Euraudio DPBsc assembly instructions
Welcome to the Euraudio DPBsc assembly instructions. The DPBsc is a protection circuit board populated with SMD components plus supplied are the remaining components, which you must install yourself. DPBsc is part of the Euraudio CTA MID, LDA MID, LDA DMx and LDA MON DiY kits. Please find the specification of the DPB here.
A certain version of the DPB board contains the breakaway LEDS board as well. Please find information on the connection of LEDs here.
Please read through these instructions before doing anything with the DiY kit.
What the DPBsc DiY kit contains and what it contains not
The kit contains the DPB double-sided, fiberglass-reinforced epoxy PCB with all the SMD components mounted on it (fig. 1.). The unmounted through-hole components, the connectors, and the NTC thermistor are also supplied (fig. 2), as well as the mechanical components for fastening (fig. 3). The 10-conductor ribbon cable, and the other necessary wires are supplied, too, but are not shown in the images.
The DPB kit doesn't contain the components needed for fan control, you must source them yourself, if you want to use DPB to control a fan.
Component list
Please download the DPBsc component list (BOM) from here.
General assembly advice
What you'll need and is not in the DiY kit
Solder iron, solder wire, wire cutter, Phillips 1 (PH1) screwdriver, Phillips 2 (PH2) screwdriver, drilling machine, 3 mm, 3.5 mm and 4 mm metal drill bits, heat-resistant glue (e.g. CX80 Autoweld). A heavier object with solderable surface (e.g. a tin can). A PCB holder jig and/or a model-making vice may come handy. A solder suction pump and/ or desoldering wick may be needed if you make soldering faults.
Soldering
Please click this link, if you need soldering tips.
Where polarity matters
There are electronic components which are polarized, these have to be soldered in the right orientation. The polarity is shown in the PCB with appropriate marking. If you solder any of the polarized components not in the correct orientation, that causes trouble when you power up the circuit; either the circuit will malfunction or even some of the components may be damaged.
Detailed help for assembling
Note: I can't help in troubleshooting assembly faults, I can only resend the whole kit on request.
Drilling the fastening holes
It's practical as a first step to drill the holes in the amplifier chassis that will hold the PCB in place. Put the PCB in its intended place within the amplifier enclosure, mark the 4 holes with a marker pen, and then drill the holes with a 3.5 mm drill bit.
Identifying components
The graphical markings and numbers printed on the PCB make it clear where the components belong and in what orientation.
Assembling the IDC connector
The Power supply & relay board is connected through J54, a ribbon cable connector (IDC). Observe the polarity: the side of the ribbon cable marked with red color should be aligned with the triangle sign on the connectors. Please crimp this connector carefully. If you're unsure how to assemble this type of connector correctly, please google "crimping IDC connectors".
The resistor setting loudspeaker protect speed
You must select the appropriate resistor value to match the specific needs of your amplifier.
|
Loudspeaker
protect speed |
fast: 40‑70W/4ohm or 30‑45W/8ohm amplifier |
medium: 70‑130W/4ohm or 45‑85W/8ohm amp. |
slow: 130‑250W/4ohm or 85‑165W/8ohm amp. |
|
DPB
(R61) |
R61 = 15k...33k (not supplied) |
R61 = 33...51k (47k supplied) |
R61 = 51...75k (68k supplied) |
Setting the overcurrent threshold value for a non-Euraudio amplifier
If you wish to use the overcurrent protection (OCP) function of DPB for your own amplifier (not Euraudio's CTA14, CTA14A or LDA17), then you yourself should calculate the value of the Rs and Rb OCP resistors.
|
OCP resistors |
OCP setting resistor Rs |
Overcurrent boost resistor Rb |
|
DPB |
R54 (2 Watts) |
R52 (0.6 Watt) |
The OCP resistor values in Ohms can be calculated as follows:
Rs = 87(IthRm - 1.1) (+/-5%),
Rb = 0.2Rs + 19 (+/-10%),
where Ith is the overcurrent threshold value you want to set in Amperes,
Rm is the output transistors' emitter resistor value in the amplifier in Ohms.
