Archive for Mike Jay

Marantz 2385/2500 Capacitor Replacement Kit

Mounting kit for replacing both power amplifier supply capacitors with modern screw-in parts

Click the link below to download the installation guide

PAE-23852500CAP-Install-GuideDownload

This kit is designed to replace both dual electrolytic capacitors used in the Marantz 2385 and 2500. The 2385 uses a set of dual 6800 uF/85 V caps, while the 2500 uses a set of dual 7200 uF/100 V caps. These dual capacitors are difficult to come by, so at the request of a customer we created a custom mounting board that fits four modern production screw-in capacitors.

The board mounts using four screw holes that were used by the mounting brackets of the original capacitors. 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, and a 3 mm thick FR-4 laminate to reduce board flex.

Included in the kit is a capacitor mounting board, the necessary board mounting hardware, and an installation guide. New capacitors and capacitor screws are not included; please refer to the section titled “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. At the time of this writing (March 2024), these are currently in active production and stocked by vendors like Digi-Key and Mouser for about $20 USD each. 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 (commonly available in tooth lock washer assortment kits online).

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. Even if the mounting studs are flush with the bottom of your cap, it is recommended that you incorporate some kind of spacer underneath the caps because the pressure relief hole on the mounting board is a bit small, though it can be drilled larger if needed. This will be corrected in future revisions

If in doubt, please refer to the drawing in the listing which shows board dimensions. Feel free to send me a message if you have any questions.

Note that due to the slight increase in capacitance with the Kemet ALS80A822DF100 capacitors compared to the original parts, you may wish to replace the original bridge rectifiers with parts capable of handling higher continuous and peak surge currents due to the increase in power-on inrush current. For reference, the Marantz 2500 schematic indicates that it uses two S5VB40 bridge rectifiers, which are rated for 6 A continuous current (when bolted to a heat sink, i.e. the chassis), 200 A peak surge forward current, and 600 V maximum reverse voltage. The 2385 uses two S5VB20, which have the same current ratings but are rated for 200 V maximum reverse voltage.

Lastly, you will need the usual tools and equipment involved in servicing stereo equipment (pliers, wire cutters, variable temperature soldering iron, multimeter, etc.) This kit requires some skill and experience to install, so if you are not thoroughly familiar with repairing electronics at the component level, please have a qualified service center install it for you.

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 and mounting brackets. Try to save as much wire length as possible
  • If using the specified Kemet parts, place five of the included spacer boards over the mounting studs of each capacitor. Make sure the third hole on the spacers all align with the pressure relief vent
  • Mount your new screw-in capacitors to the mounting board on the side opposite of the long end of the wiring turrets. This side has a small manufacturing code printed on the bottom left. Silkscreen references are included on the board to indicate polarity; be sure to triple check that they are installed correctly! I recommend using internal tooth lock washers under each screw to ensure a good electrical connection.
  • If you want to install the two bleeder resistors on the mounting board, do so at this time. Per the original Marantz schematic, they connect from the negative rails to ground
  • Mount the assembled board in place with the four included screws, nuts, and plastic spacers. The screws will attach to four of the holes used by the mounting brackets of the original capacitors. The fifth mounting hole is unused in this application. In the Marantz 2500, you may need to remove one of the plastic wire holders and replace it with a zip tie in order for the board to sit low enough.
  • Turn the unit upside down. All of the wiring turrets can be seen through the two round holes in the bottom of the chassis. After confirming the color codes with the diagram or pictures taken at the beginning, strip back each wire about 1/4″, insert them into the center holes of their respective turrets, and solder them in place. The turrets labeled V+ on the board’s silkscreen corresponds to the positive rail, V- corresponds to the negative rail, and GND corresponds to ground. Not all ground turrets will be used. If you are leaving the bleeder resistors in place rather than moving them onto the board, they can be wrapped around the V- turrets and soldered in place.
  • Triple check your wiring. If you are replacing the bridge rectifiers with parts capable of handling higher continuous and peak currents, do so now. I recommend powering the unit up slowly with a dim bulb tester and variac while monitoring the supply voltages to confirm that everything is working as expected.
  • Enjoy!

Parts Included

  • One capacitor mounting board (3 mm thick TG150 FR-4, 2 oz. copper, glossy green solder mask, lead-free HASL finish)
  • Fourteen pre-installed wiring turrets
  • Twenty capacitor spacer boards designed for the Kemet ALS80-A-DF family (5 per capacitor)
  • Four 10 mm nylon spacers to elevate the cap board
  • Four #6-32 machine screws and nuts for mounting the cap board
  • Step-by-step installation guide

3-in-1 Multi-Cap (Chassis Grounded)

Multi-section can capacitor replacement kit, 450 V max

Click the link below to download the installation guide

3-in-1-CGDownload

This kit is intended as an easy way to mount new electrolytic capacitors when replacing approximately 29 mm diameter multi section can capacitors with 37.8 mm mounting hole spacing CTC. This design was modeled after an Astron A-25-65 can. These were often used in vintage audio and radio equipment.

