ASR-33 Questions

[Dwight K. Elvey]

>From: "O. Sharp" <ohh at drizzle.com>
>
>
>Well: I finally took a leap of faith, and bought an ASR-33 from someone 
>who wasn't anywhere near Seattle. After a previous (extremely bad) 
>Teletype shipping experience (read: TTY dumped in box and packing peanuts 
>poured on top; unit largely destroyed in transit; seller refused to 
>refund and claimed damage was somehow _my_ fault; story actually got 
>worse from there if you can believe that, but maybe that's enough for 
>now), it took a leap of faith to try buying another one I couldn't 
>personally pick up. But the seller took a _lot_ of extra care packing it, 
>including bolting the typing unit to the chassis, and wonder of wonders 
>it actually arrived completely intact.  :)
>
>But in spite of that it needs some help, so I thought I'd ask a couple of 
>questions here.
>
>-The one big problem it has is its lack of a reader power supply. The last 
>owner got it from a government surplus program, but they neglected to 
>supply anything but the unit itself... and so no reader supply. Does 
>somebody have the schematic of one of these so I can build a new one? 
>(Better yet: does somebody have a spare one I can talk them out of for a 
>reasonable price?)
>
>-I'm looking at some DEC diagrams saying how the ASR-33 gets modified for 
>use with a PDP-8 series interface (thanks once more to Mr. Kossow!). It 
>says two "6RS205P484 Thyractors DEC #1100106" should be added to the unit. 
>Okay, I admit it: I don't even know what the hell a "thyractor" _is_, 
>much less what ratings I should be looking for re: these two. Can 
>someone shed a little light on this?
>
>-Right now the unit is doing a lot of chattering on both Line and Local 
>when powered on. Initially I thought something might be mechanically wrong 
>due to being shaken around in shipping, say one of the clutches on the 
>main shaft locking into an active position, but so far I haven't found a 
>culprit. I'm also wondering if I'm even looking in the right direction 
>for the problem, sooo here's the question: could the lack of a power 
>supply for the reader be causing this behavior? (The reader itself is 
>obviously inert right now, but I'm wondering if there's a missed 
>connection or somesuch which could explain it.

Hi
 If by the reader, you mean the tape reader? In local mode, it
should lock up if the tape is turned off and the keyboard
is reset ( H connector working ).
 I've made a supply from the manual for the tape reader. The
only part that is hard to get is the power resistor. I just
used two in series to get the value. Still, this is not
needed to lock up.
Dwight


>
>...At some point I'll probably ask someone with a copyholder to take some 
>tracings and measurements for me so I can fabricate a new one, but maybe 
>I'll just see if I can get it working first. :)
>
>                       -O.-
>
>