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Uniden UBC92XLT Teardown

One bit of my equipment that I’ve never looked into is my scanner, a handheld Uniden unit. I got this when Maplin Electronics had them on special offer a few years ago.

Uniden Scanner

Uniden Scanner

Here’s the scanner itself, roughly the same size as a usual HT.

Back Cover Removed

Back Cover Removed

Here the back cover has been removed, and the main RF board is visible at the top of the stack. Unfortunately the shielding cans are soldered on this unit, so no looking under there :(
On the right hand side of the board next to the antenna input is the main RF filter network, and it’s associated switching. The RF front end is under the shield closest to the front edge.

Controls & 3.3v Regulator

Controls & 3.3v Regulator

On the other side of the PCB is the Volume & Squelch potentiometers, along with a dedicated 3.3v switching supply. An NJM2360A High Precision DC/DC converter IC controls this one. A 3.3v test point is visible next to the regulator.

RF Board Reverse

RF Board Reverse

Here’s the backside of the RF board, some more interesting parts here. There’s a pair of NJM3404A Single Supply Dual Op-Amp ICs, and a TK10931V Dual AM/FM IF Discriminator IC. This is the one that does all the back-end radio functionality. The audio amplifier for the internal speaker & external headphone jack is also on this PCB, top left. A board-to-board interconnect links this radio board with the main control board underneath.

Control PCB Front

Control PCB Front

Here’s the front of the control PCB, nothing much to see here, just the LCD & membrane keypad contacts.

Control PCB Reverse

Control PCB Reverse

And here’s the reverse side of the control board. All the interesting bits are here. The main microcontroller is on the right, a Renesas M38D59GF, a fairly powerful MCU, with onboard LCD drive, A/D converter, serial interface, 60K of ROM & 2K of RAM. It’s 6.143MHz clock crystal is just below it.
The mating connector for the RF board is in the centre here.

There is also a Microchip 24LC168 16KB I²C EEPROM next to the main microcontroller. This is probably for storing user settings, frequencies, etc.

EEPROM

EEPROM

The rest of this board is dedicated to battery charging and power supply, in the centre is a dual switching controller, I can’t figure out the numbers on the tiny SOT23 components in here, but this is dealing with the DC 6v input & to the left of that is the circuitry for charging the NiMH cells included with the scanner.

PSU

PSU

The last bit of this PCB is a BU2092FV Serial In / Parallel Out 4 channel driver. Not sure what this one is doing, it might be doing some signal multiplexing for the RF board interface. Unfortunately the tracks from this IC are routed on the inner layers of the board so they can’t be traced out.

SainSmart Frequency Meter

Thanks to Lewis, M3HHY for lending me this one :)

Here’s a quick look at a Sainsmart frequency counter module. These are useful little gadgets, showing the locked frequency on a small LCD display.

It’s built around an ATMega328 microcontroller (µC), and an MB501L Prescaler IC. The circuit for this is very simple, and is easily traced out from the board.

Frequency Counter

Frequency Counter

Here’s the back of the board, with the µC on the left & the prescaler IC on the right. This uses a rather novel method for calibration, which is the trimmer capacitor next to the crystal. This trimmer varies the frequency of the µC’s oscillator, affecting the calibration.

Input protection is provided by a pair of 1N4148 diodes in inverse parallel. These will clamp the input to +/-1v.
The prescaler IC is set to 1/64 divide ratio. This means that for an input frequency of 433MHz, it will output a frequency of 6.765625MHz to the µC.

The software in the µC will then calculate the input frequency from this intermediate frequency. This is done because the ATMega controllers aren’t very cabable of measuring such high frequencies.

The calculated frequency is then displayed on the LCD. This is a standard HD44780 display module.

LCD

LCD

Power is provided by a 9v PP3 battery, which is then regulated down by a standard LM7805 linear regulator.

Readout

Readout

I’ve found it’s not very accurate at all at the lower frequencies, when I fed it 40MHz from a signal generator it displayed a frequency of around 74MHz. This is probably due to the prescaler & the software not being configured for such a low input. In the case for 40MHz input the scaled frequency would have been 625kHz.

 

Wouxun KG-UV950P Teardown & Analysis

Following on from my review, here are some internal views & detail on the components used in this radio. Below is an overview of the main PCB with the top plate removed from the radio.

Cover Removed

Cover Removed

RF Final Amplifier Stage

RF Final Amplifier Stage

Most visible are these MOSFETs, which are Mitsubishi RD70HVF1 VHF/UHF power devices.  Rated for a maximum of 75W output power at 12.5v (absolute maximum of 150W, these are used well within their power ratings. They are joined to the PCB with heavy soldering, with bypass caps tacked right on to the leads.

RF Pre Drivers

RF Pre Drivers

Here is the RF pre-driver stage, with intermediate transistors hidden under the small brass heatspreader.

