Rumble 200 turned out to be eggshell fragile

[tom dicus]

OP:



talk talk talk Later:


Story changed. Looks like what hit the back reached around the chassis and fractured a separate PCB on the front of the head. That would be really interesting to see!

Until then, no pic, no magic damage. I'm got a few posts out on the flat earth forum also.

THE EARTHS NOT FLAT!!!??? Crap. 6 years of college down the drain.

 

[Mike Whitfield]

THE EARTHS NOT FLAT!!!??? Crap. 6 years of college down the drain.

Of course it’s flat. They can’t be wrong, they’ve got members around the world.

Wait . . .

 

[DanGR]

My tech IS the regional Fender guy, Andy. Mike Fink is licensed by a dozen+ companies, and is the tech of record in the region for most of them. The motherboard is actually cracked, so this is not fixable, only replaceable, and at near 1/2 the cost of the amp. I'm going ahead with the frankensteining, not sure what we will load it with yet. Regardless of speaker, it will be getting a Shuttle 6.0 attached to the top of it. Pending tweaking, this will result in an 8ohm, 300w 115 combo that will handle an extension cab. This is a configuration that has been lacking in the market, and I've been saying for almost 2 decades: Build an ultra-light 212 combo with a head that will dish at least 800w at 4ohms with an extension cab, and you will win the amp combo war. Seriously, imagine one of your old GB 212s with a little weight shaved off, and one of your old Shuttle heads bolted to the top? Fender seemed to be heading for this, but instead of a 15 or two 12s, they loaded the rumble 500 with 10s. It sounds like an angry toaster. GK came closer, but no extension cab option.

1,000 watts at 4 ohms, 600 at 8. The Kappalite 12LF sounds like most 15's. Total weight 44 lbs.

 

[seamonkey]

THE EARTHS NOT FLAT!!!??? Crap. 6 years of college down the drain.

This actually illustrates why people are always flying off the flat earth:

 

[tom dicus]

Of course it’s flat. They can’t be wrong, they’ve got members around the world.

Wait . . .

Now THATS funny!

 

[Mike Whitfield]

This actually illustrates why people are always flying off the flat earth:

Holy Batcave! Meanwhile back in the states, snowflakes are suing merely for witnessing such an unsafe space.

 

[agedhorse]

This is why Traynor amps are generally well-regarded; they were designed by a guy who cut his teeth repairing amps.

I've got ~40 years designing and repairing stuff for the touring industry as well as being an active part of the touring industry. I'm still feeling Sunday night's load-out, 8 systems sitting in the truck waiting to be unloaded.

OP: Sorry to hear about this -- I'm guessing that to save on costs, Fender went with a low-cost multi-layer design, more reminiscent of what you'd find inside a Raspberry Pi than an electronic appliance designed to withstand the rigours of touring. It sucks, but ultimately, it comes down to the fact that there are no bargains anymore: You sometimes get what you pay for, but never more than what you pay.

No, this is not correct. There are no multi-layered boards used in these products. The only part of some Rumble products that use multilayered boards are the IcePower module (which IIRC is 4 layer and is anything but a low cost design)

See, I learn something every time @agedhorse posts. His subsequent posts provide more food for thought.

I should point out that the example I used (power jacks on laptops) tend to break a lot from moderate impacts on the plug connected to the jack. However, I'm not convinced that laptop manufacturers provide what he would consider to be a "high quality" jack to board connection.

Laptops generally use floating jacks, the jack is not fixed to the chassis. This means that when the jack takes a bump, the force is transmitted directly to the PCB and none of the force is restrained by the chassis. It's worse because that type of connector provides a fair amount of leverage too.

Of course it’s true. If the jack is mounted to the PCB, then an impact causes an impulse straight into the PCB, less only the energy dissipated in deforming the materials. If the jack is not mounted to the PCB, then the impact can only move the whole amplifier and the only force on the PCB can be from its own mass’ inertia resisting the motion of the amplifier. This is also the entire rationale behind shock mounts; if the physics weren’t sound, everything would simply be hard bolted to its case. The PCB-mounted jack is a worst case version of hard mounting too, since the impact is pushing into the board while its mounts are trying to keep it in place. Rather than suffering a bending moment from its own mass, the PCB is suffering a bending moment caused by two fixed supports with a point load somewhere in the middle.

