Quad 44 pre-amp. Minor restoration, and some sensible modifications

Along with the FM tuner I got last week, I also obtained a matching 44 pre-amp and a 405-2 power amplifier. Very nice kit!

The 44 is a very interesting pre-amp. It's got a lovely design of tone control. Quad went their own way with adding tone controls, and made theirs with 3 tone filters and an adjustable slope control.

The look of the thing is even unique.


The pre-amp has a flexible card system. Each input is selected by a CD4066 switch, which connects the selected card. This unit has the standard line-up of "Radio", "Disc" for a Moving magnet cartridge (an MC card is/was available), a CD/AUX card and two tape loops. Excellent.




Not only that, but the Disc card allows differing gains to be selected to accommodate for most carts, and switchable capacitance load too. The tape loops are similarly configurable for level and impedance. Nice....












This later "MKII" model has a re-designed main board and ALPS pots....










Issues....

CD4066? Known for introducing distortion into the signal path. Thankfully Maxim produce the MAX4066. A much better specified, and pin for pin compatible device....

So, before I start, let's make a baseline measurement of THD (Total harmonic distortion) at 1KHz....  0.059% on the CD/AUX channel.

Not too shabby....







Out with the old, and in with the new....

All 4 ICs are changed.








Whilst I'm in there I evict the Red electrolytics, as they're know to fail, although these all read OK.

Let's have a look at the disc card...

It consists of TL071 op-amps.... which are mediocre. I'll swap them out for some better NE5534, which should lower noise a bit, as well as distortion. These are the better NE5534's with 18V/uS slew rate.







... and here is the main issue for me....

The CD/Aux card....

300mV? ... 300mV!!!!

Since when?

Most CD players put out at least a volt...

All this means practically, is we'll need to turn our volume control down everytime we switch to CD. An inconvenience. We *may* overload the input.

I've seen some CD players output as much as 2V, so 300mV is not going to cut it....

It's also originally fitted with a TL072, which I'll change for an NE5532..

I do some googling, and there's various recommendations about changing the resistors in the feedback loop of the card to reduce the gain to unity... but none of the modifications seem to  relate to the input card I have fitted, an M12815:1. I don't have a schematic, so I sketch one out....

... well, it's already a unity-gain amplifier!

So, what to do? I could trace the signal through and change the gain on the main board, but that will leave me with the same discrepancy when switching between CD and disc or radio.... Nothing for it but to add a bit of attenuation in.


Simply adding a 180 ohm resistor across the existing 820 ohm resistor will divide the voltage down to a more respectable level.





... and it's easy to implement...

Don't forget to do both channels.













So after all out mods... how does it measure?

... The THD has dropped to 0.014%....


How does it sound? Noticeably quieter (noise-wise!), but to my cloth ears, I can't really tell much difference in the distortion.

Right, now to the 405-2 Power amp!

Watch this space....

Quad FM4 drifting and amnesia.

So here it is, the wonderful Quad FM4 tuner. A thing of beauty.

This one is an early example and dates from around 1982-83.

It's suffering from amnesia (it won't store stations after a power off) and even in manual tuning the frequency falls after a few minutes use....

Let's see what's wrong...


It's a simple layout. First off the memory battery is shot, and leaking. Thankfully it hasn't damaged the board, and a replacement (Varta Mempac 4.8V, 150mAH) restores it's memory... as for the frequency drift...

The tuner operates by a voltage controlled tuner, there's no synthesiser in here! The memories work by digitising the tuning voltage and storing it, recreating it with a DAC when the preset is selected. The fault is the tuning voltage is falling off. Turns out it's our best friend (and foe!) the elctrolytic capacitor. The guily parties are all 100uF 6.3V types. I changed them all. I dislike 6.3V electrolytics, they seem to give more problems than higher voltage types, even though they were all working well within voltage limits. Perhaps it's their physical size that makes manufacture difficult? ....  (perhaps they just don't like me?!)

Zoom in on the picture and you can see where they are physically leaking.

This cured the drift, but one of the 220uF 16V caps that smoothes the regulated 12V supply looked like it had seen better days, so I changed both of those too... even though they measured OK. One is adjacent to the 12V regulator transistor, which runs a little hot. Never an ideal location for an electrolytic!


