why a recap makes no difference

[gslikker]

Some aluminium volcano I guess .....anyway apparently it was no reason to reject it at the factory and they just used a thicker layer of the hard transparent glue-alike stuff when mounting the transistor....

 

[Eastham]

Some aluminium volcano I guess .....anyway apparently it was no reason to reject it at the factory and they just used a thicker layer of the hard transparent glue-alike stuff when mounting the transistor....

That'll do 'er,

 

[NAD80]

Depending on how the holes are made, punched or drilled. Reminds me of when doing Pems with the spacing too small leaves a mark in the metal of the stronger steel imprint hitting the aluminum. Not made for better heat transfer with that rise in the heat sink.

 

[ConradH]

Although I took apart the whole amp for a refurb instead of troubleshooting the cause of some failure (which included the transistor mounted on the bad spot), the following is "proof" the practice of replacing the grease also prevents overlooking the fact a heatsink may not be flat
See the "hill" of some 0.3 millimeters which was hidden below a transistor at middle of picture, before it was filed and sanded away.
So before applying the grease, make sure the heatsink is flat (another opinion).

Wow, that's one evil heat sink. There have been arguments about whether an extrusion is really flat enough for best heat transfer without finish machining, but that's ridiculous.

 

[Ray Gianelli]

Without factual data the argument for capacitor replacement is opinion at best.
Here is a frequency response curve of a 1990s speaker with new capacitors. No benefit to replacement.
View attachment 1111858
This capacitor still was working!! However it leaks hot gas from a hole in the polypropylene. Yes benefit to replacement.
View attachment 1111859
These capacitors look OK but measure 0.6 to 0.5, in spite of markings 0.22. They are from a vintage Les Paul guitar that "Sounds Good."
??? Replacement ??? (I put them back in the guitar).

View attachment 1111862

These capacitors had already been removed for other repairs (glue cleaning). I did not bother to test them, the pragmatic decision was replacement with new items of equal or better specs.

View attachment 1111874

Wise move putting the caps back into the Les Paul. If you think audiophiles can be irrational guitarists take it to the next level.

 

[Raccoon1400]

However there was one unit I recapped that I think the difference was negligible. It was a 1990 Denon PMA-900V. I think that is because the designer did a good job of keeping electrolytic out of the way of the sound. Still happy I recapped it though. And it wasn't as old as some stuff.

 

[Djcoolray]

The values of every component in a circuit, circuit design, quality of components...

If I buy a junk car and only replace the spark plugs, at best... it’s going to run a little bit better.

Some equipment with low S/N and high harmonic distortion are just going to sound a little bit better !

Like always, a person has to be smarter than the stuff they’re working with....so understanding the potential of a piece of equipment is paramount. Just because it’s silverface doesn’t mean it’s capable when it has 0.7% THD or higher...or S/N of 70dB or lower. Then of course German replacement components make a bigger difference. People have a romance with the idea of how things should be based on social expectations. Technically life is a completely different experience..

 

[restorer-john]

Here's some shots of my father's Marantz 1060 (which he bought new in '73). I recently (Dec 2016) did a full restoration on it, although it spent most of its life unused in its original box.

He mentioned it had developed a low level hum. I told him to stop using it immediately and give it to me to fix.

Here's what I found:

Brown glue direct corrosion of transistors as they are glued to plastic 'risers'.



This is a brown glue/electrolyte reaction. The cap is so well glued down that when it vents (from the bottom on old ones), the gasses and liquid force up through the sleeve and out the top. Cap leads were completely corroded away.



The power supply caps and their glue looked fine, but underneath the story was very different. The slight venting had caused the leads to corrode and eventually the cap lead vaporized leaving the black charred board (note all this was hidden from view)



This amplifier received a full complement of FGs.



And nice new Nichicon speaker coupling and PSU cap. Note, the 1060 has pre-drilled holes for a smaller diameter PSU cap as it was the same chassis used for the 1030. I used one of my NOS original 1970s Elna identical matching cap brackets.



