Rumble 200 turned out to be eggshell fragile

[bleedingfingers]

First of all tie your load down in your truck or trailer
pack your stuff with care .
Second you get what you pay for and even then sometimes you don't .

I had a Markbass amp go up in smoke from a power surge at a gig
fixing it would have been expensive as they are built with surface mount tech .
and whole section of amp would need replacing .
Not just some caps and resistors .
Many hi end amps are now built this way not just inexpensive ones.

Bought a Mesa D800 after seeing a gut shot and trying it out .
if you want something tough and built to last you gotta do some research and spend some cash .
Plenty of guys on here like the Rumble I guess you just have to take care of them .

 

[Mike Whitfield]

If the jack is solidly connected to the chassis, and the parts are high quality, it's a non-issue. Floating jacks can't be assembled as you wish no matter what they are attached to (PCB or wires)

Fender does not float the jacks in this model.

The idea is that if the jacks are solidly mounted to the cabinet but wired using conductors, any impact cannot be transmitted directly to the PCB. Thus the I/O board gets no more impulse energy than any other internal part. I have no problem with your assertion that better quality boards and/or mounting is the smarter design. My own design experience in manufacturing has been industrial manufacturing equipment and mobile recovery & towing equipment where Really hard knocks are to be expected and ruggedness is a more important consideration than cost. (You should see my vacuum cleaner; it had a 5 hp three phase motor.)

 

[Mike Whitfield]

This is exactly what I think. I've seen terminal damage to circuit boards in computers and other devices because economics mandated soldering an external connector of some kind directly to the PC board. In laptops, one of the most common failures is having the power jack break loose from the board because something bumped up against the power connector and its leverage from the impact cracked the board.

It clearly would be more durable and avoid these problems if the exterior connectors were routed to the board via wires, creating a flexible connection which wouldn't be subject to impacts against the external connection jack. In fact, that would make external jacks serviceable independent of the board. The difference? Human labor that would be required to manipulate those small wires and do the soldering. Whether that would also increase the failure rate in bad solder joints, I'm not sure.

I'm not going to throw stones at Fender based on this design. It's common practice in industry, and it's part of the reason Fender can sell those amps at their price point. If I were buying a $2,000 amp I'd expect something different, but that's not the part of the market we're discussing.

Exactly my thoughts, just better stated.

 

[agedhorse]

The idea is that if the jacks are solidly mounted to the cabinet but wired using conductors, any impact cannot be transmitted directly to the PCB. Thus the I/O board gets no more impulse energy than any other internal part. I have no problem with your assertion that better quality boards and/or mounting is the smarter design. My own design experience in manufacturing has been industrial manufacturing equipment and mobile recovery & towing equipment where Really hard knocks are to be expected and ruggedness is a more important consideration than cost. (You should see my vacuum cleaner; it had a 5 hp three phase motor.)

To be clear, there is no difference if the jacks are solidly mounted to the chassis and use a PCB or wires for the connection, there's still no relative motion... until the impact is hard enough to bend the sheet metal. At that point it qualifies as abuse from my perspective.

 

[searayus1]

I've had a newer Fender 200 combo (silver grill, not the old black one) for about a year and I get tons of compliments on the tone. And the lightweight! I hope yours was just 'bad luck' cause I love mine and am fixin to get the 210 extension cab. I hope you get some sort of consolation in the end.

 

[Mike Whitfield]

To be clear, there is no difference if the jacks are solidly mounted to the chassis and use a PCB or wires for the connection, there's still no relative motion... until the impact is hard enough to bend the sheet metal. At that point it qualifies as abuse from my perspective.

If the jacks are hard mounted to the PCB, then all the motion of the impulse, plastic deformation and non-plastic alike, gets transmitted directly to the PCB. If the jacks are attached to the case but not hard mounted to the PCB, then that portion of the impulse used up in deforming the materials isn’t transmitted to the PCB, and the balance of the impulse creates an acceleration which is resisted by the entire mass rather than a force transmitted directly into the PCB.

 

[seamonkey]

No pictures - no PCB breakage happened.

 

[tom dicus]

As for the kappalite, I have had a few cabs loaded with them. I'm hoping because the Rumble 200 box is so over-tuned to "produce" low B, it might help soften the barky-ness of the NEO 15s. I am going to rely on my pal Rolland for those calculations. Off to meet him now, will update later.