If the calculated Rs is lower than about 68 Ohms, then the OCP circuit of the DPB can't be used with your amplifier, unless you modify your amplifier, namely increase the emitter resistors of the output transistors in your amplifier. Do not install a resistor lower than 68 Ohms for Rs.
The ovecurrent threshold is specified within a certain tolerance at 25°C and at frequencies lower than 1kHz. You can read about the accuracy and frequency dependence of the OCP in the specification of the DPB.
Connecting OCP for a non-Euraudio amplifier
Connect the ERV connector (J52) in DPB to the output transistors' emitter resistors in the manner shown in the following image. Mind the polarity of J52. Reverse connection renders the OCP ineffective and may damage the protection circuit.
The J53 (LoA) jumper
Install the LoA jumper to select the normal (lower) current threshold for the overcurrent protection, which is about 6.3 A peak / output transistor for CTA14 and CTA14A, 9 A peak / output transistor for LDA17xc and about 11 A peak for LDA17hc and LDA17mc (for frequencies lower than 1kHz). Normally, LoA should be installed at all times. However, if the overcurrent protection accidentally kicks in at high volume levels while a low impedance (4 Ohms) loudspeaker is hooked up to the amplifier, then remove the jumper for an approximately 20% boost in allowed output current.
Fan control
The DPB board can control
a DC fan, but the necessary switching transistor and connector are not
supplied in the DiY kit. These are commonly available components which
are easy to purchase anywhere in the world. So if you want to use a DC
fan, these are the additionally needed components:
Q56 BC517
J56 2-pin polarized pin header 2.54mm pitch
The fan will start to operate when the heatsink temperature is about 8 °C lower than the selected overtemperature setting.
You must make a suitable power supply for the fan, ensuring proper voltage and proper current sourcing capability at the intended operational temperature. The DPB board will not provide supply voltage, it only switches the fan into the power supply circuit by providing the path to ground, as shown in the next image.
The diode, denoted "D" in the image, is not needed for the majority of DC fans, for the so-called brushless fans that have internal switching electronics. However, for brushed fans it's compulsory, because in lack of the diode the inductive flyback will damage the switching transistor in the DPB board. This diode can be an 1A diode like the 1N4004 or 1N4007. If you're unsure about the type of the fan, please install this diode, it can't do any harm if it's unnecessary there.
The rated voltage and current of the fan must be below the following maximum ratings:
If Q56=BC517: max. 24V, max. 250mA.
Overcurrent and overtemperature protection connectors
J52 (ERV) is the overcurrent sensing connector, while TH51 connects the temperature sensor (thermistor) which is supplied in the kit.
The polarity of J52 is important, the pin marked "+" must be connected to the appropriate ER+ point, while the other pin must be connected to the appropriate ER- point in the CTA14(A) or LDA17 PCB (if you use the DPB for a Euraudio CTA14, CTA14A or LDA17 amplifier). Supplied is a thin wire with red insulation for the ER+, and a thin wire with black insulation for the ER- connection.
TH51 is not polarized.
Please click this link, if you don't have a crimp tool suitable for the contacts of the connectors.
After you finish the connectors, the two wires of the overcurrent protection should be twisted together. Do the same with the two wires of the overtemperature protection.
Mounting the thermistor to the heatsink
The thermistor looks like this:
I recommend mounting the thermistor in the following way. Close to (<6 mm) one of the output transistors in the heatsink, drill a 3 mm diameter hole, and then widen the top of the hole to 4 mm in about 2-3 mm depth with a 4 mm drill bit. This is because the tip of the thermistor is 3 mm thick but it widens to about 3.5 mm near the legs. Take the heat resistant glue (e.g. CX80 Autoweld), mix its components, then apply it into the hole and spread it over the thermistor as well. Push the thermistor into the hole without making air voids. To "bubble out" possible air voids, you may push and pull the thermistor gently a few times. To hold the thermistor in position while the epoxi glue cures, you can thrust the legs of the thermistor through a sheet of paper, and then let the sheet rest on the horizontally positioned heatsink surface.
When the epoxi has hardened, shorten the thermistor legs, and check that there is no short circuit between the thermistor legs and the heatsink. Then solder the two thin wires to the thermistor legs, and twist the two wires to form a twisted pair. When it is finished, it looks like this:
