Guys im kind of board with my 5150 evh and want to mess around with it . I have like 8 amps and don't mind messing with it. Who would i have to speak to about getting info on modding it to run kt88 tubes. I would think screen grids would have to be up graded and prob tranny. Would love to do this but i want it done right with correct info and components .
Peavey 5150 with kt88's
- Thread starter jd267
- Start date
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Not designed to run KT88's. The current draw is too much for the bias circuit and the PT would sag into saturation before being able to supply the KT88's with the proper current on the anodes.
There are many other things that require modification.
Do yourself a favor and just sell it instead of trying to make it into an amplifier it is not.
There are many other things that require modification.
Do yourself a favor and just sell it instead of trying to make it into an amplifier it is not.
Its not that i don't like it im just trying to mess around with it. Do you guys no of any links to a tone shift mod how to? or other mods? thx
Seriously. You have no real reason or clear objective to be sticking your hands anywhere near the amplifier. You have zero business inside the chassis and without proper safety procedures could end up severely hurting yourself or someone else. You know nothing of circuit design and could create a safety hazard without even knowing it, creating a circuit that is very unsafe for yourself or for others to use.
If you have 8 other amplifiers then sell the 5150 and enjoy the rest. You do not know what you're doing and are asking questions that if you did know, would not require a new topic asking.
flaik
Well-Known Member
According to eurotubes (distributor for jj tubes), you can mix kt88s and 6l6s by putting the kt88s in the outermost tube sockets and the 6l6s in the middle. I have never tryed it but it is supposed to be safe for you and the amp.
I think you may be able to pull out the 6l6s in the middle to make it run with only kt88's and at half power. Im not sure though. you could probably email the guy from eurotubes though to be sure; If I recall corrrectly he is supposedto be really helpful.
link to tube set with kt88s and 6l6s: https://www.eurotubes.com/cart/index.php?page=view_products&category_id=8&sub_category_id=40
I think you may be able to pull out the 6l6s in the middle to make it run with only kt88's and at half power. Im not sure though. you could probably email the guy from eurotubes though to be sure; If I recall corrrectly he is supposedto be really helpful.
link to tube set with kt88s and 6l6s: https://www.eurotubes.com/cart/index.php?page=view_products&category_id=8&sub_category_id=40
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The tubes are hand selected and matched accordingly. All that is doing is running a KT88 in place of a 6L6. The tubes are chosen and matched for the 5150's plate voltages for proper bias. Ordering that set is 100% safe since he does the matching, but running any random set will require many modifications to the amplifier. Technically, there are still some modifications required to the screen grids that should be done to run KT88's but without them it wont do much harm - they are very stout tubes.
Dude really? I have built two amp kits and have a degree in electronics and prob no a ton more about circuit design than you ever will.. Keep your remarks to yourself.
Also fja said this is bull and will harm the head.
The 5150 can be modded to run kt88 but the op will need to be changed and screen grids as i said in my first post just like the 2203kk and like what they did on the 2203zw. bias mod will need to be done so plate voltage will be with in reason. Just was asking if any one had any links to mods in detail. Ill do some more research and find info. Would prob slay with kt88 and bias mods.
JoshuaVonFlash
SSBRO.org regular
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Aren't you the OP?
Yes why do you ask? Looking for some one who has done it and want to see what opt they went with ect ect
JoshuaVonFlash
SSBRO.org regular
Sorry about that bro read your post wrong.
I have two degrees in electrical engineering and computer engineering and working on two more as we speak. I also have 5 years experience in the field, have designed my own amp kits for others to purchase, and modified my own 5150 II. I also write software as a developer.
I suggest you keep the chest beating to yourself and heed my warnings because your own safety as well as others in the future are at risk. If you were a true electronics major you wouldn't be asking these questions on a gear forum and would know what proper resources to consider.
guess my thread is offensive to some lol. took a look in my org stein and compared it to my stein+ and looks like screen grids and opt are bigger. resistor value in bias circuit are different also. Think im going to have a go at it!
It is triode strapping a pentode tube. FJA is partially right and i know what part of the circuit he speaks of.
You're also the guy that posted this topic.
http://www.sevenstring.org/forum/gear-equipment/252032-where-buy-bias-mod-kit.html#post3769475
I will guarantee that if you attempt to modify the circuit there will be a few pieces you will overlook because the amplifier does not match the schematic. FJA can back this information as well and is partially the reason he says it will do harm. I highly suggest you stop while you're ahead.
http://www.sevenstring.org/forum/gear-equipment/252032-where-buy-bias-mod-kit.html#post3769475
I will guarantee that if you attempt to modify the circuit there will be a few pieces you will overlook because the amplifier does not match the schematic. FJA can back this information as well and is partially the reason he says it will do harm. I highly suggest you stop while you're ahead.
Your prob right about asking a tech question on here but im sure its been done. Congrats on all your success you must have a really rewarding job.. I love working on amps and building kits! also just built my own od808 circuit and sounds better than my maxon 808
. Well ill prob give jerry a call and see what he thinks.Chill out guy
Nothing wrong with looking for a kit for mods dude! Did the bias mod and removed it. sounded better in cross over.what jerry said.
If the amp was setup with dual bias circuits, upgraded screen grid resistors, and the ribbon cable hardwired so it doesn't burn up with the added heater current it might be OK. The amp was not designed to use them and you run a huge risk of damaging it if you put those tubes in it.
The 5150 has a tendency to burn up the ribbon cable now, put more heater current thru it and your gonna have problems for sure.
The 100 ohm screen grid resistors can't handle KT88's, no way!
Not having separate bias controls so you can bias the KT88's up where they sound good is a total waste of money. Why spend big bucks on KT88's and then have them barely doing anything? Like driving a Corvette 15 MPH all the time.
No matter how you look at it, it's a bad idea. There's only one person that thinks different and he's making money on the idea so what does he care? A better idea is to buy the JJ 6L6's from him and have your tech (or yourself) do the bias mod.
Jerry
If the amp was setup with dual bias circuits, upgraded screen grid resistors, and the ribbon cable hardwired so it doesn't burn up with the added heater current it might be OK. The amp was not designed to use them and you run a huge risk of damaging it if you put those tubes in it.
The 5150 has a tendency to burn up the ribbon cable now, put more heater current thru it and your gonna have problems for sure.
The 100 ohm screen grid resistors can't handle KT88's, no way!
Not having separate bias controls so you can bias the KT88's up where they sound good is a total waste of money. Why spend big bucks on KT88's and then have them barely doing anything? Like driving a Corvette 15 MPH all the time.
No matter how you look at it, it's a bad idea. There's only one person that thinks different and he's making money on the idea so what does he care? A better idea is to buy the JJ 6L6's from him and have your tech (or yourself) do the bias mod.
Jerry
