Information and Enhancements/Corrections on the Philips EE2000/EE2001 series

Keywords: Philips EE kits, EE2000 series, EE2001 series, LM3900, EE2005 superhets, IF Coil data

This page presents additional information sources and/or enhancements/corrections based on my personal experiences. Please respond if you have (other) improvements or information sources as well.

EE2000 Series (applies also to EE1000 and EE3000 series)

1.1 (EE2003/4/5/6) Suggested redesign of two-transistor audio amplifier stages

In many constructions a two-stage audio amplifier is used to drive a loudspeaker. In almost all cases (for example the EE2003 medium wave receiver 5.02, the only exception is the 5.03 SW receiver) a design is used in which the 10K potentiometer (volume control) drives two subsequent BC238 transistor stages, the latter tied together directly via a 4.7uF or 10uF elco. This approach has the following drawbacks:

• As the potentiometers age, more and more noisy disturbances are produced when turning the potentiometer. With two subsequent amplifier stages these disturbances are amplified many times as well, resulting in a low-quality audio output when changing the volume.
• In the EE2005 superhet receivers the performance of the diode detector part is degraded severely by the fact that the volume control is applied after the detector part, probably due to the fact that the loading of the detector circuit changes when adjusting the volume.

A better approach is to change the location of the volume control in the circuits; the 10K potentiometer should be put in between the two white transistors instead of before them. The SW receiver on this website shows such a configuration, as well as the way to couple the audio circuit with a preceding circuit. I have applied it succesfully to the EE2005 superhets; it eliminates the disturbances almost completely and provides for stable operation of the superhet designs.

1.2 (EE2005) Trimming of IF coils

The red transformers in the EE2005 kit contain a small ferrite bead whose position can be changed by turning it with a small (preferrably plastic) screwdriver. In this way the coils can be trimmed towards equal frequency, which is very important for the IF signal strength applied to the diode detector of the superhet designs. The best way to trim the transformers is the following approach:

1. Put the beads in the red transformers in approximately the middle position (so that they can be turned in both directions)
2. Build the superhet receiver, calibrate it using the directions in the manual and search for a relatively strong radio station.
3. Adjust the second red transformer (the one closest to the diode detector part, adjust by turning its ferrite bead) for maximum perfomance

In this way the diode detector get the maximum amount of IF signal, which is very important for the operation of the germanium diode detector as it needs a signal of more than 0.3V to operate properly ( signals with a forward diode drop of less than 0.3V will not be demodulated at all).

1.3 (EE2005) Better stability, perfomance and audio quality for the EE2005 superhet receivers

I have seen several reports of disappointing/bad or even absent performance of the EE2005 superhet receivers, and I experienced some problems too. I have found the combination of the following measures to solve all problems:

