles little to the reviews i have read. Would you think the ayre would have something like a "c3" lurking in the unit that is hindering the bass performance. Your insights is appreciated. Thanks

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  @dualityrepair477016 күн бұрын

  Yes it could very well have a “C3.” Unfortunately I can’t find a schematic anywhere to help point you at a specific component or area.

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  @johnsnowlow188316 күн бұрын

  No worries...when I find a schematic I will come consult you again. Thanks

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  @mat.b.17 күн бұрын

  5:32 That little power board, did you have to squeeze the white plastic clips to remove it, or were there screws on the other side?

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  @dualityrepair477017 күн бұрын

  No screws. Just squeeze the plastic tips on the top of the board.

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  @thatampguy17 күн бұрын

  Great video. I also love the little Dynascan era BK scopes. Especially the round crt models like the 1470. Sexy! See if you can score a little 1405. So fun!

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  @dualityrepair477017 күн бұрын

  Thanks. The 1405 does look neat.

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  @mikecampbell585617 күн бұрын

  Wow, brilliant repair!

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  @dualityrepair477017 күн бұрын

  Thank you Mike!!

• 
  @GeirRssaak18 күн бұрын

  Has adcom ever been good?!

• 
  @f430ferrari55 күн бұрын

  My Adcom GFA 5500 is nearly 30 years old. Works great and sounds great. 👍

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  @TravelOutlook18 күн бұрын

  It's always a treat when a new Duality video appears in my subscription feed!

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  @VIctorCarruyo18 күн бұрын

  If you add flux to your de-soldering wick, it pulls the solder easier, and leaves a clean pad. Great video.

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  @robertfournier705019 күн бұрын

  From experience. I hate Adcom. I never like their sound. But then again I don't like half the amplifier's I went through other than , Spendor class a amplifier and Mackintosh 252

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  @vegaslimoguy23767 күн бұрын

  Then WHY are you here??? Weird

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  @stuartnorman871319 күн бұрын

  Why did Adcom use an electrolytic c3in the signal chain?

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  @pistollero19 күн бұрын

  very good video. thank you for the explanation!!!☺

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  @jameslaidler215219 күн бұрын

  Random question, how difficult would it be to convert this to a dual monoblock? Is there space for a second toroidal there, or is there a smaller option available which can be placed side by side? Just curious.

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  @thomasschafer726819 күн бұрын

  Cool repair. Nice amp. Enough power and very high damping. 700!

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  @NackDSP19 күн бұрын

  I would look at using a Tantalum capacitor in that application as it will last a lot longer.

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  @randpresley166619 күн бұрын

  Cool! I have this amp and its 3-channel brother used perhaps 100 hours total. I bought them new and have been in the box since. I should sell.

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  @user-dh9me5ug4x19 күн бұрын

  I am a bit confused by the feedback resistor being so high at 10K ohm wirmth the other 50K ohm that would make the overall gain only X 6 or have i missed something.

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  @dualityrepair477015 күн бұрын

  Good eye.. and you're right.. a gain of 6 is ridiculous. It turns out that the schematic isn't completely correct. The feedback resistor is indeed a 49.9K, but the resistor to ground is not 10K.. it's 1.82K, making the gain ~28. Thanks for bringing this up.

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  @user-dh9me5ug4x14 күн бұрын

  The old schematic documentatio error problem . That is why we hone our fault finding skills to​ give us the tools to overcome these obstacles. Dealing with lack of or conflicting information. Maybe that would be a good subject for one of your future videos. @dualityrepair4770

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  @yttean9819 күн бұрын

  Very Informative video. You must be from Texas your arm shows a map of the state.

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  @dualityrepair477019 күн бұрын

  Minnesota actually. Thanks for the comment.

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  @BaileyWiggebutt19 күн бұрын

  Just found the channel today. Subscribed. 😊

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  @CarlVanDoren6120 күн бұрын

  Magnepans made in Minnesota 😊 Great tutorial 👌 thx for sharing 👍

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  @rankenfile20 күн бұрын

  Nice walkthrough and demonstration of the problem, along with solution.

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  @dualityrepair477019 күн бұрын

  Thanks!

