OC70 in Early Mullard packing

[Cobaltblue]

By the time I was destroying the transistors in my Philips Electronic Engineer Kit (1964 onwards) the replacement transistors were in those little fold out flat packages.

I have been trying to sort the loft out and was idly looking through a large box of NOS small valves and picked this one off the top.

It makes sense that Mullard would continue to use the same packaging but I wonder when Mullard started to make specific packaging for transistors?

Cheers

Mike T

[Karen O]

This is more interesting evidence of transistors being treated like valves in the early days. There is another thread I read recently on the shortcomings of early transistor amplifiers due to 'valve thinking'. And if you take the back off my Bush TR82C you find a chassis with transistors soldered to pins that had been pressed into the chassis, placement following valve practise. Not a PCB in sight! What I found more amusing is the long leads on said transistors, doubtless to protect them from heat damage while soldering. Good job it isn't a VHF set.

[Cobaltblue]

Hi Karen

Sounds like your describing the Bush TR82.

Not all manufacturers behaved that way Cossor's first Transistor Radio (1957) the 546 even had a printed circuit tuning scale.

But I do know what you mean even the components were still valve sized parts into the 1960's

Cheers

Mike T

[paulsherwin]

The old OC transistor coding scheme is of course deeply rooted in the concepts of valve electronics ('O' = cold cathode, 'C' = triode). Transistors were often referred to as 'crystal triodes' in the early days.

I would guess that the OC70 is a pretty early Mullard transistor.

[Hartley118]

OC70 and OC71 were the first Mullard germanium audio transistors, with OC72 claiming higher power capability. I could only afford 'red spot' out of spec rejects, but they generally worked well enough in simple TRF sets. Then there were white spot RF transistors - I guess similar to OC44/OC45.

Whether they were all manufactured to different specs, or simply selected from general production and then labelled, I'd be interested to know.

Martin

[Lucien Nunes]

I have a stock of 1960s/70s Mullard industrial semiconductors, mostly stud-mounted diodes and thyristors, that were supplied in B9A-format valve boxes, so the practice went on for some time. Philips / Mullard also used a modified form of this size box for dispenser packs of passive components. There must have been heavy investment in packing and handling resources for commodities of this size, given the number of miniature valves they were churning out.

Some CV-numbered Ge diodes and transistors used to come in packaging entitled 'Valve Electronic CVxxxx' presumably because, like the early Pro-Electron attempt to classify solid state devices using the cold cathode identifier, the nomenclature of the CV procurement had no descriptor for S/S parts. It reminds me of the story of Bleriot's 1909 airborne arrival in Dover. Lacking an official description for this novel circumstance as he was the first in history to reach British shores other than by water, the customs arrival form identified him as the master of a vessel called 'Monoplane.'

I think the convergence of valve and transistor 'styling' if not actual technological design is typified by Tektronix products containing both transistors and Nuvistors (sub-miniature valves). They sit side by side in similar sockets drilled through the chassis in the time honoured way (3-pin for the Tr, 5-pin for the Nuvistor), with similar size metal cans hiding their very different innards. I have heard tell that there are a few circuit positions where you can pull out an expired Nuvistor and put a transistor in the socket and it will work just like that without any mods.

[jim_jobe]

Originally Posted by Hartley118

Whether they were all manufactured to different specs, or simply selected from general production and then labelled, I'd be interested to know.

They were just selected from the general production Martin. OC44s also were from the same production run as OC45s and selected for higher fT. Incidentally the fTs of many OC45s overlap with those of OC44s and can therefore be used to replace OC44s. Mullard kept quiet about that though as the 44s were more expensive! The same thing applies with OC70/71 and 75s - most of my OC70s have hFEs within the characteristic spread for OC71 and ditto for my OC71s and 75s!
Jim

[Wendymott]

Maybe just prior to the OC series, there was the "Red spot" "Brown spot"....in little "Tombstone" cases......... then AEI and GEC did the Yellow/Green spot.....around 5 shillings if I remember...

[Hartley118]

I guess that the transistors in 'tombstone cases' were the Pye/Newmarket devices pictured here. http://www.wylie.org.uk/technology/s.../Newmarket.htm. My memory is of their rejects which were marked with a green/yellow spot, but still cost an arm and a leg for the junior hobbyist!

Martin

[AC/HL]

Tungsram ones came in an aluminium tube