Are Class D's Disposable?

[agedhorse]

On a chance Andy do you happen to know what the Quilter BB 800 uses for a fan?

Nope.

 

[Old Garage-Bander]

"Truly qualified techs" arent hanging out at many places these days. Not every company has such a wise agedhorse hanging about, much less local music stores. I had issues with my dual rectifier, and i had to ship it to Mesa after both local techs couldnt fix it (one was Mesa certified or whatever). Most places dont have access to good techs, and lesser manufactures dont offer the same level of support, ie, the amp designer personally fixing damaged units. While I agree with you, Andy, for many of these cheaper heads a replacement is a better option. Simple for you isnt simple for us.

Finding qualified techs these days is getting harder in many fields. I recently retired as a broadcast technician (Install, maintain, repair radio station equipment from studio to transmitter, design those systems and interface all manner of equipment to work together.) I spent many of my last years being the only tech they had where I worked. When I announced my retirement they went into scramble-mode to find someone to cover what I did. I helped them as much as I could but as far as I know, they still haven't found anyone.

The real issue is that most people with technical aspirations will go into I.T., a field that didn't even exist when I was starting out. I.T. jobs, typically are 9 - 5, Mon. - Fri. The pay and opportunities for advancement are better. I.T. is also pulling from other fields, not just broadcasting. I don't know how this impacts amp techs, but i can't imagine someone starting a technology career today would be inticed to go there any more than to my field.

In broadcasting, you're essentially on call, 24/7/365 and your a non-person until the station is off the air. And that's a rare occurrence if the tech is doing his job well. I retired at 70, but spent the last two years doing whatever I could to get things in the best shape possible, so the next guy could hopefully ease into it without having to put out fires.
Even though I provided daily attention to everything, I figured they have a minimum of six months of ignoring it all before they hit a snag.

So finding a qualified, experienced technician these days is tough. Be it to keep a radio station on the air, or to fix your amp before the next gig.

 

[Old Garage-Bander]

This is a confusing sentence. I think you're conflating solid state versus tube power sections, and the topology (i.e. A, A/B, D, H, etc.). Tubes can be A/B or D, just as solid state can be A/B or D.

Yup. Even just plain old A is a class for audio amps.
If you're wondering where class C went, we broadcasters snatched that up for our transmitters.

 

[Old Garage-Bander]

Of course but the thread is about the reliability of D class amps.

Anybody have any statistics about how non-leaded solder (part of ROHS) impacts reliability?

 

[Old Garage-Bander]

One old gentleman I knew coined what he called the fifty hour rule. “If you get to fifty hours with an electronic device , the next fifty thousand hours are free".

In my world we called it infant mortality.

 

[Old Garage-Bander]

Called the infant mortality rule by the more gruesome of the bunch.

Despicable ME.

 

[Old Garage-Bander]

Which part? I'm genuinely curious... though I think we could spare the thread a dissertation on factors that go into thermal management and design thereof. My background on thermal stuff deals with black body radiation of heat which is a different beast then dealing with thermal management in a gas. I'd have to run numbers on how much surface area is required to dissipate heat generated by some amp running at say, a watt load, and what the thermal conductivity coefficient is through that material... But that's a project for another time.

The regulatory body certs was something I totally didn't think about given I have zero background in consumer hardware engineering.

Do you have any insight on fan life with those environmental factors mentioned above?

Well, sounds like we're getting back into smoking, hairy golfball territory again.

 

[beans-on-toast]

Anybody have any statistics about how non-leaded solder (part of ROHS) impacts reliability?

If done properly, it works well. The problem is, some companies have production issues and solder joints that run hot in use can have problems.

 

[Old Garage-Bander]

If done properly, it works well.

This ^
That pretty much sums up the whole thread.

 

[rutrho]

If done properly, it works well. The problem is, some companies have production issues and solder joints that run hot in use can have problems.

We still use lead solder for space applications, for what its worth.

Well, sounds like we're getting back into smoking, hairy golfball territory again.

That sounds like half of my day job tbh... Making decisions on WAG's.

 

[Snert]

Finding qualified techs these days is getting harder in many fields. I recently retired as a broadcast technician (Install, maintain, repair radio station equipment from studio to transmitter, design those systems and interface all manner of equipment to work together.) I spent many of my last years being the only tech they had where I worked. When I announced my retirement they went into scramble-mode to find someone to cover what I did. I helped them as much as I could but as far as I know, they still haven't found anyone.

The real issue is that most people with technical aspirations will go into I.T., a field that didn't even exist when I was starting out. I.T. jobs, typically are 9 - 5, Mon. - Fri. The pay and opportunities for advancement are better. I.T. is also pulling from other fields, not just broadcasting. I don't know how this impacts amp techs, but i can't imagine someone starting a technology career today would be inticed to go there any more than to my field.