Power Section

Power Section

In the top left corner of the radio, near the power input leads, is the power supply & audio amplifier section. Clearly visible are the pair of LA4425A 5W audio power amplifier ICs, these drive the speakers on the top of the radio. Either side of these parts are a 7809 & a 7805 – both linear regulators providing +9v & +5v logic supplies respectively. The large TO220 package device is a KIA378R08PI 3A LDO regulator with ON/OFF control, this one outputs +8v. Just visible in the top right corner are the sockets for the speaker connections.

DTMF Circuits

DTMF Circuits

Here are the two ICs for dealing with DTMF tones, they are HM9170 receivers.

Glue Logic

Glue Logic

In the corner next to the interface jack, there are some CD4066B Quad Bilateral switches. These make sense since the interface jack has more than a single purpose, these will switch signals depending on what is connected.

RF Section

RF Section

Here are visible the RF cans for the oscillators, the crystals visible next to the can at the top. The shields are soldered on, so no opening these unfortunately.
Also visible in this image is a CMX138A Audio Scrambler & Sub-Audio Signalling processor. This IC deals with the Voice Inversion Scrambling feature of the radio, & processes the incoming audio before being sent to the modulator.

Output Filter Network

Output Filter Network

Shown here is the RF output filter network, this radio uses relays for switching instead of PIN diodes, I imagine for cost reasons. The relay closest to the RF output socket has had a slight accident :) This is slated to be replaced soon.

RF Output Jack

RF Output Jack

Finally, the RF output jack.

Audio Speakers

Audio Speakers

Here the speakers are shown, attached to the bottom of the top plate. They are both rated 8Ω 1W.

Active Ultracapacitor Balancing

Here’s another active balancing circuit for large ultracapacitor banks, this one is designed for a series string of 6, at 2.5v per capacitor.

Based on the design here, I have transcribed the circuit into Eagle & designed a PCB layout.

Ultracap Balancer Circuit

Ultracap Balancer Circuit – Click to Embiggen

As can be seen from the circuit diagram above, this is just 6 copies of the circuit from the above link, with screw terminals to attach to the capacitor string.

Ultracap Balancer PCB

Ultracap Balancer PCB

And here’s the PCB. the MOSFETs & OpAmps are very small SMT parts, so require a steady hand in soldering. This board can easily be etched by hand as there’s only 3 links on the top side. No need for a double sided PCB.

As always, the Eagle project files & my Eagle library collection are available below:

OpAmp Ultracapacitor Balancer (167) Eagle Libraries (198)

AD9850 VFO Board

Continuing from my previous post where I published an Eagle design layout for AD7C‘s Arduino powered VFO, here is a completed board.

I have made some alterations to the design since posting, which are reflected in the artwork download in that post, mainly due to Eagle having a slight psychotic episode making me ground one of the display control signals!

AD9850 VFO

AD9850 VFO

The amplifier section is unpopulated & bypassed as I was getting some bad distortion effects from that section, some more work is needed there.
The Arduino Pro Mini is situated under the display, and the 5v rail is provided by the LM7805 on the lower left corner.

Current draw at 12v input is 150mA, for a power of 1.8W total. About 1W of this is dissipated in the LM7805 regulator, so I have also done a layout with an LM2574 Switching Regulator.
The SMPS version should draw a lot let power, as less is being dissipated in the power supply, but this version is more complex.

DDS VFO-SMPS

DDS VFO-SMPS

Here the SMPS circuit can be seen on the left hand side of the board, completely replacing the linear regulator.
I have not yet built this design, so I don’t know what kind of effect this will have on the output signal, versus the linear regulator. I have a feeling that the switching frequency of the LM2574 (52kHz) might produce some interference on the output of the DDS module. However I have designed this section to the standards in the datasheet, so this should be minimal.

Nevertheless this version is included in the Downloads section at the bottom of this post.

The output coupled through a 100nF capacitor is very clean, as can be seen below, outputting a 1kHz signal. Oscilloscope scale is 0.5ms/div & 1V/div.

VFO Output

VFO Output (Mucky ‘Scope)

Scope Connected

Scope Connected

 

Thanks again to Rich over at AD7C for the very useful tool design!

Linked below is the Eagle design files for this project, along with my libraries used to create it.

AD9850 DDS VFO Eagle Files (448) Eagle Libraries (198) AD9850 DDS VFO SMPS Version (217)

Water Management System PCB Revisions

OK, a few revisions have been made to the water management PCB, mainly to reduce the possibility of the brushed DC motors in the water pumps from causing the MCU to crash, with the other changes to the I/O connector positioning & finally upgrading the reverse blocking diode to a 10A capable version rather than 5A.

Water Management PCB

Water Management PCB

Thanks to Mayhew Labs with the WebGerber image generator for the render.