Thank you.

Well, some time last week, my humble website slipped past 40,000 page hits.

Thank you all so very much.

Here's some stats since it's inception back in May '14

A quick look at the Quad ESL 57 loudspeaker.

Remember the Quad gear I got a while back? Included were a pair of the famous Quad ESL 57 speakers.

I've been dreading looking at these, because the serial numbers indicated they were quite early units, dating around 1960 or so... and these don't age particularly well, as the electrostatic panels start to fail with age...










Now, for those not au fait with electrostatic speakers, they work in a different manner to conventional speakers (which have a cone to radiate the sound, driven by a coil of wire and a magnet). The speaker diaphragm itself is a piece of metalised plastic film, which is charged up to several kilovolts. Audio is modulated onto this high voltage by a transformer, which causes the film to vibrate, and produce sound.

The ESL 57 is so-called because Quad started production in 1957. Each speaker has three panels, two bass and one smaller treble panel. All three panels run from top to bottom. Bass left and right of the central treble panel.

This is one of the pair with the back removed. You can see the three panels. There's a large audio transformer in the bottom left, and a smaller power supply unit to the right.

The power supply consists of a transformer, which steps-up the mains voltage to around ~650VAC and feeds a rectifier and voltage multiplier, which derives the ~4KV to charge the panels.




Here's one of the audio transformers...

... and here's one of the power supply units. You can see the transformer, and the multiplier unit above it, thankfully indicating this speaker was rebuilt sometime after May 1972. The other speaker was rebuilt at the same time by Quad.









The mains wiring (externally) was in poor shape, and lacked a safety earth, so was replaced, and the speakers gingerly powered up.... both fired up and produced audio straight away, although they were both quiet. (The temptation here is to whack the volume up, but these speakers are only rated at a few watts (maybe 20), to match the original Quad II amplifier (or a 405-2 fitted with voltage limiters as mine was here.) Winding the volume up causes the audio modulating voltage to rise, and cause the speaker to arc over, and can cause irreparable damage to the panel, necessitating a re-build. ) After a few minutes, the volume slowly increased as the panels charged up.

Now I had never heard a pair before, but I had heard comments that they don't produce much bass. Well, that's true to an extent. Don't expect trouser-flapping amounts of bass, but what there is is very detailed, and the treble is incredible. A pair image fantastically. You do really need to be sat in the right place in front of them to get the best effect, but they are something else. The music seems to be in your head.

I was hooked. I then wasted away a whole evening just listening to music.

Sadly Mrs Doz is not quite so hooked. They're big (although slim), and not exactly matching Mrs Doz' impeccable interior decorating standards... so they must sadly go.

Technics SU-V40 amplifier repair.

It's time for this thing's turn on the bench.

It's a rather tatty looking Technics SU-V40 amplifier, dating from about 1986-87

It should be a great performer, but this one isn't...

It works after a fashion, but all is not well. It has a "rustle" on the left channel. Probably a dirty pot, I thought.

The amp has a slightly unusual look to it internally, as the main output stage has a small heatsink, coupled by a "heat-pipe" to a large heatsink to it's left.

This is the current amplifier....









...It's a large "Class AA" IC...

I'm not quite sure what Class AA is, but it's really Class AB1!








This is the driver, or voltage amplifier..













I cleaned up the volume pot, which, whilst noisy, wasn't the source of the rustling sound ...

Then a clue, as the amp warmed up, the current drive LED flickered along with the rustle, indicating the amp was trying to go into "protection" mode and cut out...










Sure enough there was a small DC offset occurring on the left hand output... I cleaned up the two bias pots. This didn't help.

It turns out Q409 is thermally poor and noisy. It starts off bad when it's cold, and gets worse as it warms up! A quick squirt with freezer spray on the cheap proves it's guilt. It's a 2SC2631 in the voltage amplifier. Amazingly, I have one..






Replacing it provides a complete cure. Another saved from landfill, even if it looks like it was already there!

