orion: replace the tubes

Dear colleagues,

 

This Orion B545 device is equipped with the following tubes.

 

1R5T, 1T4T, 1S5T and 3V4.

 

The question is whether it is possible to replace the tubes with the ending T with the tubes without the letter T. The tubes without the letter "T" have a consumption of 50 mA per filament and the tubes with the letter T have a consumption of 25 mA per filament.

 

The existing catalogs do not give equivalence for the two types of tubes with and without the letter T.

 

Please help me with your experience.

 

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It's listed as having a 1.5 V LT rather than being series filaments so the downside is the high battery consumption. Also 25mA direct filament valves likely are different gain and frequency characteristics to 50 mA parts, as well as lower max anode power.a

The DK96 is 25 mA and may work instead of the 1R5T with a small change:
DK96 is: f&g5, a, g2, g1, g4, g3, f+
1R5T is: f&g5, a, g2&g4, g1, f+g5, g3, f+

So pin 5 on DK96 is g4 and on 1R5T is f&g5. The existing connections to pin 5 need to go to pin1 if not a wire link and then short pin 5 to pin 3. Though it might work anyway. A 1R5 (DK91, X17), while using 50 mA rather than 25 mA and having same connections is likely less similar.

The DF96 (=1F33, W25 etc) is 25mA and the same connections as the 1T4T. It may be more similar than the 50 mA 1T4 (=DF91).

The DAF96 (=ZD25, 1FD1 etc) is the same connections as the 1S5T and also 25 mA. It should be more similar than the 1S5 (50mA).

The 3V4 is not an issue. It's the same as the DL94 (=N19, 1P11 etc) and used instead of older 100 mA (when 1.4V) as it gives more power.

Despite that the 50 mA 1R5 is pin compatible, I suspect the 25 mA DK96 is a closer match with the small modification to wiring. It won't hurt it plugging in without the wiring change, but likely won't work.

The replacing of 1T4T with DF96 (=1F33, W25 etc) is likely better than a 50 mA 1T4 (DF91).

The replacing of 1S5T with DAF96 (=ZD25, 1FD1etc) is likely better than a 50 mA 1S54 (DAF91).

I've restored a huge number of battery valve sets and experimented with Russian Rod Pentodes as plug-in replacements, which is possible, but RF & IF needs retuned unless you add extra capacitance, and there is no AGC.
 

The RF & IF might need retuned (alligned) if the 1R5 and 1T4 are used.

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The 1H33 might be similar to the 1R5T, as it's the same filament (if it's really 25mA) and  I think same connections. However likely a lot rarer than a DK96 which is still common NOS.

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