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Old 26th Mar 2023, 2:37 am   #21
Radio Wrangler
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Default Re: Numbering Schemes.

If you come across an HP part number looking like xxxx-yyyy it is a purchased part. The digits xxxx say what sort of part, the digits yyyy were assigned in chronological order for that type of part.

0757- means resistor (as does 0698) the 280th resistor set up under 0757 is 0757-0280.
0280 carries no coded meaning, this one just happens to be 1k 1% 1/8W metal film.

If you come across xxxxx-yyyyy format, these are custom parts for a specific instrument. The xxxxx field is the instrument number sans its suffix letter so 3725A becomes 03725-

The first digit of the yyyyy field says what sort of thing it is 6yyyy is an assembly such as a loaded PCB the remaining yyyy digits give the assembly number 03725-60003 is the A3 assembly (Loaded board) of the 3725A. 03725-20003 is the bare board. Dashed suffix numbers after these relate to the drawings and artwork sheets.

The assembly numbers of PCBs were often reflected in the colours of the plastic extractor levers!

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Old 1st Apr 2023, 11:24 am   #22
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Default Re: Numbering Schemes.

For musical composition, Serialism,

Mozart once threw dices to create randomness in the development. An easy piece of software or A.I. will do the same given the parameters. After all, it’s only organized beautiful randomness. Ornette Coleman created quite a stir up within the Jazz world when he introduced his take on the matter.

It’s a system well worth studying and listening to if your mind is mathematically inclined and will draw you in very deep. (including subjectivity)

Last edited by tritone; 1st Apr 2023 at 11:31 am.
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Old 3rd Apr 2023, 9:33 am   #23
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Default Re: Numbering Schemes.

Hello,

Just seen this thread. Hopefully it’s still on topic as regards number schemes.

Over the years on mostly 60’s and 70’s PCB’s and circuit diagrams I see the use of ‘VT’ [example VT5, VT6 etc.] as part of the component ident for a transistor.

Obviously, T and TR is typically used for transistor and V is used for valve, however, I’ve wondered what is rationale behind the use of VT

It’s one of those daft questions one asks themselves when looking at something and promptly forgets to find out as there are more pressing things in life!

It could be Terry and the damn obvious, but I felt it worth asking if anyone knows.

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Old 3rd Apr 2023, 3:20 pm   #24
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Default Re: Numbering Schemes.

Transistors were once seen as a sort of valve, the idea being that they performed 'valving' and that that was more important than the matter of them being made quite differently and operating internally on different principles.

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Old 3rd Apr 2023, 5:38 pm   #25
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Default Re: Numbering Schemes.

Back in the 70s and 80s, Pye Telecom valves and transistor part numbers began with FV0. Ics began with FU0.
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Old 4th Apr 2023, 10:45 am   #26
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Default Re: Numbering Schemes.

In times-past I recall a bunch of circuits where U was used as the designation for ICs, the reasoning was something I never got to discover.

Also thinking of numbering, with the British militaty "CV" [common valve] numbering scheme, does anyone know just how the numbers were issued? It seems that in the number-range around the low-hundreds, there are a mix of Octal, B8 and the later B7G/B9A valves, which implies that when introduced the numbering might have had some sort of logic at one time and left gaps in the number-sequence, which were then back-filled.

It certainly doesn't look like the numbers were simply issued incrementally.
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Old 4th Apr 2023, 10:49 am   #27
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Default Re: Numbering Schemes.

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In times-past I recall a bunch of circuits where U was used as the designation for ICs, the reasoning was something I never got to discover.
I always thought it stood for 'Unit'

DEC used 'E' for the IC designation on circuit diagrams. I've not worked that one out yet.

And why is transistor commonly 'Q' and relay 'K'?
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Old 4th Apr 2023, 11:48 am   #28
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Default Re: Numbering Schemes.

U was a simplification for English letters of Greek Mu because early ICs were often referred to as microcircuits.

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Old 4th Apr 2023, 5:47 pm   #29
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Default Re: Numbering Schemes.