I'm curious as to why you are replacing the great factory speaker. It seems like a really good speaker. Is it because of the power rating?

 

[tom dicus]

I've had a newer Fender 200 combo (silver grill, not the old black one) for about a year and I get tons of compliments on the tone. And the lightweight! I hope yours was just 'bad luck' cause I love mine and am fixin to get the 210 extension cab. I hope you get some sort of consolation in the end.

I'd suggest you get the 115 extension. It sounds better. I had the 10" extensions but nothing else sounds as good as a matching 15.

 

[agedhorse]

If the jacks are hard mounted to the PCB, then all the motion of the impulse, plastic deformation and non-plastic alike, gets transmitted directly to the PCB. If the jacks are attached to the case but not hard mounted to the PCB, then that portion of the impulse used up in deforming the materials isn’t transmitted to the PCB, and the balance of the impulse creates an acceleration which is resisted by the entire mass rather than a force transmitted directly into the PCB.

Not true, unless the sheet metal deforms, and even then with quality parts damage is rare (unless the deformation is large). If the sheet metal deforms enough to damage the PCB, that's a pretty large impact.

 

[Koshchei]

Techs often see folly that designers overlook. Today I was over at my dad's and he asked me to put away a Crate guitar amp that he had sitting in his shop. When I picked it up, I noticed that it had a level control knob for the line output sticking way out from the back panel, just waiting for something to shear it off.

I thought if I had a hand in designing it, I would have located the control closer to the cabinet edge where it would be better protected and use a low profile knob. However, when the guy was designing this PC board, I doubt he was thinking of such an event taking place.

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

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.

 

[SoulReflection]

One should not let their search for the truth be swayed by unverified/unproven claims, IMHO.

 

[Pilgrim]

If the jack is solidly connected to the chassis, and the parts are high quality, it's a non-issue. Floating jacks can't be assembled as you wish no matter what they are attached to (PCB or wires)

Fender does not float the jacks in this model.

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.

 

[Mike Whitfield]

Not true, unless the sheet metal deforms, and even then with quality parts damage is rare (unless the deformation is large). If the sheet metal deforms enough to damage the PCB, that's a pretty large impact.

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.

 

[Mike Whitfield]

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.

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.

 

[Mike Whitfield]

No pictures - no PCB breakage happened.

Lowandfat said the preamp board was dead. This whole thread may be based on a coincidence, or else it was actually a hellacious impact that broke a solder joint, or else the impact wasn’t on the cabinet output jack. Unless I’m completely crazy.

 

[tom dicus]

Lowandfat said the preamp board was dead. This whole thread may be based on a coincidence, or else it was actually a hellacious impact that broke a solder joint, or else the impact wasn’t on the cabinet output jack. Unless I’m completely crazy.

If you're crazy, count me in. I want to be in your club, if only by default. I never heard so much physics mumbo jumbo in my life. The guys amp fried. Done deal. Fix it or get a new one. But just shut the %^^& up already!

 

[Mike Whitfield]

If you're crazy, count me in. I want to be in your club, if only by default. I never heard so much physics mumbo jumbo in my life. The guys amp fried. Done deal. Fix it or get a new one. But just shut the %^^& up already!

I appreciate the vote of confidence, but this is actually stuff every gigging musician knows. It’s just much easier to break something by directly poking it than by shaking its cabinet, and you all understand that. It’s why you carefully avoid dropping your amps even though your vehicle endures much higher impulses.

 

[tom dicus]

I hope everyone knows I posted in jest! Just trying to add some humor and fun to the physics class!

 

[seamonkey]

Lowandfat said the preamp board was dead. This whole thread may be based on a coincidence, or else it was actually a hellacious impact that broke a solder joint, or else the impact wasn’t on the cabinet output jack. Unless I’m completely crazy.

OP:

A small PA cab slid into the back of my Rumble 200 and BARELY nicked the extension speaker jack. From 5ft you can't even tell it's been touched. Well, that Rumble 200 is now a paperweight. That tiny blow that didn't even cause any cosmetic damage, cracked the freaking board rendering it totally DOA.

talk talk talk Later:

Update, it is the pre-amp board that is shot, power stage seems to be OK. Since its a modular build (sealed box behind it) I can keep the whole amp section "as is" until we see if the experimenting works. No matter what happens now, we can screw it back together and sell it as parts/salvage. Somebody with the need will get a deal, and I won't lose much if anything.

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.