from the Blacet Research design pit.
MIX3500 Assembly Photos
FD3120 Assembly Manual
for page 7 of the Manual, showing PCB to front panel mounting photos.
Pots will sometimes dry out. Depending on where they
are used, scratchy sounds can result. The pot has not "worn out" but
the lack of lubrication on the rotating parts causes jumps on the
We have had good results with WD-40 applied to the small rotating nub
at the back of the pot. Don't just spray the pot, you'll end up with a
huge mess. Using the straw on the WD-40 can, spray briefly into a paper
towel. Use the small drop remaining on the straw tip and apply it to
the nub. Rotate the pot and blot up any excess WD-40 with a paper towel.
Push Button Switch Alert
This switch is the thru the front panel right angle
switch used on a lot of our modules.
On rare occassions, when using a bit too much solder, kit builders may
find that the solder may bulge up on the component side of the PCB and
contact the metal mounting ears. If both ears happen to contact the
solder on each pad, a short will result and the switch will not work.
You can fix this by gently prying each ear out just a bit with an xacto
Maxim MAX365 IC Alert
Recently, the MAX365 has been hard to purchase, with
a long lead time and huge minimum order. Fortunately, the MAX362 is
pretty much the same component and will "drop in" to our designs with
no problem or loss of performance. You will be seeing these in most
modules currently shipping.
A similar situation may occur with the MAX364 and these may be replaced
with the MAX361.
Hex Zone Reliability Alert
A few customers have experienced failure of op amp U3
and a blank display screen. Replacing the op amp returns operation to
While we do not have a definite failure mechanism at this time, a
likely culprit is the high differential between +15 and -15 current
draw (150:1). Upon power down, due to the power supply filter caps,
this can cause the +15 to draw down much quicker than the -15. The op
amp may be sensitive to having one supply turn off a long time before
As a precaution, we are advising changing "CD" from 100uF to 1uF. "CD"
is on the lower side of the power connector.
MD2600 Scanner Mods
I was noticing that I kept using an attenuator when
patching the scanner. This was to keep the CV from causing the Scanner
to go "out of range", ie; no channel "on" at the top end.
The design of the Scanner is basically a CV level activated sequential
switch (as opposed to the nearly identical MD2650, which is a clock
toggled switch) with a "off-on-on-on-off" response. That last "off" was
proving a bit annoying in at least the patches I was using the scanner
The fix is to change R7 to 15K and R6 to 39.2K. With the Ref trimmer
(RT1) at full CCW (maximum voltage between steps), the scanner will
stay on the "C" channel even when the CV is at max. With the Scan
knob fully CCW, IN-A will come on at about 2.7V, IN-B at 5.4V and IN-C
at 7.8V. You can turn the Scan knob CW to start with IN-A "on" and thus
have one channel on throughout the CV range.
You can still turn RT1 CW and get the original response with an "off"
at the end, along with a narrower voltage range between steps.
A second mod greatly reduces
the transition noise between two of the steps. On the solder side of
the PCB, locate pins 1 and 3 of U2. Take a 10K resistor, bend one lead
over, trim the leads pretty short and solder them on to the two pads of
This works because of the different impedance of pin 1 of the bar graph
display driver chip. The 100K pull up resistor SIP used allows a
transition state at 5V instead of the expected common and +15.
These mods are now included on the modules currently shipping with the
second mod done by using a 10K SIP.
Hex Zone Assembly Tips
A couple of things that might help and some photos:
1. Handle the LCD display as you would ICs as it is static sensitive.
Also, it has a protective film over the display area. Remove this only
at final assembly of the front panel. Clean the display area only if
necessary with a soft dry lint-free cloth such as a microfiber style
commonly used for lenses and eye glasses.
2. You can use the front panel as a jig to help mount the LEDs. Use the
back side of the panel and take care to protect the front side. Install
the two long screws into the panel on either side of the display cutout
and secure with kep nuts.
