Posted on Leave a comment

nb Tanya Louise Heating System – Oxide Sludge

I wrote a few weeks ago about replacing the hot water circulating pump on the boat with a new one, and mentioned that we’d been through several pumps over the years. After every replacement, autopsy of the pump has revealed the failure mode: the first pump failed due to old age & limited life of carbon brushes. The second failed due to thermal shock from an airlock in the system causing the boiler to go a bit nuts through lack of water flow. The ceramic rotor in this one just cracked.
The last pump though, was mechanically worn, the pump bearings nicely polished down just enough to cause the rotor to stick. This is caused by sediment in the system, which comes from corrosion in the various components of the system. Radiators & skin tanks are steel, engine block cast iron, back boiler stainless steel, Webasto heat exchanger aluminium, along with various bits of copper pipe & hose tying the system together.
The use of dissimilar metals in a system is not particularly advisable, but in the case of the boat, it’s unavoidable. The antifreeze in the water does have anti-corrosive additives, but we were still left with the problem of all the various oxides of iron floating around the system acting like an abrasive. To solve this problem without having to go to the trouble of doing a full system flush, we fitted a magnetic filter:

Mag Filter
Mag Filter

This is just an empty container, with a powerful NdFeB magnet inserted into the centre. As the water flows in a spiral around the magnetic core, aided by the offset pipe connections, the magnet pulls all the magnetic oxides out of the water. it’s fitted into the circuit at the last radiator, where it’s accessible for the mandatory maintenance.

Sludge
Sludge

Now the filter has been in about a month, I decided it would be a good time to see how much muck had been pulled out of the circuit. I was rather surprised to see a 1/2″ thick layer of sludge coating the magnetic core! The disgusting water in the bowl below was what drained out of the filter before the top was pulled. (The general colour of the water in the circuit isn’t this colour, I knocked some loose from the core of the filter while isolating it).

If all goes well, the level of sludge in the system will over time be reduced to a very low level, with the corrosion inhibitor helping things along. This should result in much fewer expensive pump replacements!

Posted on 12 Comments

Panasonic NV-M5 VHS Camcorder Teardown

Overview

Panasonic NV-M5 Camera
Panasonic NV-M5 Camera

Time foe some more retro tech! This is a 1980’s vintage CCD-based VHS camcorder from Panasonic, the NV-M5. There are a lot of parts to one of these (unlike modern cameras), so I’ll split this post into several sections to make things easier to read (and easier to keep track of what I’m talking about :)).

Left Side
Left Side

The left side of the camera holds the autofocus, white balance, shutter speed & date controls.

Left Side Controls
Left Side Controls
Lens Adjustments
Lens Adjustments

The lens is fully adjustable, with either manual or motorized automatic control.

Rear Panel
Rear Panel

The back panel has the battery slot, a very strange looking DC input connector, remote control connector & the earphone jack.

Top Controls
Top Controls

The top panel of the camera holds the main power controls, manual tape tracking & the tape transport control panel.

Viewfinder
Viewfinder

The viewfinder is mounted on a swivel mount. There’s a CRT based composite monitor in here. Hack ahoy!

Camera Section

Process Board Assembly
Process Board Assembly

Here’s the camera section of the camcorder, and is totally packed with electronics! There’s at least half a dozen separate boards in here, all fitted together around the optics tube assembly.

AWB PCB
AWB PCB

On the top of the assembly is the Automatic White Balance PCB. Many adjustments here to get everything set right. Not much on the other side of this board other than a bunch of Op-Amps. The iris stepper motor is fitted in a milled opening in the PCB, this connects to one of the other PCBs in the camera module.

AWB Sensor
AWB Sensor

Here’s the AWB sensor, mounted next to the lens. I’m not all to certain how this works, but the service manual has the pinout, and there are outputs for all the colour channels, RGB. So it’s probably a trio of photodiodes with filters.

Focus & Zoom Motors
Focus & Zoom Motors

Focus & Zoom are controlled with a pair of DC gear motors. The manual operation is feasible through the use of slip clutches in the final drive pinion onto the lens barrel.

Process Board
Process Board

The main camera section process board is above. This board does all the signal processing for the CCD, has the bias voltage supplies and houses the control sections for the motorized parts of the optics assembly. There are quite a few dipped Tantalum capacitors on pigtails, instead of being directly board mounted. This was probably done due to space requirements on the PCB itself.2016-08-20_13-40-11_000357

Under the steel shield on this board is some of the main signal processing for the CCD.

