I found a schematic and with 360v on the 7189 plates, this might be too much for my el84/6bq5 stash.
In any event, the 7189 is rated for higher plate voltage than the el-84. So, you can safely replace an el-84 with a 7189, but you cannot replace a 7189 with an el-84.
Voltage is not the whole story. The more important issue is dissipation which is determined by the voltage (measured from plate to cathode) multiplied by the current.
The confusion and misinformation about the ratings of this "family" of tubes is due to the fact that some data sheets use the Design Center method and others use the Design Maximum method. The Design Maximum system results in ratings that are 10% higher.
For instance, when measured under the Design Center method, both the 7189 and the 6BQ5 have a Plate Dissipation of 12w, while the rating under the Design Maximum is 13.2w (10% higher).
The 7189 and 7189A variants are generally considered superior to the humble 6BQ5 because of the higher voltage ratings but the dissipation is the same. So - if you follow the data sheet specs - you can run higher voltages with the 7189s but you have to run it at lower current so you don't violate the 12w (13.2w) dissipation limit.
I've never been able to figure out why the voltage spec is higher for the 7189. Is there a difference in construction (materials or techniques) that would account for the 7189 having a higher plate voltage spec, yet at the same time, all the other specs (screen voltage, plate and screen dissipation) are exactly the same as the more common 6BQ5?
Interestingly, if you look at the various versions of another tube - 6L6G, 6L6GB, 6L6GC - the plate voltage specs get progressively higher BUT so do all the other specs (screen voltage, plate and screen dissipation).
This makes me wonder if "Uncle Ned", the former owner of Triode Electronics, may have been correct when he claimed that the 6BQ5 and 7189 were exactly the same tube.
I've also seen claims that the 7189A can be run harder than the 7189. Here's a link to the Sylvania data sheet that lists data for both 7189 and 7189A with both tested under the Design Maximum method. Specs are exactly the same. The only difference is that the pins are connected differently.
https://tubedata.altanatubes.com.br/sheets/106/7/7189.pdf
The 7189A can be used in place of a 6BQ5 or 7189 but only if pins 1, 6 and 8 are not connected to anything (or not used as tie points, for instance) because it has internal connections on those pins.
And then there are the Russian versions. The military versions of the 6P14P (-EV and -EB) and the EL84M are often said to be 7189 equivalents. They are supposedly "ruggedized" to be less susceptible to vibration and will supposedly last longer than the regular 6P14P. There do not seem to be any factory data sheets available for them.
I did find the data sheet for the Russian 6P14P. This is their version of the 6BQ5. It lists maximum plate dissipation at 14w vs 12w for the 6BQ5, 7189 etc. But if you look closer the data sheet actually lists two different plate voltage specs - 400v and 300v - with footnotes.
The footnotes say 400v is OK when plate dissipation is 8w or less but that the max is 300v when plate dissipation is over 8w. So, despite claiming a higher dissipation spec, it should be operated at 300v if you're going to be running anywhere close to that level of dissipation.
The Russian tubes have no connections on pins 1, 6 or 8 so they can be used in any amp designed for 6BQ5, 7189 or 7189A.
Personally, I have no experience with new production tubes but I've read enough stories about early failures that I don't trust that they actually meet the same specs as the data sheets that were developed by testing what are now old stock tubes.
Bottom line, if you use new production you might want to run them more conservatively. Buying the right to label a new production tube with a famous brand from the past is purely a marketing strategy designed to fool unsuspecting buyers.
