Class D amp long term reliability

[restorer-john]

The M50 looks puny next to a Halcro DM88

From what I hear, the Halcro also has superb reliability.

I have no idea about Halcro's reliability. Not many sold. Built to military standards and likely will outlast me and everyone else.

 

[Bjorn]

I'm behind Vera Audio and we use Hypex Ncore and Purif modules. We have not had one amplifier with failing modules or power supplies to this day. There was a problem with software issue for some of the early Purifi modules, which was solved with a new software. We started selling in the transition of 2017/2018, so I guess you can say it's still early.

But I believe, also based on my earlier years of experience with class D, that if the class D amplifiers are well built and with sufficient cooling, they will generally last very long.

 

[Petrushka]

How would you expect them to review the reliability of a product?

Just report on whether conformational coating is used on the circuit boards. Especially on expensive stuff you hope will last.

 

[NTK]

Just report on whether conformational coating is used on the circuit boards. Especially on expensive stuff you hope will last.

You mentioned metal whiskers yesterday, and conformal coating happens to be one of the mitigations. Conformal coating is widely used in high reliability electronics in harsh environment (see link), and, in an ironic twist, can be used to assist heat dissipation. It is not conformal coating (or potting) that is the problem, it is the misapplication.

https://nepp.nasa.gov/whisker/reference/tech_papers/2023-EppSchmidt-NASA-Tin-Whisker-Conformal-Coat-Study.pdf

 

[antcollinet]

Just report on whether conformational coating is used on the circuit boards. Especially on expensive stuff you hope will last.

Doesn't tell anyone about the reliability.

Plus I don't think you'll find any consumer amps that use it.

 

[Rick Sykora]

Has been a couple of decades since I was involved in industrial electronics but conformal coating was only used for harsh environments. It adds cost and makes for more work in repair too. For these reasons, likely it does not get applied in consumer electronics.

Even years ago, we had industrial products that were deemed “replace only” as their cost to repair was too high a proportion of the cost of new. More recently, the lower cost of consumer electronics makes repair less viable. For Hypex and Purifi modules (notably with heat plates) there is still value in recycling even if repair is not economically feasible. Remember though, it is the OEM who is on the front line. If the cost or time to repair a module is too high, a supplier like Hypex or Purifi may not ever make the repair or replace decision as the OEM made the call.

P.S. Not sure how widely applied the practice is, but our automation product repairs were sometimes time-bombed in repair. If the product was repairable but did not get through repair in a given timeframe, they were scrapped and replaced with refurbs or new.

 

[Petrushka]

Doesn't tell anyone about the reliability.

Plus I don't think you'll find any consumer amps that use it.

Because whiskering takes ten years or so to result in failure. Well out of warranty. Maybe not a problem for something that costs $150, but high end gear can cost thousands.

And after 10 years, there may not be replacements. I say this because I’ve seen a lot of multi-thousand dollar sewing machines become garbage because circuit boards failed.

 

[MCH]

There are very easy to apply coatings for electronics now, that don't even need masking the contacts. See link below and video where they coat a raspberry pi, it is impressive. I am even thinking of trying them in my diy projects that use fans, to protect from dust (take my comment with a grain of salt, I have not use them yet, but i have access to equipment to do it safely)

https://www.3m.com/3M/en_US/p/d/b5005005017/

 

[antcollinet]

Because whiskering takes ten years or so to result in failure. Well out of warranty. Maybe not a problem for something that costs $150, but high end gear can cost thousands.

And after 10 years, there may not be replacements. I say this because I’ve seen a lot of multi-thousand dollar sewing machines become garbage because circuit boards failed.

And there you have the problem.

Manufacturers don't really care about life out at 10 years. Further, the market has changed. The days of integrated amps being usable for 40/50 years are gone. They are filled now with digital electronics - which is driven obsolete by changes in standards and requirements in typically much less than 10 years.**

And then - as we have read in some of the articles posted above, there is no one mitigation to whiskering that solves the problem. Coating alone does not do it. The cost of implementing multiple measures, that even then probably only reduces the failure rate rather than killing it, for something that occurs 10 years down the line, is simply not going to happen.

**(How many 10 year old AVRs are any use now for modern AV program material?)

 

[Petrushka]

And there you have the problem.

Manufacturers don't really care about life out at 10 years. Further, the market has changed. The days of integrated amps being usable for 40/50 years are gone. They are filled now with digital electronics - which is driven obsolete by changes in standards and requirements in typically much less than 10 years.

(How many 10 year old AVRs are any use now for modern AV program material?)

That’s okay by me for things in the $300-400 range, recyclable plastic boxes. But for people spending multi-thousands, I’d recommend caution. I wouldn’t describe myself as a greenie, but I’m upset at refrigerators that are dead and unrepairable in seven years.

The landfill bulk of disposable stuff bothers me. I can see a ten year lifespan for small boxes, but get queasy at 10 years for speakers. I don’t own any speakers less than 25 years old.

 

[copperblue]

Is whiskering really a problem with consumer electronics operated within domestic environments?

 

[Doodski]

Is whiskering really a problem with consumer electronics operated within domestic environments?

It is a phenomenon that happens with the metals having immense pressure such that they eject a whisker. Those metals are used in pretty much all electronics so anything is possible. I have repaired mystery repairs where I can't figure out the fault so I go to troubleshooting mode and clean the PCB with a toothbrush and isopropyl alcohol and voila the device works again and upon testing no further faults found and the customers where happy as clams and never came back for the 90 day warranty.