Sound quality is great, and will give many years of service now!

Nakamichi RX-202E

This arrived in the workshop.

It's a Nakamichi RX-202E Unidirectional Auto-reverse cassette recorder. A thing of rare beauty and quality. I must say the quality of reproduction on this unit, knocks the Pioneer CT-F1250 we looked at earlier in the year into a cocked hat, but it is substantially younger!

It unidirectional, because the tape only ever travels in one direction, so no need for two capstans, two pinch rollers, and a complicated and compromised head which will play both sides of the cassette or a complicated mechanism to rotate the head.

Oh no, this uses a complicated mechanism to remove the cassette from the transport and turn it over!

A video is worth a thousand words....



All this machine wanted was a service, and a repair to the position sensor pot.

Arduino Astronomical Clock (and pond pump controller) - now with master clock update!

Well, the DS1307 clock module has a tendency to drift about a bit on my Pond pump controller. It can lose a few minutes each month. Irritating at best.

Now the GPS master clock as been created, it should be fairly easy to synchronise the DS1307 with the 433MHz data from the master clock.

The receiver hardware is connected to 5 volts, GND and it's data line is connected to pin 9 of the Arduino. The antenna is simply 17cm of stiff wire.

Once again, the wonderful Virtualwire library is used, and we simply call the receiver routine (remoteClockSet) in the main loop to see if any data has been received. If it has, update the DS1307, and recalculate the sun rise and set times.

There's a few more variables to declare to deal with the incoming time, and, to be honest the whole thing was written a while ago, and is now horribly un-weildy, and could do with a damn good tidy up and re-write, but it works.

No more difting clock!

Here's the code.