Soak tested with Debut by Björk, a fine album I'd forgotten about...

Nakamichi Dragon.

Nate called.

"Can you give my Dragon a service?"

Yeah ... why not?

I though I'd share a few photos.

This must be the Rolls-royce of cassette decks. Adjustable everything.

There's a lot going on inside...

It's auto reverse, but in standard form, with two pinch rollers, rather than the "flip the tape round" of the Nakamichi RX series

... here's what makes it special...











... see those 4 gear wheels? They are used to alter the azmuth alignment of the head on the fly.

A truly remarkable piece of engineering, and the pinnacle of cassette reproduction!








I've heard some rumours on various forums that the playback of pre-recorded and tapes recorded on other machines is not so good on these decks. I must say that's not my experience at all. Playback is superb.

"Solder creep" and an unpleasant smell...

Just been sat in the workshop doing a few little jobs, and there's a funny small of something getting too warm. I've noticed it on and off for a couple of days, thought it was the wood burning stove in the other room yesterday, but tonight, it's definitely coming from round the computer area.... immediate investigation required.

After a couple of mins I found it.

There's an extension block connected to the output from a UPS. It's warm. Damn warm....


Further investigation shows the neutral has been overheating. I've disconnected it here. The wire has been soldered! Never, ever solder a mains cable (or any stranded cable for that matter) before fitting it into a screw type fitting. The solder "creeps" up the cable, and leaves a resistive loose connection behind.

This lead was carrying less than 500W ... so nowhere near maximum load.

I wonder how many more of this brand I have?

Not many I hope. This one's for the bin...

Arduino 1.6.x compiler options...

I'd noticed recently that since I'd upgraded the Arduino IDE to 1.6.x, some programs compiled and were smaller than they used to be. Great!

... the also don't run so fast... not so great.

After some googling around, the compiler options for optimisation had been changed.

So if you need something to compile and run quickly, you can.

Here's how to change it...

Navigate your way to the default Arduino directory in program files, and locate the platform.txt file

On my windows box, it's at C:\Program Files (x86)\Arduino\hardware\arduino\avr
On my Ubuntu box it's Home\Downloads\arduino-1.6.12\hardware\arduino\avr  (Why did I ./install.sh from the downloads folder!!!)

there's also one in the \hardware directory itself. That's not it!

Mine looks like this :