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  @adrianespino292320 күн бұрын

  Its easy to know why caps failed like that, its caused by heat you can see discolored pcbs in almost all Nelson, Adcom and Nakamichi top end amplifiers he likes to design time bombs deliverately, that amplifier also has a small heatsink in the differential pair that almost all the times (have seen that small metal thing missing in almost all of that model amplifier) and if it didnt went missing it will short ccircuit some transistor or something after the glue fail under the heat...... the same heat that caused the video capacitor fail 😅

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  @phloodpants20 күн бұрын

  This isn't Nelson Pass's fault, he only provides the circuit design. Adcom did all the actual board design, including decisions on heatsinking.

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  @phloodpants20 күн бұрын

  This failure is likely caused by heat. The input mosfets run super hot, which causes eventual failure of the capacitor. You can tell how hot the board gets by how browned it is in that area. There is usually a copper heat-spreader bar installed across the two mosfets, meant to keep them thermally tracking, and dissipate some heat. It looks like yours either fell off, or it wasn't included in that particular production run. What I do is install a DIP-16 heatsink across the two of them, with thermal heatsink epoxy, and that dissipates heat better than the original copper bar, as well as thermally coupling them. Also, the heat cycling eventually cracks the solder joints, resulting in a crackling sound, a common issue with this amp. The solder joints just need a touch-up.

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  @Trucam202020 күн бұрын

  Excellent explanations of the problem

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  @dualityrepair477020 күн бұрын

  Thank you.

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  @fikretdogulu41320 күн бұрын

  Great job.. I did the same repair on my GFA 5500 a while ago. Turned out to be one my favorite power amp.. Now I got two more...

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  @airgead539120 күн бұрын

  O.K. but why did the elcaps went bad? Strange, but it is as it is of course.

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  20 күн бұрын

  Both channels had the same cap fail in the same way, from age or something else?

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  @dualityrepair477020 күн бұрын

  I believe they failed in the nearly the same way and at nearly the same time. The caps were probably from the same manufacturing batch, so suffered from the same issue. And since both channels would always be running together, each cap would be subject to the same amount of use. My other thought is that one channel did fail before the other, but it wasn’t noticeable to the owner until the other channel failed too.

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  @Dickmanthetard20 күн бұрын

  @@dualityrepair4770 I was an Adcom dealer back in the 90's. The GFA-565 and '5500 amps had issues due to bad caps. It wasn't Adcoms fault, the cap manufacturer had a bad run of caps. Sometimes the amps failed under warranty, and on some they ran fine for several years before they failed. Nice video!

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  @jim993019 күн бұрын

  @@dualityrepair4770 POOR design - you don't reverse voltage an electrolytic by more than a volt or so - had there been enough current, you'd be picking fuzz out of the box after the cap exploded. Peak AC voltage on that cap under worst case could be 10 volts - dumb oversight by engineering or mistake in parts procurement.

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  @randpresley166619 күн бұрын

  @@jim9930 Seems suspicious in most cases it might have been by design. I've seen computer CRT monitors fail back in the day, just days if not weeks after reaching the limited warranty. The failure was due to the power supply capacitors running at the cap-rated voltage. In most cases, caps should have been rated double the application voltage.

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  @RanTausi20 күн бұрын

  Many thanks for this video, 5500 is a great amp. I have the GFA555 and the 545 both MK2. Please make more ADCOM stuff videos ❤ Thanks for sharing

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  @dualityrepair477020 күн бұрын

  I hope to find more Adcom gear to work on in the future.

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  @AudioGearhead17 күн бұрын

  ​@@dualityrepair4770I've got a GFA-5400 I can send you! When powered on the right channel sends a really bad crackling sound to the speaker, that is until it warms up. I have no clue what's going on with it.

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  @dualityrepair477017 күн бұрын

  Ahh interesting. Send me an email and we can discuss further. [email protected]

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  @AudioGearhead17 күн бұрын

  @@dualityrepair4770 E-mail sent.

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  @linjia953920 күн бұрын

  Perfect👍

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  @poormanselectronicsbench202120 күн бұрын

  Wow, seeing that the capacitor that went defective isn't subjected to a life of high ripple current or voltages near its rating, I am surprised that it failed in the way it did. I am thinking there was a very poor selection of quality when purchasing. Nice repair presentation!

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  @crazyzakirnaik326219 күн бұрын

  that capacitor was subject to ac - the amp's output - thats the reason for the early failure. in other words, poor selection of parts by adcom

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  @jim993019 күн бұрын

  Because it is a low gain power amp stage (Av=6), the peak AC voltage of the output divided by 6 is far greater than is smart to reverse voltage a polarized electrolytic. He should have replaced it with a nonpolar cap - it will just fail again. Most amplifiers have gains around 20-30, the problem rarely happens at normal listening levels - you might get peak reverse voltages high enough to damage an electrolytic. Stupid design error trying to replace high Gm bipolar transistors with low Gm FET's. Audiofoolery at it's finest!

