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Cisco 1760/1840/2610/2621 power supply repair

March 2023

Introduction

The Cisco 1760, 1840, 2610 and 2621 routers share a common power supply unit. All use the Astec AA21430 power supply. Unfortunately, these supplies can be difficult to find through larger IT/telecom distrbutors. At the time of writing, there are still many eBay and Amazon listings, as well as independent websites of unknown reputation.

Thankfully, this power supply can have its internals replaced with a common open frame model - the Artesyn LPT42. While this replacement supply has a much lower current rating on the +5v rail, it appears to be ample for the router to function properly. This process has been tested with a Cisco 1760 with a single WIC-4ESW Ethernet interface card and a WIC-1T serial interface card fitted. Other models have not been tested, but should work.

Parts required

The distributors listed below are not an exhaustive list. These parts may also be available from other sellers.

Purpose	Manufacturer	Manufacturer part	Quantity	Distributors	Distributor parts
Power supply	Artesyn	LPT42	1	Element14 Mouser Digi-Key RS Online	1171491 826-LPT42 454-1075-ND 455-7689
AC input to power supply	Molex	09-50-8031	1	Element14 Mouser Digi-Key RS Online	2751620 538-09-50-8031 WM2123-ND 679-5158P
DC output from power supply	Molex	09-50-8061	1	Element14 Mouser Digi-Key RS Online	2112408 538-09-50-8061 WM2126-ND 679-5170
Pins for AC input and DC output connectors	Molex	08-52-0113	8	Element14 Mouser RS Online	1756640 538-08-52-0113 679-4723
Earth connection to power supply	Various	0.8x6.35mm crimp spade receptacle	1	RS online Most automotive electrical stores Most hobbyist stores	534-351 (100pk)
Earth connection to chassis	Various	3.5mm crimp ring terminal	1	RS online Most automotive electrical stores Most hobbyist stores	267-3650 (100pk)
Earth wire	Various	1.5mm2 stranded conductor Coloured green with yellow stripe	Approximately 5cm	Most automotive electrical stores Most hobbyist stores Most electrical wholesalers/supply stores Can be harvested from old electrical appliance supply cords
Active wire from switch	Various	1.5mm2 stranded conductor Coloured brown	Approximately 5cm	Most automotive electrical stores Most hobbyist stores Most electrical wholesalers/supply stores Can be harvested from old electrical appliance supply cords
Neutral wire from switch	Various	1.5mm2 stranded conductor Coloured blue	Approximately 5cm	Most automotive electrical stores Most hobbyist stores Most electrical wholesalers/supply stores Can be harvested from old electrical appliance supply cords
Coverage of mains connections from switch Optional	Various	5mm (unshrunk) diameter heatshrink	Approximately 4cm (2x 2cm lengths)	Most automotive electrical stores Most hobbyist stores

Tools required

The following tools will be required to perform this swap.

• Phillips/pozi drive #1 screwdriver or similar
• 5mm wide slot head screwdriver
• Soldering iron, ideally with chisel tip fitted
• Solder. Lead or lead free is ok
• Wire strippers
• Wire cutter (may be integrated in stripper)
• Spade terminal crimp tool
• Molex KK/JST crimp tool or clone. Sometimes generic spade terminal crimp tools include these.

Replacement process

This process details instructions for a 1760 router, but most of the process should be the same for the other routers.

1. Disconnect the router from power and allow two minutes for any residual charge to disappear.
2. Remove the three screws holding the case on the rear of the router.
3. Slide the router cover towards the back of the router and then upwards to remove it.
4. Disconnect the power supply from the mainboard.
5. Unscrew the single screw holding the power supply in place.
6. Slide the power supply towards the front of the router and then up to remove it.
7. Put the router chassis and covers to the side so that you can work on the power supply.
8. Remove the three screws from the top of the power supply.
9. Use the flat head screwdriver to lever up and release the two clips on the vent side of the power supply. Avoid permanently bending these clips, as they will help re-seal the unit later.
10. Remove the lid of the power supply to reveal the internals.
11. Unscrew the three screws holding the board in to the chassis.
12. Slide the board out of the chassis and desolder the brown and blue wires from the switch to release the board. Do not remove any of the plastic insulating sheets or stickers from the inside of the power supply case, these will remain in place with the new supply.
13. Desolder the output cable from the board and cut off the soldered and/or crimped ends from the wires.
14. Strip the green/yellow wire and crimp the ring terminal on one end and spade terminal on the other. The final wire should be about 5cm long.
15. Unscrew the earth screw between the switch and mains input plug, add the ring terminal and refasten the earth screw. The earth screw should be fastening both the new earth wire and the earth wire from the plug to the same point in the chassis. The crimp terminals should be oriented toards the mains plug so that they will not get in the way of the new power supply PCB.
16. Replace the blue and brown wires from the switch with the new wires about 5cm long. If desired, add heatshrink to cover the solder connections on the back of the switch.
17. Strip the insulation and crimp a Molex connector pin on to the other end of the new mains wires.
18. Fit the pins in to the 3 pin connector per the following table:

    Pin number	Function	Wire colour
    1	Mains active	Brown
    2	Not fitted	N/A
    3	Mains neutral	Blue

19. Slot the new LPT42 power supply in to the chassis. Some wiggling may be required to make the new board fit in the slot near the mains connector. Do not cut the board to fit, as it needs to be supported by the slot in the corner.
20. Fasten the LPT42 with the three screws from the original board and connect the mains (SK1) and earth (spade) connection.
21. Strip the ends of the wires in the output cable removed in step 13 and crimp Molex connector pins to each.
22. Fit the output cable pins in to the new six pin connector per the cable below:

    Mainboard pin	PSU pin	Function	Wire colour
    1	6	-12v	Purple
    2	5	Common	Black
    3	4	Common	Black
    4	3	+5v	Red
    5	2	+5v	Red
    6	1	+12v	Yellow

23. Connect the output cable to the DC output (SK2) of the LPT42. The end with the new Molex connector should be plugged in to the LPT42.
24. Refit the power supply cover removed in step 10 and refasten with the three original screws. Ensure that the two clips on the vent side of the case are engaged and that the lid is secure.
25. Slide the repaired power supply back in to position in the router chassis. Ensure that the two tabs on the router chassis mate with the corresponding slots in the power supply case.
26. Secure the power supply in the router chassis with the single screw at the back and reconnect the power supply output cable to the mainboard.
27. Replace the router chassis cover by placing on top and then sliding forward in to position. Ensure that all of the edge clips have mated with the front of the router.
28. Refasten the three screws holding on the lid of the power supply.
29. Power on the router and test. Your router should now be operational again.