Peavey 5150 with kt88's

[mesaboogie6l6]

Yep, same guy told me it was ok to run KT88's in my Mesa Dual Rec and Triple, been going strong for a year, with no problems. I know the thread is about a 5150, but Bob Pletka knows his stuff, there are also informative people on here as well, advice is well given and respectful for sure.

Good luck!

 

[myampslouder]

The Peavey 5150 cant physically fit 4 kt88s. The sockets are too close so you can run into overheating problems if you run a full quad of kt88s. you can look into just running a pair in the outside socket but I looked into it a while back when I had a 5150 and just decided it wasn't worth the cost or the hassle.

 

[Krucifixtion]

1. Sell 5150 or don't sell it

2. Buy VHT Pitbull UL that comes stock with KT88's

3. Profit...

 

[Chris_ONiP]

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

So pretty much what glpg80 said from the start haha

 

[Sinborn]

Each KT88 draws .8 more amperes current on the heaters. 3.2 more amps might be too much. Don't do this to your 5150. Mod the preamp, there are easy things you can do there that will give you some new sounds. Sorry to link to a different forum but this thread led me into some stuff I did to my 5150 that I was quite pleased with: Rig-Talk • View topic - 5150 mods... revealed w/ pictures

 

[NinjaRaf]

Talk to Jerry at FJAmods. He is THE 5150 guy.

 

[glpg80]

Talk to Jerry at FJAmods. He is THE 5150 guy.

He did talk to FJA mods thinking he would get a different answer. Jerry's reply was copied and pasted previously on the first page. He reiterated the same points posted in my original reply.

Not worth the time or money

EL34's and KT77's? Sure. It can be done. KT88's and 6550's? Sell it and get a different amplifier.

 

[jd267]

He did talk to FJA mods thinking he would get a different answer. Jerry's reply was copied and pasted previously on the first page. He reiterated the same points posted in my original reply.

Not worth the time or money

EL34's and KT77's? Sure. It can be done. KT88's and 6550's? Sell it and get a different amplifier.

Like i said i like the amp for what it does why would i sell it? But yes it seems like a stupid idea. Just wanted to do some mods. I paid cheep money for it and don't mind tinkering with it ill look into pre amp mods. I posted in my first post about the screen grids and transformer ect. Its not like any one told me something i did not all ready no from the start but was asking WHO has done it AND what they modded to pull it off.

 

[Chris_ONiP]

Like i said i like the amp for what it does why would i sell it? But yes it seems like a stupid idea. Just wanted to do some mods. I paid cheep money for it and don't mind tinkering with it ill look into pre amp mods. I posted in my first post about the screen grids and transformer ect. Its not like any one told me something i did not all ready no from the start but was asking WHO has done it AND what they modded to pull it off.

Don't take it personally man he wasn't trying to be a dick, he's just confirming what he suspected all along and trying to save you your time

 

[glpg80]

If you want to hack it to pieces? Sure. Ill summarize everything you will need to do it.

Order a custom wound transformer with increased current supply on the primaries and filament current output along with the other taps needed to operate the amplifier. You will need to reverse engineer the current PT successfully and know the proper VA rating. You will need to know what value to offset by doing a load test on the secondary of the PT which involves extremely dangerous voltages.

Weld in plates to fill the socket locations, grind and clean them up, and relocate all socket locations to wider stance.

Throw away the power amp board and do a full PTP SLO poweramp side. The poweramp board will be useless since the sockets are mounted to the board.

Relocate and replace the standby switch. The switch will no longer be able to handle the higher B+. A redesign is necessary.

You will need greenleaf punches to relocate and wire new ceramic sockets.

screen grids will need beefed to hiwatt specifications using ceramic sockets.

The preamp is extremely high gain and prone to oscillation. There are provisions that keep the amplifier safe. You will need to find these provisions and add them to the redesign. Failure will cause redplating.

all filament wiring will need upgrading and complete rework to a custom board or said PTP layout.

bias circuit will need rework to supply increased current demand. Dont forget 5150's are DC floating on AC potential.

Headshell will need modification because the tubes are too tall to fit.

Preamp board will need relocation to make room for the socket width change.

the OT primaries will be at the incorrect primary plate impedance. You will need to order a new OT and spec it accordingly for proper load reflection.

Speaker terminals will need re-installation and shielded wiring.

The list goes on and on.

 

[TheWarAgainstTime]

Why not just run the preamp out of the 5150 into a KT88 power amp like a VHT 2/90/2?

Seems like a lot less headache than gutting a perfectly good 5150, and you still get the kt88 power section along with presence and resonance controls like the 5150 power section

 

[op1e]

Or just run a Rockmaster into a 2/90/2 and have a real clean channel.