# Arduino AVR Core and platform. # ------------------------------ # # For more info: # https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5-3rd-party-Hardware-specification name=Arduino AVR Boards version=1.6.14 # AVR compile variables # --------------------- compiler.warning_flags=-w compiler.warning_flags.none=-w compiler.warning_flags.default= compiler.warning_flags.more=-Wall compiler.warning_flags.all=-Wall -Wextra # Default "compiler.path" is correct, change only if you want to override the initial value compiler.path={runtime.tools.avr-gcc.path}/bin/ compiler.c.cmd=avr-gcc compiler.c.flags=-c -g -Os {compiler.warning_flags} -std=gnu11 -ffunction-sections -fdata-sections -MMD -flto -fno-fat-lto-objects compiler.c.elf.flags={compiler.warning_flags} -Os -flto -fuse-linker-plugin -Wl,--gc-sections compiler.c.elf.cmd=avr-gcc compiler.S.flags=-c -g -x assembler-with-cpp -flto compiler.cpp.cmd=avr-g++ compiler.cpp.flags=-c -g -Os {compiler.warning_flags} -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD -flto compiler.ar.cmd=avr-gcc-ar compiler.ar.flags=rcs compiler.objcopy.cmd=avr-objcopy compiler.objcopy.eep.flags=-O ihex -j .eeprom --set-section-flags=.eeprom=alloc,load --no-change-warnings --change-section-lma .eeprom=0 compiler.elf2hex.flags=-O ihex -R .eeprom compiler.elf2hex.cmd=avr-objcopy compiler.ldflags= compiler.size.cmd=avr-size # This can be overridden in boards.txt build.extra_flags= # These can be overridden in platform.local.txt compiler.c.extra_flags= compiler.c.elf.extra_flags= compiler.S.extra_flags= compiler.cpp.extra_flags= compiler.ar.extra_flags= compiler.objcopy.eep.extra_flags= compiler.elf2hex.extra_flags= # AVR compile patterns # -------------------- ## Compile c files recipe.c.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.c.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.c.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{object_file}" ## Compile c++ files recipe.cpp.o.pattern="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{object_file}" ## Compile S files recipe.S.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.S.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.S.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{object_file}" ## Create archives # archive_file_path is needed for backwards compatibility with IDE 1.6.5 or older, IDE 1.6.6 or newer overrides this value archive_file_path={build.path}/{archive_file} recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{archive_file_path}" "{object_file}" ## Combine gc-sections, archives, and objects recipe.c.combine.pattern="{compiler.path}{compiler.c.elf.cmd}" {compiler.c.elf.flags} -mmcu={build.mcu} {compiler.c.elf.extra_flags} -o "{build.path}/{build.project_name}.elf" {object_files} "{build.path}/{archive_file}" "-L{build.path}" -lm ## Create output files (.eep and .hex) recipe.objcopy.eep.pattern="{compiler.path}{compiler.objcopy.cmd}" {compiler.objcopy.eep.flags} {compiler.objcopy.eep.extra_flags} "{build.path}/{build.project_name}.elf" "{build.path}/{build.project_name}.eep" recipe.objcopy.hex.pattern="{compiler.path}{compiler.elf2hex.cmd}" {compiler.elf2hex.flags} {compiler.elf2hex.extra_flags} "{build.path}/{build.project_name}.elf" "{build.path}/{build.project_name}.hex" ## Save hex recipe.output.tmp_file={build.project_name}.hex recipe.output.save_file={build.project_name}.{build.variant}.hex ## Compute size recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf" recipe.size.regex=^(?:\.text|\.data|\.bootloader)\s+([0-9]+).* recipe.size.regex.data=^(?:\.data|\.bss|\.noinit)\s+([0-9]+).* recipe.size.regex.eeprom=^(?:\.eeprom)\s+([0-9]+).* ## Preprocessor preproc.includes.flags=-w -x c++ -M -MG -MP recipe.preproc.includes="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} {preproc.includes.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {includes} "{source_file}" preproc.macros.flags=-w -x c++ -E -CC recipe.preproc.macros="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} {preproc.macros.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{preprocessed_file_path}" # AVR Uploader/Programmers tools # ------------------------------ tools.avrdude.path={runtime.tools.avrdude.path} tools.avrdude.cmd.path={path}/bin/avrdude tools.avrdude.config.path={path}/etc/avrdude.conf tools.avrdude.upload.params.verbose=-v tools.avrdude.upload.params.quiet=-q -q tools.avrdude.upload.params.noverify=-V tools.avrdude.upload.pattern="{cmd.path}" "-C{config.path}" {upload.verbose} {upload.verify} -p{build.mcu} -c{upload.protocol} -P{serial.port} -b{upload.speed} -D "-Uflash:w:{build.path}/{build.project_name}.hex:i" tools.avrdude.program.params.verbose=-v tools.avrdude.program.params.quiet=-q -q tools.avrdude.program.params.noverify=-V tools.avrdude.program.pattern="{cmd.path}" "-C{config.path}" {program.verbose} {program.verify} -p{build.mcu} -c{protocol} {program.extra_params} "-Uflash:w:{build.path}/{build.project_name}.hex:i" tools.avrdude.erase.params.verbose=-v tools.avrdude.erase.params.quiet=-q -q tools.avrdude.erase.pattern="{cmd.path}" "-C{config.path}" {erase.verbose} -p{build.mcu} -c{protocol} {program.extra_params} -e -Ulock:w:{bootloader.unlock_bits}:m -Uefuse:w:{bootloader.extended_fuses}:m -Uhfuse:w:{bootloader.high_fuses}:m -Ulfuse:w:{bootloader.low_fuses}:m tools.avrdude.bootloader.params.verbose=-v tools.avrdude.bootloader.params.quiet=-q -q tools.avrdude.bootloader.pattern="{cmd.path}" "-C{config.path}" {bootloader.verbose} -p{build.mcu} -c{protocol} {program.extra_params} "-Uflash:w:{runtime.platform.path}/bootloaders/{bootloader.file}:i" -Ulock:w:{bootloader.lock_bits}:m tools.avrdude_remote.upload.pattern=/usr/bin/run-avrdude /tmp/sketch.hex {upload.verbose} -p{build.mcu} # USB Default Flags # Default blank usb manufacturer will be filled in at compile time # - from numeric vendor ID, set to Unknown otherwise build.usb_manufacturer="Unknown" build.usb_flags=-DUSB_VID={build.vid} -DUSB_PID={build.pid} '-DUSB_MANUFACTURER={build.usb_manufacturer}' '-DUSB_PRODUCT={build.usb_product}'