In broadcasting, you're essentially on call, 24/7/365 and your a non-person until the station is off the air. And that's a rare occurrence if the tech is doing his job well. I retired at 70, but spent the last two years doing whatever I could to get things in the best shape possible, so the next guy could hopefully ease into it without having to put out fires.
Even though I provided daily attention to everything, I figured they have a minimum of six months of ignoring it all before they hit a snag.

So finding a qualified, experienced technician these days is tough. Be it to keep a radio station on the air, or to fix your amp before the next gig.

I laughed so hard at this as I know the experience well.
I got out of broadcast a couple of decades ago and the on call 24/7/365 and expected to fix it over the phone instantly with a non technical person on the other end gave me a dose of the s**ts. Mobile phones meaning I was always expected to be in contact, and I was paid a wage, so my work hours were defined. Even when I went far more than the extra mile my work was not appreciated, so I left and I didn't give a stuff.

I gave up fixing gear for musos about a decade later because many musos are a pain to deal with. One of my new neighbours has found out I used to repair gear and in 1 day, I have 3 potential repairs which I don't want. There's no one for a long way around here who can do it.

In my world we called it infant mortality.

Despicable ME.

I first heard the term when I read it in a USAF maintenance document I found in the archives where I worked. It was dated from the 50s. First I recall hearing the bathtub curve too.

We still use lead solder for space applications, for what its worth.

Does it? I recall reading papers some time back where eutectic was used because Pb free tended to grow tendrils in zero G and potentially cause issues.

 

[Old Garage-Bander]

I laughed so hard at this as I know the experience well.
I got out of broadcast a couple of decades ago and the on call 24/7/365 and expected to fix it over the phone instantly with a non technical person on the other end gave me a dose of the s**ts. Mobile phones meaning I was always expected to be in contact, and I was paid a wage, so my work hours were defined. Even when I went far more than the extra mile my work was not appreciated, so I left and I didn't give a stuff.

In spite of all that I really loved what I did. Aside from being past my "sell by" date, I might have hung in a little longer except new management came in and would openly undermine, in front of other staff, the work I did for the station. Made saying adios a little easier.

 

[rutrho]

Does it? I recall reading papers some time back where eutectic was used because Pb free tended to grow tendrils in zero G and potentially cause issues.

Yep, its pretty well documented in this industry, but they're present in a bunch of different terrestrial applications too. From a RoHS perspective, lead free solder is great, but it requires some adjustments in production. I'm not qualified to speak from a consumer production perspective with RoHS processes however.

NASA has a great high level explanation of what they are and factors that contribute to them: Basic Info on Tin Whiskers

 

[beans-on-toast]

We still use lead solder for space applications, for what its worth.

I prefer working with tin-lead-silver solder.

———

Reliability of lead-free solder joints is a concern. Whiskers are an ongoing problem from what I understand.

NASA Goddard Tin Whisker Homepage

 

[Snert]

Yep, its pretty well documented in this industry, but they're present in a bunch of different terrestrial applications too. From a RoHS perspective, lead free solder is great, but it requires some adjustments in production. I'm not qualified to speak from a consumer production perspective with RoHS processes however.

I don't do much consumer design any more, mainly speakers. I've made sure I have a ton of eutectic solder for me, more than enough to last the rest of my life as I hate lead free. Apart from some custom gear and commissions, I'm out of consumer and MI design, just some restos and repairs.

Whiskers! That was the term on the tip of my brain and couldn't find.

 

[agedhorse]

Lead free solder isn't a problem when done right with the geometries that many of us use in this industry. Zero problems from my experience. I started with lead free solder before RoHS came into being required.

There are also alloys that are easy to work with.

 

[baddarryl]

Nope.

Same question for the Walkabout? Fan? Lol

 

[pepj]

I probably have around $1400 in each of my class D and probably that when I bought my SWR new...there or thereabiuts so not especially cheap amps.
One class has 'over heated more than once' which is basically a power reset, annoying but a fail safe.
The other has a fan and I think that has cut out mid gig, activating the power safe.
My old SWR runs super super hot, not fan and has been ultra reliable albeit serviced and repaired when if fell off a stage under power.

I'm finding I'm taking 2 class D's out now...just as well they are small and light.

 

[agedhorse]

Same question for the Walkabout? Fan? Lol

Yes.

I probably have around $1400 in each of my class D and probably that when I bought my SWR new...there or thereabiuts so not especially cheap amps.
One class has 'over heated more than once' which is basically a power reset, annoying but a fail safe.
The other has a fan and I think that has cut out mid gig, activating the power safe.
My old SWR runs super super hot, not fan and has been ultra reliable albeit serviced and repaired when if fell off a stage under power.

I'm finding I'm taking 2 class D's out now...just as well they are small and light.

Yet there are class D amps with a documented history of being reliable and never shutting down. Just putting this in pedspective.

 

[pepj]

Talking of perspective, are you currently working on any non class D amps?