Optics Assembly
Optics Assembly

The back of the optics tube is a heavy casting, to supress vibration. This will be more clear later on.

Position Sensor Flex
Position Sensor Flex

The position of the lens elements is determined by reflective strips on the barrel & sensors on this flex PCB.

Sub Process Board
Sub Process Board

There’s another small board tucked into the side of the tube, this hooks into the process PCB.

Process Delay Line
Process Delay Line

According to the schematic, there’s nothing much on this board, just a delay line & a few transistors.

Piezo Focus Disc
Piezo Focus Disc

Here’s the reason for the heavy alloy casing at the CCD mounting end of the optics: the fine focus adjustment is done with a piezoelectric disc, the entire CCD assembly is mounted to this board. Applying voltage to the electrodes moves the assembly slightly to alter the position of the CCD. The blue glass in the centre of the unit is the IR filter.

IR Relective Sensors
IR Relective Sensors

The barrel position sensors are these IR-reflective type.

Iris Assembly
Iris Assembly

The iris is mounted just before the CCD, this is controlled with a galvanometer-type device with position sensors incorporated.

Iris Opening
Iris Opening

Pushing on the operating lever with the end of my screwdriver opens the leaves of the iris against the return spring.

Tape Transport & Main Control

Main Control Board
Main Control Board

Tucked into the side of the main body of the unit is the main system control board. This PCB houses all the vital functions of the camera: Power Supply, Servo Control, Colour Control,Video Amplifiers, etc.

Tape Drum
Tape Drum

Here’s the main tape transport mechanism, this is made of steel & aluminium stampings for structural support. The drum used in this transport is noticeably smaller than a standard VHS drum, the tape is wrapped around more of the drum surface to compensate.

Tape Transport
Tape Transport

The VHS tape sits in this carriage & the spools drive the supply & take up reels in the cartridge.

Main Control PCB
Main Control PCB

Here’s the component side of the main control PCB. This one is very densely packed with parts, I wouldn’t like to try & troubleshoot something like this!

Main PCB Left
Main PCB Left

The left side has the video head amp at the top, a Panasonic AN3311K 4-head video amp. Below that is video processing, the blue components are the analogue delay lines. There are a couple of hybrid flat-flex PCBs tucked in between with a couple of ICs & many passives. These hybrids handle the luma & chroma signals.
Top left is the capstan motor driver a Rohm BA6430S. The transport motors are all 3-phase brushless, with exception of the loading motor, which is a brushed DC type.

Delay Line
Delay Line

Here’s what is inside the delay lines for the analogue video circuits. The plastic casing holds a felt liner, inside which is the delay line itself.

Internal Glass
Internal Glass

The delay is created by sending an acoustic signal through the quartz crystal inside the device by a piezoelectric transducer, bouncing it off the walls of the crystal before returning it to a similar transducer.

Main PCB Centre
Main PCB Centre

Here’s the centre of the board, the strange crystal at bottom centre is the clock crystal for the head drum servo. Why it has 3 pins I’m not sure, only the two pins to the crystal inside are shown connected on the schematic. Maybe grounding the case?
The main servo controls for the head drum & the capstan motor are top centre, these get a control signal from the tape to lock the speed of the relative components.

Main PCB Right
Main PCB Right

Here’s the right hand side. The main power supply circuitry is at top right, with a large can containing 4 switching inductors & a ferrite pot core transformer. All these converters are controlled by a single BA6149 6-channel DC-DC converter controller IC via a ULN2003 transistor array.
The ceramic hybrid board next to the PSU has 7 switch transistors for driving various indicator LEDs.
The large tabbed IC bottom centre is the loading motor drive, an IC from Mitsubishi, the M54543. This has bidirectional DC control of the motor & built in braking functions. The large quad flat pack IC on the right is the MN1237A on-screen character generator, with the two clock crystals for the main microcontroller.

Erase Head
Erase Head

The full erase head has it’s power supply & oscillator on board, applying 9v to this board results in an AC signal to the head, which erases the old recording from the tape before the new recording is laid down by the flying heads on the drum.

Audio Control PCB
Audio Control PCB

The Audio & Control head is connected to this PCB, which handles both reading back audio from the tape & recording new audio tracks. The audio bias oscillator is on this board, & the onboard microphone feeds it’s signal here. The control head is fed directly through to the servo section of the main board.

Drum Motor
Drum Motor

The motor that drives the head drum is another DC brushless 3-phase type.

Hall Sensors
Hall Sensors

These 3 Hall sensors are used by the motor drive to determine the rotor position & time commutation accordingly.