Quote:
And why is transistor commonly 'Q' and relay 'K'?
Maybe because 'T' (Transformer) and 'R' (Resistor) were already taken. 'RL' is also commonly used for relay prefixes.
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Old 4th Apr 2023, 7:52 pm   #30
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Default Re: Numbering Schemes.

The BBC devised an equipment numbering system which I think is still in use. I believe it dates from the 1950s, and possibly earlier and will be familiar to many people if only through loudspeakers such as the LS5 series and loudspeaker amplifiers, e.g. LS8/6.

The system covers both BBC designed and commercial equipment. The numbers would often be used as the standard term for a piece of equipment, such as a RP2/1 twin turntable unit.

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Old 5th Apr 2023, 1:54 pm   #31
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Default Re: Numbering Schemes.

Thanks for the reply.

Ah, that explains the VT then. I clearly remember coming by a 'scrap' PCB from the local component shop, Radio Constructors Centre, Westcliffe, which would have dated back the early/mid 1960's with OC44/71 etc., and that had VT idents.

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Transistors were once seen as a sort of valve
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Old 5th Apr 2023, 2:47 pm   #32
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Default Re: Numbering Schemes.

Have also seen N used for ordinary ICs, presumably an abbreviation of Network. Though I would have expected that to be used for those biscuit-coloured encapsulated thick film modules used in a lot of 80s test gear.
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Old 5th Apr 2023, 3:09 pm   #33
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Default Re: Numbering Schemes.

Quote:
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The BBC devised an equipment numbering system which I think is still in use.
Not any more - the need for it ceased when the BBC stopped making its own equipment.
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Old 5th Apr 2023, 7:47 pm   #34
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Default Re: Numbering Schemes.

Re. Post 11.

Reminds me of a story I heard about an engineer in the GPO days who got a digit wrong on a stores requisition for a small diode. He had a communication the item would take some time, but thought nothing of it until a low loader arrived a few weeks later, with a massive substation type transformer on the back. The delay apparently was because said item had to be ordered from the manufacturer!

The huge transformer which sat in a depot for many years.
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Old 5th Apr 2023, 7:54 pm   #35
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Default Re: Numbering Schemes.

Occasionally, BT sold some brand new stuff off as scrap. That may be why!
I once bought a brand new 110V 1.5KVa petrol generator, made by Haverhill generators.
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Old 5th Apr 2023, 8:08 pm   #36
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Default Re: Numbering Schemes.

I always thought “Q” for a transistor reminded me of a top view of the old TO18/TO5 metal package.
BT refers to grey wires as “ slate”. I think it was because they only used two letters to denote wire colours on drawings etc. and “gr” was already in use for green, or maybe it was to avoid confusion.
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Old 5th Apr 2023, 8:12 pm   #37
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Default Re: Numbering Schemes.

Hi Rob. Yes, I have found some good stuff in skips over the years, and when staff were able to purchase redundant items as “ scrap” I managed to get some useful test equipment.
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Old 5th Apr 2023, 9:03 pm   #38
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Default Re: Numbering Schemes.

One firm I worked for years ago had to buy components in from within its own group.
Now they received a 66% discount on the same items than somebody else buying the same parts from outside of the group, however parts incorrectly ordered were subject to a 33% handling charge for return, this though was 33% of the book or list price not the 66% discounted price!

This meant it cost more to return than it cost! needless to say the stores were full of hidden inventory which was 'disappeared' over the years
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Old 5th Apr 2023, 9:14 pm   #39
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Default Re: Numbering Schemes.

Quote:
Originally Posted by Tim View Post
BT refers to grey wires as “ slate”. I think it was because they only used two letters to denote wire colours on drawings etc. and “gr” was already in use for green, or maybe it was to avoid confusion.
BOGBnS (Blue Orange Green Brown Slate), for those who worked in the Beeb which of course borrowed heavily from Post Office practice.
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Old 6th Apr 2023, 4:41 am   #40
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Default Re: Numbering Schemes.

And of course Blue, Slate, Brown, Pink, Orange for the 5 wires to a telephone dial. Always remembered by 'BilL Said B****R the Post Office'

I normally use 'Gy' for grey and 'Gn' for green on my diagrams.

At least one manufacturer of things we can't mention here used 'U' for blUe on their wiring diagrams.
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