Archive for Parts

Marantz 2245, 2270 Capacitor Replacement Board

MZ-CAP-2

Click here to order

Click here to download the installation guide

  • Marantz 2245, 2270 Capacitor Kit

This kit is designed to replace both 9000 uF/55 V electrolytic capacitors used in the Marantz 2245 and 2270 receivers. Other models may also be compatible. A custom designed PCB attaches to the mounting holes used by the original capacitors, providing footprints for two snap-in capacitors and eleven robust wiring turrets. This simplifies future capacitor replacement and allows for more flexibility when selecting new caps.

Included in the kit is a fully-assembled capacitor board with two Nichicon LGY series 10,000 uF/63 V capacitors pre-installed, all necessary mounting hardware, and an installation guide.

Installation

An install guide is included with the unit, but is also briefly listed below:

  • Take pictures or make diagrams of the color codes that were used to wire up the original capacitors in your unit
  • Remove the original capacitors, their mounting brackets, and the grounding post screwed into the chassis between them. Try to save as much wire length as possible
  • With the unit on its side, insert the new capacitor board through the bottom of the unit into the mounting holes of the original caps. Orient the board so that the “-V” (negative supply) terminal is closest to the AC line fuse
  • Mount the new capacitor board in place with the five included machine screws. It may help to loosen the screws on the board first in order to help the mounting holes line up
  • Make sure all screws are installed tightly
  • Wire up the capacitor board, referring to the pictures or diagrams of your original caps. On the new board, the three “+V” turrets correspond to the positive supply rail, the three “-V” turrets correspond to the negative supply rail, and the five “GND” turrets in the middle correspond to ground. Strip back each wire about 1/4″, then either insert them into the tops of each turret or wrap them around before soldering
  • Triple check your wiring. We recommend powering up the unit slowly with a dim bulb tester and variac while monitoring the supply voltages to confirm that everything is working as expected

Parts Included

  • One capacitor mounting board (1.6 mm thick TG150 FR-4, 2 oz. copper, matte black solder mask, Pb-free HASL finish)
  • Eleven pre-installed wiring turrets
  • Two pre-installed Nichicon LGY series 10,000 uF/63 V snap-in capacitors (105°C, long lifespan)
  • Five #4-40 female to female threaded hex standoffs
  • Ten #4-40 machine screws
  • Step-by-step installation guide

Oberheim OB-Xa Program ROM Set

OB-XA-R1

Click the link below to download the installation guide

  • Oberheim OB-Xa ROMs

This is a set of two replacement program ROMs for the Oberheim OB-Xa synthesizer, preprogrammed with the latest OB-Xa software revision (XA-GA0 and XA-G1) released in February 1982.

The new ROMs are based around modern CMOS EEPROM devices manufactured by Atmel Corporation (now a part of Microchip), adapted to a 24-pin DIP footprint with a custom PCB and gold plated pins. These devices are fully compatible with the original NMOS UV EPROMS (ST M2732A-2), have TTL and CMOS compatible inputs and outputs, and offer a significant reduction in current draw: up to a 68% decrease under normal operating conditions, and up to a 94% decrease in standby mode.

All ROM boards are hand assembled in the USA and tested in an Oberheim OB-Xa to guarantee their functionality.

If you are ordering these to repair an OB-Xa with a nonfunctional computer, please note that in our experience it is not uncommon for these units to have one or more dead logic ICs on the upper or lower control boards. Thus, it is possible that your original ROMs are fine, but another component in the system has failed.

ROM CRC-32 Checksums:
XA-GA0: F8268EA0
XA-G1: B32DCB5D

Technical notes about the waveform comparison screenshots:

This image compares how data line 0 changes when the CPU accesses the original XA-GA0 ROM versus the new XA-GA0 ROM. Two equivalent opcode fetches are shown in each screenshot. A CMOS Z80 CPU was used in this case, but the original NMOS Z80 will also work fine with these new ROMs.

From top to bottom, the waveforms shown are the chip select/output enable signals going to the ROM (active low and tied together in the OB-Xa; pins 18 and 20), data line 0 (pin 9), the M1 output from the Z80 CPU (pin 27), and the Z80 clock input (pin 6).

