i haven't had to replace a tube yet, but if i do have to , will i need to do anything? people have mentioned rebiasing and whatnot and i don't know what they're talking about...</p>
also, how would i get at the 6au6 tubes?</p>
what tubes need to have matched output?
</p>
and which positions are most critical on an m100?
</p>
You may be over thinking this a bit. Hammond designed their amps so the tubes are coasting and not critical.</p>
There is a fixed bias on the output tubes that is not adjustable. You don't have to do anything but change your tubes. That said, there are failures that can cause the bias to be off so not a bad idea to check it.</p>
I guess any tube that through it's failure causes the organ to go silent is a critical tube. That would include the 6AU6's, 12AX7, 12AU7, 6V6 outputs, and 5U4 rectifier. You can pull all three percussion tubes out and the organ will play normally except no percussion. The 6BA6 only affects the pedals. I suspect the 5U4 is the most likely tube to fail.</p>
To get to the tubes under the shields, just twist or pull the sheilds off, remove and replace the tubes, and replace the sheilds. You may want to do a tube pin cleaning. I pull the tubes, bruch the pins with a small wire brush or you could use an eraser. Then I spray a small amount of contact cleaner on the pins and reinstall them. This reduces intermittant static and noise.</p>
Try ebay seller "ak6r" item # 380073158839. I have purchased several tube sets from this seller and all went well. Prices are reasonable as well. He has NOS and tested good tubes in the values you need. Always has shipped the next business day and packed well with all tubes in seperate boxes to avoid damage.</P>
Try ebay seller "ak6r" item # 380073158839. I have purchased several tube sets from this seller and all went well. Prices are reasonable as well. He has NOS and tested good tubes in the values you need. Always has shipped the next business day and packed well with all tubes in seperate boxes to avoid damage.</P>
H101</P>
[/quote]</P>
I can also recommend this guy. His ebay store is Capt. Bob's Electronic Emporium. I've bought sets as well and have been pleased. One set came with a bad 5U4 rectifier, but he sent a perfect replacement very quickly.</P>
... stay away from all vacuum tubes made in china?</p>
the country doesn't always denote the quality, but there usually are tonal differences... from a single company there will be tubes made all over the world because of the differences in sound...</p>
</p>
lots of people like the chinese 12ax7 from groovetubes... it just sounds different than their american/russian/european offerings...</p>
</p>
audiophiles do go overboard- perhaps a little bit too much for me.</p>
i just thought i'd ask, because i know i can get NOS tubes from many sources, but brand new 6au6 are impossible to find...</p>
i guess i'll have to keep asking around, i'm sure someone may have tried their tubes... (i'm glad i don't NEED a replacement yet)
</p>of course, buying tubes directly from china is a bit different than from groovetubes... they at least have some quality control... directly from china they could be dead on arrival...
Capt Bob is a stand up guy. I too got a bad rectifier from him (5U4) and he says he will send out a replacement when the one I sent back reaches him. Drag to pay the extra shipping, but overall I am pleased (assuming he replaces it).
</p>
You may be over thinking this a bit. Hammond designed their amps so the tubes are coasting and not critical.</p>
There is a fixed bias on the output tubes that is not adjustable. You don't have to do anything but change your tubes. That said, there are failures that can cause the bias to be off so not a bad idea to check it.</p>
I guess any tube that through it's failure causes the organ to go silent is a critical tube. That would include the 6AU6's, 12AX7, 12AU7, 6V6 outputs, and 5U4 rectifier. You can pull all three percussion tubes out and the organ will play normally except no percussion. The 6BA6 only affects the pedals. I suspect the 5U4 is the most likely tube to fail.</p>
To get to the tubes under the shields, just twist or pull the sheilds off, remove and replace the tubes, and replace the sheilds. You may want to do a tube pin cleaning. I pull the tubes, bruch the pins with a small wire brush or you could use an eraser. Then I spray a small amount of contact cleaner on the pins and reinstall them. This reduces intermittant static and noise.</p>
</p>
George
</p>
[/quote]</p>
</p>
Are those shields absolutely critical to have in place? Would it be okay to leave them off? I noticed that some tubes have them and some don't. They seemed to be more frequently used on newer products.
</p>
The shields are there to help keep the amp quiet. They keep the tube from picking up magnetic fields that may transmit hum and other niose into the amp. It will run without them but in certain circumstances be noisey. When I retubed my RT3's AO-28, 52 years old and all original tubes, the 12AX7 (Mullard)that came with the tube set was toofat to fit in the shield. I elected to use another tube that was a little smaller in diameter so I could install the shield.</P>
Interesting. One of the replacement tubes I picked up was a little too far for the shield. I left it off. I always worry whether I am going to crack a tube when putting those things back on. Especially when a new tube is a different width than an old one.
The shields are there to help keep the amp quiet. They keep the tube from picking up magnetic fields that may transmit hum and other niose into the amp. It will run without them but in certain circumstances be noisey. [/quote]</P>
cheers H101! --I always wondered what those shields were for. TD</P>
Nobody loves me but my mother,
And she could be jivin' too...
--BB King
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