Stator
Stator

The stator on this motor is of interesting construction, with no laminated core, the coils are moulded into the plastic holder. The tach sensor is on the side of the stator core. This senses a small magnet on the outside of the rotor to determine rotational speed. For PAL recordings, the drum rotates at 1500 RPM.

Motor Removed
Motor Removed

Not much under the stator other than the bearing housing & the feedthrough to the rotary transformer.

Head Disc
Head Disc

The heads are mounted onto the top disc of the drum, 4 heads in this recorder. The signals are transmitted to the rotating section through the ferrite rotary transformer on the bottom section.

Head Chip
Head Chip

The tiny winding of the ferrite video head can just about be seen on the end of the brass mounting.

Capstan Motor Components
Capstan Motor Components

The capstan motor is similar to the drum motor, only this one is flat. The rotor has a ferrite magnet, in this case it wasn’t glued in place, just held by it’s magnetic field.

Capstan Motor Stator
Capstan Motor Stator

The PCB on this motor has a steel backing to complete the magnetic circuit, the coils for the 3 motor phases are simply glued in place. The Hall sensors on this motor are placed in the middle of the windings though.
Again there is a tach sensor on the edge of the board that communicates the speed back to the controller. This allows the servo to remain locked at constant speed.

Viewfinder

Viewfinder Assembly
Viewfinder Assembly

As usual with these cameras, this section is the CRT based viewfinder. These units take the composite signal from the camera to display the scene. This one has many more pins than the usual viewfinder. I’ll hack a manual input into this, but I’ll leave that for another post.

Viewfinder Circuits
Viewfinder Circuits

Being an older camera than the ones I’ve had before, this one is on a pair of PCBs, which are both single-sided.

Main Viewfinder Board
Main Viewfinder Board

The main board has all the power components for driving the CRT & some of the adjustments. The main HV flyback transformer is on the right. This part creates both the final anode voltage for the tube & the focus/grid voltages.

Viewfinder Control PCB Top
Viewfinder Control PCB Top

The viewfinder control IC is on a separate daughter board in this camera, with two more controls.

Control IC
Control IC

The control IC is a Matsushita AN2510S, this has all the logic required to separate the sync pulses from the composite signal & generate an image on the CRT.

Viewfinder CRT Frame
Viewfinder CRT Frame

The recording indicator LEDs are mounted in the frame of the CRT & appear above the image in the viewfinder.

Viewfinder CRT With Yoke
Viewfinder CRT With Yoke

Here the CRT has been separated from the rest of the circuitry with just the deflection yoke still attached.

M01JPG5WB CRT
M01JPG5WB CRT

The electron gun in this viewfinder CRT is massive in comparison to the others that I have seen, and the neck of the tube is also much wider. These old tubes were very well manufactured.

Viewfinder Optics
Viewfinder Optics

A simple mirror & magnifying lens completes the viewfinder unit.

Posted on Leave a comment

Motorised Valve

This is the internals of a motorised valve for central heating systems. Here the top is removed showing the motor & microswitch.

Left side of the valve, showing the gearing under the motor, & the valve body under the powerhead.

Right side of the valve, showing the sprung mechanism of the valve quadrant.

Here the motor has been removed from the powerhead, showing the microswitch & the sprung quadrant gear. This spring keeps the valve closed until the motor is energized. The motor remains energized to hold the valve open.

Here the valve body has been opened showing the internal components. The rubber valve rotates on the shaft, blocking the lower port of the valve when in operation.

The motor’s protective cap has been removed here showing the rotor. This is a synchronous motor, of a special type for use in motorised valves. As the windings need to be continuously energized to hold the valve open, it is designed not to burn out under this load. 240v AC 50Hz, 5RPM.

Posted on Leave a comment

Dremel MultiPro

Front
Front

Here we have a Dremel MultiPro rotary tool, a main powered 125W 33,000RPM bit of kit.

Motor Assembly
Motor Assembly

Here the field & controller assembly is removed from the casing.

Armature
Armature

Here is the armature, which rotates at up to 33,000RPM. The brushes rise against the commutator on the left, next to the bearing, the cooling fan is on the right hand side on the power output shaft, the chuck attaches at the far right end of the shaft.

Speed Controller & Brush Box
Speed Controller & Brush Box

Here is the speed controller unit, inside is an SCR phase angle speed controller, to vary the speed of the motor from 10,000RPM to the full rated speed of 33,000RPM.

Mains Filter
Mains Filter

This is the mains filter on the input to the unit, stops stray RF from the motor being radiated down the mains cable.