Modifications


EPT06960Z Main Board Modifications

(Galaxy DX959 & DX949)

By: Firebreather


Overview

This is the new main board being used in the Galaxy DX959 and DX949 dedicated 11-meter radios. The board is a hybrid of the EPT690010Z board used in the latest Galaxy and RCI (RG99 & RG66) 10-meter radios.

The designers used the RCI8719 PLL Synthesizer IC for frequency stability and to make raw board frequency modifications difficult. I am sure this was a design specification that Galaxy was forced to adhere to in order to receive FCC approval for standard 11-meter sales in the U.S. A fundamental portion of the board is lacking the Binary Adder ICs which normally are found by the PLL IC. These Binary Adder ICs are responsible for the many channels that most 10-meter Export radios have. Because these are missing on the EPT06960Z board, and the fact that the RCI8719 PLL is being used, the radio is not easily modified for channels. But don?t get nervous! We will show you how the channeling can be done!

The RF output of the radio is considerably choked via factory adjustments for presumably the same reasons as stated in the above paragraph. Nonetheless, one should not be concerned with the "out of the box" performance of the radio. As we shall outline below, obtaining excellent performance from this radio is rather easy and can be done by simply turning selected on-board potentiometers. It should also be noted that obtaining maximum "peak" performance is also rather easy, although it does require that the operator be competent in basic component-level replacement.

Since this board is very similar to the EPT690010Z, many of the modifications and improvements that have been tested and verified on the EPT690010Z may also be applied to the new EPT06960Z board. I have performed and tested these improvements and have included a brief description of the results with each of the modifications below.

Disclaimer

Before you read any further, you must know that the Author (FireBreather), John Mahoney, and Panther Electronics will accept no responsibility for any damage, physical or legal, which may incur as a result of performing any or all of these modifications. Although each of these modifications has been performed and tested by the Author, they were done so in a testing environment and are provided here solely for informational or Export use only.


DX959 & DX949 Variable Adjustments

VR1 AM S-Meter VR12 Driver Bias
VR2 SSB S-MeterVR3 SSB Squelch VR13 SSB ALC
VR4 AM Squelch VR14 AM High Power
VR6 SSB Carrier Balance VR15 AM Modulation Meter
VR7 TX Offset VR17 SSB Power VR16 AM Modulation
VR9 RF Meter VR18 AM Low Power
VR10 Final Bias VC1 10.240


Modulation Limiter:

Q39 is the modulation limiter for the EPT06960Z board. For the Galaxy DX949, you may remove the limiter. For the Galaxy DX959, I recommend placing a 1K resistor in series with the emitter leg of Q39. Removing the limiter on the SSB model causes severe "garbling" while in the SSB mode. Ample performance may be achieved by simply turning up VR16 and wiring a good aftermarket power microphone for use with the radio. I am using the Astatic D104M6B microphone and I can not run the microphone and radio fully open without massive audio distortion. This radio has plenty of audio to spare.

AGC (Automatic Gain Control) Improvement

Like the EPT690010Z, the automatic Gain Control response is controlled via resistor R42 (100K). If you find that your local buddies sound "garbled" on SSB, you can remedy this by changing R42 to anywhere between a 33K to a 56K resistor. All radios seem to respond differently depending on the value used. You may have to experiment with different values within this range. Like the EPT690010Z, you can make the AGC variable by installing a 100K potentiometer.

Power Amp Improvement (2SB754) - Q54

This is the best improvement you can make to this chassis. The stock device is a 2SB754, which is a 60-watt, 7A power amp device. This does fine for stock radios. However, in order to stabilize the voltage on the board after improving the RF output and boosting the modulation, the 2SB817 becomes the better choice. The 2SB817 is a 100-watt, 12A device which allows greater voltage stability for the entire radio as a whole. I ran my test DX959 with the stock device and noticed quite a bit of wobble and light dimming. After replacement, the radio responded with almost no blinking, zero wobble and a healthy increase in RF output as well as swing. Replacing this device also allows you to increase the input voltage to 14.5VDC, provided you also replace all the 10V caps in this section of the board to 16V ones.

AM AF Amplifier Improvement - Q55

This is another improvement, which has previously been published for the EPT690010Z. The stock AF Amplifier is the 2SA473. Replacing this with the 2SA1012-0 or the ECG153 will improve the clarity and volume of the modulation. It will also run much cooler which provides stability for the device. If you plan to use the DX959 or DX949 with the provided stock microphone, this upgrade is highly suggested for maximum AM modulation.

Receive Improvement - D30 & D31

The stock AM Detection diodes are 1N60P devices. These are adequate but can be greatly improved by replacing them with the ECG583 Schottky devices. The replacement diodes allow greater copy of distant stations without allowing your local buddies to overdrive your radio. I have obtained a gain increase of approximately 3db on stations more than 20 Miles away. This modification is especially noticeable in mobile installations where you are forced to use an inferior antenna system (as compared to a base station setup).

Noise Blanker Improvement - D1 & D2

The Noise Blanker diodes can also be replaced with the ECG583 Schottky devices. The improvement over the stock diodes can be rather dramatic, depending on how noisy the environment is around the operating location. Again, this modification is most noticeable in radios being used in mobile installations.

