Twin Reverb gets a “spring” clean

The Twin Reverb, whilst sounding remarkably clean was looking anything but. Time for a good clean.

The tolex is quite badly knocked about in places so I wanted to make sure it didn’t get too wet.

I dismantled everything, removing the valves and the amp chassis too. While it was apart I took pictures of the valve chart and serial number for future reference.

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I gather from this site that the “F09” denotes 1979-80.

In small sections with slightly soapy water and a firm nail brush I’d work in small circles, wipe dry and repeat a couple of times until all the ingrained dirt had lifted.

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Here’s a before and after of the top.

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Not a massive difference on first appearance until you look at what it did to the water and detergent mix.

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The reverb bag was particularly dirty but cleaned up very nicely.

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There had been an intermittent problem with the reverb disappearing which I’d traced to a dodgy connection on RCA Phono plug on the return from the reverb tank. I replaced the whole cable with one I had in my parts drawer.

The interior of the chassis itself was pretty clean but I gave it a light dusting and checked everything looked OK.

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I put everything back together, returned the valves to their original position and checked that everything worked. Now the outside is almost as clean and sparkly as the sounds it makes. The valves fitted all look pretty recent. They’re Electro-Harmonix in the power tubes and a full set of JJs for the preamp.

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One last job for today was to make myself a “fake” footswitch for the tremolo. As standard you need to have the footswitch plugged in for the tremolo to operate, whereas by default the reverb is on. I like to keep the tremolo on all the time but at a very low, almost imperceptible level. Rather than connecting up the footswitch and leaving it rattling about in the cavity at the back, I simply took an old RCA Phono plug, soldered the centre to the shield and hey presto, full-time tremolo with no footswitch.

Next job will be to experiment with the preamp tubes. I’ve got a spare 12AT7 knocking about and this can be used in place of the 12AX7 in V1 or V2 for the Normal and Vibrato channels, respectively, dropping the gain slightly, giving even more clean headroom (if such a thing is possible).

Another interesting idea I want to try out is that, because unlike most amps, the two channels are totally independent and can be used at the same time, you can take the return from the reverb tank and feed it directly into the normal channel, allowing you to control the volume and EQ independently of the dry signal. All that is required is an RCA Phone to 1/4″ adapter.

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