Old School Fault Finding

[PeterO]

I've spent today doing some old school fault finding and repair

Proper fault finding with a 'scope


Space for a replacement for the faulty part to be installed


PeterO

[gregeric]

Germanium transistors? Lovely pictures.

Is that a red thing that's faded orange, or white thing that's burnt orange? And what is "thing"?

[Hove]

I love the smell of germanium in the morning!

[PeterO]

Germanium transistors? Lovely pictures.

Yes , lots of OC84s, a few OC23s and lots of ferrite cores ( the "things" in the coloured blocks)
PeterO

[Heater]

PeterO,

Wow. What is that?

I have not seen an OCxx transistor since the early 1970's.

We kids scraped the black paint of off Mullard OC71 transistors to make photo detectors.

Only recently found out there was an OCP71 photo transistor. Same thing but in a transparent package.

[gregeric]

We kids scraped the black paint of off Mullard OC71 transistors to make photo detectors.

Been there, done that... lost the t-shirt ages ago.

[PeterO]

PeterO,

Wow. What is that?

One of the boards in the first CPU cabinet seen here : https://www.youtube.com/watch?v=Wa7KVU_e8U8

PeterO

[Heater]

Incredible!

500cps paper tape reader. Never seen such a fast tape reader.

I used to get severely reprimanded for using so much of the plotters time on the 2960 in uni.

I have to get myself over to Bletchley.

Coincidentally, I saw an Enigma machine in the Science Museum in Berlin before Christmas. Also a Cray super computer and various Zuse machines. Well worth a visit. Sadly none of the exhibits are operational.

[boyoh]

My workshop in the loft ,photo taken 1992. At 85 can't get up there much now
Made most of test gear on night shift.
Regards BoyOh

[boyoh]

My workshop in the loft ,photo taken 1992. At 85 can't get up there much now
Made most of test gear on night shift.
Regards BoyOh

[Heater]

boyoh,

What a wonderful picture. Every nerd should have a shed or loft. Thank you.

Now what is that spirally thing on the wall behind you? Some kind of weird antenna or a plan for a model railway layout or what?

[PeterO]

Incredible!
500cps paper tape reader. Never seen such a fast tape reader.

The ultimate development of that design (Used by Elliotts on the 4100 range and ICL on the 1900 range) ran at 1000 cps. I've never seen one working

I used to get severely reprimanded for using so much of the plotters time on the 2960 in uni.
I have to get myself over to Bletchley.

Make sure you let me know if you are comming so I can be there to meet you.

Coincidentally, I saw an Enigma machine in the Science Museum in Berlin before Christmas. Also a Cray super computer and various Zuse machines. Well worth a visit. Sadly none of the exhibits are operational.

This is a major failing of most museums (London Science Museum included). They are so focused on preservation and glitzy, dumbed down presentations that they fail to actually give their visitors any idea about what these machines were like to use.

PeterO

[rpdom]

Classic stuff. Thank you for sharing

[boyoh]

boyoh,

What a wonderful picture. Every nerd should have a shed or loft. Thank you.

Now what is that spirally thing on the wall behind you? Some kind of weird antenna or a plan for a model railway layout or what?

Thanks Heater for the compliment, The board in the back ground , is a model railway mimic con troll layout.
I built a model railway , based on combinational logic con troll ( Points set to First Come /First Go ).
All home built controllers. All sold a few year's ago

[jahboater]

that they fail to actually give their visitors any idea about what these machines were like to use.

I read elsewhere on these forums that the web browser requires 100MB just to load a new tab.
Whoever wrote that code should do some programming on a 60's computer!

[drgeoff]

We kids scraped the black paint of off Mullard OC71 transistors to make photo detectors.

Been there, done that... lost the t-shirt ages ago.

Don't know if Mullard did it deliberately to stop that (I seem to recall that OC71 were 6s6d - that's 32.5 pence in new money - whereas OCP71s were about 3 times that) but they changed from using a translucent goo inside the glass tube to a light blue one.

I used a test tube centrifuge in the school's chemistry lab to move the goo down to the leads end of the enclosure.

[gregeric]

Hi Peter - should you be going to the Pi party this weekend I can pass you four or so germanium transistors, should they can be useful to you in maintaining those old machines.

[PeterO]

Thanks but I won't be there.
PeterO

[Heater]

PeterO,

Make sure you let me know if you are comming so I can be there to meet you.

That would be wonderful.

I could probably waste your whole day hanging around watching you restore thing and asking stupid questions

[PiGraham]

We kids scraped the black paint of off Mullard OC71 transistors to make photo detectors.

Been there, done that... lost the t-shirt ages ago.

Oh yes. Happy memories.

[PeterO]

Thanks but I won't be there.
PeterO

Change of Plans ! I will be there on Sunday

PeterO

[PeterO]

PeterO,

Make sure you let me know if you are comming so I can be there to meet you.

That would be wonderful.
I could probably waste your whole day hanging around watching you restore thing and asking stupid questions

I'll probably bore you stupid with facts about the machine and details of how it works !

PeterO

[gregeric]

Change of Plans ! I will be there on Sunday

Saturday for me. Pity. I'll leave them at reception or other, & tell them father xmas will collect

[PeterO]

Leave them with Jamie on the PiHut stand.
PeterO

[scruss]

Your pictures are timing out, Peter — are you sure you're not hosting 'em on that 803?

Regarding memory usage, I'm learning you can do quite a bit with 32 Kw (@ 12 bits/word) in an emulated PDP-8 on the Pocket DEC Pretender (PDP) Zero …