As for the original heat transfer compound condition- these pictures show how little Marantz cared, as they pushed these out the door:







Cost cutting on heatsink compound if ever I saw it..




Opening up an amp exposes the good and the bad. Often, it opens up a can of worms that have been hidden for decades as the next posts will show. Replacing capacitors often uncovers safety issues, poor wiring and dangerous situations.

 

[restorer-john]

This is the mains wiring of the same Marantz 1060. They were rewired (and voltage set to 240v) with a three core Australian lead/plug by the distributor's service department in Australia before being sealed up and shipped off to HiFi dealers.

You can see the evidence of the old black two core lead they simply just cut off:



Even in the 1970s, the safety earth legally had to be an eyelet, screwed to a chassis point. This was splash soldered onto the cap earth strap.



More quality mains (active) wiring:



This is also quality work (see the cut off black original cable):



Here is the preferred wiring setup after making it electrically compliant and safe. (wires removed, terminals cleaned and wire wrapped though the holes and soldered. Earth lug twisted through hole, soldered, covered and screwed with lock washer to chassis/transformer bolt:



Here's another safety issue in a JVC amp (another brown glue horror story). The mains wiring active and neutral are less than 1mm apart due again to lazy ass Australian distributors when rewiring.



Again, an example of quality earth work...



So, going in for a recap often exposes (pun intended) safety issues that have been there since day one.

 

[NAD80]

Those Fine Golds look good. Nice finds on the "BAD" original work. Great repair work on the safety issues restorer john.

 

[restorer-john]

So, did the replacement of capacitors in the 1060 make a difference?

Absolutely. It had deteriorated in its box unused essentially for over 40+ years. It was working, but it was essentially an unexploded bomb about to go off.

Many capacitors had vented and corroded. Transistors had corrosion from the glue that had eaten right through and up the gold plated leads into the package. Pots and switches were noisy and it had a hum.

I couldn't do my usual before and after testing as this 1060 was in a precarious state.

Here is what the lovely little 1060 achieved after her rebuild and an hour at 1/3 power preconditioning (she got a bit warm at 49 degrees C on exterior casework above the heatsink):



Here's the 'magic' of the 1060. An exaggerated bottom end and nice fat mid bass, smooth mid and a rolled off top end. All 1060s I've had exhibit this same response. ie, not remotely accurate, but oh, so good.



Note, these are 2.5V divisions...Plots offset at rated power and 20 watts approx IIRC.

Here, for comparison, is what a Sony TAE77es preamplifier FR plot looks like...


Note, 0.25V divisions, ch plots offset for visibility each pixel is 0.01V.(my ancient DOS based AudioLab) How's that for flat?

 

[drumbum]

Excellent post John!

 

[yotems]

that sony is flatter than nebraska!

 

[Oldsansui441]

ie, not remotely accurate, but oh, so good.

Thanks for the info restorer john, l guess this just goes to show that our ears care little for specification figures and response curves . I have had some nice mid range amps from the 80's that look great on paper but in reality are sterile, fatiguing and frankly boring.

 

[tarior]

In the process of cleaning up hygroscopic glue from circuit boards, I've pulled up plenty of perfectly good caps. No hint of leaking electrolyte, ESR and capacitance spot on. But then I ask myself, "does it really make sense to put a 40 year old capacitor back?"

 

[Karl vd Berg]

Here, the "famous" Matsushita lavender capacitors (photo by AK member jheu02)...

When you spot them, replace them... it will make a difference.

 

[steveUK]

Thanks for the info restorer john, l guess this just goes to show that our ears care little for specification figures and response curves . I have had some nice mid range amps from the 80's that look great on paper but in reality are sterile, fatiguing and frankly boring.

Well, some people's ears care little for specification figures and response curves and that's why there will never be an end to this debate. It'called the psychoacoustic effect and never more prevalent than when we hear 'what we want to hear' ie an improvement following a mod or work done.

