Re: EL-84 substitute for 7189A
Simply, if the B+ is around 400V, use 7189/7189A, and if it's around 300V use either 7189 or EL84s. If it's over 400V, 7189As are mandatory.
A cheap source of Russian 7189A are either Gintaras (kwtubes - ebay or www.kwtubes.s5.com) or Tony Welsh (tonywelsh - ebay, or www.tonywelsh.com). Both are reputable traders and I have used them myself, Gintaras many times. Typically a set of 8 will cost $US40 plus about $5-9 in postage. I haven't used them myself yet, but have heard favourable reports on their sonics, not as good as the best NOS, but for the price, more than acceptable. I've also heard they are as tough as nails, and even mondo-crazy guitarist types have trouble killing them. I will be getting some in my next order from Gintaras.
The best datasheet I've found for the 6BQ5/EL84 is http://www.retrovox.com.au/STC6BQ5.pdf bit it's nearly 2meg in size. Well worth the download for the excellent data it contains.
A 7189/7189A datasheet can be found here. http://www.mif.pg.gda.pl/homepages/frank/sheets/106/7/7189.pdf
HTH
Cheers
That depends. The 7189A is an improved version of type 6BQ5/EL84. It has identical characteristics, but is designed to withstand higher plate voltages and higher plate dissipation. So is the amp you have designed to run both, ie B+ and plate dissipation are acceptable for EL84 and now has 7189As in it, or was it designed for use with 7189As from the start? I'm not familiar with your amp so I can't say.zacknorton said:
Simply, if the B+ is around 400V, use 7189/7189A, and if it's around 300V use either 7189 or EL84s. If it's over 400V, 7189As are mandatory.
A cheap source of Russian 7189A are either Gintaras (kwtubes - ebay or www.kwtubes.s5.com) or Tony Welsh (tonywelsh - ebay, or www.tonywelsh.com). Both are reputable traders and I have used them myself, Gintaras many times. Typically a set of 8 will cost $US40 plus about $5-9 in postage. I haven't used them myself yet, but have heard favourable reports on their sonics, not as good as the best NOS, but for the price, more than acceptable. I've also heard they are as tough as nails, and even mondo-crazy guitarist types have trouble killing them. I will be getting some in my next order from Gintaras.
The best datasheet I've found for the 6BQ5/EL84 is http://www.retrovox.com.au/STC6BQ5.pdf bit it's nearly 2meg in size. Well worth the download for the excellent data it contains.
A 7189/7189A datasheet can be found here. http://www.mif.pg.gda.pl/homepages/frank/sheets/106/7/7189.pdf
HTH
Cheers
I had a Scott 222C and used OLD 6BQ5/EL84 RCA black plates and they were running in the blue but didn't seem to mind. If you are going to have to buy new tubes you might as well get the correctly rated tube. I just happened to have a quad of the old RCAs and decided that the safety factor built into the Scott should allow me to get away with it. Most any other major brand and I would have been looking for the 7189s.
David
David
Hello!
A while back I bought a cheap Tubeamp i sort of stumbled over. Basicly because I didn't have the time to build one and it was cheap enough so what the he**?
Anyway, the amp uses 4 tubes labeled "Beijing 6N3" and after some googling I found the amp and a review that said EL84s could be used. And that the writer changed a good deal between different brands but since it didn't say anything about bias I didn't thing so much about it.
Now, some time later I wanted to test a retalier so I ordered some tubes for a sum that I wouldn't miss if I got screwed. The tubes I bought where the Russian EL84 - 7189A - 6BQ5 Tubes.
The arrived some time later well pakaged and in good condition and here's when I'm doing something stupid.
Since they are compatible and I dont have any info regarding bias and such I just pull the original ones out and replaces them with the new ones. Upon startup the glow as they shall but no music, I crank the volume a bit and the tubes gives of a brisght flash... Burned probably?
So, just as I know till next time, what did I do wrong?