Per the Z80 user manual, the CPU initiates an opcode fetch (M1 cycle) with the falling edge of the M1 line (purple). One half clock cycle later (green), the CS/OE line (yellow) goes low, forcing the ROM to assert the data pointed to by the current address onto the data bus (blue; D0 is shown). Note how the original NMOS ROM has brief “glitches” in the data output when the CS/OE line changes while the new CMOS ROM does not; this is inconsequential to the operation of the CPU, as the data bus is sampled with the rising clock edge of state T3, by which time the data lines are at a well-defined logic level. The period of slow rise seen on the data line is also normal and inconsequential; this occurs whenever the data bus is in a high-impedance state and climbs to supply at a rate determined by the time constant of the pull-up resistors and bus capacitance.

C26 Power Supply Capacitor Replacement Kit

C26-MCPS

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Click here to download the installation guide

  • McIntosh C26 can capacitor replacement

This kit is designed to replace both multi-section can capacitors used in the power supply section of the McIntosh C26 preamplifier. Two custom capacitor mounting boards and four 220uF/200V Nichicon electrolytic capacitors are included. These provide a slight improvement in supply filtration compared to the original parts which, depending on serial number, typically included one 160uF/200V and one 200uF/150V capacitor per can. If you need different capacitor values, feel free to send us a message and we can order them for you.

Parts Included

  • Two 4-in-1 capacitor mounting boards
  • Four Nichicon 220uF/200V 105°C aluminum electrolytic capacitors
  • Mounting hardware
  • Installation guide

4-in-1 Capacitor Insulator Kit

Insulator board and hardware for floating 4-in-1 capacitor boards

This kit can be used to isolate our 4-in-1 can capacitor replacement PCBs from chassis ground. This is useful in cases where the original installation used an insulated can floating from chassis.

Includes one insulator PCB for 1-3/8 inch diameter cans with 46 mm CTC mounting holes, two nylon #6-32 screws, and two nylon #6-32 hex nuts.

4-in-1 Can Capacitor Kit (Wide)

Replaces multi-section cans with 46 mm CTC mounting holes. Fits four 7.5 mm lead spacing, 16 mm diameter capacitors

  • Multi section can capacitor replacement

This kit is intended as an easy way to replace old multi-section can capacitors around 1-3/8″ diameter (approx. 35 mm) with 46 mm CTC mounting hole spacing. These cans were often used in vintage audio and radio equipment, such as McIntosh, Marantz, Heathkit, and Dynaco.

The capacitor board fits up to four 7.5 mm lead spacing16 mm diameter radial capacitors. Smaller 5 mm lead spacing capacitors will also fit. An alternate version of this kit designed specifically for 5 mm lead spacing, 12.5 mm diameter capacitors is also available.

The negative leads of all capacitors are connected to a thick outer copper ring and two plated mounting holes. This means the negatives will be tied to chassis ground by default. If you need to isolate this board from chassis, take a look at our isolation kit.

Includes one capacitor mounting board, one spacer board, 5 wiring turrets (one extra), a mounting hardware kit, and a link to installation instructions. Capacitors are not included. In order to save on paper and toner, we are now including a link to a PDF copy of the installation guide. If you would prefer a hard copy, please let us know and we’d be happy to accommodate.

Based on the IPC-2221B standard, this kit is not to be installed in circuits that will see peak voltages greater than 600 V.

Specifications:

  • Board material: FR-4 Kingboard KB-6165F (TG150, CTI >175)
  • Board finish: HASL (Lead-free solder), matte black solder mask
  • Copper thickness: 2 oz.
  • Screw hole spacing: 45.95 mm center-to-center
  • Screw hole size: 3.5 mm (#6-32 machine screw fits snug)
  • Wiring/turret hole size: 2.4 mm
  • Width: 55.39 mm
  • Length: 39.50 mm
  • Board thickness: 1.6 mm
  • Height from surface of mounting board to top of a turret: 7 mm
  • Spacer board diameter: 39.5 mm
  • Spacer board thickness: 2.0 mm
  • Capacitor lead spacing: 5 mm to 7.5 mm
  • Max capacitor diameter: About 16 mm
  • Capacitor lead hole size: 1.2 mm
  • Diameter of turret’s hole: 1.63 mm

Note: Dimensions are nominal values. Outline dimensions may vary by ±0.15 mm, and hole sizes by ±0.076 mm

Marantz 2385, 2500 Capacitor Replacement Board

MZ-CAP-1

Click here to order: With Capacitors, Without Capacitors

Click here to download the installation guide: With Capacitors, Without Capacitors

This kit replaces both dual electrolytic capacitors used in the Marantz 2385 and 2500 with four modern-production, Kemet 8200uF/100V 105°C screw-in capacitors. Available with or without capacitors.

