8
•
The 2N3954 dual JFET footprint in the VCO2 section (still) has reversed pins 5 and 6.
Instructions are included below to correct for this during construction.
•
On the power sub-board, there are a couple of test pads marked +15.00 and -15.00,
respectively. These points are, in fact, common with the V+ and V- (main system) rails, and
not the +15.00 / -15.00 (LED) rails.
•
Signal traces transiting under some jacks can become shorted to the jack
’
s ground connection
via the jack enclosure. This problem affects 19 of the jacks. A further explanation, the
locations of these jacks, and suggested fixes are below in the section covering the jack
installation.
QUIRKS
Questions may arise due to some of the silkscreened information on the boards.
•
As stated abo
ve, the main board is marked “REV8” whereas the 4V TTSH is a subsequent
revision.
•
In the speaker amp section, there are two capacitor footprints marked “u1”. Thes
e are .1u
(100n) film capacitors.
•
There are some resistors marked with an alternate value in parentheses. Ignore the alternate
value.
•
There is an oddly marked resistor location next to the pad for the reverb return RCA jack. It
says “TOBU3 1K”. This i
s just a 1K resistor location.
•
Some capacitor values are marked with non-standard values, and these are traditionally
substituted with standard values. See the preceding
section “Standard Substitution
s
”.
•
Power connection points marked on the board +15.00 and -15.00 will typically read on the
DMM ~ +15.8v and -15.8v.
MAIN BOARD POWER SYSTEM
The power rails are distributed to all sections in a middle layer of the main board. This is hidden from
view, and cannot be modified. This means you cannot drill holes in the main board without risk of
permanent damage to the system. It also means you cannot selectively power individual sections.
There are two power distribution systems. Power rails are tapped on the DC-DC converter both pre and
post the LDO regulators. On the 5 pin headers that connect the DC-DC converter to the main board, the
pre-regulator rails are identified as +15.00V and -15.00V. When you measure them, you will find them to
be more like +/-15.8V. This is intentional, and provides for the ~.5V drop incurred by the LDO regulators.
The regulated outputs are V+ and V-. All of these are
referenced to the “0” pin. Misleadingly, there are
two test points on the DC-DC converter 15.00 and -15.00, when in reality they are V+ and V-,
respectively. These test points are used to initially set the regulated output voltages for V+ and V-, via the
500R trimmers. +15.00 and -15.00 power the LED sections. V+ and V- power everything else.
Although the power and ground planes are internally routed in the board, the old power connector pads
from TTSH V1 (where power was wired up with jumpers) are still in the design, and now function as vias
from the internal power layer. These consist of twelve sets of pads for .1 pitch 2x3 pin headers. There is
one in each of the major sections on the main board. Nothing needs to be installed in these locations, but