CHAMP ELECTRONICS -" THE VINTAGE VALVE AMP HOSPITAL"

NOTTINGHAM, ENGLAND

 

    SERVICING A MARSHALL VBA 400 AMPLIFIER HEAD

 

 

The Marshall VBA (Valve Bass Amp) 400 is one hell-of-a-mother-' bass amp.

 

 

The 5 inch cooling fan: needed to keep the 8 x 6550 output bottles cool! (or KT88’s).

 

 


 

There were a few faults needing attention on this baby; mainly the duff output transformer!

 

 

Note two of the “Luca (spade) connectors” (W31 & W32) ripped out of the board with over tightening the cable-ties!

 

 

When a VBA 400 is working correctly they are really good. However, though I do like most of the Marshall equipment I’m afraid that the use of this many Luca/spade connectors in an amp of this magnitude is, in time, asking for trouble! Plus the fact that they are crimped & not soldered too! Not one of my favourite Marshall designs!

 

 

 

 

Along with the duff output transformer & a couple of other small issues, I replaced just two kaput 6550’s, re-biased the whole amp, and whoo…….away she went……..Cool!

 

 

The thermal “cut-out” protection switch, mounted on the back panel. Yet another sensible and essential feature for an amp like this!

 

 

 


 

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