PDP-11/40 Servicing

On this page, I have documented all the things I have repaired on my PDP-11 and things to watch out for with your PDP-11

Power Supply Modules

The first time I powered up the PDP-11 a full full bridge rectifier failed in one of the power supply modules. I have since replaced all the rectifiers out of precaution. Except in the h742 as it's hard to get to.

Replacement Bridge rectifiers - 200 V@ 35 A

GBPC3502W-E4/51 - https://www.digikey.co.nz/en/products/detail/vishay-general-semiconductor-diodes-division/GBPC3502W-E4-51/2139833

GBPC3502-E4/51 - https://www.digikey.co.nz/en/products/detail/vishay-general-semiconductor-diodes-division/GBPC3502-E4-51/754833

Added AC Fuse to h744 & h745

GitHub - ashlin4010/PDP-11-regulator-fuse: A fuse module for a PDP-11 h744 & h745 regulator

A fuse module for a PDP-11 h744 & h745 regulator. Contribute to ashlin4010/PDP-11-regulator-fuse development by creating an account on GitHub.

GitHubashlin4010

h7441 Replacement Caps

In my older h7441 the caps have just started to crack and leak, not enough to be problematic but as they are a high-stress part they are worth replacing.

Replacements
687ALG025MGBJ - https://nz.mouser.com/ProductDetail/598-687ALG025MGBJ

870135175007 - https://nz.mouser.com/ProductDetail/710-870135175007

Replacement Lamps

-15v Supply (18v T-1 3/4) https://nz.mouser.com/ProductDetail/560-7370
5v Supply (5v T-1 3/4) https://nz.mouser.com/ProductDetail/560-7362

Power Control 861B

I have seen the oil-filled input filter fail and explode. Also, there is a little electrolytic capacitor that can fail, which can result in the power supply turning on and off rapidly.

Replacement Lamps

125V Dome Panel Mount Indicator - https://nz.mouser.com/ProductDetail/593-1092QA3125VAC

Backplane

Take care when pulling the processor out, the backplane has several power cables that can get snagged.

Fix Power Cable Nicks

To fix cable nicks I have used "Liquid Electrical Tape".

Replacement Right Angle Spade Connectors

4.75 mm x 0.81 mm, 14 AWG (TE Connectivity 63647-3)
https://nz.mouser.com/ProductDetail/571-63647-3

Replacement Connect & Pins

1-480278-0 | DigiKey Electronics

Order today, ships today. 1-480278-0 – 12 Rectangular Connectors - Housings Receptacle Natural 0.202″ (5.13mm) from TE Connectivity AMP Connectors. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

DigiKey ElectronicsTE Connectivity AMP Connectors

1-480275-0 | DigiKey Electronics

Order today, ships today. 1-480275-0 – 12 Rectangular Connectors - Housings Plug Natural 0.202″ (5.13mm) from TE Connectivity AMP Connectors. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

DigiKey ElectronicsTE Connectivity AMP Connectors

1-480319-0 | DigiKey Electronics

Order today, ships today. 1-480319-0 – 2 Rectangular Connectors - Housings Receptacle Natural 0.200″ (5.08mm) from TE Connectivity AMP Connectors. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

DigiKey ElectronicsTE Connectivity AMP Connectors

1-480318-0 | DigiKey Electronics

Order today, ships today. 1-480318-0 – 2 Rectangular Connectors - Housings Plug Natural 0.200″ (5.08mm) from TE Connectivity AMP Connectors. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

DigiKey ElectronicsTE Connectivity AMP Connectors

https://www.digikey.co.nz/en/products/detail/te-connectivity-amp-connectors/61116-1/290257

https://www.digikey.co.nz/en/products/detail/te-connectivity-amp-connectors/61314-1/290258

Fixtures

Fascia Panel Clip

https://www.printables.com/model/165368-dec-pdp-11-h960-rack-fascia-panel-clip

Front Panel Mounting Screws

#6-32 Length - Overall (12.70mm) 1/2"
https://www.digikey.co.nz/en/products/detail/essentra-components/020632A050/9677359

Mounting Box Fans

The power cables for the fan can wear because of vibration and import installation, I fixed this with more "Liquid Electrical Tape".