NAD 3020A No sound after changing capacitors.

[Jez1234]

Originally Posted by stevehertz

I have a large collection of high end, mainly Japanese hifi receivers and tuners from the late 70s to the early 90s when Japanese companies largely pulled out of the true hifi market and moved towards faux stacking systems with flashing multi coloured LEDs. Virtually all of the sets came to me faulty, often with hard to find, complex faults. Apart from main smoothers I have not needed to replace a single board mounted electrolytic capacitor. All of my sets have been restored to - to my ears - perfect working order; RF, audio, the lot. And as a qualified electronics engineer, musician, former small studio owner and builder of monitor level speakers I'm no mug when it comes to assessing sound quality. Now.. will any of those thousands of electrolytics in those sets be 'faulty'. The answer is almost certainly yes to some degree. The point is, the 'degree of faultiness' that they may have is not affecting my listening enjoyment. Compare that situation (essentially 'nothing' is wrong) with the time, money and hassle of replacing all of those caps? My experience tells me that the shotgun replacement of all electrolytic caps in modern hifi equipment is, in many cases, more for the 'heads' of those wanting it, and a nice earner for those doing it on professional basis. The latter I have no qualms with whatsoever.

The electrolytics in 70's to mid 80's Japanese gear are very good and rarely fail. I have seen the odd few go though. These sets were well engineered and they generally rated everything suitably conservatively. With some more modern units (and like I said in earlier comments, not all) then even after only 8 years or so of being used a few hours per week you will find leaking electrolytics I assure you. The silly fad for leaving kit on 24/7 is the worst of course. I had a Krell integrated amp in that was only about 5 years old and had been left on 24/7 and over half of the (SMD) electrolytics had leaked over the PCB and most of the ones that hadn't were very high ESR. The snap in smoothing caps were fine.

Yes there are many hi fi users who want perfectly good electrolytics replaced en masse in gear that is not plagued by leaking caps and has only seen an hour a weeks use and due to what they've read on audiophool sites... "a nice little earner Terry"

[Radio Wrangler]

Aw, it makes them feel happier, and it feeds the families of repairers. That the improvements in a significant fraction of cases must be imaginary is unimportant, the happiness is real and lasts until the next guru pontificates that it either must be done all over again to some newly preferred brand, or has moved onto some other fad.

They say it's a lot easier to con someone than to convince them that they have been conned. But how much harder it is to convince someone that they have conned themselves.

In fairness, sprinkled amongst all this will be cases where real improvements have been achieved, but without careful and impartial evaluation it's hard to be sure. One good thing would be to check the out-going parts for ESR and value, perhaps also leakage and then to look at the circuit and ponder what effects they would have.

Human perception is a bit variable, so it's nice to have some non-human back-up whenever possible. It also creates the possibility of interesting discovery, If I hear something yet check up and measure nothing, have I imagined it? or have my measurements missed something? Either way I want to know. Either my senses aren't doing what I expected or my theories need sorting out. The only stupid answer is to do nothing.

Done diligently with wise choice of components and their sources, recapping should do no harm, but possibly create an improvement, whether or not to as original versus better than original. There's cost in parts and man-hours, of course.

Where things go wrong it lies in the quality of workmanship, remembering that it's not all soldering. Deciding on and getting new parts is part of the work. This introduces a probability of error. If something goes wrong, then man-hours and a need for some threshold of fault-finding ability enter the scene and costs go up dramatically. Pride has forced the scrapping of a lot of gear rather than calling someone else in and admitting fault.

Everyone makes mistakes. It's the proportion which varies. Blanket recapping is fine only for those with good enough workmanship to not turn it into a disaster. Recapping in small groups tolerates a worse error rate without such a large increase in diagnostic demands.

In the words of Mr Eastwood, how lucky do you feel?

I've got it wrong on various occasions.

As a designer I fiddle around with sketched diagrams, maths, analysis and in later years sims. Then I decide it's time to breadboard one. So I do.

How much of a design do I build in one sitting before I can test it? It's the same problem. How much do I trust my design and construction skills? Remember this is probably a section of an instrument moving the state of the art on a bit and nothing like it has been done before... so no stress, then! Diagnosis is also more scary. As a prototype, the outcome isn't known. I think it ought to be, but I could be wrong and as I'm both the designer and the tester any gaps in my thinking line up to create a total oversight. I don't know that one like this ever worked. I don't have any working examples to compare against. I'm on my own. These conditions force the development of severe diagnostic skills. They are glacially slow. People coming from the repair trade direction are much much faster than me and make me look incompetent. But I can work out problems from first principles and handle ones they've never seen before. Horses for courses, again.