Now I'd rename this to platform.old, so it's there if we screw it up, or wish to revert to slower, but more space-efficient code.

Now, open this file in your favorite text editor (mine's Notepad++ on windows) and do a find and replace on all instances of -Os (that's the letter O) and replace it with -O2 (again, the letter O) There are 3 instances of it in my file...

Bingo, save that as platform.txt in the directory, and you're done.

Here's my modified file...

# Arduino AVR Core and platform. # ------------------------------ # # For more info: # https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5-3rd-party-Hardware-specification name=Arduino AVR Boards version=1.6.14 # AVR compile variables # --------------------- compiler.warning_flags=-w compiler.warning_flags.none=-w compiler.warning_flags.default= compiler.warning_flags.more=-Wall compiler.warning_flags.all=-Wall -Wextra # Default "compiler.path" is correct, change only if you want to override the initial value compiler.path={runtime.tools.avr-gcc.path}/bin/ compiler.c.cmd=avr-gcc compiler.c.flags=-c -g -O2 {compiler.warning_flags} -std=gnu11 -ffunction-sections -fdata-sections -MMD -flto -fno-fat-lto-objects compiler.c.elf.flags={compiler.warning_flags} -O2 -flto -fuse-linker-plugin -Wl,--gc-sections compiler.c.elf.cmd=avr-gcc compiler.S.flags=-c -g -x assembler-with-cpp -flto compiler.cpp.cmd=avr-g++ compiler.cpp.flags=-c -g -O2 {compiler.warning_flags} -std=gnu++11 -fpermissive -fno-exceptions -ffunction-sections -fdata-sections -fno-threadsafe-statics -MMD -flto compiler.ar.cmd=avr-gcc-ar compiler.ar.flags=rcs compiler.objcopy.cmd=avr-objcopy compiler.objcopy.eep.flags=-O ihex -j .eeprom --set-section-flags=.eeprom=alloc,load --no-change-warnings --change-section-lma .eeprom=0 compiler.elf2hex.flags=-O ihex -R .eeprom compiler.elf2hex.cmd=avr-objcopy compiler.ldflags= compiler.size.cmd=avr-size # This can be overridden in boards.txt build.extra_flags= # These can be overridden in platform.local.txt compiler.c.extra_flags= compiler.c.elf.extra_flags= compiler.S.extra_flags= compiler.cpp.extra_flags= compiler.ar.extra_flags= compiler.objcopy.eep.extra_flags= compiler.elf2hex.extra_flags= # AVR compile patterns # -------------------- ## Compile c files recipe.c.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.c.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.c.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{object_file}" ## Compile c++ files recipe.cpp.o.pattern="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{object_file}" ## Compile S files recipe.S.o.pattern="{compiler.path}{compiler.c.cmd}" {compiler.S.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.S.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{object_file}" ## Create archives # archive_file_path is needed for backwards compatibility with IDE 1.6.5 or older, IDE 1.6.6 or newer overrides this value archive_file_path={build.path}/{archive_file} recipe.ar.pattern="{compiler.path}{compiler.ar.cmd}" {compiler.ar.flags} {compiler.ar.extra_flags} "{archive_file_path}" "{object_file}" ## Combine gc-sections, archives, and objects recipe.c.combine.pattern="{compiler.path}{compiler.c.elf.cmd}" {compiler.c.elf.flags} -mmcu={build.mcu} {compiler.c.elf.extra_flags} -o "{build.path}/{build.project_name}.elf" {object_files} "{build.path}/{archive_file}" "-L{build.path}" -lm ## Create