A custom capacitor mounting board attaches to the Marantz via four pre-existing screw holes. Wiring is done from the bottom of the unit and is made easier by the use of robust wiring turrets. Footprints are provided for installing the bleeder resistors on the circuit board, but they can also be left where they are and attached to the wiring turrets. The mounting board itself is manufactured with double-sided 2 ounce copper and large copper pours to ensure very low impedance connections to the turrets, a 2.4 mm thick FR-4 laminate to reduce board flex, and a gold finish.

If you are ordering this kit without capacitors, please see the section What You Will Need below:

What You Will Need

The mounting board was designed to fit four Kemet ALS80A822DF100, which is an 8200 uF/100 V screw-in capacitor. These do not ship with the necessary screws, so you will also need eight M5-0.8 x 12 mm machine screws with head diameter 11 mm or less (e.g. Prime-Line 9131367) and eight M5 internal tooth lock washers.

The dimensions of the Kemet capacitors are 36 mm diameter, 107 mm height, 12.80 mm CTC mounting stud spacing, and it uses M5-0.8 threads. I recommend using this specific part (or one in the same family, ALS80-A-DF). If you need to select a different capacitor, there are some important caveats listed below:

  • Make sure the capacitor diameter does not exceed 36 mm and the height does not exceed 107 mm, otherwise the capacitors may not fit on the board or inside the unit
  • Make sure the screw stud spacing is 12.80 mm and the thread type is no larger than M5-0.8, otherwise the screws may not fit through the holes in the board
  • Make sure the rubber plug for the capacitor’s pressure relief vent aligns with the hole on the mounting board. You may need to drill new holes if the orientation of your capacitor’s positive and negative terminals differs
  • This kit includes a set of spacer boards for each Kemet ALS80-A-DF style capacitor that account for the length of the mounting studs to reduce mechanical stress on the mounting board. If you select different capacitors that have long mounting studs, the included spacers may not fit

If you have any doubts about the fitment of your choice of replacement capacitors, feel free to send us a message.

Parts Included (With Caps)

  • One capacitor mounting board (2.4 mm thick TG150 FR-4, 2 oz. copper, green solder mask, immersion gold finish)
  • Twelve wiring turrets
  • Four 3″ lengths of 16 AWG wire for connecting the grounds of each capacitor bank
  • Four Kemet 8200uF/100V 105°C screw-in aluminum electrolytic capacitors with screws and tooth lock washers
  • Twenty capacitor spacer boards designed for the Kemet ALS80-A-DF family (5 per capacitor)
  • Mounting hardware (four #6-32 threaded standoffs, nuts, and screws)
  • Step-by-step installation guide

Parts Included (Without Caps)

  • All of the above except the four Kemet capacitors and capacitor screws

3-in-1 Can Capacitor Kit

Replaces multi-section cans with 1.5 inch CTC mounting holes. Fits three 5 mm or 7.5 mm lead spacing, 12.5 mm diameter capacitors

Click the link below to download the installation guide

This kit is intended as an easy way to mount new radial electrolytic capacitors when replacing 1 inch diameter multi section can capacitors with 1.5 inch mounting hole spacing CTC. This design was modeled after an Astron A-25-65 can. These were often used in vintage radio equipment.

Up to three different caps can be installed, and they all share a common lead located in the center. The center common lead has a trace connecting it to one of the mounting holes, making it convenient to tie to chassis ground; if you need to isolate this board from chassis ground, take a look at our insulation kit. The spacer board sits between the new caps and mounting board and adds clearance between the turrets and cans of the caps. Four turrets provide a robust post for wires and other components to attach to when installing.