• Change the audio part (i.e. around the white transistors) according to point nr 1.1 above. This will guarantee undisturbed operation of the diode detector when the volume is changed.
• Trim the red IF transformers according to point nr.1.2 above. This will deliver the maximum signal to the detector. As a result very weak, remote radio stations can be received without the use of an antenna. For example, the performance (sensitivity) of the SW superhet appeared to be even somewhat better than the redesigned regenerative SW receiver on this site
• If the MW/LW superhet (or sometimes the 1.7 - 4.0MHz superhet) tends to oscillate, use a small capacitor (10pF or smaller) to connect the base of T1 (first red transistor) to mass (0V). Apparently, the oscillator produces an additional signal (probably higher harmonics) that tends to destabilize the receiver; the bypass capacitor removes this signal directly. Note that the 1978 version of the EE2004/5/6 manual (i.e. the second edition) shows an extra 1000pf ceramic capacitor in parallel with the electrolytic capacitor that stabilizes the T1 supply voltage. This ceramic capacitor serves the same purpose; apparently it was recognized by the circuit designers that the stability of the receiver was problematic and needed treatment (Tor Gjerdes diagram of the MW/LW superhet shows the location of the 1000pf capacitor near the ferrite antenna rod).
• Connect the antenna directly to the point where the main receiver coil is connected to the variable capacitor. The original point (at the connection of the coil with the 2700pf capacitor) does not work. Still, with the measures above an antenna is probably never needed.
• Use two small trimmers (10pF each) on the breadboard instead of the trimmers on the double variable capacitor. Adjusting these trimmers is extremely important for good reception, and is much easier to do on the breadboard. These trimmers can be seen on the 3-IC superhet on my "New Designs" page. Without careful trimming the superhets may not function at all.
• The following trimming policy gave very good results: First set the receiver at the low frequency region by turning the tuning dial right (the oscillator trimmer may be used to change the frequency range a bit). Now the reception part has to be adapted to the oscillator. Firstly change the position of the receiver coil for optimal reception of a radio station. Now turn the tuning dial to the left (high frequency area), search for a (weak) radio station and only use the other (reception circuit) trimmer for optimal performance.
• Short-Wave superhet: This design has a frequency range of 4 to 10 MHz. However, the 4 to 5.5 MHz range is not very interesting, so it is appropriate to limit the frequency range a bit by including two 470pF ceramic capacitors in series with the double variable tuning capacitor (or use an even smaller value, like 330pF of 220pF).
• The 1.8 - 4 MHz superhet and the 80m amateur band converter (3.5 - 4 MHz) are not very interesting designs anymore, as virtually all communications on these frequencies have shifted from AM mode to SSB mode. The 80m version of the regenerative SW receiver mentioned on my "New Designs" page is an interesting alternative design for this frequency range, as it provides for both AM and SSB reception modes.

1.4 (EE2005 2nd version with new, modern coils [applies also to EE3004, EE2000GK]) IF and OSC Coil Data

At the end of the lifetime of the EE2000 series the EE2005 coils types that were already present in the EE1000 series (and were tailor-made by Philips for the EE series) were replaced by modern types. The manual update leaflet included in the kit does not specify any technical information on these coils. A variety of IF and oscillator coils currently exists on the market, and here I try to explain the differences between them and provide some technical data that I am confident of and which seems to apply to the coils in the Philips EE kits:

• In contrast to the old (red) IF coils, the two new IF coils are technically different. The reason for the differences between the modern white resp. black IF coils is that these coils are specifically designed for the very popular and cheap standard transistor radio architecture of the seventies. This architecture defines a combined oscilllator/mixer transistor stage followed (through coupling by a first, yellow IF transformer) by the first IF transistor amplifier, followed (through a second white IF transformer) by a second IF transistor amplifier stage, which is then followed (through a third, black IF transformer) by a diode detector. Each of the stages has different impedance characteristics, which implies that each IF transformer needs different coil windings in order to match these impendances for optimal performance. The EE2005 superhets largely follows this architecture (and they even include a rudimentary AGC action), but contain only the second IF amplifier stage (which explains why the first, yellow IF transformer is absent in the EE kits. I have the impression that weak regeneration in the second IF stage is used to increase IF gain as a compensation of the absent IF amplifier).
• Even for each IF transformer type (i.e white and black) several versions exist (see www.mouser.com for an overview), but the differences are small (mostly wrt. the number of coil windings) and are not very relevant. The following data common to these versions can be established and most probably characterize the two IF coils present in the EE kits very well:

• IF type (color)	Primary impedance (Ohm)	Secondary impedance (Ohm)	Unloaded Q	Internal capacitor. (pF)	Inductance (uH)	Probable Mouser type numbers
  white	30K	500	80 +/- 20%	180 + 5 (ext.)	680	42IF102, 42IF302
  black	20K	6K	75 +/- 20%	180 + 5 (ext.)	680	42IF103, 42IF303

• I have no clue to where the tapping of the primary coil is actually located, so therefore information on the number of turns is not presented.
• The internal capacitor (180 pF) causes the IF transformers to be fixed at 455KHz, in contrast to the old versions where the capacitor is external and is made parallel to the coil by explicit wiring, thus allowing different frequencies.
• The orange AM oscillator coil most probably has the following characteristics (with differences between various types in the number of turns but not in the center frequency or inductance, but I have no clue to which option applies to the Philips EE component version, and therefore I present the values of a particular coil type (Mouser 42IF110). Note that the tap numbers mentioned in the rightmost column of the table are corresponding to the Philips EE circuit diagrams, not the Mouser diagrams:

