Modifying Weber Mass 100

[Boy Howdy]

Curious: Does the "speaker motor" vibrate in use?

Not that I've ever been able to observe. I seem to recall debate about whether or not it has any effect on the sound/performance at all.

[Helmholtz]

Not that I've ever been able to observe. I seem to recall debate about whether or not it has any effect on the sound/performance at all.

If it's blocked, it no longer acts as a motor but as a (frequency dependent) small value inductor.

[g1]

Hmm, could sworn . . . .

There may be minimums for special order/non-stocked parts, and minimums to qualify for free shipping. That may have been what you saw.

I could possibly draw one up, but it may be a while before I could get to it, and I wouldn't have any way to get it online (that I can think of at the moment anyway.).

You can attach the same way you did with the pictures, or use the 'upload attachments' button below the text box.

[Boy Howdy]

Yeah, I thought of that five minutes later.

And as luck would have it, I drew it up last night. It's not totally complete. I'm not familiar with the internal configuration of the ohmage selector. So I just drew lines pointing to it, rather than connected to it. Other than that it should be okay.

Anybody willing to take my photo of the hand drawn schematic and put it in good order?

I didn't bother with the line out circuit, by the way.

[Boy Howdy]

Okay, well here it is. Again, I didn't know how to draw the connections to the impedance selector.

[Boy Howdy]

Oddly, the rheostat is a 25 ohm (2 amp) unit. The ceramic resistors have no markings on them at all, and I'm getting strange readings on my meter: 4 ohms for the bottom pair, and 6.5 for the upper ones (all four together).

[Boy Howdy]

So take a look at that treble boost circuit. It just bypasses everything. Am I not right about that? Any ideas on how to reduce the treble? Kinda looks like all I'd have to do is stick some resistance between the cap and switch. And leave everything else as is.

Has anybody got any thoughts on how to complete the schematic, how to draw the connections to the impedance selector? On the actual unit, the two lines I drew pointing to the top of the selector connect at the top in reality. The two lines pointing to the bottom connect in reality to the bottom of the selector.

[Chuck H]

Ok... Look at the schematic you've drawn. Provided it is accurate the treble boost mode simultaneously implements a capacitor AND a resistance for it to bypass. In the un-treble boosted position the switch shorts the parallel resistors.

I'm actually thinking the schematic must be wrong because all that would be needed for a 2-way selection as shown would be to simply short the resistors. No need to take the capacitor in and out. That doesn't mean your unit isn't wired as shown. Just an observation. And,.. But,..

If it IS wired as shown you could achieve a lower level of boosted treble by REDUCING resistance at the parallel resistors (circled in red, perhaps replace them with the rheostat depending on value) rather than adding resistance in series with the capacitor.

EDIT: Note: if you were to , say, half the total resistance of the parallel resistors in question you would also need to double the value of the capacitor to maintain the same frequency being boosted. That is to say, the boosted frequency would be the same but less boosted. Which I took to be your goal. This assessment isn't entirely accurate because there are other circuits within the bypassed circuit. So this solution is just an approximation, but should probably prove close enough. This, provided the schematic IS accurate.

[Boy Howdy]

I spent some time studying the schematic last night. It looks to me like I might just be able to get what I want by simply bridging the right and center lugs on the treble boost switch. That would give me the original boosted option, and the unboosted original option with the treble cap added to it. I never use this thing in the un-boosted position anyway, so I wouldn't be losing anything. Anybody see any reason why I shouldn't try it?

[Boy Howdy]

[QUOTE=Chuck H;n948700]Ok... Look at the schematic you've drawn. Provided it is accurate the treble boost mode simultaneously implements a capacitor AND a resistance for it to bypass. In the un-treble boosted position the switch shorts the parallel resistors.

I'm actually thinking the schematic must be wrong because all that would be needed for a 2-way selection as shown would be to simply short the resistors. No need to take the capacitor in and out. That doesn't mean your unit isn't wired as shown. Just an observation.



I saw this post after I posted the question above. Anyway . . . I will study it a bit before commenting, except for the following. I checked the schematic several times, but of course there is always the possibility that made a mistake. But I will check it again, and probably several more times before I actually make any changes, if any.

I think what they're doing with that switch is making it do double duty as a cost saving measure. I've been looking at four different Mass schematics, all different. In some of the units they have a separate range switch that brings in and out one or two extra resistors. I don't at present know what this range switch does. I imagine it decreases further the volume. [Yes, I just confirmed this at the Weber site.]

See below:


WeberMASS100.gif (1200×783) (freestompboxes.org)

[Boy Howdy]

I double checked the relevant section. The drawing is correct.

[Boy Howdy]

Okay, I think I see what you're saying about the switch. But with a two-position switch you would get the treble boost with both positions. That's what I'm actually proposing to try by bridging the two rightmost terminals. Apparently, Weber deemed the un-boosted option a desirable one, and maybe it is at high volume.

Edit: Or you'd get the stock no boost option and/or the boost before the resistors. Which may be desirable. Who knows?

[Chuck H]

Please do this:

With the "bypass" switch for the attenuation set to bypass and the treble boost switch set to boost you should be able to measure the net value of the circled resistors in circuit.

What is the value of those parallel resistors?

[Chuck H]

Hold up!.. The posted schematic IS wrong. More later. Off to work for now though.

[Boy Howdy]

Please do this:

With the "bypass" switch for the attenuation set to bypass and the treble boost switch set to boost you should be able to measure the net value of the circled resistors in circuit.

What is the value of those parallel resistors?

Survey says! 4.2 ohms.