If you use a positive-common configuration, be wary that the cans of electrolytic caps are often tied to the negative lead (cathode), but not always. Thus, voltages may exist between the cans depending on the circuit, so space them apart as needed.

Based on IPC-2221B guidelines, this board is not to be used in circuits that may see peak voltages above 450 V assuming a typical negative-common configuration.

Specifications:

  • Board material: FR-4 Kingboard TG150 (CTI >175)
  • Board finish: HASL (lead-free solder), green solder mask
  • Copper thickness: 2 oz.
  • Screw hole spacing: 37.79mm center-to-center (Approx. 1.5 inches)
  • Screw hole size: 3.8mm (#6-32 fits slightly loose to allow adjustment)
  • Wiring/turret hole size: 2.4mm
  • Width: 47.59mm
  • Length: 34.14mm
  • Board thickness: 1.6mm
  • Height from surface of mounting board to top of a turret: 7mm
  • Max capacitor diameter: 12.5mm
  • Capacitor lead spacing: 5mm and 7.5mm
  • Insulator board diameter: 29mm
  • Insulator board thickness: 2mm
  • Insulator board hole size: 4.2mm for turrets, 2.6mm for capacitor leads
  • Diameter of turret’s hole: 1.63mm

Note: Dimensions are nominal values. Outline dimensions may vary by ±0.15mm, and hole sizes by ±0.076mm.

4-in-1 Can Capacitor Kit

Replaces multi-section cans with 46 mm CTC mounting holes. Fits four 5 mm lead spacing, 12.5 mm diameter capacitors

Click the link below to download the installation guide

  • Multi section can capacitor replacement

This kit is intended as an easy way to replace old multi-section can capacitors around 1-3/8″ diameter (approx. 35 mm) with 46 mm CTC mounting hole spacing. These cans were often used in vintage audio and radio equipment, such as McIntosh, Marantz, Heathkit, and Dynaco.

The capacitor board fits up to four 5 mm lead spacing12.5 mm diameter radial capacitors. An alternate version of this kit designed for larger 7.5 mm lead spacing, 16 mm diameter capacitors is also available.

The negative leads of all capacitors are connected to a thick outer copper ring and two plated mounting holes. This means the negatives will be tied to chassis ground by default. If you need to isolate this board from chassis, take a look at our isolation kit.

Includes one capacitor mounting board, one spacer board, 5 wiring turrets, a mounting hardware kit, and a link to installation instructions. Capacitors are not included. In order to save on paper and toner, we are now including a link to a PDF copy of the installation guide. If you would prefer a hard copy, please let us know and we’d be happy to accommodate.

Based on the IPC-2221B standard, this kit is not to be installed in circuits that will see peak voltages greater than 600 V.

Specifications:

  • Board material: FR-4 Kingboard KB-6165F (TG150, CTI >175)
  • Board finish: HASL (Lead-free solder), matte black solder mask
  • Copper thickness: 2 oz.
  • Screw hole spacing: 45.95 mm center-to-center
  • Screw hole size: 3.5 mm (#6-32 machine screw fits snug)
  • Wiring/turret hole size: 2.4 mm
  • Width: 55.39 mm
  • Length: 37.96 mm
  • Board thickness: 1.6 mm
  • Height from surface of mounting board to top of a turret: 7 mm
  • Spacer board diameter: 27 mm
  • Spacer board thickness: 2.0 mm
  • Capacitor lead spacing: 5 mm
  • Max capacitor diameter: About 12.5 mm
  • Capacitor lead hole size: 1.2 mm
  • Diameter of turret’s hole: 1.63 mm

Note: Dimensions are nominal values. Outline dimensions may vary by ±0.15 mm, and hole sizes by ±0.076 mm

Ohm’s Law/Joule’s Law PCB Wheel

  • Ohm's Law Wheel Ornament

This is a 10 cm diameter wheel made of FR-4 (typical PCB material) that combines Ohm’s Law and Joule’s Law into one handy reference chart. To calculate one of the inner quantities, use two known quantities and the appropriate outer expression. Example: the power dissipated by a 1 kOhm resistor with 100 mA flowing through it is P = I2R = 0.12 A * 1000 Ohm = 10 W. This particular relationship is called Joule heating or Joule’s first law.