output files (.eep and .hex) recipe.objcopy.eep.pattern="{compiler.path}{compiler.objcopy.cmd}" {compiler.objcopy.eep.flags} {compiler.objcopy.eep.extra_flags} "{build.path}/{build.project_name}.elf" "{build.path}/{build.project_name}.eep" recipe.objcopy.hex.pattern="{compiler.path}{compiler.elf2hex.cmd}" {compiler.elf2hex.flags} {compiler.elf2hex.extra_flags} "{build.path}/{build.project_name}.elf" "{build.path}/{build.project_name}.hex" ## Save hex recipe.output.tmp_file={build.project_name}.hex recipe.output.save_file={build.project_name}.{build.variant}.hex ## Compute size recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf" recipe.size.regex=^(?:\.text|\.data|\.bootloader)\s+([0-9]+).* recipe.size.regex.data=^(?:\.data|\.bss|\.noinit)\s+([0-9]+).* recipe.size.regex.eeprom=^(?:\.eeprom)\s+([0-9]+).* ## Preprocessor preproc.includes.flags=-w -x c++ -M -MG -MP recipe.preproc.includes="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} {preproc.includes.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {includes} "{source_file}" preproc.macros.flags=-w -x c++ -E -CC recipe.preproc.macros="{compiler.path}{compiler.cpp.cmd}" {compiler.cpp.flags} {preproc.macros.flags} -mmcu={build.mcu} -DF_CPU={build.f_cpu} -DARDUINO={runtime.ide.version} -DARDUINO_{build.board} -DARDUINO_ARCH_{build.arch} {compiler.cpp.extra_flags} {build.extra_flags} {includes} "{source_file}" -o "{preprocessed_file_path}" # AVR Uploader/Programmers tools # ------------------------------ tools.avrdude.path={runtime.tools.avrdude.path} tools.avrdude.cmd.path={path}/bin/avrdude tools.avrdude.config.path={path}/etc/avrdude.conf tools.avrdude.upload.params.verbose=-v tools.avrdude.upload.params.quiet=-q -q tools.avrdude.upload.params.noverify=-V tools.avrdude.upload.pattern="{cmd.path}" "-C{config.path}" {upload.verbose} {upload.verify} -p{build.mcu} -c{upload.protocol} -P{serial.port} -b{upload.speed} -D "-Uflash:w:{build.path}/{build.project_name}.hex:i" tools.avrdude.program.params.verbose=-v tools.avrdude.program.params.quiet=-q -q tools.avrdude.program.params.noverify=-V tools.avrdude.program.pattern="{cmd.path}" "-C{config.path}" {program.verbose} {program.verify} -p{build.mcu} -c{protocol} {program.extra_params} "-Uflash:w:{build.path}/{build.project_name}.hex:i" tools.avrdude.erase.params.verbose=-v tools.avrdude.erase.params.quiet=-q -q tools.avrdude.erase.pattern="{cmd.path}" "-C{config.path}" {erase.verbose} -p{build.mcu} -c{protocol} {program.extra_params} -e -Ulock:w:{bootloader.unlock_bits}:m -Uefuse:w:{bootloader.extended_fuses}:m -Uhfuse:w:{bootloader.high_fuses}:m -Ulfuse:w:{bootloader.low_fuses}:m tools.avrdude.bootloader.params.verbose=-v tools.avrdude.bootloader.params.quiet=-q -q tools.avrdude.bootloader.pattern="{cmd.path}" "-C{config.path}" {bootloader.verbose} -p{build.mcu} -c{protocol} {program.extra_params} "-Uflash:w:{runtime.platform.path}/bootloaders/{bootloader.file}:i" -Ulock:w:{bootloader.lock_bits}:m tools.avrdude_remote.upload.pattern=/usr/bin/run-avrdude /tmp/sketch.hex {upload.verbose} -p{build.mcu} # USB Default Flags # Default blank usb manufacturer will be filled in at compile time # - from numeric vendor ID, set to Unknown otherwise build.usb_manufacturer="Unknown" build.usb_flags=-DUSB_VID={build.vid} -DUSB_PID={build.pid} '-DUSB_MANUFACTURER={build.usb_manufacturer}' '-DUSB_PRODUCT={build.usb_product}'

