Use 8417 instead of 6V6?

[pompeiisneaks]

Question.  would I need a different OT if I were to use a 8417 I was given by a coworker?  It seems the 8417 wants a lot more voltage normally, and has about 16k impedance vs 6v6 around 8k if I'm reading the datasheets correctly, but does that mean it would need a new OT, or how do I check that kind of thing?  It seems to me that the OT in the champ I have (the one Doug sells).

Also, though, it seems like it has more like 100mA Plate current vs the 34mA of typical current for a 6V6... so I would wager that alone means it needs more current handling right?

Just trying to think that part through.  (I don't know that I want to redo that much of the champ, I just am curious, I may build some other new SE off of this tube for fun.)

~Phil

[kagliostro]

You must say more about the circuit in which you want to swap 8417 in place of 6V6

or are you talking about a project from scratch ?

However ...




And this tube has a sensisivity of 23mA/V where a 6V6 has 4.1mA/V a  6L6 6mA/V and an EL34 11mA/V

this mean that is way more sensible than a 6V6

a 6V6 has an heather consumption of 450mA vs the 8417 that has a consumpion of 1.6A

Franco

[Ed_Chambley]

This is sort of a rare tube, but I have used them in place of 6550.  Certainly not a good substitute for 6V6.  In push pull it will vary some, but the data sheet has 400vdc plate AB1 2.8K and 550vdc plate at 4.2k.


The 8417 was a little later design, around 1976.  Nice Power Tube, but I think too much for a SE Champ OT.


I would consider looking at some of the KT88 Designs SE designs some of the guys have been making for this tube. 16K is what I read as well, but these tubes really shine in a pair.  They will get 100 watts from a pair.

[pompeiisneaks]

Kagliostro, the new idea is still forming, but the original question was in a hoffman champ, with the standard hoffman champ OT.

Thanks Ed, I'll think of that,  Sadly right now I only have one, and I do see how expensive they are so I'm not keen on buying another hehe.

~Phil

[kagliostro]

If you are thinking to an SE this will be a big one, 8417 has a plate dissipation of 35W

a powerfull SE (that requires an adequate OT and PT, note that G2 is planned to be at a voltage that is way lower than B+)

Franco

[DummyLoad]

8417 are $#!tty & unreliable tubes. run away from them - far way. they arc: elements are too close and thermal component drift is catalyst to catastrophic failure, vibration is also the enemy of these tubes: guitar and bass amps rattle, shake, and rumble. use a KT88 or 6550 drive it a little harder, save a lot of heartache.


my 2cents... just mine.



--pete

[pompeiisneaks]

oh good info, guess maybe I'll just keep it around for giggles then :)

Don't think I want that failure state in an amp :D

[DummyLoad]

oh good info, guess maybe I'll just keep it around for giggles then :)

Don't think I want that failure state in an amp :D

if you're planning to upgrade a 6V6 SE amp, then the PT and OT will need to be beefed up or they won't last very long - depending on how you run them. you can use the 6L6 but then you'll need to keep the plate dissipation in the 6V6 realm. the heater current is an issue, but if the heater loading of a 6L6 of the heater secondary is still in spec, you should be ok. if you do that, then may as well just keep the 6V6: build a NEW amp instead! 


respectfully,


--pete


 

[PRR]

The 8417 will work in a 6V6 Champ. Re-biasing needed for good result (get the same 37mA-40mA of the Champ's 6V6). Heater demand is much higher, the usual Champ/DeLuxe PT may not have enough Amps on the 6V line. Power output will rise from 5.7 Watts to 5.8 Watts. Sensitivity about double (about like using EL84 in a Champ).

To "USE" the 8417 as a "Super Champ" you will have to upgrade both PT and OT about 3X. You can touch 16 Watts. This is big expensive iron.

And as said, 8417 come in two original types: marginal and flaky. They have been out of production so long, with enough "good" amps made for them, that existing stockpiles have been sorted and resorted down to the bottom of the barrel. The odds that you lucked into one *good* 8417 are very low. (The odds of lucking into, or even buying, a pair of good 8417 are even slimmer.)

Check and maybe change pinout (I can't remember). Pop 8417 in. Check cathode current. If not "Wrong!!", just low, start estimating a smaller cathode resistor to get to 37mA. Don't bother until you see if the PT is gonna run hot with the added heater load, 20-30 minutes at least.

It is not a "magic" tube. Just a big audio truck, with a sensitive throttle, and some too-close design flaws. A quad of 8417 makes an impressive sound. I used to run 12 (700+ Watts). I did have failures even in fairly light gigging. (However before I got them, they had run 24/7 making 115VAC 59.9Hz for film-video transfers, so not impossibly unreliable, in days when fresh 8417 were widely stocked.)

6550 is a more reliable truck, in current production, makes the same power with slightly more drive.

[Ed_Chambley]

8417 are $#!tty & unreliable tubes. run away from them - far way. they arc: elements are too close and thermal component drift is catalyst to catastrophic failure, vibration is also the enemy of these tubes: guitar and bass amps rattle, shake, and rumble. use a KT88 or 6550 drive it a little harder, save a lot of heartache.


my 2cents... just mine.



--pete

Thanks for the info, I did not know that.  I believe I have a few tubes I will be selling.  I just cannot afford a Leslie repair going south when I do have a stock of =C= 6550.


I know if a pair in a church Leslie I retubed with them 3 years ago and as hard as the B3 hits the Leslie I am amazed they still functioning.  Did some reading and sure enough, construction problems do appear.