Fault finding is interesting. I had to write test procedures for in-factory and for field use. I got interested in where normal fault-finding failed. What threw someone off the trail? If I can know this, I can do a better job writing future procedures.

Factory test procedures even with limitless test gear and fixtures isn't 100% successful and big dog-piles (I think meaning the boards were called dogs, na allusions to piles left by dogs...) of unfixable boards can reach embarrassing proportions. I wanted a decent spectrum analyser for the radio shack and did a deal with the top manager. I'd pull boards from the dog pile and fix them, doing a write up on the fault, how to find it and how to fix it to full quality, and I'd train the test engineers as needed. I'd then have the board I'd fixed to build myself an analyser. The folk on the line were delighted. Getting the dog pile down took pressure off of them, and the write-ups and training meant they could keep the pile down. I got a good supply of slight seconds to build my analyser and the company got a million dollar investment in unfixable assemblies converted into shippable product.

So understanding things which look like failures is the key to not having more of them. It may be the only defence.

Recapping without testing the old parts is dumb. Without the tests you'll never learn whether you needed to have done it. A bit late, but an insight for next time.

David

[Jez1234]

100uF 16v electrolytic, 17p each. Desolder the old cap, test it for ESR, capacitance and leakage and then re-fit the part worn cap or just put a brand new one in for 17P and save 80% of the time it would have taken to test it. Which is dumber? Economies V false economies.... yeah if it's a 22,000uF 100V computer grade electrolytic you do all the tests... well you do if it's your own money you're spending anyway! When I get a customer with a £4K power amp and the instructions to replace all electrolytics then I follow my customers instructions. The perfectly good computer grade caps I remove save me a fortune when designing and breadboarding etc my own gear

I already covered the issues of spec'ing, sourcing and ordering up thread.

I'm right with you on the designing V fault repairing bit though. I consider myself primarily a designer, one who being self employed has to also do repairs to pay the bills, but I ain't quick at it.
I've been there in doing temporary "between jobs" in fast turnaround TV and video etc repair shops and felt rather incompetent in that some of the guys could fix 4 TV's in the time it took me to do one... even though I could have redesigned a circuit to avoid similar faults in the future and many of them could not. It's a different skill set and some of them seemed to almost be able to sniff out a fault by divination or something!

[Station X]

Most of us on here are hobbyists and not professional repairers. The restoration work we do isn't economically viable, so who cares how long it takes?

[Jez1234]

As far as I can see a good proportion of people here are professionals or retired professionals and with varied backgrounds including repair and design. I was responding in particular to aspects of David's post re the speed some repair guys can fix something and was also giving some re-capping insights from the perspective of someone who is often tasked with just this by customers, which I believe will be interesting and relevant to many readers

[Ted Kendall]

Originally Posted by Jez1234

It's a different skill set and some of them seemed to almost be able to sniff out a fault by divination or something!

Rather like the picture restorer at the National Gallery who, when asked how he distinguished between several infinitesimally different shades of sky blue on his palette, replied "I do this all day, you know!"

[Chris55000]

Of the many pieces of audio, radio, hi–fi and TVs I have looked at, listened to or repaired in a 44 year career of fixing things, whole–sale "recapping" simply is NOT necessary!

If there is a fault, it is down to a definite failure of one or two components, dry–joints, or an obvious problem in the interconnecting wiring and switching that can be traced from the correct circuit diagram (as the OP found, like I have done over many years, what you're looking at does NOT always resemble any of the available diagrams, despite what the maker's label and the front cover of the S.M. says!), or there is a simple problem of defective controls, either electrical or mechanical!

Once you've gone down the "re–capping" rabbit–hole, you may have introduced many unknown potential faults into the equation, from disturbance of the wiring, and original components, dry–joints introduced where there weren't any originally, failure of a semiconductor device somewhere in the circuit because much larger switch–on surges produced by the much lower impedance of new components (compared to the originals!) damaged a device that may have been selected or rated by the equipment designer to suit the capacitors in use at the time, or introduced an unknown circuit or pcb fault that may not be immediately obvious afterwards, and at the very least, "re–capping" is likely to alter the audio quality in ways that may affect the future listening pleasure, because of the altered source and output impedances between amplifying stages, compared with those the original components provided!

