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Old 23rd Sep 2019, 12:59 am   #21
red16v
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Default Re: Mullard glass transistors

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Originally Posted by AC/HL View Post
The red dot is the collector, but there is also a difference in the leadout spacing. They will work either way round, but with greatly reduced gain, maybe that's what is being tested.
All Mum told me was that they picked up a transistor and put the three leads on some sort of test bed and observed a centre zero meter. If the needle went to the left they painted a red dot on the case on the left hand side and vice versa. Happy to accept my error with emitter and collector marking rather than Mum!

I worked with a few Mullard apprentices some years later myself as part of an ond course. They said the first years output of the factory was underneath one of the factory perimeter roads as they tried to get to grips with mass production! They also said site security was very very tight as a whole weeks worth of production could be put in the back of a transit van and if the van got nicked well .. you can imagine the consequences. All bulldozed now of course.
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Old 27th Sep 2019, 7:54 pm   #22
whyperion
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Default Re: Mullard glass transistors

Question are the Russian made ones suitable for true replacement use ( can one tell the difference in use by scope or ear between Old Stock/NOS and modern equivalents in the same circuit. For Valves and Transistors generally I have an idea of replicating some of my Dads Equipment wholly in new components.
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Old 28th Sep 2019, 5:54 am   #23
Radio Wrangler
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Default Re: Mullard glass transistors

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Question are the Russian made ones suitable for true replacement use ( can one tell the difference in use by scope or ear between Old Stock/NOS and modern equivalents in the same circuit. For Valves and Transistors generally I have an idea of replicating some of my Dads Equipment wholly in new components.
Some people would say that for true replacement, they would have to look the same.

Functional replacement is much easier. Early transistors had huge tolerances on their parameters. Well-designed circuits were made to handle this. Not-so-well-designed circuits might have a select-on-test resistor value to accommodate the spread in transistors. The worst circuits needed selected transistors.

The question is in rather general terms so the answer would have to be along the lines of 'it depends', which isn't terribly helpful.

If you have a tolerant circuit design, you can get away with murder. If you allow yourself to fiddle with bias resistors, you can do a lot and often even use current silicon devices. It gets more difficult if the supply voltage is low, though because the turn-on voltage of silicon becomes significant. Also, with low supply voltages, the things designers could have done to make the circuit tolerate device spreads are badly limited.

David
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Old 28th Sep 2019, 11:12 am   #24
Bazz4CQJ
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Default Re: Mullard glass transistors

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Originally Posted by whyperion View Post
Question are the Russian made ones suitable for true replacement use ( can one tell the difference in use by scope or ear between Old Stock/NOS and modern equivalents in the same circuit.
I suspect that you could well ask the same question about any two batches of Mullard glass transistors. Although Mullard might have seen fit to label them with a particular type number, as Wrangler says, the variations between devices was huge. 30 years later I was working at Plessey when much the same thing was happening in our attempts to make gallium arsenide FET's. The expitaxial growth process used to put down the active layers was a total black art. The devices varied greatly from wafer to wafer, and even whereabouts they came from on any one wafer.

Personally, I would not get too distracted by such issues; life's too short. If Russian devices work, just press on with them!

B
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