// Dawn & Dusk controller with frost protection. // (C) A.G.Doswell 2014 - 2016 // // Date and time functions using a DS1307 RTC connected via I2C and Wire lib // // Designed to control a relay connected to pin A3. Pin goes low during daylight hours and high during night. Relay uses active low, so is // "On" during the day. This is connected to the fountain pump in my garden. // // Time is set using a rotary encoder with integral push button. The Encoder is connected to interrupt pins D2 & D3 (and GND), // and the push button to pin analogue 0 (and GND) // The RTC is connections are: Analogue pin 4 to SDA. Connect analogue pin 5 to SCL. // A 2 x 16 LCD display is connected as follows (NOTE. This is NOT conventional, as interrupt pins are required for the encoder) // Arduino LCD // D4 DB7 // D5 DB6 // D6 DB5 // D7 DB4 // D12 RS // D13 E // // In this revision, there is a Dallas 18B20 Temperature sensor connected to pin 8, enabling frost protection. This is pulled up to +5volts via a 4.7K resistor. // // Use: Pressing and holding the button will enter the clock set mode (on release of the button). Clock is set using the rotary encoder. // The clock must be set to UTC. // Pressing and releasing the button quickly will display the current sun rise and sun set times. Pressing the button again will enter the mode select menu. // Modes are AUTO: On when the sun rises, off when it sets. // AUTO EXTEND : same as above but goes off 1 hour after sunet (nice for summer evenings!) // ON: Permanently ON // OFF: Permanently OFF (Who'd have guessed it?) // // Change the LATTITUDE and LONGITUDE constant to your location. // Use the address finder from http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html to find the address of your temperature sensor and enter it where required in DeviceAddress. // 28th Dec 2014 - Slowed the rate at which the temperature is requested down to once per minute. It has improved the clock display, and solved an issue whereby the temp sensor wasn't always ready to send data, and hung up. // 10th Jan 2015 - Altered the method of updating the temp to something simpler and more sensible! // 17th April 2015 - Stored Mode settings in EEPROM // 3rd Sept 2016 - Updated to run with 433MHz master clock updates. // // // Be sure to visit my website at http://andydoz.blogspot.com #include <Wire.h> #include "RTClib.h" // from https://github.com/adafruit/RTClib #include <LiquidCrystal.h> #include <Encoder.h> // from http://www.pjrc.com/teensy/td_libs_Encoder.html #include <TimeLord.h> // from http://swfltek.com/arduino/timelord.html. When adding it to your IDE, rename the file, removing the "-depreciated" #include <OneWire.h> // from http://playground.arduino.cc/Learning/OneWire #include <DallasTemperature.h> // from http://www.hacktronics.com/code/DallasTemperature.zip. When adding this to your IDE, ensure the .h and .cpp files are in the top directory of the library. #include <EEPROM.h> #define ONE_WIRE_BUS 8 // Data wire from temp sensor is plugged into pin 8 on the Arduino OneWire oneWire(ONE_WIRE_BUS); // Setup a oneWire instance to communicate with any OneWire devices DeviceAddress outsideThermometer = { 0x28, 0x1A, 0x1A, 0x3E, 0x06, 0x00, 0x00, 0xC7 }; // use the address finder from http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html to find the address of your device. RTC_DS1307 RTC; // Tells the RTC library that we're using a DS1307 RTC Encoder knob(2, 3); //encoder connected to pins 2 and 3 (and ground) LiquidCrystal lcd(12, 13, 7, 6, 5, 4); // I used an odd pin combination because I need pin 2 and 3 for the interrupts. //the variables provide the holding values for the set clock routine int setyeartemp; int setmonthtemp; int setdaytemp; int sethourstemp; int setminstemp; int setsecs = 0; int maxday; // maximum number of days in the given month int TimeMins = 0; // number of seconds since midnight int TimerMode = 2; //mode 0=Off 1=On 2=Auto int TimeOut = 10; int TimeOutCounter; // These variables are for the push button routine int buttonstate = 0; //flag to see if the button has been pressed, used internal on the subroutine only int pushlengthset = 3000; // value for a long push in mS int pushlength = pushlengthset; // set default