The reverse side features the likenesses of Georg Simon Ohm and James Prescott Joule. Electrical engineers, technicians, and hobbyists alike utilize these laws on a daily basis.

Available in green/gold, black/gold, red/gold, and laser etched wood. Note: The wood version does not have the portrait of Ohm and Joule on the back.

“If I have seen further, it is by standing on the shoulders of giants.”

— Excerpt from a 1675 letter from Sir Isaac Newton to Robert Hooke

Specifications:

  • 1.6 mm thick FR-4, immersion gold finish (wood version is 5 mm thick)
  • One hole provided for mounting or hanging

If you know a friend or family member who would appreciate a PCB medallion with custom artwork on it as a gift (e.g. a picture of a pet, loved one, etc.), we’d love to help you get some manufactured. They also make great Christmas ornaments. Please contact “parts (at) proaudioe.com” for more information. We can order as few as 5 PCBs.

MLD7020 Line Memory Replacement

MN4760S-PAE

  • McIntosh MLD7020 Laser Disc Player MN4760S

This is an FPGA implementation of the MN4760S line memory used in the time base corrector (TBC) sections of some LaserDisc players. This board was designed specifically for an MLD7020 with a dead line memory, breathing some new life into a unit that would have otherwise been a paperweight due to the original part no longer being manufactured.

This board is not available for order at this time. Please contact “parts (at) proaudioe.com” if you would like additional information.

MAC4100 RCA Jack Replacement Kit

MAC4100RCA

Click here to order

Click here to download the installation guide

  • McIntosh MAC4100 RCA Jacks

This kit is designed to replace the original riveted RCA jacks used on the back of McIntosh MAC4100 receivers. A custom RCA mounting board re-uses the original rivet holes for attaching to the back panel and provides plated holes for soldering the input/output shielded cables. The mounting board uses 2 ounce copper and wide traces to connect each RCA jack to their respective solder pads, and the star ground arrangement of the original wiring scheme is maintained. A matte black cover plate is included for replacing the original black shrouds around the RCA jacks.

Please note that the installation process for this kit is fairly complex and will involve drilling out the original RCA rivets, soldering the new RCA jacks to the mounting board, stripping and soldering each shielded cable to the new board, and mounting the new board in place. We recommend testing your unit before installation to ensure everything is working as expected, and then taking plenty of pictures throughout the process to use as reference.

Note: The included black machine screws will be slightly shorter than those in the listing photos to avoid having extra thread length sticking off of the back.

Parts Included

  • One RCA mounting board
  • One matte black RCA cover plate
  • 12 white, 10 red RCA connectors
  • Wire jumpers
  • 10nF/250V C0G phono ground capacitor
  • Mounting hardware kit
  • Installation guide

Additional Details

  • Connection of each group of RCA jacks to the star ground is facilitated via wire jumpers. The mounting board comes with these jumpers pre-installed in the most common configuration, but depending on your unit, you may need to add or remove a jumper. This is documented in the included installation guide
  • The 10nF ceramic capacitor connecting the phono shields to chassis ground also comes pre-installed on the mounting board, eliminating the need to re-use the original

MC2500 Replacement Power Guard Indicator PCB

PAE-045622

  • McIntosh 045622 MC2500 Power Guard Indicator board

This is a replacement power guard display PCB for McIntosh MC2500 amplifiers. This board is used to mount four bi-pin incandescent lamps which indicate the power guard status for both channels of the MC2500.

Includes one unpopulated PCB and one 5 pin right angle Molex connector. Lamps are not included. Boards may have minor cosmetic surface defects, but this will not impact their functionality.

The hole sizes for the lamps were increased to accommodate PC pin sockets (not included) for simplifying future lamp replacement. If you have LED replacements for 7382 lamps that are designed to be powered with AC (11.2 VAC is typical according to the MC2500 schematic), they should also work just as well on this board.