 

[Oldsansui441]

Well, some people's ears care little for specification figures and response curves and that's why there will never be an end to this debate. It'called the psychoacoustic effect and never more prevalent than when we hear 'what we want to hear' ie an improvement following a mod or work done

Very true steveUK, but l would like to think l have fairly good ears (learnt music for many years). I can normally tell when an improvement has been made and also when no improvement has been made and will be the first to admit if many hours of work has amounted to nothing in sound quality improvement .

I was just saying that like with many things in life, figures/specs vs real world practical usage is often two different things.

 

[steveUK]

Very true steveUK, but l would like to think l have fairly good ears (learnt music for many years). I can normally tell when an improvement has been made and also when no improvement has been made and will be the first to admit if many hours of work has amounted to nothing in sound quality improvement .

I was just saying that like with many things in life, figures/specs vs real world practical usage is often two different things.

Well, if you're that confident in your ears who am I to argue. But in many cases, a person's ears identify a preference, not necessarily something that is objectively shown and proven to be an improvement, and also subject to - whether we like it or not - psychoacoustic effects. Generally, valve amps are demonstrably 'worse amplifiers' (measurably higher distortion levels) than solid state ones, however it is quite understandable that lots of people prefer 'the valve sound'. It doesn't make valve amps better, it signifies a preference. I have good ears. I have been an accomplished musician for 45 years, built and owned by own studio, recorded in commercial studios, mixed bands live, been part of a team developing monitor standard speakers, I'm a qualified electronics engineer, built amplifiers, etc etc. I pride myself on being able to hear and differentiate very fine detail when listening to hifi components and systems. Yet, concerning my present interest, vintage receivers, when I listen to each and every one of them in isolation, I have to laugh at myself in thinking, "Does this one sound different to the other one on the bench last week?". Without A/B testing it is very hard, and like I say, I do feel that 'psychoacoustic effects' can play a huge part in all this. I do my utmost not to be taken in by those effects. Even after many hours restoration it's tempting to hear an improvement, I prefer to just say to myself, "I like how it sounds, I'm happy".

 

[stereoguy70]

it's a fact that e-caps age
they are Chemical based to keep the aluminum clean.
they are sealed but do dry out
I have seen rotted off legs, either the chemical or glue or just age.
I've found enough failed ones in "working, sort of" gear that there is no question that they are the weakest link.

if a recap makes no difference in sound, either the unit was still working well or your ears are not working well.

fwiw, a total recap does not make it sound stunningly better.
the difference can be minor unless the cap was totally failed.

if your source material and or speakers are lousy, a recap won't do much.

I'm gonna chime in with my experiences on this one.....and I agree that a recap is in order when you get over 30 years old on equipment. Most of the units I work on are Henry Kloss units....meaning KLH or Advent. These were made to a price point and do sound very good when completely up to specs. I've done three KLH 27 receivers, a 24 and a 20 all in one unit....these are over 50 years old now and just about every electrolytic in the ones I've come across have been junk, well past their prime. Doing a complete electrolytic recap on all these units made a huge difference....how so? They now work! Same thing with the Advent 300 receivers I've restored....every one had some kind of issue, most related to the electrolytic caps failing, and a few with failing/failed 15v regulator semiconductors, and one with failed output transistors (which was related to failed caps).

So if anyone tells you that doing a full recap is a waste of time, they don't know what they are talking about. It makes a difference, especially with non-working gear, as it usually makes it work again! Now, if you can't hear a difference after recapping a working unit, then the unit was probably fine and I agree with others that its preventative maintenance........caps age and fail, period. If they were 30+ years old and have not failed yet and you just recapped, you just gained another 30 years of use without fear of a cap failing.....hello!!??!!! No brainer.

If it still sounds "lousy" to you, then I also must agree with the above poster I quoted, that either your source material is low quality, or you have not found the right speaker for your gear yet. Its called synergy.