 

[theREALdotnet]

That’s okay by me for things in the $300-400 range, recyclable plastic boxes. But for people spending multi-thousands, I’d recommend caution.

Absolutely. An equally relevant question one should ask is, for how long is this going to be relevant? I’d hate to be the guy who spent big bucks on a Nakamichi Dragon just before the demise (collapse?) of the compact cassette market. Or on an Oppo 205 just before 4K streaming took off.

 

[Bjorn]

That’s okay by me for things in the $300-400 range, recyclable plastic boxes. But for people spending multi-thousands,

I think the problem is rather that most who buy class D amps aren't spending multi-thousands.

They are looking for the cheapest deal in the market. And these are generally built with chassis of thin plates and modules placed at the bottom. There's no serious cooling of components, thus they will not last long under various conditions.

 

[copperblue]

It is a phenomenon that happens with the metals having immense pressure such that they eject a whisker. Those metals are used in pretty much all electronics so anything is possible. I have repaired mystery repairs where I can't figure out the fault so I go to troubleshooting mode and clean the PCB with a toothbrush and isopropyl alcohol and voila the device works again and upon testing no further faults found and the customers where happy as clams and never came back for the 90 day warranty.

Appreciate the insight. I put it out as a rhetorical device; long thread. It is not something I could reasonably expect to disable my 26 y/o Technics turntable one guesses. Anecdotally and on topic, if my NORD integrated Class D dies, Colin's workshop is an easy 90 minutes drive from my house...

 

[DonH56]

There are very easy to apply coatings for electronics now, that don't even need masking the contacts. See link below and video where they coat a raspberry pi, it is impressive. I am even thinking of trying them in my diy projects that use fans, to protect from dust (take my comment with a grain of salt, I have not use them yet, but i have access to equipment to do it safely)

https://www.3m.com/3M/en_US/p/d/b5005005017/

I do not believe that is a true conformal coating used for high-rel (air, ship, space) applications but rather the typical coating used for consumer or high-rel gear not needing to meet more stringent ratings for harsh environments. But I am not sure, been far too long, do you know off-hand? The conformal coatings I had to deal with in the past were much more difficult to apply (and rework) and created a much harder, thicker coating.

For many years exemptions were allowed for lead-free solder for medical and high-rel military and related products. Those exemptions were due to expire a few years ago, but I have been out of that world for about a decade, so have no idea what happened or what is required now.

Whiskers (tin, for lead-free solder, but other metals like Zn also create whiskers) are a problem for anything, not just electronics, though might be more a problem for electronics since they can create leakage paths and shorts affecting performance (to say the least). Last I heard the fundamental mechanism was still being debated, but it happens under normal conditions and over time. They do not shoot out but grow slowly (usually) over time. There are other problems with lead-free solder, such as voids created and expanding over time that reduce current capacity and increase resistance, but whiskers and good adhesion are typically cited as problems for consumer products with which I have dealt. It takes good cleaning and higher temperatures for lead-free solder to adhere, and even a good joint can exhibits voids (as well as whiskers) over time.

 

[Doodski]

my 26 y/o Technics turntable

Nice. I have had Technics turntables and had a nice one from the upper end of Technics. What turntable do you have?

if my NORD integrated Class D dies, Colin's workshop is an easy 90 minutes drive from my house...

Yes, a decent repair person could trouble shoot all the external and internal but when it comes to the PCB and circuitry it might get a bit hairy and parts might not be handy.

 

[Petrushka]

I reused computer cases for many years,

I do not believe that is a true conformal coating used for high-rel (air, ship, space) applications but rather the typical coating used for consumer or high-rel gear not needing to meet more stringent ratings for harsh environments. But I am not sure, been far too long, do you know off-hand? The conformal coatings I had to deal with in the past were much more difficult to apply (and rework) and created a much harder, thicker coating.

For many years exemptions were allowed for lead-free solder for medical and high-rel military and related products. Those exemptions were due to expire a few years ago, but I have been out of that world for about a decade, so have no idea what happened or what is required now.

Whiskers (tin, for lead-free solder, but other metals like Zn also create whiskers) are a problem for anything, not just electronics, though might be more a problem for electronics since they can create leakage paths and shorts affecting performance (to say the least). Last I heard the fundamental mechanism was still being debated, but it happens under normal conditions and over time. They do not shoot out but grow slowly (usually) over time. There are other problems with lead-free solder, such as voids created and expanding over time that reduce current capacity and increase resistance, but whiskers and good adhesion are typically cited as problems for consumer products with which I have dealt. It takes good cleaning and higher temperatures for lead-free solder to adhere, and even a good joint can exhibits voids (as well as whiskers) over time.

the smaller the components, the greater the problem. I can see surface mount chips getting shorted out much more quickly than TTL stuff. Modern stuff is more reliable in the short run.

I have this vision of things like streaming devices having standardized mounts and connectors, so the circuit boards could be replaced or upgraded by consumers. Worked for computers.

 

[Doodski]

I can see surface mount chips getting shorted out much more quickly than TTL stuff.

I am of the opinion that the tinned leads on such a thing like say DIP ICs could create whiskers too.

 

[DonH56]

the smaller the components, the greater the problem. I can see surface mount chips getting shorted out much more quickly than TTL stuff. Modern stuff is more reliable in the short run.

Of course, and the stuff I worked with included a lot of SMT components, it wasn't quite the dinosaur age despite the rumors... The higher heat required for wave soldering lead-free components was also an issue in some cases, and required a different temperature profile. I designed mainly ICs, but often enough had to design the test boards and ultimately higher-level products using those ICs. ICs have their own whiskering/sintering problems, natch.