How the criminal procedure works
Hits: 14415 Replies: 12EL84: pin 8
08 Jan 05
the pin 8 is actually NOT an internal connection (IV),
but simply open (English: nc, not connected)!
I know a radio
this pin is used as a wiring support point.
08 Jan 05
You are of course right, according to the Telefunken tube manual 1969, pins 1, 6 and 8 are free.
I have re-uploaded the socket image for the tube.
With the best collector's regards
08 Jan 05
The pins labeled "iV" are always to be left free and not to be used as a soldering terminal. The manufacturer's data sheets usually state that the pins designated as "iV" must not be used.
On my EL84 (Telefunken, Valvo, RFT, Funkwerk Erfurt, Polam), also PL84, UL84 and the Russian replacement types, pins 1 and 2 are internally connected to the control grid. In the Russian replacement types, pins 6 and 8 are partially connected to the electrodes as a support for the system. Pins 1, 6 and 8 of the Telefunken PL82 are free.
09 Jan 05
what I said is only valid for the EL84 and there only for pin 8.
It is officially an "iV",
but as I said I saw on a radio
that a capacitor and a wire were soldered to pin 8.
This "wiring" confused me at first,
then I took a close look at some EL84s,
and seen that pin 8 is always open internally.
09 Jan 05
in the tube pocket table (RTT) from Schwandt you will find the note:
"No switching connection may be connected to the pins marked with iV, as this could result in short circuits!"
In the RTT, the base circuit of the EL84 (No 20) indicates "iV" at pin 8. Also in the tube manual from Ratheiser (see below only with "i").
At that time, the tube manufacturers warned against wiring the iV pins otherwise, especially for all-glass types, because they are needed inside as a base for the system. Even if it was not the case with many of the tubes that came on the market, like here with pin 8 of the EL84 - there was no guarantee that this could ever result from design changes.
Therefore iV connections should not be used as soldering terminals.
The fact that it still happened in some radios is certainly due to the fact that the designers had to use the soldering points sparingly and simply saved additional soldering strips. But as I said: There was and is no guarantee that all EL84s available on the market from different production batches and from different manufacturers will work in these devices.
10 Jan 05
"If something is connected to pin 8 in a radio,
then that's just a soldering point.
Pin 8 in the tube is open "
I Agree ?
11 Jan 05
The reference would be better with the corresponding device and not with the tube. I found an EL84 in my collection by chance with the anode connected to pins 7 and 8. It is similar with the UL84 and the PL84.
11 Jan 05
12 Jan 05
The conclusion from this thread should be: every time you change a tube, first check the wiring of the tube socket for the assignment of pins labeled "n.c" /"i.c"/"i.v "in the tube data sheet. It's just terrifying that Hertseller allowed himself to be carried away by such dangerous nonsense. I can hardly believe the reasons for the cost. I rather think that even then it was about only using spare parts from the manufacturer. The fact that one accepted that another component might be destroyed when a tube was replaced or that the function was simply made impossible, throws a very bad light on such manufacturers.
At Sony, for example, another "trick" was used in later years: components were used that were simply not available on the free market and did not even appear in comparison lists. As a result, you were at the mercy of the manufacturer and its pricing. I've never bought a Sony device, but repaired it often enough - a simple thyristor could then cost 25 DM, if you could get it at all ...
Greetings Jürgen Heisig
13 Jan 05
here is an excerpt from a picture of the EL84 from a Valvo publication from the 1960s. Here you can see that pin 8 is used as a support for the right web of G3.
Peter von Bechen
13 Jan 05
the manufacturers usually thought something when they kept the neighboring points of the anode connection free in order to avoid flashovers.
In addition, extremely high voltage peaks occur at the anode when the loudspeaker connection is open, which can cause further damage to the device through arcing if adjacent contacts are occupied. Pertinax bases in particular are charred very quickly.
See also Mr. Knoll's contribution in Treat:
13 Jan 05
19 Jan 05
I wrote out the text under the tube again because otherwise it is hardly legible.
Free pins or free socket contacts
may not be used as support points for switching
medium can be used.
Kind regards. Wolfgang Bauer
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