18-09-2023, 12:27 PM
We all know about the tin whisker problems in AF11x and the packaging troubles of Lokfit devices such as BF194. What other transistors give grief?
I've had problems with leads that fracture as soon as you look at them. 2N706, in a proper metal TO18 can, has been an offender for me.
At the BECG charity one thing we do is restore vintage broadcast TV cameras. These are typically orders of magnitude more complex than receivers, though they are not usually built down to a price. As a result, components are usually well chosen and sensibly rated. Replacing paper and electrolytic capacitors is no mystery, it's just that there are often a awful lot of them. I don't think any of us would even dream of restuffing except perhaps where it might solve a mechanical mounting problem. Function takes 100% priority over appearance inside the covers.
But what about the transistors? Marconi used metal can parts in their Mk VII colour cameras. They are basically reliable. The EMI 2001 was a direct competitor and much liked by the BBC. It used mainly plastic cased transistors which are failing in their droves. This makes the restoration of such a camera something of a nightmare. Shotgun the lot? 100s of them. Replace the dead ones knowing that others will fail soon? Or just don't bother. So far we, at the BECG, haven't bothered to restore a 2001 to working order. Partly because we are prejudiced towards Marconi kit, partly because effort is limited.
So what's wrong with all those perfectly ordinary plastic case transistors?
We look at the people who restore early computers, where complexity can be another order of magnitude greater, and wonder how on earth they manage.
I've had problems with leads that fracture as soon as you look at them. 2N706, in a proper metal TO18 can, has been an offender for me.
At the BECG charity one thing we do is restore vintage broadcast TV cameras. These are typically orders of magnitude more complex than receivers, though they are not usually built down to a price. As a result, components are usually well chosen and sensibly rated. Replacing paper and electrolytic capacitors is no mystery, it's just that there are often a awful lot of them. I don't think any of us would even dream of restuffing except perhaps where it might solve a mechanical mounting problem. Function takes 100% priority over appearance inside the covers.
But what about the transistors? Marconi used metal can parts in their Mk VII colour cameras. They are basically reliable. The EMI 2001 was a direct competitor and much liked by the BBC. It used mainly plastic cased transistors which are failing in their droves. This makes the restoration of such a camera something of a nightmare. Shotgun the lot? 100s of them. Replace the dead ones knowing that others will fail soon? Or just don't bother. So far we, at the BECG, haven't bothered to restore a 2001 to working order. Partly because we are prejudiced towards Marconi kit, partly because effort is limited.
So what's wrong with all those perfectly ordinary plastic case transistors?
We look at the people who restore early computers, where complexity can be another order of magnitude greater, and wonder how on earth they manage.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