A while back I bought a cheap Tubeamp i sort of stumbled over. Basicly because I didn't have the time to build one and it was cheap enough so what the he**?
Anyway, the amp uses 4 tubes labeled "Beijing 6N3" and after some googling I found the amp and a review that said EL84s could be used. And that the writer changed a good deal between different brands but since it didn't say anything about bias I didn't thing so much about it.
Now, some time later I wanted to test a retalier so I ordered some tubes for a sum that I wouldn't miss if I got screwed. The tubes I bought where the Russian EL84 - 7189A - 6BQ5 Tubes.
The arrived some time later well pakaged and in good condition and here's when I'm doing something stupid.
Since they are compatible and I dont have any info regarding bias and such I just pull the original ones out and replaces them with the new ones. Upon startup the glow as they shall but no music, I crank the volume a bit and the tubes gives of a brisght flash... Burned probably?
So, just as I know till next time, what did I do wrong?
Guys,
Time out, please. The 7189 is rated for a higher plate voltage than the 6BQ5/EL84, but its dissipation ratings are the same. The 7189A, in addition to being rated for a higher voltage, is also rated for a higher dissipation. The basing arrangement for the 7189A is different too. Check the data sheets.
6BQ5 7189 7189A
If a unit is designed for 7189As, NOS is the only option, AFAIK. OTOH, if a unit is designed for 7189s, Russian EL84M/6p14p-ev tubes will be just fine.
Time out, please. The 7189 is rated for a higher plate voltage than the 6BQ5/EL84, but its dissipation ratings are the same. The 7189A, in addition to being rated for a higher voltage, is also rated for a higher dissipation. The basing arrangement for the 7189A is different too. Check the data sheets.
6BQ5 7189 7189A
If a unit is designed for 7189As, NOS is the only option, AFAIK. OTOH, if a unit is designed for 7189s, Russian EL84M/6p14p-ev tubes will be just fine.
It's been found that the JJ EL84 can handle spec bending that the Russian 6P14P cannot (which includes all of the New Sensor reissued tubes available today). The JJ is probably your only bet for modern production tubes. Otherwise NOS or modify the amp...assuming it's really running at the high end of the spec. Some plate and screen voltage measurements would help answer your question.
I have an old japanese amp that uses a 7189A power tube, I can't find much information out there but from what I read here the EL84 is not a correct substitute...the problem is that the owner has placed a new JJEL84 in and it is squealing...I have replaced all the electrolytic caps. The power tube that was previously in there is unmarked but the result is the same so I suspect that it's also an EL84. I have done some voltage tests on the 7189A socket and the output transformer:
Primaries on OT across to ground:
0.23VAC on both lugs
dc resistance is 260ohms on primaries
7189A tube socket voltages:
Pin 1: 3.04vDC
Pin 2: 3.04vDC
Pin 3: NA
Pin 4: 6.7vAC
Pin 5: NA
Pin 6: NA
Pin 7: 384vDC
Pin 8: NA
Pin 9: 380vDC
Question: shouldn't there be heater voltage on pin 5 too?
Voltage readings were taken with all tubes in place except power tube.
Primaries on OT across to ground:
0.23VAC on both lugs
dc resistance is 260ohms on primaries
7189A tube socket voltages:
Pin 1: 3.04vDC
Pin 2: 3.04vDC
Pin 3: NA
Pin 4: 6.7vAC
Pin 5: NA
Pin 6: NA
Pin 7: 384vDC
Pin 8: NA
Pin 9: 380vDC
Question: shouldn't there be heater voltage on pin 5 too?
Voltage readings were taken with all tubes in place except power tube.
pin 5 might be grounded as 4 has 6.7VAC
If the amp is squeeling it not not with the power tubes to do. Seek the problem
elsewhere.
Is it modified in any way ? Can this be undone ?
Schematic or brand of amp ?
There is no obvious reason that using EL84s should make the amp squeal, unless those JJs are defective. You just need to make sure that the socket wiring had been modified to account for the minor difference in pin-out between the two different types of tubes.