Place some spacing material under the panel so the LEDs will have space
to drop all the way through. Lay it
flat and position the PCB and installed LEDs over it. You will need a
3/4" piece of foam, etc to hold up the top side of the PCB. Get the
LEDs lined up in the FP holes and check the alighment in both axis
3. When installing the four angle brackets, they can be slid all the
way toward the rear of the boards. Be sure to install before mounting
jack PCBs on mother board.
4. Solder only the four corner pins mentioned on the 6 pin headers for
the jack PCBs. Solder the remaining pins after the front panel is
attached. This allows some play when mounting the panel.
5. You can do a preliminary function test before mounting the panel if
you first install the ICs. Power up the module and wait until the
"Sequence Mode" appears. Push the right arrow button, then the Play
button. You should see the 16 LEDs sequence.
Our handy production jig.
Don't forget to install the angle brackets before you mount the
Installing the LCD
Installing the switch PCB.
Installing the rotary encoder.
"Taming of the Q"
The DF 2420 Dual Filter has an awful lot of Q; more
than is reasonable for some folks. But who said the designer was
The fix is very simple though. Just change R11 to 68K for the "A"
channel and R21 to 68K for the "B" channel. It will still self
oscillate just fine but at a point closer to the end of the pot travel.
Errata in SB2780/2790 Manual
A couple of minor bugs crept into the Parts Lists.
These will probably not cause any assembly errors. These include a
couple ref des errors on the power input filter caps (CA-CD), a missing
reference to RT2 on the Mixer and wrong board and front panel part
numbers on the 2790 (says "2780").
The corrected Parts Lists are below:
Errata in VCA2200 Manual
Please note that a line has been omitted in the
"Options" section. Please add the following step if you are doing this
"Change R7 to 82K."
for the Dark Star Chaos
This module has had excellent reliability An
exception is the last version, that used a "shrink DIP" 76477 and a
less than well engineered socket. The IC would tend to pop out of the
socket, causing erratic operation.
There are two fixes: wrap a ty wrap around the IC and socket lengthwise
or solder the four corner pins to the socket while pressing down on the
It is also possible to remove the socket and solder the IC directly to
the PCB, although this has to be done very carefully to avoid damage to
for the Final Filtre and Time Machine
Based on repair records for these two modules, a likely culprit for
problems are the high frequency clock ICs in each module. These are the
13600s; U13 in the FF and U7 in the TM. We suggest that you try
replacing these if your module starts acting strange. See the FF note
also immediately below.
FF2030 (Final Filtre) Long
Term Reliability Advisory
Based on some long term testing being done here and by one of our
customers (thanks, JP!), there is evidence that changing R44 and R45 to
10K (from 5.6K) will significantly improve the reliability of U13
(13600). Over the years, this IC has shown failure in most units
returned for repair.
If U13 is bad, the filter will not self oscillate or may have
a noisy spot as you rotate the frequency knob. Sometimes cycling the
power will restore IC function, but it may work only sporadically.
We are advising that you change the two resistors and replace U13.
Assembled units that shipped after Oct 2004 have already been
modified. If in doubt, check your board.
Overloading the Time
When the audio input is too high, the TM cuts out. Reducing the
level and waiting a few seconds restores normal operation. This applies
to no rev and rev A PCBs.
This problem is caused by the limited headroom of U4, the "front
anti alias switched cap filter, which is running off +/-7.5V supplies.
This results in a maximum input signal level of +/-7V (with input
trimpot RT4 FCW).
The TM will happily run along with typical +/-5V signal levels, but
if you introduce amplification in your system prior to the TM, I would
suggest keeping an eye on the levels. You can adjust RT4 to allow
input signals. For example, positioning the trimmer at mid rotation,
could use signals up to about +/-14V, which is around the limit of the
op amps in the rest of the system. This comes at the cost of 50%
through the module.
Modules built at the factory have this trimmer set at about 70%
which allows +/-10V signals.
