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Power supply Filter cap solutions - method one |
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There is more helpful
info on this page |
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Click on the small
images to see the full sized photo. |
This is the standard 5F6A
Bassman cap can arrangement like you would find on the
original amps. I will be using 5 - 20uf/500v Sprague atom
filter caps. The negatives of all the caps are soldered to
the can itself and then the can must be screwed down tight
to the back of the chassis so that the four corners of the
can make good contact with the chassis. That way you will
get a good ground contact between the can and the chassis.
The positive ends of the caps are clipped short. There will
be four positive wires that are soldered to the filter caps
and then exit out of the can through a rubber grommet. The
four wires go to each of the four filtration stages you
find on the Bassman circuit. You can secure the caps to the
metal can with double stick tape, glue or RTV silicon.
All of these parts can be found in my on line parts
catalog. See the link at the bottom of this page.
The cap can and the grommet are on the Hardware/Handles
page. The 20uf/500v caps are on the capacitors page. |
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Here you can
see that I have taken a small Fender re-issue cap can and
drilled 5 holes for each negative/ground connection. |
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Twist the first two capacitors positive leads together to
make two 20uf capacitors in parallel. This is the first
stage of filtration downstream from the rectifier. 20uf +
20uf = 40uf total filtration on stage one. Stages 1 through
4 are numbered in the photo. |
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Push the negative leads of each cap through the drilled
holes, bend them at a 90 degree angle and then clip them to
about 10cm or roughly 3/8". Solder all the negative leads
to the filter can. You may need a 50 watt or more soldering
iron to be able to solder the leads properly. The can will
suck the heat right out of a small solder iron. |
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Here you can see that I took one of the 1/2" grommets that
I sell and cut out a small wedge so that it would fit into
the cap can hole. The four positive wires exit through this
grommet and go inside the amp to the circuit board. |
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Power supply Filter cap solutions - method two |
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Click on the small
images to see the full sized photo. |
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Here is another way to do the
filter caps without a cap can. All the filter caps are
inside the chassis going point to point. The stage one
filter caps are between the power transformer and the
circuit board on an 8 lug terminal strip. The remaining
three stages are along the front edge of the chassis, under
the pot harness. |
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Here you can
see the whole chassis and all five filter caps. |
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These are the two main stage one filter caps mounted to an
8 lug terminal strip. I have done a series arrangement here
of two 100uf/350v caps. You could do a parallel arrangement
here also. The bottom lug (#1), and the top lug (#8), of
the 8 lug terminal strip are bolted to the choke holes in
the chassis. The choke is on the other side of the chassis
bolted to the same holes. The resistors are bleeder
resistors. You can see more info about parallel and series
cap arrangements on this page.
The bottom lug #1 acts as the chassis ground for the filter
caps. You can also run a wire from this lug to the main
power transformer ground lug.
Lug #2 is the main B+ connection.
Lug #7 is where the two caps and two resistors are all
soldered.
Lugs 3, 4, 5, 6 and 8 are not used.
Note that the top lug, #8 of the terminal strip is not
connected to anything except the chassis. |
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Here you can see the last 3 stages of filtration. The
positive ends of the caps go right to the lug on the
circuit board. The negative ends are all soldered to the
buss wire that runs down the back of the pot harness. I
have put some #18 gauge red wire jacket on the positive
ends of the cap leads as a safety feature. The caps are all
tucked neatly under the pots and out of the way. |