• Center frequency	Primary (oscillator) inductance	Unloaded (primary) Q	Turns (primary 4-5-6 and secondary 1-2)
  796 KHz	360 uH	80	4-5: 105, 5-6: 2, 1-2: 3 (typical)

• I was not successful in retrieving any data for the blue SW coil. The metal coil housing bears the mark SW (for "Short Wave") on the side, and the name "Yocom" on the top, but this did not help in identifying any information. Currently I have the impression that this coil is of special design. To retrieve more information the use of an LC-meter would be appropriate here. Also some information may be derived from the circuit diagram for the SW receivers (in particular the coil inductance). Note also that the SW oscillator coil is not tapped (the secondary is), as opposed to the AM oscillator coil, and this explains the differences bweteen the schematics of the AM and SW superhets.

1.5 (EE2005 2nd version with new, modern coils [applies also to EE3004, EE2000GK]) Errors/deficiencies in manual update leaflet

In the kits that contain the new type of coils a leaflet is included that describes some updates of the original EE2005 circuit diagrams that use these coils, and some extensions of the various receivers. However the leaflet contains some flaws, and does not provide any technical data on these coils (but see item 1.4 above on this matter). Here I present some information and updates:

• The schematics contain some errors:
  • For the IF transformers the internal capacitors between taps 4 and 6 are not shown.
  • In some diagrams the feedback line (containing a 22nF capacitor and 10 Ohm resistor) between tap 6 and the emitter of T1 is not drawn.
  • Schematics 5.10 and 5.11 should be reversed
• I have the impression that all construction diagrams are correct though.
• The superhet construction diagrams are drawn quite different from the original versions and (at least to my impression) may require the bending of many components. I would rather recommend to use the original superhet construction diagrams in the EE2004/5/6 manual and just replace the old coils and rewire the new types.
• The explanation of the 5.10 SW superhet pertains to the original version with the old type of coils. The new construction does not use the first harmonic of the AM oscillator coil, but uses the base frequency of the SW oscillator coil that has been included in the new kit versions.
• I do not think that the fine tuning option for the SW receiver (5.11) works well, as I have experienced that the narrow 455KHz IF frequency filtering causes the system to get detuned very quickly. I have the impression that fine tuning is not needed anyway as the tuning knob is large and allows for quite precise frequency adjustment.
• Use the suggestions of item 1.2 for trimming the IF coils. After careful trimming they should not be adjusted (separately) again (as suggested in the leaflet), as this will severely degrade both selectivity and sensitivity due to a mismatch between their resonant frequencies.

EE2001 Series

2.1 Information on the LM3900 Norton OpAmp

In the EE2001 series constructions the LM3900 plays a central role. It is quite an old chip (released in 1972 by National Semiconductor, still in production by Texas Instruments); in fact is was the first chip that provided four opamp gates on a single chip, which was possible because of the relative simplicity of the gates when compared to the "de facto standard" 741 opamp. Since internet access has almost become a commodity we now have the opportunity to have access to this well-documented chip. Here follow links to the LM3900 Data Sheet containing electrical characteristics, and the important AN-72 Application Note (43 pages!) which contains a wealth of basic LM3900 circuits (some interesting ones are not in the EE2010/13 manual).

• Link to: LM3900 Data Sheet (Texas Instruments)
• Link to: AN-72: The LM3900: A New Current-Differencing Quad of Plus or Minus Input Amplifiers (PDF, National Semiconductor)

It is important to stress that the LM3900 is not a regular quad opamp: instead of Vout = A*(Vin+ - Vin-) (which is what a regular opamp does; the output voltage equals A times the voltage difference between the +/- input terminals) the LM3900 basically delivers Vout = A*(Iin+ - Iin-), i.e. the output voltage equals A times the input current difference between the +/- inputs. As a consequence the LM3900 as low-impedance inputs, in contrast to regular opamps which should have high-impedance inputs. However, in the EE2001 series manuals the LM3900 circuits are always designed and explained as if the chip contained regular opamps (see issues 2.2 and 2.3 for the consequences)