Specifications:

  • Board material: FR-4
  • Board thickness: 1.6 mm
  • Copper thickness: 1 oz., traces duplicated on both sides

MC2100, MC2105, MC2300 Can Capacitor Replacement Kit

066-095-PAE

Click here to order

Click here to download the installation guide

  • McIntosh MC2100 MC2105 MC2300 Capacitor Kit

This is a replacement kit for the GE multi-section can capacitors used inside the McIntosh MC2100, MC2105, and MC2300 power amplifiers. These cans were stamped with McIntosh part number 066-095. Other models may also use this can. High quality, genuine Nichicon capacitors rated for operation up to 105°C are used to ensure a long operational lifespan, and a custom PCB with thick 2 oz. copper provides a robust and elegant mounting solution. Four wiring turrets facilitate the connections to each of the four caps. No more gutting the old cans and sticking new caps inside!

Includes four Nichicon capacitors, one cap mounting PCB, one spacer PCB, a hardware kit, and a thorough step-by-step installation guide.

Installing this kit will require soldering, drilling out the original can’s mounting rivets, and stripping/attaching wires in a tight space. If you do not have prior experience safely testing and repairing amplifiers at the component level, please have a qualified professional install this kit in your unit.

The following capacitor values are included:

  • 82uF 200V (Replaces 80uF 200V)
  • 82uF 200V (Replaces 80uF 200V)
  • 150uF 160V (Replaces 150uF 150V)
  • 56uF 160V (Replaces 50uF 150V)

Note: The capacitor symbols (square, triangle, half-circle, dash) on the cap PCB were arranged based on the orientation of the original can in the MC2300. Other models, such as the MC2100, typically had the cans oriented differently, meaning the position of the symbols on this board may not align with your original installation.

MC2100, MC2105, MC2300 Input Preamp Board

128-165-PAE

Click here to order: Assembled, PCB Only

Click here to download the installation guide: Assembled, PCB Only

  • McIntosh 128-165 MC2100 MC2105 MC2300 Input Preamp Board

This is a new-production input preamp board for the McIntosh MC2100, MC2105, and MC2300 power amplifiers. This board follows the original component layout closely, and no changes were made to the original circuit design. Available assembled and tested, or as an unpopulated PCB.

The new PCB is double-sided and uses 2-ounce copper, plated through-holes, an immersion gold finish, and matte black soldermask. Silkscreen reference designators and symbols are provided on both sides. Robust wiring turrets replace the original hollow posts that cables solder to. All component footprints are sized to fit the original parts. In addition, all axial electrolytic capacitors have footprints for radial parts of various sizes, both input film caps support two different lead spacings, and both electrolytic output caps can be substituted with film caps of the appropriate physical size. A capacitor sizing guide is included with unpopulated kits.

Assembled boards are built using high quality components, including Vishay MRS25 series low noise metal film resistors (1% tolerance, 600 mW, 50 ppm TCR), Nichicon electrolytic capacitors (UPM series for supply filters, UKZ for audio stages), WIMA film capacitors, and new transistors. All assembled boards are burn-in tested for 24 hours and run through an Audio Precision analyzer to confirm that they meet the performance specifications listed below.

Parts Included (Assembled Board)

  • Assembled and tested MC2100/2105/2300 input preamp board
  • Anti-static bag for storing your original input board
  • Two 22 kOhm resistors for MC2300’s below S/N 4Y426
  • Installation guide with redrawn schematic, board layout, and parts list

Parts Included (Unpopulated PCB)

  • Unpopulated MC2100/2105/2300 input preamp PCB
  • 16 wiring turrets (one extra)
  • Anti-static bag for storing your original input board
  • Resistor lead forming tool
  • Installation guide with redrawn schematic, board layout, and parts list

Typical Performance

Typical performance of both channels (Audio Precision analyzer, 2 Vrms output from DUT):

  • Gain: 20.83 dB @ 1 kHz
  • Frequency response: +0.01 dB, -0.25 dB from 20 Hz to 20 KHz
  • Signal to noise ratio: -97.1 dB below 2 V output (20 Hz – 22 KHz analyzer fltr, unwtd)
  • THD+N: Less than 0.007% from 20 Hz – 20 KHz (no analyzer fltr, unwtd)
  • IMD: Less than 0.005% (DIN 250 Hz/8 KHz 4:1)

Note that these specifications apply to the preamp board by itself and do not reflect the overall performance of your McIntosh amplifier. We have tested an original MC2100 input board in the same manner and found that this new board slightly exceeds the performance of the original.