pushlength int pushstart = 0;// sets default push value for the button going low int pushstop = 0;// sets the default value for when the button goes back high int knobval; // value for the rotation of the knob boolean buttonflag = false; // default value for the button flag float tempC; // Temperature // Over-Ride feature flag for Raminda Subhashana boolean OverRideFlag = false; const int TIMEZONE = 0; //UTC const float LATITUDE = 51.000, LONGITUDE = 2.000; // set YOUR position here int Sunrise, Sunset; //sunrise and sunset expressed as minute of day (0-1439) TimeLord myLord; // TimeLord Object, Global variable byte sunTime[] = {0, 0, 0, 1, 1, 13}; // 17 Oct 2013 int SunriseHour, SunriseMin, SunsetHour, SunsetMin; //Variables used to make a decent display of our sunset and sunrise time. DallasTemperature sensors(&oneWire); // Pass our oneWire reference to Dallas Temperature. #include <VirtualWire.h> // set up virtual wire for connection to 433MHZ Rx. #include <VirtualWire_Config.h> // set up integers for remote master clock int TX_ID = 1; int Hours; int Mins; int Secs; int Day; int Month; int Year; boolean Output; char buffer[5]; void setup () { //Serial.begin(57600); //start debug serial interface Wire.begin(); //start I2C interface RTC.begin(); //start RTC interface lcd.begin(16, 2); //Start LCD (defined as 16 x 2 characters) lcd.clear(); pinMode(A0, INPUT); //push button on encoder connected to A0 (and GND) digitalWrite(A0, HIGH); //Pull A0 high pinMode(A1, INPUT); // Over ride push button connected to A1 (and GND) digitalWrite(A1, HIGH); pinMode(A3, OUTPUT); //Relay connected to A3 digitalWrite (A3, HIGH); //sets relay off (default condition) sensors.begin(); sensors.setResolution(outsideThermometer, 12); // set the resolution to 12 bits (why not?!) //Checks to see if the RTC is runnning, and if not, sets the time to the time this sketch was compiled, also sets default mode to 2 and writes to EEPROM lcd.clear(); lcd.print("Waiting for RTC"); delay (3000);// wait a few seconds for the RTC to sort itself out. DateTime now = RTC.now(); if (! RTC.isrunning()) { RTC.adjust(DateTime(__DATE__, __TIME__)); EEPROM.update (0, 2); // set the auto mode as 2 (auto) for default } vw_set_tx_pin(10); // Even though it's not used, we'll define it so the default doesn't interfere with the LCD library. vw_set_rx_pin(9); // RX pin set to pin 9 vw_setup(1200); //sets virtualwire for a tx rate of 300 bits per second, nice and slow! vw_rx_start(); lcd.print("Dawn Dusk Pond"); lcd.setCursor(0, 1); lcd.print("Pump Controller"); delay (2000); lcd.clear(); lcd.print("Version 1.37"); lcd.setCursor(0, 1); lcd.print("(C) A.G.Doswell "); delay (5000); lcd.clear(); //Timelord initialisation myLord.TimeZone(TIMEZONE * 60); myLord.Position(LATITUDE, LONGITUDE); CalcSun (); TimerMode = EEPROM.read (0); // Read TimerMode from EEPROM delay (1000); } void printTemperature(DeviceAddress deviceAddress) { lcd.setCursor (9, 1); tempC = sensors.getTempC(deviceAddress); if (tempC == -127.00) { lcd.print("Err"); } else { lcd.print(tempC); lcd.print((char)0xDF); lcd.print("C "); } } void loop () { remoteClockSet (); DateTime now = RTC.now(); //get time from RTC //Display current time lcd.setCursor (0, 0); lcd.print(now.day(), DEC); lcd.print('/'); lcd.print(now.month()); lcd.print('/'); lcd.print(now.year(), DEC); lcd.print(" "); lcd.setCursor (0, 1); lcd.print(now.hour(), DEC); lcd.print(':'); if (now.minute() < 10) { lcd.print("0"); } lcd.print(now.minute(), DEC); lcd.print(':'); if (now.second() < 10) { lcd.print("0"); } lcd.print(now.second()); lcd.print(" "); //current time in minutes since midnight (used to check against sunrise/sunset easily) TimeMins = (now.hour() * 60) + now.minute(); //Get and display temp every minute if (now.second() == 7) { sensors.requestTemperatures(); // Request temperature delay (249); printTemperature(outsideThermometer); // display on lcd. } // Calculate sun times once a day at a minute past midnight if (TimeMins == 1) { lcd.clear(); CalcSun (); } // Reset Override flag if the sun is up! if (TimeMins == Sunrise) { OverRideFlag = false; } if (TimerMode == 2) { if (TimeMins >= Sunrise && TimeMins <= Sunset - 1 && tempC >= 2 && OverRideFlag == false) { //If it's after