1. Home
  2. Electronics Repair
  3. Marshall MBC115 15 inch speaker lump

Marshall MBC115 15 inch speaker lump

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.

Reply to
N_Cook
Loading thread data ...

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

Are you saying it has a large voice coil?

and 15W dropper on pcb

What is a dropper?

What is a speakon?

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

Huh?

I think heating the plate is good.

Mikek

--
This email is free from viruses and malware because avast! Antivirus protection is active. 
http://www.avast.com
Reply to
amdx

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

Reply to
N_Cook

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

Reply to
dave

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)

Reply to
N_Cook

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.