Schematic diagram for Mordaunt-Short MS309-W

[shotokan101]

oops sorry , i forgot to post the manual here it is now..

Did you actually post the manual?

Jim

 

[Roy L]

Re. MS309 W Sub

posting in the hope a few may still be active..

attached photo of the main board of this Amp, seems there is a C1815 has been attached to the heatsink by means of a self-tapper and adhesive, bit heath-robinson! I`ve had the usual cut outs from this amp and notice one of the ribbon cables attached to the leg has come adrift.
Maybe this could be the main problem of my cut-outs?

 

[Mooly]

That transistor looks to be being used for thermal compensation (vbe multiplier) and any lead coming adrift may well cause very high quiescent current. That could cause all sorts of issues up to self destruction of the output stage.

The transistor type should not be critical (general purpose small signal NPN) but the fixing method is appalling.

 

[Roy L]

thanks Mooly, have ordered a couple of these up plus the relays and caps mentioned earlier in the thread,.. they must have been running too hot directly on the board and this was the make-shift fix ! Strange as the rest of the Mordaunt-Short items seem pretty decent quality.

 

[Roy L]

Thanks to Sonics part list the sub is up and working again, seems our old enemy heat is the problem, a few bulging caps and dry solder joints looks the main problem here.

 

[Mooly]

that good to hear. Thanks for the update.