The only types of equipment that warrant complete re–capping are industrial and switch–mode power supplies where the effects of heat in a small space, the large amounts of ripple current and the tendency of makers to fit poor quality originals means that most of them will have dried out after a relatively short service life!

Chris Williams

[stevehertz]

I agree Chris, pretty much in-line with my own mumblings in the past.

[ms660]

How hard can it be to change capacitors, when I was an apprentice R&TV service tech. back in the year yonder I used to regularly replace all the wax capacitors in one go in some radios and TV's, why? because I knew that some would be leaking enough to affect the sets performance and also it improved the reliability of the set.

If someone gets its wrong then so what, sometimes learning from mistakes is the best way.

I dislike "preachers"

Lawrence.

[Radio Wrangler]

We get a wide variety of people visiting the forum and there's a fair proportion who haven't had much experience at repairing.restoring things haven't yet built up any soldering skills, but have come across people telling them that 'recapping' is the done thing and that it not only fixes things, it cures all sorts of ills. For want of experience or hearing a different viewpoint, they swallow it.

So they do this. Many don't understand that some capacitors are polarised, that some are RF types in positions which require re-alignment on replacement, and nore don't understand that some are chosen for special temperature coefficients to counteract drift from other components.

There are replace-on-sight things like waxed paper capacitors, moulded paper ones, Plessey electrolytics. But electrolytics in general are interesting. On the whole they are useful components and difficult to do without, but they do have a wear-out mechanism. Loss of water vapour through ambient heat, internal heating and the quality of sealing means that they are all little clocks ticking away. Bung a new one in and even that has a limited life. So it comes down to finding out how much life is left in each. An ESR meter is a good tool.

Once you've got a set dismantled and the soldering iron hot, for the cost of the parts it would seem efficient to just change the lot. Components buried away under switches in multi-band coil packs might cause second thoughts. But the recapping thing can come crashing down due to simple statistics due to workmanship.

A lot of the recappers that appear here are not wondering whether to do it, they've done it, and stirred up faults. They wanted to improve a set, but now it doesn't work and they go looking for deeper advice.

An experienced repairer, wanting to do a good job and return a working and reliable set is going to have a good standard of workmanship as well as stocks of known reliable types of components. He might just as well change the lot and has a good chance of success.

But for a novice, not understanding the needs for different types of capacitor and not particularly careful, with limited experience at soldering, the statistics are unfavourable.

These different people need different advice, some don't need any. What we do want is a successful outcome and a working set. This will build someone's confidence, help them learn new skills. Failure will discourage them and drive them away from vintage stuff.

So, in writing guidance for someone, it's crucial to assess their level of experience and tailor what is said to help and encourage them. Other people with other levels of experience would either think 'That flew over my head' or would be left feeling insulted to be given basic guidance. You can't write things which are optimum for all because 'all' encompasses such a wide variety of experience, so readers of the forum can't expect to see everything pitched at their level.

David

[stevehertz]

Originally Posted by ms660

How hard can it be to change capacitors, when I was an apprentice R&TV service tech. back in the year yonder I used to regularly replace all the wax capacitors in one go in some radios and TV's, why? because I knew that some would be leaking enough to affect the sets performance and also it improved the reliability of the set.

If someone gets its wrong then so what, sometimes learning from mistakes is the best way.

I dislike "preachers"

Lawrence.

I think you're missing the point here Lawrence, there's a big difference between replacing 'on sight' ten waxies in a vintage radio - something I always do - and replacing many tens of small, PCB mounted electrolytics (that are most probably perfectly ok) in a mechanically complex piece of 70s or 80s hifi. The latter being the salient point of this post. Chalk and cheese.

[knobtwiddler]

One point that is also worth making is that 'solder suckers' are rarely kind to fragile PCB tracks. Some boards only have to look at an iron and the track de-laminates. You can end up in a pickle, whereby you have to bodge loads of new tracking from copper wire. Unless you know there are rogues such as Frako or Plessey, it's best done only if there is a known fault in that area. And it's best done with a temp-controlled vacuum desoldering machine, going in and out quickly!

