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7189A tubes in Magnatone M-8


 
8/4/2000 9:22 PM
Glen H.
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7189A tubes in Magnatone M-8
I have a line on a Maggie M-8, but I am unfamiliar with 7189A power tubes. I understand they are "rare". Can EL84's be swapped out for 7189A's. If so, under what conditions (ie. mods).  
 
Any tips would be greatly appreciated:)!  
 
Cordially,  
Glen H.  
 
8/4/2000 9:35 PM
Richie{~}==:::
The 7189 is a high grade 6BQ5/EL84..  
Should just need to bias when installing them.. but they are very good tubes..and are run higher voltages,look at them and see if they say 7189A..these have higher screen voltages too.. probably better tubes than you can buy anywhere today. grab um.  
Richie{~}==:::  
 
8/4/2000 9:42 PM
Glen H.
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Thanks Richie!  
I noticed some 7189's are also marked EL84S.  
So I figured there was some connection there...  
 
Glen H.  
 
8/4/2000 9:53 PM
Graywater
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Re: 7189A tubes in Magnavox M-8
Glen,  
 
6BQ5s/EL84s can be substituted although the 6BQ5 has a lower max plate voltage in theory and lower screen grid dissipation. The trick is the pinout as the basing for both lists pins 1, 6, & 8 as "IC" - internally connected but don't show what connected to. I've seen 6BQ5s with pin 1 connected to pin 2 creating another G1 connection. Examine your tube socket and if nothing is connected to these 3 pins then there shouldn't be a problem - if they are connected then note what's connected to them. If they're used as tie points (unused pins often are) then make sure that the replacement EL84 dosen't have internal connections to another tube element that uses these pins.  
 
GW  
 
8/7/2000 4:46 AM
dutch
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Re: 7189A tubes in Magnatone M-8
quote:
"I have a line on a Maggie M-8, but I am unfamiliar with 7189A power tubes. I understand they are "rare". Can EL84's be swapped out for 7189A's. If so, under what conditions (ie. mods).  
 
Any tips would be greatly appreciated:)!  
"
 
 
Glen-  
I used to own one of these. EL84 tubes will do fine in these amps. They wired the output tube sockets to use either tube, and the B+ is only about 300V, so there's no worry there.  
 
I hope this helps!  
 
C ya,  
Dutch  
 
8/7/2000 7:14 AM
Glen H.
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Thanks once again!  
I now just procured an early '70's Traynor YGM-3 Guitar Mate, with chicken head knobs - I don't know if I need that Magnatone now. The Guitar Mate has a similar tube layout, decent reverb and tremolo. But I'd still like to have a Magnatone, especially for the cool vibrato. Too many amps out there, not enough money!  
Come to think of it, I have about 15 amplifiers now - do I really need another...?:D  
 
Cheers,  
Glen H.  
 
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