[GreenKeys] [External] Re: Just bought an Ebay ASR33 in the UK

[Jones, Douglas W]

From: ian parr <parrid at hotmail.com> -- Thursday, February 6, 2025 10:42 AM

> Disconnected from the pedestal - a rat or mouse seemed to have made its home

Ick.  I've had to remove a mouse nest from a Flexowriter. Their urine is rather corrosive and does no good at all to anything it touches.  After you remove disgusting debris, you may find that you have more fine cleaning to do.

I just read the US Military writeup on using citric acid as a soldering flux.  Turns out that it is a chelating agent that does a good job of removing metal oxides without attacking the metal, and it can be completely removed with rinse water.  Use about 1/4 cup citric acid to 1 cup of water for a near optimal solution (1/2 molar) for derusting and soldering.  Add starch to thicken it if you want it to cling while it works.

> Case removed (one small crack in the main body) 

Cracks can be repaired.  See:
-- https://homepage.cs.uiowa.edu/~dwjones/pdp8/UI-8/bugs.shtml#17

In summary, the case (both gray and cream colored parts) is made of ABS and can be repaired by solvent-welding using the same solvents used to build plastic models.  I was even able to make a replacement for one of the broken ears that serves to hinge the lid over the typing mechanism to the case.

> The print head hammer seems to have most of its original rubber in place

Good, but you definitely want to replace it.  One of the GreenKeyers has manufactured new ones that are exact replacements for the original.  You can also use a chunk of vinyl tube to fake it.

> Some signs of heat/burning from the large resistor board on the RHS as the board

I've never seen a Model 33 that didn't show this symptom.  It is of no importance.  Ignore it.

> The keyboard keys are really 'chalky'

This is common.  There have been a few people who've de-chalked their keys by very careful sanding, but I suspect there are better ways to deal with that.  It is purely cosmetic until the keys begin to crack and delaminate. (They are of two part construction, white plastic core with grey plastic shell.  The core shows through to make the lettering on the key caps.)

> The 'here is' button seems to be stuck down.

Keyboard assembly and disassembly is a tricky business, and you may need to do this to get the button unstuck.  Here-is has its own link to the rear of the machine where it triggers a music box mechanism to transmit a "programmed" message.  You program it by breaking prongs off of the drum.

         Doug Jones