You can now enjoy faster, but fatter sketches!

.. or not!

NAD 5425 CD player - no display

Just a quick one. This delightful NAD 5425 CD player.

Arrived skipping / not reading discs and no display.


Skipping and intermittently not reading discs was an easy fix, a quick clean up of the optics with an airduster, and very careful cleaning of the lens (DON'T USE IPA HERE! - it can damage the optical coating on the lens. It's easy just to breathe on it, and give it a gentle wipe with something lint-free). That had it playing even the most mangy looking disc!




No display?



Let investigate...

The main board is removed ....









.. and the display cowl removed (there's a couple of screws underneath, and a plastic clip.)












... and an open-circuit incandescent lamp is the culprit...










To improve reliability, and LED and 1K limiting resistor is fixed in place. Note the capton tape to insulate it electrically from the links on the board below. Anode (+ve) is to the right in this picture.

The LED I chose was a wide-angle, warm white LED, which I hope will match the original incandescent lamp closely.







... which is does nicely!














I've not tried these wide-angle LEDs before. They're quite good. These are both warm white examples, although they differ in colour slightly! You can clearly see the focussed "beam" coming from the right hand LED, and the much more diffuse spread of light from the left hand "wide-angle" LED.





Job done. Another saved from landfill!

Leak 2100 amplifier repairs.

A while back, David (from the motherland) donated some stuff to the cause.

This Leak amplifier was amongst the things he dropped off...

Dating from around 1974, and mostly valueless... eBay prices these at about £30 at the time of writing.

Still, there's no point in it just sitting in a pile...






It's been through the wars a bit, but that's OK. I need something to practise my veneering skills on, for a forthcoming turntable project, so this may do as a test bed...










Typical 70's construction.

I'd labelled the amp up "Hums" ....










There's something unpleasant oozing out of the top of the positive rail smoothing cap... It's a 6,800uF 40V part....










... I have some 10,000uF 63V parts, which are slightly fatter, but much shorter. The fit in the clips OK, so they'll do....

Powering up instantly blows both 5A fuses on the main board. You can see in the photo, I've lifted R3 and R5 on the small vertical PCB. This is the protection board. It's purpose in life is to blow fuses by shorting out the supply rails with a triac in the event of there being more that 0.5VDC on the speaker outputs. A sort of crowbar circuit.

Powering up again, with new fuses and checking the speaker outputs (with no speakers attached) for DC shows everything in order.

R3 and R5 are soldered back into position and power is applied again. All is well. I wonder if one rail came up before the other due to the new/larger caps?

I check round the caps on the main board for ESR. Remarkably, they all check out OK. Every last one of them! I even checked the calibration on the ESR meter because I doubted it!


The power indicator lamp on the front doesn't work, because, well... it's missing. I'll make up some white LED's to go in...