[Ted Kendall]

Quite agree - only problem is that Hakkos cost a mint and go obsolete in months, it seems, and the Chinese thing I got from Amazon was so bad I sent it back for a refund.

The Philips EL3312 I revived a while ago was absolute hell - first touch of the iron and up came the print...

[knobtwiddler]

Sending you a PM, Ted!

[ms660]

Originally Posted by stevehertz

I think you're missing the point here Lawrence, there's a big difference between replacing 'on sight' ten waxies in a vintage radio - something I always do - and replacing many tens of small, PCB mounted electrolytics (that are most probably perfectly ok) in a mechanically complex piece of 70s or 80s hifi. The latter being the salient point of this post. Chalk and cheese.

Not really, it's all about having the nouse and the confidence, I replaced virtually all the capacitors (and there were lots of 'em) in a Hallicrafters communications receiver of note without having to reassemble and switch on to test every wip and flip, I didn't take any photo's and the only wiring diagram I did was to show which wire(s) went to which connection of the multi section tuning gang and guess what...it worked.

To add to that, the mechanical aspects of replacing the said capacitors was in my view more "complex" and demanding than doing the same in yer average 70's or 80's lump of hifi stuff.

Lawrence.

[Wellertcp]

My approach to soldering and desoldering is to use a hot iron, an oversized chisel-bit if possible, and be in and out as quickly as possible.
Use solder-wick if you need to. But ideally; cut out the component, apply a hot iron, whip-out the component lead before the board realises what's happened, and then cleanup.

You are more likely to do damage to fragile tracks sitting there for ages with a cooler iron.

And for fragile tracks, a solder sucker is a definite no-no, as has been mentioned. Also vacuum desoldering tools can do more harm than good, in the wrong hands.

There are some very good methods in the HP video I posted in the soldering thread.

[Jez1234]

I use a Chinese made "Duratool" desoldering station like this https://cpc.farnell.com/duratool/d00...lug/dp/SD01384 (also available from Amazon so it may be the one Ted is talking about) and find it works well. TBH I quite expected it to be rubbish and unreliable but it has served me very well for about 5 years so far. It's good enough that I would buy another one if needed to replace the present one after some terminal disaster with it.

It's somewhat maintenance intensive but desoldering guns as a breed generally are. I'm talking about having to empty the chamber when it fills up, keeping the tips unclogged and cleaning filters as required. Emptying of the chamber is messy and potentially dodgy from a health and safety perspective as the solder it sucks into the chamber generally takes the form of a mixture of solder as you would expect it to be/look and a fine very dark grey powder making up half of it and this fine powder is worrying as it has a vastly higher surface area for skin absorption etc (if that's a thing!), gets all over your hands meaning thorough washing before touching anything else and there is the possibility of breathing it in if not careful. Hence I treat cleaning out the chamber as a hazardous chemicals operation to be carried out with great care.

Replacement tips are a fair price (about a quid) and are available in various size nozzles. Other spares for them are available at a decent price.

It has variable temperature, thermostatically controlled, and has a clear readout on an LCD display of the tip temp.

I don't recall the £800 ish Weller etc ones I've used at past employers premises as being much better so a thumbs up for them from me

[Radio Wrangler]

Constant-suck desolderers are lot gentler than the spring-pump impulse ones.

I was very underwhelmed with a chinese hor air station, kept blowing out bits of broken glass. So work-work replaced it with a Weller which I also found underwhelming. Then we got a JBC station. Soldering iron, hot air and constant-suck desolder. Oh boy, this was how it should be! If I ever need to replace my Metcals, or go hot-air, this is the one.

David

[Jez1234]

There's a version of the Duratool one with a hot air rework gun included but I haven't tried one. They also do a separate hot air gun that's even cheaper than the desoldering station. I've considered getting one but the small amount of SMD stuff I do doesn't quite justify it for now.

[knobtwiddler]

We have 'em all at work: Hakko (several different types, station and hand), De-non Instruments, Pace etc. The Weller ones have always underwhelmed me. The Hakko FR300 has the highest power to suck ratio IMO. The Pace is pretty good, but very expensive and not as good as the Hakko.

I would agree about taking care with any vacuum machine. If you can nip the legs off, remove them quickly with tweezers - and then suck the hole clean - that would be my tip for fragile boards.