Peavey Windsor100 head power section 6550 mod...

[tunghaichuan***]

A couple of things come to mind:

If you have to ask which resistors to change, I'm guessing that you haven't worked on a lot of amps. The Windsor is a 100 watt amp with high voltages present inside. That amp can kill you dead in a hurry if you don't know what you're doing.

The other thing is that being a guitar amp, the OT is probably not suitable for bass. It probably is only spec'd down to 80 Hz or so. A four string bass goes down to what, 40 Hz? So it may overdrive even if you do put in different tubes and rebias.

I would take the amp to a tech and discuss it with him/her. If all that needs to be done is to change out a few resistors, it shouldn't be too expensive, if you already have the power tubes.

From the schematic it looks like you'd need to change out one or two resistors in the bias supply and the grid leak resistors on the power tubes. Not complicated, but dangerous.

I don't mean this to insult you as I don't know your background.

Does anyone know what modifications I need to perform on my Peavey Windsor 100 watt amplifier to make it operate on 6550/kt88 power tubes. I am using the amp as a bass amp and need more headroom to power my Ampeg 2X15 cabinet .

I understand that the Windsor was designed to be a high gain amp, but I have already performed a clean mod and changed the tone stack to get the amp voiced the way I like it as per these threads(http://www.thefret.net/showthread.ph...Peavey-Windsor , http://www.talkbass.com/forum/f15/pe...s-bass-522387/ ). Please note that I did not do the power section mod that Bill did on his amp.

After the preamp mods I can get some great clean tones up to around 2 o’clock the pre amp. Now I need more from the power section to combat the power tube distortion that I get when I turn my master volume up. It gets dirty around 1 o’clock… Is the 6550 mod as easy as changing the tubes and adjusting the bias pot or do I need to change some capacitor/resistor values to make it work? If so, which caps/resistors and what will values be? Will I need to change my power transformer?
Here is a link to the schematic:
https://rs312l3.rapidshare.com/#!dow...r.pdf|3257|R~0

[ttenroc]

Tunghaichuan- I appreciate your concern with safety. You are right to assume that I haven't worked on a lot of amps. Guys like you keep folks from shocking themselves to death due to ignorance or carelessness.

However I do understand the lethality of the voltages stored within the various caps throughout this amp, and have been shown by one of my EE student friends how to test and safely discharge caps with a MM. He is also a member of my band and is present for most of the work I perform.

I have been talking to him about this project and also has reservations about the OT, but he is so busy with everything else that he hasn't had time to devote to sitting down and figuring out answer or consult his professors.

I am beginning my freshman semester as an EE Tech in a few days because I love doing this kinda stuff... I have built, modded and repaired a few effects pedals and performed the mods/repairs to a Windsor Studio(with the help of Bill P and an email reply from peavey's tech support team) and to my Windsor 100 amp as mentioned in my OP. I have found forum to be vast wealth of folks, like you and Bill P, who know the answer to any question about electronics that can be asked.

It is because of the things stated above and that the last time I brought my local amp tech my amp it cost me a couple of hundred $$ to have him "repair" my previous amplifier which still has the same issue it had when I took it to him sans the new tubes that he swore fixed the issue. Turns out all he did was put my preamp and power tubes in a tubes tester and changed the bad ones he didn't even plug it in and turn it on to see if the tube swap fixed the issue. He didn't even look to see what the problem was that caused all my tubes go bad. I got home excited to have my Traynor amp back and fried my circuit board as soon as I powered it up. When I confronted him about it he said that he didn't have a guitar cab with a high enough wattage rating to plug my amp into. I would have gladly dropped my bass cab off for him to test his work.
It is now sitting in the corner of the room waiting for me to learn all I need to learn so I can fix it my self. I'm sure he has all sorts of knowledge, but he was lazy and careless with my amp, and therefore with my money, so I will never "donate" to his business again. And not only will I never do business there again, but after I get graduate I plan on getting authorized by every major amp manufacturer and opening a shop right across the street from him with a sign that says I repair what he "fixed" for free.


The long story paraphrased is I am determined to do this project at my house with my soldering iron.

Sorry for the amp tech rant...