For an interesting explanation between regular OpAmps and "Norton"-type amplifiers like the LM3900 see the following link (especially chapters 8 and 9 on voltage vs. current differencing amplifiers):

• Link to: Opamps for Everyone (PDF, Texas Instruments)

The LM359: A successor of the LM3900

Although not a pin-compatible replacement, the LM359 is a successor of the LM3900 with improved technical specifications:

• User programmable gain bandwidth product, slew rate, input bias current, output stage biasing current and total device power dissipation
• High gain bandwidth product (I_SET = 0.5 mA) 400 MHz for A_V = 10 to 100 30 MHz for A_V = 1
• High slew rate (I_SET = 0.5 mA) 60 V/µs for A_V = 10 to 100 30 V/µs for A_V = 1
• Current differencing inputs allow high common-mode input voltages
• Operates from a single 5V to 22V supply
• Large inverting amplifier output swing, 2 mV to V_CC - 2V
• Low spot noise, for f > 1 kHz

The LM359 is a dual "programmable" opamp in a 14-pin package. The two opamps each have two extra input pins for external frequency compensation. This chip is interesting for designers who are accustomed to the LM3900 but need a much faster chip (all LM3900 circuits can be applied with the LM359 too). Please refer to the following links for detailed information:

• Link to: LM359 Data Sheet (PDF, National Semiconductor)
• Link to: AN-278: Designing with a New Super Fast Dual Norton Amplifier (PDF, National Semiconductor)
• Link to: Bench Testing LM3900 and LM359 Input Parameters

2.2 {EE2010/13) Flaws in the explanation of LM3900 circuits in the EE-manuals

2.3 (EE201X) Starting problems of LM3900 multivibrator circuits

2.4 (EE2015) Powering suggestions

The EE2015 kits contain chips that are implemented in the original TTL technology. As a result the EE2015 circuits consume quite some battery power (I didn't measure) and consequently the batteries get exhausted quite rapidly (which I do remember). Currently there are a few powering options available:

• Use a 9V supply (i.e. two batteries) in combination with a 5V Voltage regulator (7805 or equivalent). This is the simplest solution; it extends the time of use, but doesn't decrease power consumption
• Exchange the chips for their much less power consuming LS-TTL (Low-power Schottky) counterparts (i.e. 74LS02 etc.). This probably is the best solution, as all chips have the same functionality, and the EE2015 circuits do no need to be changed.
• Exchange the chips for CMOS versions. This is the best solution regarding power consumption. However, be aware of the following issues:
  • Not all chips are available in the same CMOS technology, or even not fabricated in CMOS at all: there exist 74HC02, 74HC05 (HC series), and 74C90 (CMOS, but not in HC technology). The 7447 is not available in any CMOS technlogy, so you probably would use an LS-TTL version (74LS47)
  • As CMOS chips have high-impedance inputs, a pull-up resistor is necessary when connecting an open-collector output (which is the case for 7405, 74LS05 and 74HC05, as explained in item 2.5 below) to a CMOS input. As a result some pull-up resistors would have to be added to several EE2015 circuits

2.5 (EE2015) Erroneous LED connections to 7402 outputs

The EE2015 kit uses logic gates which have different output ports. The 7405 inverter has so-called "open collector" outputs, which means that the output of this gate merely contains a switch connected to ground. As a result a pull-up resistor is needed to drive a device like a led or a transistor, as shown in the figure below in case (a). Most other gates however (7402,7490) have active-drive outputs, which means that these outputs themselves directly drive a device whithout the need for pull-ups, as shown in case (b).

In the EE2015 manual however , concerning all circuits, the 7402 active-drive output circuits are erroneously designed as if they were open-collector outputs, i.e in fashion (a) instead of (b). As a result the current flow through the device is limited only by the output-drive capability of the 7402, not by the protective resistor in case (b), and this may in the end damage the LED or other attached device. So, case (b) descibes the correct way of treating 7402 outputs, whereas case (a) pertains only to 7405 outputs.

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