Related Manuals for DYNACO PAT-4
Summary of Contents for DYNACO PAT-4
- Page 1 PAT-4 UPGRADES ASSEMBLY MANUAL Line amp distortion reducer Tone control switch © 2013-2020 AkitikA, LLC All rights reserved Revision 1p94 January 11, 2020 Page 1 of 20...
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Page 2: Table Of Contents
Before You Begin ......................10 Pre-wiring the Tone Control Switch ................10 Optional Gain Reducing Resistors ................13 Disassembling the PAT-4 Preamp ................13 Removing the HI FILTER switch................14 Mounting the tone control switch ................14 Wiring in the tone control switch................14 Installing the Treble No-Click Resistors .............. -
Page 3: Section 1: About This Manual
Section 1: About This Manual This manual gives the information you need to build and install the various upgrades to the Dynaco PAT-4 Preamp. As of this writing, the following PAT-4 upgrades are available from Updatemydynaco, a division of Akitika LLC: ... -
Page 4: Project Overview
Project Overview Line Amp Distortion Reducer The project consists of the following steps: 1. Labeling, then desoldering 7 wires from each circuit board. 2. Removing and replacing 1 transistor from each circuit board. 3. Re-attaching the wires to the circuit boards. Tone Control Switch The project consists of the following steps: 1. -
Page 5: Section 2: Line Amp Distortion Reducer
Section 2: Line Amp Distortion Reducer Line Amp Characteristics The line amp in a properly working PAT-4 has about 0.02% distortion when driving a 100K Ohm load at 1 Volt RMS. Typical units measure about -74 dB for the second harmonic of a 1 kHz test signal, and perhaps -90 dB for the third harmonic. -
Page 6: Modifying The Left Channel Circuit Board
c. Eyelet 4 d. Eyelet 5 e. Eyelet 6 f. Eyelet 7 7. Repeat the process for the right channel PC board, the one closer to the front of the preamp. As you remove each wire, place a clearly marked masking tape label on the wire with the number of the eyelet from which the wire was removed. -
Page 7: Figure 1-Applying Thermal Compound And Installing The Heat Sink
emitter of the transistor goes toward the bottom of the PCB (away from the eyelets, see Figure 4). d. Solder the three leads of the new transistor in place. Figure 1-applying thermal compound and installing the heat sink Page 7 of 20... -
Page 8: Figure 2-New Transistor With Heatsink Installed On Pcb
Figure 2-New transistor with heatsink installed on PCB Figure 3-MPSW45A Pinout Figure 4-circuit board as seen from solder side. The modification replaces Q4 Page 8 of 20... -
Page 9: Modifying The Right Channel Circuit Board
Modifying the Right Channel Circuit board Now it’s time for a second judgment call. You probably have enough access to the right channel PCB that you can remove Q4, the metal transistor with the clip-on heat-sink, with no further disassembly. You can even replace Q4 with the supplied TO-92 transistor and heat sink with no further disassembly. -
Page 10: Section 3: Tone Control Switch
It’s important to check C16 for leakage. The quickest and easiest way to do so is to rotate the bass control while the PAT-4 is connected to your power amp and speakers. Listen carefully for a scratching sound as you rotate the Bass pot. - Page 11 inserting it in the adjacent terminal, as marked by the yellow line in Figure 5. Solder the wire to both terminals. 8. Dress the wires from steps 5-7 off to the right, keeping them together. A second piece of masking tape around the wires may be helpful. Prepare the following 4 wires: 1.
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Page 12: Figure 5-Switch Wiring Diagram. The Gray Dashed Lines Indicated Relations Between
Figure 5-Switch Wiring Diagram. The gray dashed lines indicated relations between poles (center terminals) and throws (outer terminals). These gray lines are not on the actual switch. The gain resistors are optional, and not included with the kit Check Your Work Review your work against Figure 5. -
Page 13: Optional Gain Reducing Resistors
1 minute before starting this section. Here are the steps to disassemble the PAT-4 preamp to the extent you’ll need to in order to gain access to remove the Filter switch and replace it with the Tone Control Switch. -
Page 14: Removing The Hi Filter Switch
4. Carefully loosen the set screws in all the knobs. Remove the knobs and store them in a safe place. 5. Remove the retaining nuts on the control shafts which hold the front panel to the sub-chassis. 6. Remove the front panel and set it aside in a safe place. 7. - Page 15 2. Desolder the other end of this wire from the center terminal of the treble pot. The right channel treble pot is closest to the front panel of the preamp. 3. Similarly, desolder the wire that connects to the LEFT channel circuit board eyelet 17.
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Page 16: Installing The Treble No-Click Resistors
Figure 6-Installing the treble no-click resistors on eyelets 16, 17, and 18 Reassemble the PAT-4 Check the 10 added wires to assure that your solder joints are strong and that nothing has come udone. -
Page 17: Using The Tone Control Switch
Connect the negative lead of the meter to ground. 4. Remaining clear of the exposed 120 Volts, plug the PAT-4 in and power it up. 5. Observe the DC micro-ammeter. As the capacitor charges at first, there will be significant charging current. -
Page 18: Gain Trim Resistors
Gain Trim Resistors A gain trim resistor is a bit of a two-edged sword. The 1210 Ohm value is about the lowest value that should be used. It reduces the gain, but it also increases the loading on the output stage. The net effect is positive...if indeed you needed less gain, then the 1210 resistor drops the gain, increasing the SNR for the high level stage. -
Page 19: Schematic
Schematic Figure 8 shows how the tone control switch fits into the high level amplifier stage. Figure 8-Schematic of the preamp high level stage showing the addition of the tone control switch Page 19 of 20... -
Page 20: Appendix: The Toothpick Trick
Appendix: The Toothpick Trick This appendix describes an easy way to clear the solder from a hole in the PCB. It can also be used to clear the solder from terminals on pots or jacks. Doing so makes it easier to install a new component, or reinstall wires that were temporarily removed to allow access to some other component.