Cornford Hurricane Reverb issue

[mattbreaker]

Howdo everyone, I've recently come into possession of a 2nd hand cornford hurricane, I have re valved it and I have 2 mullard el84's in for the power section, 4 12ax7's EH pre amp drivers, one of those acts as a reverb valve (apparently)

With the reverb pot down to 0 it sounds typically cornford, sweet as a nut crystal clear tone, with the reverb cranked up it suddenly loses its low end and clean sounds and becomes a little fizzy, there is reverb there but its not loud.

The reverb is springs located at the base of the combo, 2 phono jacks go into the head itself via the phono inputs. There is a footswitch jack input which isn't used.

Does anyone know what could be causing this? could one of my resistors be dead? The dead is all point to point wiring, no PCB's so its fairly easy to work with.

Cheers folks look forward to hearing from you.

Matt.

[Robert M. Martinelli]

Hi Matt,
it' s pretty difficult to point in one direction with no details, but the first thing you can do is to swap ( mark them beforehand with a permanent felt tip pen ) the 12AX7s in the preamp section to see if the problem moves to another stage, if so, one of the preamp tubes is defective. If nothing changes let us know, but we'll need more details and ( possibly ) the schematic diagram.

Best regards

Bob

[mattbreaker]

Hey Bob thanks for the very rapid response!

Its not a duff valve, tried swapping the previous valves and the new valves around, all of which do the same thing.

There are no schematics that I know of, thats partly why I am here as I wouldn't know where to begin a diagnostic.

Regards,

Matt.

[Robert M. Martinelli]

Hi again,
if the valves are good, the next step would be to take a look at the reverb unit ; you should try to measure the input and the output coils to see if they' re both good, the best way to do this would be to pull the reverb unit off the amp and measure the coils' DC resistance and continuity from the connectors to the coils as well, as measuring the coils from the input-output connectors could be deceiving ( time ago, measuring a reverb unit at the connectors I thought I had an open coil, but opening it I found one of the wires from the connector to the coil was open and luckily the coils were good ).

Hope this helps

Best regards

Bob

[mattbreaker]

Nice one Bob I'll get it on the bench and check that out,

Thanks again mate!

Matt.