........

[fivecoyote]

Wow. Amazing. Wonder if Ben and/or Mark have a hand in this!

[dirtycooter]

[bognermatchless]

Anyone know how to properly bias this particular amp? What tools/devices will I need?

Always had cathod bias amps before, never had to do the whole fixed bias deal.

[bognermatchless]

Nobody wants to help a fellah out??

I have a bias probe and multimeter....I just don't know where the test point is and how to adjust it.

[Strat78]

Looks like a basic bias setup with the 1ohm resistors on the ground from the power sockets. The forumula is 17.5 devided by plate voltage = target between 1ohm resistor and pin 1 and 8 of power socket (17.5 /380 = .046 or 46ma between resistor and socket). The instructions are in George's 100w plexi kit somewhere in this forum.

[Maverick]

About to buy this amp. Buyer says he bought it from a guy who had Mark do his Mod5 to it. Just want to cover all my bases before I purchase it and make sure everything checks out.

Pics:

http://oi46.tinypic.com/2lx9qgz.jpg" onclick="window.open(this.href);return false;

http://oi50.tinypic.com/2evso6q.jpg" onclick="window.open(this.href);return false;

http://oi50.tinypic.com/1zgw2t0.jpg" onclick="window.open(this.href);return false;

http://oi49.tinypic.com/a2rt6c.jpg" onclick="window.open(this.href);return false;

WoW looks alot like one of my mods only a little neater

I can do those

I have a plexi RI that is the benchmark of everything I do mods on!

PM me if your interested in those type mods and dont want to shell out stupid $$$

[SteadyEddie]

Looks like a basic bias setup with the 1ohm resistors on the ground from the power sockets. The forumula is 17.5 devided by plate voltage = target between 1ohm resistor and pin 1 and 8 of power socket (17.5 /380 = .046 or 46ma between resistor and socket). The instructions are in George's 100w plexi kit somewhere in this forum.

Yep, if the resistors are there, biasing is easy peasy.

[TJB]

Well, you can see that a larmar has been added.

There is definitely some sort of cascade installed, I cannot tell of it is a mod 5, but I do not think it is. I don't see the 25uf sprague atom anywhere, or the little red .0022uf coupler he liked.

Most of what you added to the back of the amp (besides the larmar) is a power amp conversion. The same one you have seen posted in recent threads based on interest by jnew. This one is a little different than those schematics because it has the switch jack added to the back. It could be Mark's work. One of the godfathers of the forum showed him (and me) this version of the power amp mod.

Really? Are you sure about that? Are you saying a power amp-in? The reason I ask is it looks like there could be a 25u/25v with a resistor over it on that first pre amp tube socket. And if it is a power amp in would that tap in on the center lug of the low input volume pot?
I thought maybe it was a foot switchable extra channel. It would be nice if there were more pics to get a better look at the parts and jack wiring.
Maybe the new owner could post more pics and confirm what your saying.

[vh junkie]

Yes I am sure.
It is a 25uf/25v Sprague Atom on the tube socket, in parallel with a 1.5k to make the cathode pair for the first stage of the power amp. You can see the rest of the parts mounted nearby, and the 250k pot to the left of the jack. The switching jack on the back engages or bypasses the tone stack, etal.

The 25uf/25v for a mod 5 would be where the big .68uf mustard is in the middle. Perhaps this is an interim version of the mod5, or perhaps this is just what sounded best with this particular amp.

[stef]

Nobody wants to help a fellah out??

I have a bias probe and multimeter....I just don't know where the test point is and how to adjust it.

there's a SEARCH option, works every time
http://forum.metroamp.com/search.php" onclick="window.open(this.href);return false;

maybe you should find a good tech and pay him a visit, biasing procedure can cost you much more - your life in the worst case scenario
high voltage -400 - 500 volts

[bognermatchless]

I would rather learn how to do it than have to take the amp to a tech every time I want to change power tubes.

I still have no idea how to change the bias. I get where the 1ohm resistor is and the tube pins...but what if it's too hot/too cold, what do I do to adjust the bias? What do I turn and which way does what? Counter clock-wise for hotter bias?

[vanhalen5150]

I would rather learn how to do it than have to take the amp to a tech every time I want to change power tubes.

I still have no idea how to change the bias. I get where the 1ohm resistor is and the tube pins...but what if it's too hot/too cold, what do I do to adjust the bias? What do I turn and which way does what? Counter clock-wise for hotter bias?

It's that little mini pot connected to the bias resistor on the board for adjusting the bias. Have you done anything on amps before? The procedure is in the Metro 100w instruction build at the end. It's in the wiki section I think.

[TJB]

Just set your volt meter to millivolts and plug your black lead into com and red lead to V/OHM ma on your meter. I recommend using clip leads on your test probes. Hook black lead to chassis ground and attach red lead between the 1 ohm resistor and pin 8 on output socket.
I recommend plugging a speaker into output jack before turning the amp on.
Turn on amp and let warm up and stabilize for 5 min.
Always where rubber soled shoes and probe with your right hand and left hand in your pocket for safety.
The Peacemaker does have an adjustable bias control on the circuit board and you need to use a very small insulated handled screw driver to fit in the slot in the middle of the bias pot. Be very careful not to touch any other components with the screw driver.
Don't plug anything into the inputs of the amp as this should be measured at idle. After amp has warmed up for 5 min. or so flip the stand by to activate the output. You should now have a reading on your meter and turning the control either way will raise or lower the reading. Webber has a bias calculator on there site and I think you can find it in the tube section on this forum on one of my posts unless you already know what to set is at.

Check the reading on all the output tube sockets at pin 8 so you can reach the adjustment average you want.
Hope that helps and I take no responsibility for this info. Do it at your own risk!

[TJB]

Does this amp have a Marstran OT or Mercury Magnetics OT? I thought Ben installed a 50W Marstran in one of his Peacemakers. I always wondered why he would put a 50 watt tranny in a 100 watt amp. If that is the case your amp my be a 50w and not a 100w. Did it come with (4) output tubes or (2). I would check to see what output tranny you have before you start on the bias to be sure.

[bognermatchless]

Thanks for the info!

It has a mercury OT, so it's 100 watts. Stock transformer that came with the peacemaker.