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.
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7189A sub?
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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
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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.
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Originally posted by jrfrond View PostIt 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 AholaThe Blue Guitar
www.blueguitar.org
Some recordings:
https://soundcloud.com/sssteeve/sets...e-blue-guitar/
.
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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
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Originally posted by Steve A. View PostFWIW 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
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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.
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Originally posted by Garydean View PostThe internal pin connections on the 7189A are unique so even if there is a direct replacement voltage wise, it still may not work.
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"Take two placebos, works twice as well." Enzo
"Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas
"If you're not interested in opinions and the experience of others, why even start a thread?
You can't just expect consent." Helmholtz
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Originally posted by Diablo View PostHow 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...
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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
BobHoc unum scio: me nihil scire.
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