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  @poormanselectronicsbench202119 күн бұрын

  @@jim9930 Did you take into account that, there is a 49.9K Ohm ( lets' call it a 50K for all intents and purposes) resistor between the amps output, and the 47uF cap? With that cap being loaded to ground with a 10K resistor, that would only give it a max of 5 volts AC across it at a 250 watt - full output of the amp. That cap will also have a DC bias on it, seeing that it is connected to the gate on the negative feedback differential IRFD210, but the swing of a max AC signal would be less than that AC signal, and that AC voltage across the cap should be less than 6 volts, creating a current through that cap of less than 2mA according to a SPICE modeling circuit I made @ everycircuit. IMO, it was more of a poor quality cap being used than the circuit it was applied in.

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  @jim993019 күн бұрын

  @@poormanselectronicsbench2021 Somewhere else in the comments I explained it would have been confetti if it wasn't current limited by the 50k. Electrolytics act like a lousy diode when reverse biased - they can take some abuse. Think of it as a dartboard with a piece of paper; keep punching tiny holes in the electrolyte (hot spots) till it fails. X and Y caps (polypropylene) fail the same way from voltage spikes on the ac line.

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  @jim993019 күн бұрын

  @@poormanselectronicsbench2021 The source of the D210's will have a negative bias , gates will be at DC offset of the amplifier. (zero) High AC line, peak ac output divided by 6 could be minus 10 volts worst case - more than enough to slowly 'cook' the electrolyte - 2 or 3 volts can do it.

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  @D1N0220 күн бұрын

  Any tips for the GPT-500?

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  @dualityrepair477020 күн бұрын

  I’m not familiar with that model. Does it have issues or are you just planning on maintenance?

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  @D1N0220 күн бұрын

  @@dualityrepair4770 it's a matching Adcom pre-amp / tuner. I just think it sounds a bit meh.. May work on it some day.

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  @Fidelity_Sound20 күн бұрын

  Awesome!!!! I’m glad this showed up on my feed. Liked and Subscribed!!! Great job sir!!!

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  @dualityrepair477020 күн бұрын

  Thank you very much.

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  @brentslone20 күн бұрын

  When I checked the calculations, I came up with 26.5Mohms for the 0.3nF cap at 20hz. So NFB attenuation was even worse.

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  @dualityrepair477020 күн бұрын

  Yes that’s correct for the 0.3nF cap alone. I was calculating based off both caps in parallel (0.2uF + 0.3nF).

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  @Techelfe20 күн бұрын

  Moment Q607 und Q609 sind ja normale To92, die werden mit Wärmeleitkleber zusammengeklebt und mit Schrumpfschlauch zusammengehalten... Gott, wer hat sich so etwas einfallen lassen.

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  @akirchner320 күн бұрын

  Great video! I worked over my 5500 a few years ago. I replaced all the electrolytics on the amp boards with Elna SILMIC IIs though I think they've been discontinued. Also replaced the polyester caps with polypropylene units. Also replaced all eight of the 1000 uF electrolytics in the power supply as they were bulging. The amp sounds amazing!

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  @ThePerkri20 күн бұрын

  Can’t believe this randomly showed up in my feed! I acquired a GFA5500 (along with a Krell KSA 200) in a trade for a turntable I had restored. Tge deal was actually for the Krell, but he threw in the 5500 because he was clearing out some space. Neither unit was in working order. Figured I would take a look at the 5500 first, as it’s a bit less intimidating than the Krell…. Powered it up, no speakers just to do some quick measurements. No smoke - that was good :) But, I was seeing the full rail voltage on the speaker terminals. I poked about a bit, got some help on DIYAudio trying to figure out what the issue was, but no luck. So, I sent it out to a tech, and they didn’t want to repair it (Also sent them a Marantz 7T that I had done a full recap on, which was working wonderfully until I was trying to run a sub off the center channel, and right channel went pop - but that’s another story) All that to say, tech either couldn’t or didn’t want to fix that either. I was informed that all the semis in the 5500 were bad. They also said there was a 16A automotive fuse in the 5500. I am subscribed and excited to watch the rest of the videos in this series. The 5500 is supposed to be a very capable amp! P