The "cutting out" of the TM is not a typical symptom of overloading
an IC, but in this case, the LTC1063 disturbs the power rails and shuts
down both the +7.5V and -7.5V regulators! This causes the "crash" of
clock driving the filters and the MN3005, which also use the +/-7.5V
This is annoying to say the least but can be fixed with one 1N4148
(Dxx, shown below). Rev B boards include this mod.
The diode is connected between pin 14 of U6 (anode) and the +7.5V
(cathode/band). The right hand side of R26 can be used for the first
and a PCB feedthru can be used for the +7.5V. A bit of heatshrink will
protect from shorts.
Rev B PCBs have this change incorporated into the board.
Negative CVs into Time
Machine Delay Input
This applies to no rev versions of the PCB only.
The rev A and rev B versions have this change made to the board.
If the Delay CV mix goes more than about a
volt negative, the high frequency clock will stop and the delayed
effect will stop working. Removing the negative voltage source and
cycling the power will restore normal operation.
To fix this, locate R11 and unsolder the left
side, pulling up the resistor to about a 45 degree angle.
Clean out the vacant pad with a solder sucker
and insert one end of a 1K 5% resistor. Solder that end to the pad and
lift up the free end to mate with the free end of R11.
Take two 1N4148 diodes and connect one cathode
to the other's anode. Connect the unattached anode to the junction of
the two resistors above and solder the junction.
Place some heatshrink over the two diodes and
solder the unattached cathode to the feedthru just under the "2" in the
silkscreen "Q2". (This is common.)
Kit Assembly Tip: top 1/8"
The new Blacet Rack has less clearance for the
top and bottom front panel jacks. The bottom jack should have it's
lug bent upward a bit. This is covered in most of the assembly manuals.
The upper jack's "switch" contact tends to
the upper Blacet Rack rail. While this contact is not used in any of
modules, mounting the module can be made a bit easier by mounting the
at 45 degrees or greater as shown below:
Existing modules can be modified simply by loosening the jack nut
turning the jack. You should not have to modify the wiring except to
sure nothing shorts out.
Newer runs of front panels have more clearance for these two jacks.
Final Filtre Rev A
"What changes have been made to the Final
Filtre and is it a good idea to attempt changes on older boards?"
Most of the changes involved making the gate
more sensitive. This involves about 5 new components and these cannot
added to the old board. (They would have to be built up on a bit of
or perf board.)
The three 150 pF anti alias and smoothing
caps (C1, C9, C10) have been changed to 100 pF. This results in a
increase in filter output level and possibly a small change in the
at the same Q setting.
R9 has been changed to 15K, resulting in more
range for the Frequency pot.
We also employed a different transistor pair
the expo converter due to availability.
Blacet to Doepfer Power Connector
Some Blacet Modules will work on +/-12V and some Doepfer Modules will
on +/-15V...Check the Doepfer Web site for voltage info.
Frac Rack/ Blacet Rack Standards
Paia invented the "Rack". We engineered a slightly different version to
meet our quality and delivery needs. Modules from Paia, Blacet and some
of Wiard's will fit in either rack. A typical front panel drawing is
below for making compatible DIY modules. Note that the maximum PCB
is 4.22" to allow clearing the Blacet Rack mounting rails. Click on the
drawing for a much larger version.
To achieve the same "feel" as Blacet
units, use Panasonic Pots (Digi-Key P3T9503-ND), Rean knobs (Rean is
out of business 2010) and jacks: Mouser 16PJ012 (old style),
161-3142M-E (new style), Digi-Key CP1-3524N-ND (PCB mount).
Power input protection and filtering is
highly recommended for all modules! See below.
PS1 and PS2 are polyfuse resettable
fuses available in various mA ratings. A typical module with a 50 mA
current draw would use 100mA versions.
A power supply reversal
causes the diodes to conduct, creating a short circuit. That condition
or a short on the PCB causes the polyfuses to heat up and go into