I just did 2 Leslie's with them.

[DummyLoad]

8417 are $#!tty & unreliable tubes. run away from them - far way. they arc: elements are too close and thermal component drift is catalyst to catastrophic failure, vibration is also the enemy of these tubes: guitar and bass amps rattle, shake, and rumble. use a KT88 or 6550 drive it a little harder, save a lot of heartache.


my 2cents... just mine.



--pete

I just did 2 Leslie's with them.

now why on earth would you do that? 8417 are much less common than 6550, even in the wilds of the NOS realm... the sovtek kt88 is the best tube on the market now: construction is very, very good. if you have some winged C, save them for hi-fi use, if you're into that sort of thing. 


respectfully, 


--pete

[pompeiisneaks]

As usual, the forum delivers tons of great info, thanks!

~Phil

[Ed_Chambley]

8417 are $#!tty & unreliable tubes. run away from them - far way. they arc: elements are too close and thermal component drift is catalyst to catastrophic failure, vibration is also the enemy of these tubes: guitar and bass amps rattle, shake, and rumble. use a KT88 or 6550 drive it a little harder, save a lot of heartache.


my 2cents... just mine.



--pete

I just did 2 Leslie's with them.

now why on earth would you do that? 8417 are much less common than 6550, even in the wilds of the NOS realm... the sovtek kt88 is the best tube on the market now: construction is very, very good. if you have some winged C, save them for hi-fi use, if you're into that sort of thing. 


respectfully, 


--pete

Cause I am stupid.


Long story short.  I know someone (he has passed away) who has 63 Leslie 147's and he had a lot of the 8417, I mean a LOT of them.  He used them and when he passed away his widow gave me all his tubes.  Very nice thing to do.  I never considered not using them until I saw you post.


So I have numerous NOS GE, RCA and Tung Sol from his widow and the =C= and since no one really asks for 8417 I thought it would be a good way to use them.


See now that you told me the problem, I am sure the tubes heard you too.  Now the one that have been running them for 3 years, if they go south I figure they goth their moneys worth.  The other 2 I will fix this weekend.  It is not a big deal to change the tubes as I did leave the K resistor.


Now I have gotten very reliable chinese Valve Art KT88, but I will definitely pickup some Sovtek.  Did you mention HiFi?  Of course I am into HiFi.  Truthfully, it is easier for me to listen to Solid State guitar amps than your normal transistor HiFi, except one.  I still have a Sony WEGA from 1977 or 78 that has as close to a tube hifi as I have heard.


Sincerely Pete, thanks for the info.  I would hate for the 2 churches services to get interrupted by faulty tubes I installed.  Of course, I will do the third one as well, but it is time for theirs to be serviced.  I never thought when I converted a silver face Super Reverb to a AB763 that one day I would be working on Leslie amps and visiting Captian Foldback.

[DummyLoad]

ed, i have repaired 2 gibson SG bass amps that use that tube. both had a blown output transformers due to failed 8417. that's when i started searching online for a fix: the most common resolution was to replace them with 6550/kt88 and tweak the driver ckts. i have a third chassis that i have stripped for parts for the other two. one SG got the OT, the other got a rotary switch, pots, and knobs, and for it i used a dynaco clone A431 OT.

both amps left without a warranty and the owners now understand the risks. my sources have either depleted all stock or will not sell me any more. i have one pair left that are used that have some life left in them for when one of the SG's comes back - after that, they're at the mercy of the fleabay "NOS" market.

personally i prefer to stay away from ebay for mainstream "NOS" audio tubes: burned too many times.



--pete

[HotBluePlates]

ed, i have repaired 2 gibson SG bass amps that use that tube. both had a blown output transformers due to failed 8417. that's when i started searching online for a fix: the most common resolution was to replace them with 6550/kt88 and tweak the driver ckts.  ...

I have a Sano amp that still has the 8417's in it.  I'm going the opposite direction, bumping them down for EL34's as the power output of this amp doesn't call for 6550 and because 6550's almost won't fit side-by-side in the existing sockets.

So if anyone needs 2x G.E. 8417's, I'm sure we can work out a deal.  I originally planned on dumping them because they just can't be found.  Then I noticed the very close spacing of the plate, screen, control grid & cathode...  Saw a Gm of 23mA/V on a data sheet and thought, "Yeah, that tube's gonna be super-twitchy..."

[DummyLoad]

ed, i have repaired 2 gibson SG bass amps that use that tube. both had a blown output transformers due to failed 8417. that's when i started searching online for a fix: the most common resolution was to replace them with 6550/kt88 and tweak the driver ckts.  ...

I have a Sano amp that still has the 8417's in it.  I'm going the opposite direction, bumping them down for EL34's as the power output of this amp doesn't call for 6550 and because 6550's almost won't fit side-by-side in the existing sockets.

So if anyone needs 2x G.E. 8417's, I'm sure we can work out a deal.  I originally planned on dumping them because they just can't be found.  Then I noticed the very close spacing of the plate, screen, control grid & cathode...  Saw a Gm of 23mA/V on a data sheet and thought, "Yeah, that tube's gonna be super-twitchy..."

yeah, 14Vpk on average to go to full power... hmmm yeah, them things are pretty tightly wrapped in there.

PM me asking price. always be good to have a spare set for repairs. oh, and how much estimated life left in them?

--pete

[HotBluePlates]

Sending PM.