Marshall MBC115 15 inch speaker lump

[N_Cook]

For 250 quid you'd expect some engineering. Just as well problem made
itself known at practise power levels.
Large coil and 15W dropper on pcb which is only held to the mounting
plate by the longish speakon and 1/4 inch socket pins. Bad enough with
proper solder but a definite no-no with PbF, vibrating in a box.
Wired-in 0.25 socket will go back in there and punched pads of woven
copper mesh in the other usual suspect remade-solder joints.
Could cut electrically isolated areas on the pcb and 2 little brackets
but I think I'll give hot hot-melt a go. Rough,as possible, grind off
the black paint and some undercut grind gouges into the steel as well .
Then heat the plate prior to first run of hot-melt , gives very good
keying that way. Then normal glooping of hot-melt to bind together to
the pcb.

 

[amdx]

On 6/7/2014 11:37 AM, N_Cook wrote:

For 250 quid you'd expect some engineering. Just as well problem made
itself known at practice power levels.

Well, it seems you have a problem with the quality of your speaker.

> Large coil

Are you saying it has a large voice coil?

and 15W dropper on pcb

What is a dropper?

pcb which is only held to the mounting
plate by the longish speakon

What is a speakon?

and 1/4 inch socket pins. Bad enough with
proper solder but a definite no-no with PbF,

What is PBF? Oh, lead free solder or very low lead.

vibrating in a box.
Wired-in 0.25 socket will go back in there and punched pads of woven
copper mesh in the other usual suspect remade-solder joints.

Huh?

Could cut electrically isolated areas on the pcb and 2 little brackets
but I think I'll give hot hot-melt a go. Rough,as possible, grind off
the black paint and some undercut grind gouges into the steel as well .
Then heat the plate prior to first run of hot-melt , gives very good
keying that way. Then normal glooping of hot-melt to bind together to
the pcb.

I think heating the plate is good.

Mikek


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[N_Cook]

Next time remove the bar code label, its plastic , not paper like the
RoHS and laughable QC ones.
Marked the exclusion area on the plate and pock-marked with a dozen
undercut gouges with a diabolo ended cintride bit in a "dremmel", then
ground off the paint in the relevant area. Hold the plate over a surface
with 4 ptfe feed-through insulator/pins. Blob of water on the plate and
heat with hot air until the blob has evaporated, then apply hotmelt.
You cannot pick it off with a fingernail, when cool, even picking off
with a dart point is difficult. Fit the bits and hotmelt a bridge-over
fillet. 2 more cable ties around the 1 looose cable tie.
Holes through the pcb and silicone rubber sleeving around the ceramic R,
and reinforced resoldering on the usual suspects. And of course wired in
a replacement quarter incher, before hotmelting . The archives are full
of people annoyed by the lack of the "designed,engineered and quality
conrolled by Marshall" printed on the plate of these and similar big boxes

 

[dave]

On 06/07/2014 10:05 AM, amdx wrote:

On 6/7/2014 11:37 AM, N_Cook wrote:
For 250 quid you'd expect some engineering. Just as well problem made
itself known at practice power levels.

Well, it seems you have a problem with the quality of your speaker.

Large coil

Are you saying it has a large voice coil?

and 15W dropper on pcb

What is a dropper?

pcb which is only held to the mounting
plate by the longish speakon

What is a speakon?

A 4 conductor Neutrik power connector that shields humans from exposed
power amp voltages. Comes in 2 sizes NL4 NL8.

 

[N_Cook]

On 09/06/2014 15:07, dave wrote:

On 06/07/2014 10:05 AM, amdx wrote:
On 6/7/2014 11:37 AM, N_Cook wrote:
For 250 quid you'd expect some engineering. Just as well problem made
itself known at practice power levels.

Well, it seems you have a problem with the quality of your speaker.

Large coil

Are you saying it has a large voice coil?

and 15W dropper on pcb

What is a dropper?

pcb which is only held to the mounting
plate by the longish speakon

What is a speakon?


A 4 conductor Neutrik power connector that shields humans from exposed
power amp voltages. Comes in 2 sizes NL4 NL8.

I would have said the primary justification was greater contact areas
for both voltage and current, and even if anything was to heat up
inside, far less likely than 1/4 inch plug to go short inside the barrel
(from the conducted heat initiated in the socket)