Every material, no matter how brittle, has a non-plastic deformation zone. Within that zone, the jack moves into the PCB, introducing a bending moment, when the jack is impacted. In the plastic zone, the material deforms as within the non-plastic deformation zone, again introducing a bending moment. There’s certainly a difference in how much of the impulse is dissipated, but both cause flexing in the PCB. This is why a sturdier PCB helps avoid breakage; it take more energy without breaking.

Adit: For those feeling bumfuzzled, plastic deformation is when a material deforms without returning to its original shape. Elastic or non-plastic deformation is when a material deforms, but returns to its original shape. Strike the jack and it moves inward, then springs back; this is elastic deformation. Strike it sufficiently harder and it moves inward, but the metal and perhaps the cabinet don’t fully return to their original shape; this is plastic deformation. Everyone here understands how this works, even if you don’t know the terminology. I promise you, this is much simpler than the music theory you know. In fact, the physics of cabinet structural design are quite simple. The difficulty lies not in the physics, but in formulating likely impulses (e.g. forces) and striking a balance between mass, construction and cost.

No Mike, there is no relative motion between the jack and the PCB because the jack is solidly attached to the chassis and in most cases the PCB itself floats or is held by adjacent parts attachments to the chassis. This is all part of the "design for impact survival" process. It's quite easy to calculate and/or test for elastic displacement and the design is based around this. There is enough range of motion within the assembly, but different PCB materials have different ranges. I don't use paper-phenolic PCB laminate, but it has less range of motion than FR-4 (fiberglass-epoxy) laminates (which are VERY tough and abuse resistant, especially when double sided with plated holes)

Where problems occur is when an impact is hard enough to deform the sheet metal, at this point it's about 50%-50% that the part itself breaks rather than anything to do with the PCB.

I've been designing gear for a long time, that's what I do as an engineer and I simply haven't had the issues that you accuse these methods of having. Not a sample size of a few units, but tens of thousands. I do know what I am talking about.

Agreed, but in this case he’s simply wrong. If an impact on the jack didn’t directly transmit force into the PCB, then an impact on the jack would have an equal chance to break any PCB in the laptop. Instead, it almost always breaks the PCB onto which the jack is attached.

No Mike, you are missing the fact that in a laptop, the jack is not attached to the chassis (jack floating, PCB rigidly fixed). This is not a method of assembly that most quality amps use.

Here's an example of a PCB mounted jack where the jack is chassis mounted and the PCB is fully floating. You could deform the sheet metal beyond any reasonable impact and there would be ZERO difference between wires and a PCB.

 

[Mike Whitfield]

I've got ~40 years designing and repairing stuff for the touring industry as well as being an active part of the touring industry. I'm still feeling Sunday night's load-out, 8 systems sitting in the truck waiting to be unloaded.



No, this is not correct. There are no multi-layered boards used in these products. The only part of some Rumble products that use multilayered boards are the IcePower module (which IIRC is 4 layer and is anything but a low cost design)



Laptops generally use floating jacks, the jack is not fixed to the chassis. This means that when the jack takes a bump, the force is transmitted directly to the PCB and none of the force is restrained by the chassis. It's worse because that type of connector provides a fair amount of leverage too.



No Mike, there is no relative motion between the jack and the PCB because the jack is solidly attached to the chassis and in most cases the PCB itself floats or is held by adjacent parts attachments to the chassis. This is all part of the "design for impact survival" process. It's quite easy to calculate and/or test for elastic displacement and the design is based around this. There is enough range of motion within the assembly, but different PCB materials have different ranges. I don't use paper-phenolic PCB laminate, but it has less range of motion than FR-4 (fiberglass-epoxy) laminates (which are VERY tough and abuse resistant, especially when double sided with plated holes)

Where problems occur is when an impact is hard enough to deform the sheet metal, at this point it's about 50%-50% that the part itself breaks rather than anything to do with the PCB.

I've been designing gear for a long time, that's what I do as an engineer and I simply haven't had the issues that you accuse these methods of having. Not a sample size of a few units, but tens of thousands. I do know what I am talking about.



