Instructions - DYNACO ST-70 Assembly Manual

NOTE – You may or may not want to construct the VTA driver board BEFORE or AFTER you attach the
chassis parts. If you wish to construct the VTA driver board at this time skip ahead to the VTA driver
board instructions which are inside the VTA package and proceed with its construction. When you are
through come back to this point and begin mounting the chassis parts.
Obtain the chassis. Remove the four stainless steel 6 X 32 screws. Taped inside the chassis are
four one inch round rubber "feet" which you may stick on the outside of the chassis bottom cover over
the four holes in the cover. Orient the chassis with the power transformer cutout facing you and mark
"V1", "V2", "V3", "V6" and "V7" with a felt tip marker on the inside of the chassis next to the
appropriate tube socket. The tube socket numbers are shown on the pictorial.
1. Mount the FIVE octal sockets that fit on the chassis TOP from the BOTTOM OF THE CHASSIS
with ¼ inch long 4-40 stainless steel screws and 4-40 kep nuts. Use the pictorial to orient the
keyway of each tube properly. On V2, V3, V6 and V7 mount a GROUND LUG around the outside
screw closest to the side of the chassis and face this ground lug towards pin 8. Tighten all nuts
securely. DO NOT MOUNT the two front power take off tube sockets at this time.
2. Disassemble the two gold plated speaker binding posts from the mounting plates. Attach the
LEFT and RIGHT mounting plates to the back INSIDE of the amp with 4-40 hardware.
Reassemble the speaker binding posts on to the mounting plates. One of the black spacers with
rounded edges goes INSIDE the chassis and the other black spacer goes OUTSIDE the chassis.
Make sure that the BLACK terminal is on the side that says "G" on the outside of the chassis
frame. Tighten the two studs with the gold plated nuts provided.
3. Mount your rubber grommet in the 3/8 inch hole in the back CENTER of the chassis.
4. Mount the fuse holder in the "D" shaped hole in the back of the chassis. Tighten the nut but do
not over tighten as this may cause the plastic threads to break. Check and make sure that your
3 amp SLO-BLO fuse is inside the fuse holder.
5. Mount the SPST on/off switch on the REAR of the chassis with 4-40 hardware. Make sure that
the two terminals on this switch are close to the UNDERSIDE OF THE CHASSIS TOP SURFACE.
Check the pictorial.
6. Mount the power transformer in the large center cut out. The wires should face the FRONT of the
chassis. Fasten the power transformer to the chassis with four 8-32 kep nuts. In the original amp
a cable clamp was used on each of the two front bolts as seen in the pictorial. These clamps are
not really needed since, once soldered, the wires will stay in place. If you have your original
clamps use them.
7. Mount your C-354 choke on the RIGHT side of the chassis with two 8-32 screws and matching
kep nuts. Make sure that the two choke leads face towards the FRONT of the chassis.
8. Remove all components from lugs 1 through 4 of the 7 lug terminal strip and mount your SEVEN
lug terminal strip on the LEFT side of the chassis with two 4-40 screws and kep nuts as shown
on the pictorial.
9. Mount the TWO A-470 output transformers with 8-32 hardware. The side of the transformer with
the YELLOW-ORANGE-BROWN-BLACK leads must face the BACK of the amp. NOTE – If you are
reusing older original A-470 transformers mount the transformer with the LONGER RED LEAD
on the LEFT side.

INSTRUCTIONS

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