RI Bassman Mods
From powe–(at)–wdc.com Mon Nov 4 08:51:39 CST 1996
> >Help! I bought a ’59 Fender Bassman Reissue because a buddy has one
A customer of mine had the same complaints about his “re-issue” Bassman.
1) There are likely to be rattling problems if you try the tube rectifier
2) Replace the ‘presence’ pot with a 1-meg audio taper
3) Add a pair of 1k5 grid-stopper resistors to the power tubes (one per
4) Rewire the ‘presence’ control to be a ‘cut’ by: slashing a trace on
5) For best versatility of tube selection; Add a second bias circuit and
6) Install some 1-ohm current sense resistors in series withpin-8 of each
The grid-stoppers roll off the high end a little in the power amp, and
These mods allow a mellow vintage tone to be obtained from the new amp,
Article: 26469 of alt.guitar.amps
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From: O’Connor
Subject: Re: ’59 Bassman Reissue (Help!)
Date: Mon, 04 Nov 1996 06:12:47 -0800
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> >that sounds great! But mine sounds too bright and brittle. I turn the
>
> >treble, presence and bass to “0″ and the middle to “5″ and I still get
> >the bright sound!! Are there any mods that will “warm up” the amp?
The amp is not an exact copy of the 59, so there are a couple of things
you can have a tech do:
route. I installed a couple of power resistors in series with the
solid-state rectifiers to achieve tube-like sag with better reliability
and no tube rattles!
tube)
the control PCB; move the end of the 4k7 to ground; with a shielded
2-wire cable, tie the new pot across the grid-leak side of the 1k5
grid-stoppers, with a 5nF-400V plastic cap in series with one of the pot
leads (NOTE: You only have to use the wiper and one end of the pot)
connect the existing one to one power tube and the new one to the other.
This allows hum-free performance to be obtained from any set of tubes.
power tube to ground. This makes reading bias currents a lot easier and
safer (than the transformer-shunt method).
makes the circuit truer to original form. The re-wired ‘presence’ gives
at ’10′ what tone you used to have at ’1′– now you can smooth out the
highs at will, while a non-zero setting of your ‘treble’ pot allows some
high-end sparkle.
with greater reliability.