No Mike, you are missing the fact that in a laptop, the jack is not attached to the chassis (jack floating, PCB rigidly fixed). This is not a method of assembly that most quality amps use.

Here's an example of a PCB mounted jack where the jack is chassis mounted and the PCB is fully floating. You could deform the sheet metal beyond any reasonable impact and there would be ZERO difference between wires and a PCB.
View attachment 3417645

If that were the board in question, I’d agree completely. Here we’re dealing with a long I/O board which isn’t attached to a single jack, but multiple jacks. When an impulse is introduced to one jack, it travels inward - how far depends on whether the sheet metal and/or cabinet are deformed in the elastic region or the plastic region. As that jack travels inward, it necessarily moves the PCB with it. However, the PCB is secured at multiple points, which either don’t move inward or move inward less, so a bending moment is introduced into the PCB and being brittle, it cracks. Only if the PCB is attached only to a single jack and has neglible mass (compared to its strength) would your statement be true.

Doesn’t much matter as it appears the pre-amp board is actually the one that failed. Unless I’m misremembering, the pre-amp board isn’t directly connected to any exterior ports.

 

[agedhorse]

I'm not sure we really know what happened to the OP's amp, but eggshell fragile it's not.

Here's another PCB, plenty of jacks and switches (pardon the rotated photo). Have never seen one broken or heard of one breaking ever. Designed right, with appropriate parts and materials, the grouping of actually reinforces itself much like a truss's elements reinforce themselves. Of course because there's a 5 year warranty on the products I design, I have plenty of analysis and plenty of verification/testing data.

 

[Mike Whitfield]

I'm not sure we really know what happened to the OP's amp, but eggshell fragile it's not.

Here's another PCB, plenty of jacks and switches (pardon the rotated photo). Have never seen one broken or heard of one breaking ever. Designed right, with appropriate parts and materials, the grouping of actually reinforces itself much like a truss's elements reinforce themselves. Of course because there's a 5 year warranty on the products I design, I have plenty of analysis and plenty of verification/testing data.

View attachment 3417663

I wouldn’t disagree. It’s possible to design a common plane PCB with replaceable jacks using offset connectors whose wire can’t transmit enough force to break the particular PCB used - one form of the connectors I referenced. Cheaper PCBs have the jacks soldered directly to the board, only replaceable with desoldering. It’s possible to use a PCB strong enough to withstand that maximum impulse as well, but don’t forget we were told that an impact to a jack HAD broken the PCB; that would mean the PCB wasn’t designed strongly enough to resist the particular impact’s impulse. It now appears that something else entirely actually happened. Also, please note that a sufficient impulse to one chord of a truss along that chord’s axis can easily take a truss into plastic deformation if sufficiently high.

 

[Koshchei]

I've got ~40 years designing and repairing stuff for the touring industry as well as being an active part of the touring industry. I'm still feeling Sunday night's load-out, 8 systems sitting in the truck waiting to be unloaded.



No, this is not correct. There are no multi-layered boards used in these products. The only part of some Rumble products that use multilayered boards are the IcePower module (which IIRC is 4 layer and is anything but a low cost design)


Here's an example of a PCB mounted jack where the jack is chassis mounted and the PCB is fully floating. You could deform the sheet metal beyond any reasonable impact and there would be ZERO difference between wires and a PCB.
View attachment 3417645

Thanks for the correction! And yeah - the ICE boards are very high quality. I've had my SB500 apart a few times, and it's built VERY well.

Apple laptops seem to be the only "sort-of" exception to the floating port issue. While they are technically floating, the chassis forms the outer mating surface and seems to be thick enough to resist any cantilever action from the plugged in accessory. Of course, they are rather pricey, so sweating the details is something they SHOULD be doing.

 

[agedhorse]

I wouldn’t disagree. It’s possible to design a common plane PCB with replaceable jacks using offset connectors whose wire can’t transmit enough force to break the particular PCB used - one form of the connectors I referenced. Cheaper PCBs have the jacks soldered directly to the board, only replaceable with desoldering. It’s possible to use a PCB strong enough to withstand that maximum impulse as well, but don’t forget we were told that an impact to a jack HAD broken the PCB; that would mean the PCB wasn’t designed strongly enough to resist the particular impact’s impulse. It now appears that something else entirely actually happened. Also, please note that a sufficient impulse to one chord of a truss along that chord’s axis can easily take a truss into plastic deformation if sufficiently high.

