ECL85

Hi,

Can anyone explain me if there's a difference between ECL805 and ECL85 ? They look so similar and internal values also. Am I right or wrong ?

ECL805:
P_amax= 8W (10,5W with fixed grid bias)

ECL85:
P_amax= 7W (9W with fixed grid bias)

PCL85/PCL805 have the same limits.

In some later documents the PCL85 is listetd with the same limits as PCL805. I am in doubt that that is really correct. But perhaps the later 85 types have got the construction elements of the 805 types, too.

The 805 types are redesigned 85 types, because the 85 types often failed, and because a stronger version became necessary with the start of colour tv in europe.

Hi,

many thanks for your answer. What would happen if I replace ecl85 with/by ecl805 ? Can it damage the device ?

If you replace an 85 type by an 805 type, then there will happen nothing. Due to both types have identical characteristics (except of P_amax), it will work properly. But you should be careful when replacing an 805 type by an 85 type: In most cases it will work, too, but the 85 type could fail earlier than usual.

Dear Matthieu,

due to reliability Problems the PCL85 (Pa= 7W [1]) became the successor PCL805 (Pa= 8W [2]) where nothing else had been changed except the pentode power rating.
For the same reason the pentode part had been put into a single envelope, which was named PL805 then (with "E"-Heater also produced as EL805).
The following article from "Funkschau", 1967 Heft 1 page 16 is showing this.

[1] Siemens Röhren, Halbleiter, Bauelemente, Taschenbuch 1966/67

[2] Valvo Taschenbuch 72

Found the answer... ECL802 (9W) is quite similar to ECL805... and in no case similar to ECL82

The listing of later PCL85 with the same characteristics as the PCL805 is likely correct. The rumor is that the characteristics were improved before the new type number was introduced, but it is also plausible that the number PCL85 was used on some percentage of the later tubes to be able to sell them without having to explain that the PCL805 really is backwards compatible.

I once noted down some of the overlapping Philips factory codes, I think somewhere around VXC or VXD (which means the valve design was already revised more than a dozen times). Unfortunately, I didn't enter the notes in my later database so for confirmation I'll have to find some valves again.

I never saw enough ECL85/ECL805 to confirm any overlap there, though. Also, I don't know anything about valves from other manufacturers that didn't print revision codes on the valves.

Apparently, the triode is somehow improved in the ECL805/PCL805 too.

In the early 60's, the swedish manufacturer Luxor had lots of vertical sync problems in their tv's with PCL85 in the vertical deflection. They published several service informations about the problem, blaming it on the triode getting secondary emission from the control grid and drawing grid current when the valve became too hot. Among the suggested remedies were using specially selected PCL85 valves, connecting a 22 kohm resistor in series with the triode control grid (it was used in a blocking oscillator), and not the least, connecting an extra dropping resistor in the heater chain if the least overvoltage on the electrical mains was suspected. When the PCL805 appeared on the market, it seems to have solved all those problems.