I had a short length of LED strip left over from when I fitted some lighting in my kitchen, so I cut off a short length. The voltage supply for the lamps is half wave rectified, with no smoothing. It peaks at around 20 volts, so I added a 470 ohm resistor to limit the current a bit, and added 100uF to smooth the supply a bit, so the LED's don't flicker.




I removed the original lamp holder, and fixed the strip in place with a spot of hot-melt.

Looks good....








After a prolonged test in the workshop, the amp remains well-mannered, and sounds decent. It's quiet and produces around 30 watts into 8 ohms. I'm actually quite taken with it, so much so, I'm going to put it in the main hifi set up for a bit.. one issue though... the input sensitivity. It's a tiny 140mV for line inputs. We'll need to fit an attenuator on the input I intend to use for the CD player. Thankfully there's an attenuator switch fitted to the Tuner input, which is switched on the back for two different levels. Looking at the circuit, my calculations show it'll do as it stands. Good news!

Now to make up some 5-pin DIN to RCA leads, and order some veneer!

Talking of 5-pin DIN plugs... this Leak doesn't quite follow convention....


1 is Right input
2 is GND
3 is Left input.


4 is Right output for Tape/cassette
5 is Left output for Tape/cassette....

Wharfdale Airedale SP2 Speakers.

Well, there appears to scant information on the web about these wonderful speakers, so I thought I'd share some pictures of mine up. Sadly they're not going to be with me long, as they're not exactly wife-friendly, due to there huge size (H 88cm W 46.5cm D 44cm!)

They were Wharfdale's top-of-the-range speakers in the mid 70's.

Tweeter. I saw a thread on a forum that said these were ribbon tweeters, but I don't think so. How do you make a round ribbon?

Upper mid-range, with felt suspension...

4" mid-range, again with felt suspension.












... and the 10" bass driver, with rubber suspension.

They sound fantastic, and are in really good condition. Speakers of this age generally start to have problems with the suspension breaking up, but these are just great. Sadly they're just too big...so it's off to eBay with them :(

Quad 405-2 Amplifier - restoration.

The next part of the Quad series. The mighty 405-2 power amplifier. Famed for it's current dumping design.

This amplifier was made around 1984, as some of the RCA transistors are nicely dated.

This amplifier isn't performing too well. It's distorting, and humming slightly.
















The amplifier is nicely laid out, although I'm not too impressed with the safety earthing arrangements. The earth is taken to a point a long way from where the supply is grounded. This can exacerbate ground loop issues. This amp hums, and I also have a friend whose 405 hums quite badly. Could this be the cause?





The ground connections to the speakers are also made separately...










Removal of each amplifier board is made easy by removing the two rubber bungs thoughtfully supplied by Quad, which allow insertion of a long screwdriver to gain access to the lower screws securing each board to the large heatsink at the front. The boards fitted to this amplifier are rev. 7 boards, and are also fitted with voltage limiters, so It's suitable for driving Quad's ESL speakers.







First inspection of the amplifier show some of the Red cased electrolytic capacitors are showing signs of age, looking a bit "sweaty" and having cracked cases.

Two of the caps in my amp (C17 & C2) are bi-polar, which is a pain. C2 can be replaced by a conventional electrolytic, with the positive side to ground, but C17 must remain bi-polar... which is a pain , because they're awful and I don't stock any!









Low-and-behold, C5, a 6.3V Electrolytic is leaking and has turned the pin green!

Both of the large 10,000uF capacitors test like new, so they can stay.
















I decided, in an effort to mitigate any ground-loop issues, to ground the speakers and the mains safety earth back to the same point.








So after a blanket change of the capacitors, the amplifier powers up, and tests very well, with no adverse behaviour, and there's certainly no perceivable hum! All the unpleasant distortion has gone :)

There are quite a few websites detailing modifications to this amplifier, in particular Keith Snook's site (here), I did think about implementing some of these modifications, but I'm rather taken with it in stock form, so it will stay like that!

Guilty as changed, your honour ! (There's a joke in there!)