We recommend testing your unit first to ensure it is working properly. If you are repairing your unit, please make sure your symptoms are originating from the preamp board before you replace it. Replacing this board will not resolve problems present in the rest of the unit, such as the power supply or amplifier sections. If you have not replaced the original multi-section can capacitor in your unit’s power supply, we recommend doing so; we offer a replacement capacitor kit with a custom designed PCB for this task.

Please do not attempt to install these boards if you are not thoroughly familiar with safely diagnosing, repairing, and testing amplifiers at the component level with test equipment (signal generator, oscilloscope, load, etc.) and a current-limited power supply.

MC2100, MC2105, MC2300 New Production Driver Boards (Unpopulated)

128-077-PAE

Click the link below to download the installation guide

March 2024: These boards are currently out of stock, however we are working on a revision that will use all modern-production semiconductors and an improved circuit design.

These PCBs are intended to replace damaged driver boards in the McIntosh MC2300 amplifier. The PCB itself was also used in other models such as the MC2100 and late-revision MC2105 units, and the new board should work in these models with some component changes. Bear in mind that the silkscreen reference designators/symbols are based on the MC2300 schematic, which largely matches the schematic of late-revision MC2105 units, but does not match the schematic of the MC2100. Early revision MC2105 units (s/n 10M01 to 26M07) used a slightly different PCB with multiple circuit and layout changes that would require modifications to the board to implement.

Includes two unpopulated PCBs, four TO-39 spacers, and a thorough install guide with re-drawn schematic, board layout, and parts list.

Please do not attempt to populate and install these boards if you are not thoroughly familiar with safely diagnosing, repairing, and testing amplifiers at the component level with test equipment (signal generator, oscilloscope, load, etc.) and a current-limited power supply.

Here are the main differences between this board and the original:

  • Plated through-holes, wider traces, 2 oz. copper with ENIG (gold) finish and hard-gold plated fingers (better long-term repairability)
  • Silkscreen with reference designators and symbols based on the MC2300 schematic
  • Footprint for the TO-66 (“football” shaped) transistor Q105/106 has pads for substituting it with a TO-220, TO-126, or similar package transistor
  • All original wire jumpers (driver collectors and feedback line) are implemented on the board as traces
  • A footprint is provided for the compensation cap that was put in parallel across the feedback resistor in some revisions (labeled C123/124*), as well as the resistor across the driver input (R175/176)
  • Two different lead spacings are provided for the ceramic disc cap footprints
  • Diode footprints use square pads for the negative terminals and polarized electrolytic capacitors use square pads for the positive terminals
  • Chamfered board edge around the fingers
  • Footprint for axial electrolytic capacitor C121/122 is a bit shorter than the original; please use axial caps around 25mm in length or less. C101/102 is the same length as the original; use axial caps 23mm in length or less.

Specifications:

  • Board material: FR-4 Kingboard KB-6160 (TG130, >175 CTI)
  • Copper thickness: 2 oz.
  • Board finish: ENIG (immersion gold), hard-hold plated fingers, glossy green solder mask
  • Width: 127.45 mm
  • Length: 105.10 mm
  • Thickness: 1.6 mm

Other Notes:

  • The PCB follows the general layout of the original, and no changes were made to the schematic, but it is not an exact replica. The parasitic elements of the board itself (inductance, capacitance, resistance) will thus be slightly different from the original board, and you may find that the values of the compensation capacitors need to be slightly adjusted for good stability. Substituting semiconductors may also require changes to the circuit and should be done with caution.
  • C101/102 on the silkscreen was drawn as a nonpolar cap, but polarized caps are typically used here. The positive terminal is the pad closest to the edge of the board.
  • The symbol for D103/104 bias diode was drawn as a Zener to indicate that it is not an “ordinary” diode, however it is not a Zener; it is a stabistor/forward reference diode with a typical forward voltage of around 1.4V (see service manual/semiconductor datasheet).
  • If using a TO-66 device for Q105/106, take care when installing the heatsink because the base/emitter leads have small pads on the top of the board that could touch the heatsink (i.e. collector) due to the size of the mounting holes. Using short standoffs, fish paper, or a TO-66 insulator underneath can help here.
  • The silkscreen reference designators follow a L/R pattern, so transistor Q105/106 is Q105 on the left channel and Q106 on the right channel.