I have never had this happen with FR-4 PCB laminate, played holes and the quality of jack that I use. Done properly it's amazingly robust.

In fact, this is exactly how touring analog consoles were built, including all pots and switches (both vertical and horizontal format parts) and again, for quality parts and materials, not an issue.

It's possible to design something that will break, but that's either because the design is "cheap", or because the designer didn't understand structures.

 

[Lowandfat]

I stand corrected, my amp obviously received a blow from Thor's hammer that rendered it dead by barely moving the sheet metal around the jack. I suggest all of you who are denying Fincks assessment and Rolland Brunet's assessment that it is dead fly here and tell them you think they are dumb to their faces. As for not posting recently, there is a thing called busy, you armchair life coaches should try it some time. The point of the thread was not who thinks Fender shouldn't be questioned, or whether or not the amp is fixable. The point was "I am doing a little frankenrig building with the help of some friends. Whaddya think?" That's it. The head swap is coming along nicely, Rolland even flew out the horn switch assembly to a new spot. Anybody who swears the rumble amp is worth fixing can send me $150 and they can have it to repair at their leisure.

 

[Lowandfat]

By the very minor cosmetic damage, it APPEARED the blow was rather minor, and I was pissed to find out it was silent. Sue me. As QUALIFIED PEOPLE dug into it and I learned more, I shared that info here. Forgive me for being forthright as I learned new info. Again, any of you want to call Mike Finck dumb/lazy feel free to ring him up. Good grief.

 

[Giffro]

Dunno why I feel like i've been told off by someone I was trying to help. I must try to stop trying to help the hopeless lol. Live and learn as they say.

 

[SoulReflection]

Then there is this saying in my signature:

"I will not even try to make sense out of nonsense"...

 

[Mike Whitfield]

I stand corrected, my amp obviously received a blow from Thor's hammer that rendered it dead by barely moving the sheet metal around the jack. I suggest all of you who are denying Fincks assessment and Rolland Brunet's assessment that it is dead fly here and tell them you think they are dumb to their faces. As for not posting recently, there is a thing called busy, you armchair life coaches should try it some time. The point of the thread was not who thinks Fender shouldn't be questioned, or whether or not the amp is fixable. The point was "I am doing a little frankenrig building with the help of some friends. Whaddya think?" That's it. The head swap is coming along nicely, Rolland even flew out the horn switch assembly to a new spot. Anybody who swears the rumble amp is worth fixing can send me $150 and they can have it to repair at their leisure.

Chill, man. It's the Internet - can't take these things personally, they often read more harshly than intended. Especially from people who are busy and can't easily take the time to frame things diplomatically. Personally I've been on forums since around 1981 and I've developed rhino hide, so when someone thinks I'm an idiot I'm happy for them to tell me so. (Just like real life!) Don't mean nothing, and sometimes it's helped me stop being an idiot. Of course, other times I've persevered.

Glad things are working out to your liking; since the Rumble wasn't really working out well for your particular application, you made a smart choice.

 

[Gravedigger Dav]

You are obviously and rightly upset that you motherboard broke. Your situation is a rare anomaly that really doesn't reflect on the quality of Rumble amps. I own several Rumble amps and have had no such issues. Was your 200 not still under warranty?

 

[Mike Whitfield]

You are obviously and rightly upset that you motherboard broke. Your situation is a rare anomaly that really doesn't reflect on the quality of Rumble amps. I own several Rumble amps and have had no such issues. Was your 200 not still under warranty?

Would any amp be warranted against breakage from a blow that leaves permanent deformation? I agree that it's a bizarre anomaly that a preamp board physically snaps from an external impact to a jack on a different board, especially an impact that leaves so little external damage. I just think of warranties (perhaps erroneously!) as something covering faults in components absent any physical damage, which are presumed to be components that fail prematurely.

 

[Gravedigger Dav]

Would any amp be warranted against breakage from a blow that leaves permanent deformation?

I don't know, but it wouldn't hurt to ask. If the blow were that light, could it be the board was already defective and the bump finished the break?