"Super Ears" Modification - D9

Here?s one that many folks ask me about and I was hesitant to include it here. This modification significantly lowers the effectiveness of diode D9 and greatly increases the injected received signal to the radio. This was very popular when the Galaxy 10-meter radios first hit the market (D7 on the Galaxy DX-series 10-meter chassis). The modification requires that you remove the banded end of diode D9 and add a 1/4W, 1.5K resistor in-line with the banded end and the now vacated board location. This actually works very well for any distant station giving you an S-1 to an S-5 signal. A typical example is a station giving you an S-3 will increase to an S-9 (relative) without any increase in background noise (as is the case with most preamps). The downside is that anyone in your immediate vicinity keying up will tremendously overdrive the front end of your radio, possible causing damage to the receive portion of the board. Because of this, I ALWAYS perform this modification with a SPDT sub-miniature or micro-mini switch so that the modification can be turned ON and OFF as needed. The Galaxy DX959 and 949 front panels are heavily populated so your installation options are limited. I installed my switch between the Clarifier and Talkback controls.

DISCLAIMER: Although this modification works great, I can not stress enough the care that must be taken when using it. Careless use of this modification can lead to radio damage. Engage this circuit modification only when copying distant stations. I take no responsibility for any damage incurred as a result of this modification.

Having said that, go ahead and experiment with this carefully. You will be surprised at the results.

RF Output Increase Modification

This modification will allow the DX959 & DX949 to exhibit the RF output and swing of the Galaxy DX-series 10-meter radios. The board was always capable of this type of output; it was simply choked off by the design engineers in order to meet FCC 11-meter specifications.

The first thing you need to do is turn up VR14 which is the AM high power variable. If you?ve already done the modulation improvements, you should be able to dead key about 8-10 watts and swing around 15 watts. 18 watts is probably the best you?ll get (using a peak-reading Bird wattmeter). Now, perform the following modifications:

    1. Remove C218 (3pf) and discard.
    2. Change C216 (470pf) to a 1000pf (100V mylar-type)
    3. Remove C210 (470pf) and discard.
    4. Remove C199 (560pf) and reinstall it in the C210 spot.

Adjust your dead key to around 5 watts. I was able to achieve average peak swing readings of around 35 watts. Depending on the audio input (voice or whistle), I was able to whistle myself to readings of over 40 watts peak! There was a slight decrease in modulation and it seemed as though I was really pushing it. I found that I was able to regain the modulation level by lowering the dead key (using the RF Power control on the radio face) to around 2.5 watts. This netted peak swing readings of just around 28 watts! More than enough given the fact that the modulation was over 95% and crystal clear! This is just about the same performance that I got from my Galaxy DX66V after performing the 1N4001 diode heavy swing modification. Like I alluded to earlier, this new radio has "the stuff." You just have to work slightly harder to get at it.

Super Swing Modification - R264

Again, since it is asked for so often, I have included the Super Swing modification for this radio. Locate resistor R264 and lift the right leg (as you are viewing the radio ? component side up and front of radio facing you) of the resistor from the board. Install a 1N4001 diode in series with the resistor, being sure to place the banded end of the diode in the vacated main board hole. This will allow you to lower the dead key and still have the full swing capability of this radio. If you plan to use this radio with an external low drive amplifier, I do not recommend performing this mod. It makes it next to impossible to match the radio to a low drive amp. Also, if you performed the RF Output Increase Modification above, this modification may not be necessary. I tested this modification first and then reversed it before performing the RF Output Modification (to preserve the validity of the output modification results). Since I was very pleased with the results of the RF Output Modification, I did not re-do the Heavy Swinger Modification. If anyone does both of these, I would be interested to hear the results.

Known Factory Defects (SWR Alert LED Fix)

There is one known factory defect for which Galaxy has posted a fix. This involves the SWR PC board. The front panel SWR ALERT LED will light when the actual SWR is below 3:1. There is no danger to the radio with the LED lighted. The only concern is that if the SWR should suddenly shoot up, the operator would not know since the ALERT LED is always lit. In order to fix this, you must locate C5 on the SWR PCB. Replace C5 with a 1/4 watt, 22K resistor.

Full Modification Compliment Part Listing

Here is the parts list for performing all of the modifications listed in this article.


Galaxy 959 & 949 Makeover Parts (EPT06960Z PCB)

Modification Component Required Qty. Required
Modulation Limiter: ?-watt, 1K resistor Qty. 1
AGC Improvement: ?-watt, 33K resistor Qty. 1
Power Amp Improvement: 2SB817, 100-watt, 12A Qty. 1
AM AF Amp Improvement: ECG153 (2SA1012-0) Qty. 1
AM Detection Improvement ECG583 Schottky Barrier-type Qty. 2
Noise Blanker Improvement ECG583 Schottky Barrier-type Qty. 2
Super Ears Modification: ?-watt, 1.5K resistor Qty. 1
. SPDT Submini switch Qty. 1
RF Output Modification: 1000pf, 100V mylar Cap Qty. 1
Super Swing Modification: 1N4001 Diode Qty. 1
Channel Modification (120 Ch.): . Qty. 1
SWR Alert LED Fix ?-watt, 22K resistor Qty. 1

Additional Information

Please keep in mind that all of this research takes time and effort on the part of many people. The resulting tested modifications are provided here to you for free.

73s and Happy Modifying!

-Firebreather


DX959 Extra Channels Modification

This was sent to me by Jason.


I noticed you don't have the channel mod for the galaxy 959 so I figured I would send you one, I have done this mod on my radio and it works great but it does not change channels 1-6 and 34-40 other than that it tracks the full range.


1) On the Main board, just to the right and below the PLL (8719) locate J33, locate wires in J33 marked P6 and P5. Take note of their colors.
2) Cut open these control lines and place a SPST switch in line with them.

 

For your info the binary codes are: 91 (CH1) - 135 (CH40) (actual code is 7 not 135 due to there only being 7 pins).

All codes are BINARY not BCD.


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