sunrise and before sunset, and it's not frozen, and our override isn't set, switch our relay on digitalWrite (A3, LOW); lcd.setCursor (13, 0); lcd.print ("On "); } else { //otherwise switch it off digitalWrite (A3, HIGH); lcd.setCursor (13, 0); lcd.print ("Off"); } } if (TimerMode == 3) { if (TimeMins >= Sunrise && TimeMins <= Sunset + 60 && tempC >= 2 && OverRideFlag == false) { //If it's after sunrise and before sunset + 1 hour, and it's not frozen, and our override isn't set, switch our relay on digitalWrite (A3, LOW); lcd.setCursor (13, 0); lcd.print ("On "); } else { //otherwise switch it off digitalWrite (A3, HIGH); lcd.setCursor (13, 0); lcd.print ("Off"); } } if (TimerMode == 0) { // Off digitalWrite (A3, HIGH); lcd.setCursor (13, 0); lcd.print ("Off"); } if (TimerMode == 1 && tempC >= 2) { // TimerMode is On, but it's not frozen digitalWrite (A3, LOW); lcd.setCursor (13, 0); lcd.print ("On "); } buttonstate = digitalRead(A1);// check to see if our override button is pressed, if it is, set the flag if (buttonstate == LOW ) { OverRideFlag = true; } pushlength = pushlengthset; pushlength = getpushlength (); delay (10); if (pushlength < pushlengthset) { lcd.clear (); ShortPush (); lcd.clear (); } //This runs the setclock routine if the knob is pushed for a long time if (pushlength > pushlengthset) { lcd.clear(); DateTime now = RTC.now(); setyeartemp = now.year(), DEC; setmonthtemp = now.month(), DEC; setdaytemp = now.day(), DEC; sethourstemp = now.hour(), DEC; setminstemp = now.minute(), DEC; setclock(); pushlength = pushlengthset; }; } //sets the clock void setclock () { setyear (); lcd.clear (); setmonth (); lcd.clear (); setday (); lcd.clear (); sethours (); lcd.clear (); setmins (); lcd.clear(); RTC.adjust(DateTime(setyeartemp, setmonthtemp, setdaytemp, sethourstemp, setminstemp, setsecs)); //set the DS1307 RTC CalcSun (); //refresh the sunrise and sunset times delay (1000); } // subroutine to return the length of the button push. int getpushlength () { buttonstate = digitalRead(A0); if (buttonstate == LOW && buttonflag == false) { pushstart = millis(); buttonflag = true; }; if (buttonstate == HIGH && buttonflag == true) { pushstop = millis (); pushlength = pushstop - pushstart; buttonflag = false; }; return pushlength; } // The following subroutines set the individual clock parameters int setyear () { lcd.setCursor (0, 0); lcd.print ("Set Year"); pushlength = pushlengthset; pushlength = getpushlength (); if (pushlength != pushlengthset) { return setyeartemp; } lcd.setCursor (0, 1); knob.write(0); delay (50); knobval = knob.read(); if (knobval < -1) { //bit of software de-bounce knobval = -1; } if (knobval > 1) { knobval = 1; } setyeartemp = setyeartemp + knobval; if (setyeartemp < 2014) { //Year can't be older than currently, it's not a time machine. setyeartemp = 2014; } lcd.print (setyeartemp); lcd.print(" "); setyear(); } int setmonth () { lcd.setCursor (0, 0); lcd.print ("Set Month"); pushlength = pushlengthset; pushlength = getpushlength (); if (pushlength != pushlengthset) { return setmonthtemp; } lcd.setCursor (0, 1); knob.write(0); delay (50); knobval = knob.read(); if (knobval < -1) { knobval = -1; } if (knobval > 1) { knobval = 1; } setmonthtemp = setmonthtemp + knobval; if (setmonthtemp < 1) {// month must be between 1 and 12 setmonthtemp = 1; } if (setmonthtemp > 12) { setmonthtemp = 12; } lcd.print (setmonthtemp); lcd.print(" "); setmonth(); } int setday () { if (setmonthtemp == 4 || setmonthtemp == 5 || setmonthtemp == 9 || setmonthtemp == 11) { //30 days hath September, April June and November maxday = 30; } else { maxday = 31; //... all the others have 31 } if (setmonthtemp == 2 && setyeartemp % 4 == 0) { //... Except February alone, and that has 28 days clear, and 29 in a leap year. maxday = 29; } if (setmonthtemp == 2 && setyeartemp % 4 != 0) { maxday = 28; } lcd.setCursor (0, 0); lcd.print ("Set Day"); pushlength = pushlengthset; pushlength = getpushlength (); if (pushlength != pushlengthset) { return setdaytemp; } lcd.setCursor (0, 1); knob.write(0); delay (50); knobval = knob.read(); if (knobval < -1) { knobval = -1; } if (knobval > 1) { knobval = 1; } setdaytemp = setdaytemp + knobval; if (setdaytemp < 1) { setdaytemp = 1; } if (setdaytemp > maxday) { setdaytemp = maxday; } lcd.print (setdaytemp); lcd.print(" "); setday(); } int sethours () { lcd.setCursor (0, 0); lcd.print ("Set Hours"); pushlength = pushlengthset; pushlength = getpushlength (); if (pushlength != pushlengthset) { return sethourstemp; } lcd.setCursor (0, 1); knob.write(0); delay (50); knobval = knob.read(); if (knobval < -1) { knobval = -1; } if (knobval > 1) { knobval = 1; } sethourstemp = sethourstemp + knobval; if (sethourstemp < 1) { sethourstemp = 1; } if (sethourstemp > 23) { sethourstemp = 23; } lcd.print (sethourstemp); lcd.print(" "); sethours(); } int setmins () { lcd.setCursor (0, 0); lcd.print ("Set Mins"); pushlength = pushlengthset; pushlength = getpushlength (); if (pushlength != pushlengthset) { return setminstemp; } lcd.setCursor (0, 1); knob.write(0); delay (50); knobval = knob.read(); if (knobval < -1) { knobval = -1; } if (knobval > 1) { knobval = 1; } setminstemp = setminstemp + knobval; if (setminstemp < 0) { setminstemp = 0; } if (setminstemp > 59) { setminstemp = 59; } lcd.print (setminstemp); lcd.print(" "); setmins(); } int setmode () { //Sets the mode of the timer. Auto, On or Off lcd.setCursor (0, 0); lcd.print ("Set Mode"); pushlength = pushlengthset; pushlength = getpushlength (); if (pushlength != pushlengthset) { EEPROM.update (0, TimerMode); //write the mode setting to EEPROM return TimerMode; } lcd.setCursor (0, 1); knob.write(0); delay (50); knobval = knob.read(); if (knobval < -1) { knobval = -1; } if (knobval > 1) { knobval = 1; } TimerMode = TimerMode + knobval; if (TimerMode < 0) { TimerMode = 0; } if (TimerMode > 3) { TimerMode = 3; } if (TimerMode == 0) { lcd.print("Off "); lcd.print(" "); } if (TimerMode == 1) { lcd.print("On "); lcd.print(" "); } if (TimerMode == 2) { lcd.print("Auto "); lcd.print(" "); } if (TimerMode == 3) { lcd.print("Auto Extend"); lcd.print(" "); } setmode (); } int CalcSun () { //Calculates the Sunrise and Sunset times DateTime now = RTC.now(); sunTime[3] = now.day(); // Give Timelord the current date sunTime[4] = now.month(); sunTime[5] = now.year(); myLord.SunRise(sunTime); // Computes Sun Rise. Sunrise = sunTime[2] * 60 + sunTime[1]; // Sunrise returned in minutes past midnight SunriseHour = sunTime[2]; SunriseMin = sunTime [1]; sunTime[3] = now.day(); // Uses the Time library to give Timelord the current date sunTime[4] = now.month(); sunTime[5] = now.year(); myLord.SunSet(sunTime); // Computes Sun Set. Sunset = sunTime[2] * 60 + sunTime[1]; // Sunset returned in minutes past midnight SunsetHour = sunTime[2]; SunsetMin = sunTime [1]; } void ShortPush () { //This displays the calculated sunrise and sunset times when the knob is pushed for a short time. for (long Counter = 0; Counter < 604 ; Counter ++) { //returns to the main loop if it's been run 604 times //(don't ask me why I've set 604,it seemed like a good number) lcd.setCursor (0, 0); lcd.print ("Sunrise "); lcd.print (SunriseHour); lcd.print (":"); if (SunriseMin < 10) { lcd.print("0"); } lcd.print (SunriseMin); lcd.setCursor (0, 1); lcd.print ("Sunset "); lcd.print (SunsetHour); lcd.print (":"); if (SunsetMin < 10) { lcd.print("0"); } lcd.print (SunsetMin); //If the knob is pushed again, enter the mode set menu pushlength = pushlengthset; pushlength = getpushlength (); if (pushlength != pushlengthset) { lcd.clear (); TimerMode = setmode (); } } } void remoteClockSet () { typedef struct rxRemoteData //Defines the received data, this is the same as the TX struct { int TX_ID; int Hours; int Mins; int Secs; int Day; int Month; int Year; }; struct rxRemoteData receivedData; uint8_t rcvdSize = sizeof(receivedData); if (vw_get_message((uint8_t *)&receivedData, &rcvdSize)) { if (receivedData.TX_ID == 1) { //Only if the TX_ID=1 do we process the data, and set the DS1307 int TX_ID = receivedData.TX_ID; int Hours = receivedData.Hours; int Mins = receivedData.Mins; int Secs = receivedData.Secs; int Day = receivedData.Day; int Month = receivedData.Month; int Year = receivedData.Year; RTC.adjust(DateTime(Year, Month, Day, Hours, Mins, Secs)); //set the DS1307 RTC CalcSun (); //refresh the sunrise and sunset times lcd.clear(); lcd.setCursor (0, 0); lcd.print ("Clock Updated"); delay (1000); lcd.clear(); } } }