7189A sub?

[jrfrond]

Anyone have a viable sub for this rare bird? In lower-voltage applications, EL84's can be used, but we are talking about 400V here. 7189A was essentially a beefier version of the 6BQ5/EL84. FYI- I am restoring a Magnatone M10A. Of course, I can always do NOS, but these are getting a bit pricey. There are 4 on eBay BIN at $129.00. That's the cheapest I've found.

[Garydean]

Hi John,
Have you considered an E84L? It's rated higher than an EL84. If your screen voltage is under 300 you'll be fine. Prices are all over the map but you may be able to get a pair for under $50

E84L specs.
13.5 watts max plate dissipation with 450V max plate volts. Slightly higher specs than a 7189A.

Gary

[jrfrond]

It won't work. The screen voltage is up around 390V and it's a UL-tapped transformer, BUT in a cathode-bias scheme. Not yer everyday circuit design or tube requirement, for sure.

[Steve A.]

It won't work. The screen voltage is up around 390V and it's a UL-tapped transformer, BUT in a cathode-bias scheme. Not yer everyday circuit design or tube requirement, for sure.

FWIW the Peavey Classic 50 has something like 392 volts going to the plates of four EL84's and I don't believe that amp is known for trashing output tubes. As I recall the screens are a few volts lower than that.

I know that exceeds the specs of EL84's but it doesn't seem to cause any problems. (Or does it? I dunno)

Steve Ahola

[Garydean]

The internal pin connections on the 7189A are unique so even if there is a direct replacement voltage wise, it still may not work.

try here

http://www.tubedepot.com/nos-7189a.html

[hasserl]

FWIW the Peavey Classic 50 has something like 392 volts going to the plates of four EL84's and I don't believe that amp is known for trashing output tubes. As I recall the screens are a few volts lower than that.

I know that exceeds the specs of EL84's but it doesn't seem to cause any problems. (Or does it? I dunno)

Steve Ahola

And the Carvin Nomad and BelAir amps run EL84's in the 390 and even low 400's, with the screens ~ 6 - 8 volts below the plates. The tubes run fine at those voltages. I've got a Nomad that I've had no tube failure issues with at all. And I've seen dozens of these amps, as I do a lot of Carvin amp mods, with the original tubes in them with years of service on them, still running just fine.

[jrfrond]

The amp is PTP, so I am not concerned about rewiring the sockets. However, it MUST be reliable, and it is for a big-name client, so I think I will just go NOS. I'm not stoked by the quality of current EL84's from any manufacturer. I've just seen too many fail.

[tubeswell]

What about EL84Ms? (I think they can handle about 400V)

[Chuck H]

The internal pin connections on the 7189A are unique so even if there is a direct replacement voltage wise, it still may not work.

You just need to rewire so the "unused" pin sockets are not used. Then any el84/6bq5/7189 tube will "function" in the socket. Not too far to go when retrofitting an amp that used obsolete tubes. FWIW I mean obsolete in the sense that they are not made anymore, not that they aren't good tubes.

Many amps run the plates of el84 tubes at 400 volts and the screens a bit lower. These ARE guitar amps and not "hi fi". But the tubes will live, even if they are creating more THD than a stereo could accept. I personally know of a Messy Booger amp with 398vp and 385 on the screens that still sounds good after 2 years using old Sovtek tubes. Some Traynor amps will put 420+ vp on el84s with modern wall voltages and yet they survive. I think if you pay attention to the bias limitations and buy good tubes that you'll be fine. Rewire the amp for el84's. What else is going to be plugged into it from this date foreward?

Chuck

[Diablo]

How many 7189A tubes do you need?
I have one NOS Westinghouse.

[kvflyer]

How many 7189A tubes do you need?
I have one NOS Westinghouse.

Don't know if you got your tubes yet. Have you considered the Soviet Military surplus (USSR) tube 6П14П -ЕВ? While they are drying up quickly, they are an excellent replacement and usually sell for about $11 each. Many places have them.

JMHO...

[6267]

I thought 6p14p-ev was a 7189A sub, but I'm not sure...no russian data sheets around.

[kvflyer]

I thought 6p14p-ev was a 7189A sub, but I'm not sure...no russian data sheets around.

Yes! That is exactly what it is. Very good tubes, priced right.

[kvflyer]

I thought 6p14p-ev was a 7189A sub, but I'm not sure...no russian data sheets around.

Try this page. It is the tube pinout:

http://translate.google.com/translat...%3Den%26sa%3DG

[Robert M. Martinelli]

I admit it's not as thorough and complete as an old datasheet, but check this out...

http://www.tubes.ru/techinfo/HiFiAudio/6p14p.html

BTW I used some of these russian mil-spec tubes and they're very good value for the money, and they're a little bit beefier than 7189s and E84L too.

Best regards

Bob