Up to three different caps can be installed, and they all share a common lead located in the center. Both 5 mm and 7.5 mm lead spacing caps up to 12.5 mm in diameter are supported. 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 don’t want the common tied to ground, you will need to either cut out a large section of the connecting trace, or use plastic stand-offs. The spacer board sits between the new caps and mounting board and adds clearance between the turrets and cans of the caps. The optional turrets provide robust terminals 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
  • Board finish: HASL (lead-free solder), green solder mask
  • Copper thickness: 2 oz.
  • Screw hole spacing: 37.79mm center-to-center
  • 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

4-in-1 Multi-Cap (Can Negative, Chassis Grounded)

Multi-section can capacitor replacement kit, 450 V max

Click the link below to download the installation guide

4-in-1-CGDownload

This kit is intended as an easy way to mount new electrolytic capacitors when replacing multi section can capacitors that are around 35 – 38mm in diameter with 46mm mounting hole spacing CTC. These cans are often used in vintage audio and radio equipment, such as McIntosh, Marantz, and Dynaco. This particular version is designed for cans where the negatives of each capacitor are common (“CAN NEG”) and directly tied to chassis ground.

Includes one capacitor mounting board, one spacer board, a hardware kit, and an installation guide. Capacitors are not included.

Capacitors of 5 mm lead spacing with a diameter of 12.5 mm or less are ideal, but larger capacitors with different lead spacings can also be used. Up to 4 different capacitors can be installed. Four extra plated through-holes tied to the outer ground ring are also provided.

A spacer board is included to be inserted between the new capacitors and the mounting board, giving them a flat surface to sit on.

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

Ohm’s Law/Joule’s Law PCB Wheel

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.

MN4760S-PAE

McIntosh MLD7020 Line Memory Replacement

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.

PAE-MAC4100RCA

McIntosh MAC4100 RCA Jack Replacement PCB (Unpopulated)

This board was created as a solution for replacing the original riveted RCA jacks on the McIntosh MAC4100. The new RCA jacks (CUI RCJ-022 and RCJ-023) are not the most premium connectors in the world, but if your original jacks are loose and intermittent, these will certainly perform better.

Includes one unpopulated PCB and a schematic of the board. RCA jacks are not included, but the part numbers are listed above.

This board is quite involved to install and will require the back panel of your unit to be taken off. Please do not attempt to assemble and install it if you are not familiar with safely diagnosing and repairing electronics. Be sure to take lots of pictures of your original installation so you know where everything goes.

The rivets holding the original RCA jacks in will need to be removed and replaced with #6-32 screws. The board will also need standoffs or spacers to keep it far enough away from the back panel. The original black plastic shrouds can be placed over the new RCA jacks so that the green PCB is not seen from the back panel. (Please see the installation photos above).

Depending on the serial number of your unit, the wiring scheme may be slightly different. This board has the following optional solder jumpers:

  • JP1 or JP2: Short to connect the shields of the “TAPE 1 and 2 IN” jacks to chassis ground (JP1 and JP2 are redundant, use either one)
  • JP3: Short to connect the shields of the “AUX 1 and 2” jacks to chassis ground
  • JP4: Short to connect the shields of the “SCOPE VERT” jack to chassis ground
  • JP5: Short to connect the shields of the “SCOPE HOR” jack to chassis ground
  • JP6: Short to connect the shields of the “PREAMP OUT” and “POWER AMP IN” jacks to chassis ground
  • JP7: Short to connect the shields of the “TAPE 1 and 2 OUT” jacks to the shields of the “TAPE 1 and 2 IN” jacks

For example, in the unit I installed this board in, the shields of the AUX, TAPE OUT, TAPE IN, and PRE OUT/POWER IN jacks were tied to the chassis grounding screw by the factory. This corresponds to shorting JP3, JP1 or JP2, JP7, and JP6. Additionally, there was a 10nF capacitor between the shields of the PHONO jacks and chassis ground, which is implemented as the capacitor footprint C1.

PAE-045622

McIntosh MC2500 Power Guard Indicator PCB (Lamps Not Included)

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

066-095-PAE

McIntosh MC2100, MC2105, MC2300 Can Capacitor Replacement Kit

Click the link below to download the installation guide

066-095-PAEDownload

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.

128-165-PAE-A

McIntosh MC2100, MC2105, MC2300 Input Preamplifier Board (Assembled & Tested)

Click the link below to download the installation guide:

128-165-PAE-ADownload

This is a new-production input preamp PCB 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.

Includes one board that has been assembled and tested, a thorough installation guide, and a performance specification sheet.

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.

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

  • Hand assembled with high quality components: 1% tolerance 50ppm TCR metal film resistors, Nichicon electrolytic capacitors (UPM in supply filters, UKZ in audio stages), WIMA film capacitors, and new transistors. Robust wiring turrets replace the original hollow posts that wires are soldered to
  • All boards are burn-in tested for 24 hours and come with a performance spec sheet
  • Thick 2 oz. copper with gold finish (ENIG) and matte black soldermask
  • Silkscreen reference designators and symbols on both sides
  • All component footprints are sized to fit the original parts. In addition, all axial electrolytic capacitors have footprints for radial parts of various sizes, and both input film caps support two different lead spacings

128-165-PAE-U

McIntosh MC2100, MC2105, MC2300 Input Preamplifier PCB (Unassembled)

Click the link below to download the installation guide

128-165-PAE-UDownload

This is a new-production input preamp PCB 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.

Includes one unpopulated PCB with wiring turrets pre-installed and a thorough installation guide with redrawn schematic, board layout, and parts list. We also offer these boards assembled and tested here.

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:

  • 2 oz. copper with a gold finish (ENIG), plated through-holes, and matte black soldermask
  • Silkscreen reference designators and symbols on both sides
  • 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
  • Robust wiring turrets replace the original hollow posts that wires are soldered to

128-077-PAE

McIntosh MC2100, MC2105, MC2300 Driver Cards (Unpopulated)

Click the link below to download the installation guide

128-077-PAEDownload

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.