ASSEMBLING THE KIT
If you purchased an unassembled kit, you will have all the parts, including printed circuit board.
Parts are in marked bags, with reference numbers and value written on a bag. Reference
numbers are the ones printed on the PCB, so locating parts positions should be very easy. PCB
layout printout is also part of this document and you can use it to locate parts. Power transformer
is purchased separately, and not included in the kit.
First step is to review all the materials received, compare to the part list and prepare all tools and
a well lit work area. Tools that you need are very basic – soldering iron, tweezers or flat pliers, and
cutters. You will also need solder wire and a digital multimeter.
- Start assembly with jumpers, grounding negative end of plate and heater power supply. In some
specific (and very rare) situations it is not required to ground the power supplyand you will not
install the jumpers.
- Follow with resistors and fuses, keeping in mind that both, resistors and fuses should be slightly
elevated off the PCB (1/32” is sufficient). Main reason is that power resistors get warm and this
will help air circulation and prevent overheating. Also, some resistors have circuit connections
underneath and there is a possibility of malfunction if the resistor body touches exposed trace.
This is not very likely, since the PCB connections are protected by a solder mask and resistors
have durable coating. However, this could be a matter of safety and, also, troubleshooting of such
problems is really difficult, so it is better to spend some extra time up front to come up with great
assembly.
- Next step is assembly of all capacitors. Make sure to follow polarity directions for electrolytic
capacitors. All electrolytics have markings designating leads to be connected to the negative
voltage. PS-1 printed circuit board has a plus sign for the positive terminal of an electrolytic
capacitor. Positive terminal on the PCB also has a square pad around the hole, for easier
identification on the bottom of the board.
- After capacitors are installed you can proceed with connectors.
Once everything is installed, take a short break and then come back and carefully inspect your
work. Check component locations and proper orientation of electrolytic capacitors. Inspect all
solder joints and make sure there are no solder bridges or splashes on the board. All joints should
look clean and shiny. If you are not sure that a solder joint look right, touch it with a hot soldering
iron again, until it looks right. Cold solder joints may create problems few hours (days, months)
down the road and are extremely difficult to troubleshoot.
Then, connect the power transformer and proceed with slowly powering the unit. Variable
autotransformer (a.k.a. variac) is a very helpful tool during this initial phase.
Measure voltage on the primary and all secondaries, as well as output voltages for plates and
filaments. Keep in mind that during this test there is no load and measured voltages may be up to
25% higher than expected. Transformer secondary voltages and output DC voltages are specified
for the maximum load and will be significantly lower once you connect your equipment.
After the test is done, shut down the power, wait 5 minutes for capacitors to discharge and then
connect your equipment and repeat the process. After reaching the steady state, your voltages
should be very close to the nominal ones.
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