I would however recommend using EL84Ms as a closer substitute for 7189As, as they are intended to handle those high voltage and power levels.
Sent from my phone with Tapatalk. Please excuse any typpos.
I would however recommend using EL84Ms as a closer substitute for 7189As, as they are intended to handle those high voltage and power levels.
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Wow - original post was 2002, then a few more in 2006, then a few in 2011 and now 2017.
As mentioned earlier, 7189A has a different pinout than either 7189 or EL84 / 6BQ5:
http://www.mif.pg.gda.pl/homepages/frank/sheets/135/7/7189A.pdf
http://tubedata.milbert.com/sheets/093/6/6BQ5.pdf
Since guitar amps like this little 5 watter are generally run flat out, unlike stereo amps, I'd suggest either sticking with a 7189A or rewiring the socket and using the Russian 7189 equivalent, the EL84M or the military version.
Could you post a pic of the internal parts?
The problem you mention may have nothing to do with the use of an incorrect output tube. This being a Japanese amp, if the circuit is stock, never rebuilt or modded, there are definitely parts that need to be replaced. The Japanese stereo amps likely used many of the same parts and they are notorious for using parts that don't hold up well, especially the grey PIO caps and the PS caps.
I'd suggest a complete rebuild using stock value parts - not a mod, just a rebuild. Basically, just replace all the caps and any resistors that aren't in spec.
As mentioned earlier, 7189A has a different pinout than either 7189 or EL84 / 6BQ5:
http://www.mif.pg.gda.pl/homepages/frank/sheets/135/7/7189A.pdf
http://tubedata.milbert.com/sheets/093/6/6BQ5.pdf
Since guitar amps like this little 5 watter are generally run flat out, unlike stereo amps, I'd suggest either sticking with a 7189A or rewiring the socket and using the Russian 7189 equivalent, the EL84M or the military version.
Could you post a pic of the internal parts?
The problem you mention may have nothing to do with the use of an incorrect output tube. This being a Japanese amp, if the circuit is stock, never rebuilt or modded, there are definitely parts that need to be replaced. The Japanese stereo amps likely used many of the same parts and they are notorious for using parts that don't hold up well, especially the grey PIO caps and the PS caps.
I'd suggest a complete rebuild using stock value parts - not a mod, just a rebuild. Basically, just replace all the caps and any resistors that aren't in spec.
7189's are the bane of my existence -- i have a pair of Madison Fielding 440 receivers and they are used in both. They usually run over $50 each. The Sam's PhotoFact shows that the anode voltage should be 350, but it actually runs to 400.
One of the receivers was a gift from an uncle, and it was really very nice, although no multiplex adapter. The other was bought off Ebay pretty inexpensively.
I did say 7868, but it's a 9 pin Compactron!
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I have also found some regular EL84s running in amps at 400V+, such as the Marshall 20/20 stereo power amp. I don't know if those were tubes that had been specifically factory-tested for high voltage operation. The key thing is to run the screen grids below 300V and have residues of at least 1k on the screens to limit excess currents. I would still generally prefer to use EL84Ms with those high voltages.
Sent from my phone with Tapatalk. Please excuse any typpos.
Sent from my phone with Tapatalk. Please excuse any typpos.
NOS 7189s - if you can find them - are expensive. Fortunately, the EL84M is a good sounding sub and you can find new matched quads for about $80.
I pay more attention to plate and screen dissipation than voltage. While 7189s are rated for a higher plate voltage their dissipation is still 12 watts, same as the 6BQ5. So if the dissipation is within spec you can usually get away with using 6BQ5s despite the higher voltages. I wouldn't try this with current production "re-issue" tubes but I haven't had any issues with older production European or American tubes. Still, with the EL84M option available, if you can afford it I'd suggest going that route.
Voltages on vintage gear will be higher due to higher modern wall voltages. To compensate for this you can use higher value resistors in the power supply to adjust the voltages back down to where the schematic says they should be.
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