Oh - didn't realize you were over there. Then skip that idea - find something more local!

Nik is also an authorized mercury dealer - meaning he can sell you the mercury trannies at his dealer price. You send him the money, Mercury send you the trannies directly, which if you're in the US saves a lot on shipping. Don't forget the shipping costs on these things from wherever you end up getting them - they weigh around 25 lbs, which is expensive to ship.

This is a great thread - now I'm starting to feel like I know how to do this adjustment.

Only problem - my scope doesn't seem to have a math function - it's an older Heath 4226. Can I use the X-Y mode? Or is there some other way to set the thing? Actually it might have some kind of math mode, just that I don't have a manual and can't find anything obvious on the panel.

Thanks guys! I stole the grill idea from a Vernet version of these amps - see - and got the grill and the other hardware from Reliable Hardware - http://www.reliablehardware.com/ .

I probably won't help you find your sound, but I can at least tell you what seems to be working for me after some experimentation. I also have a BM 50w, but have only had it for a few months. My musical tastes are more on the rock side of things, so adjust my settings accordingly.

I have the od trim set on about 11 oclock - I find that above that doesn't add much more to the sound except compression, although it's fun to turn it up and see what happens sometimes. The drive knob is currently between 7 and 8.

Don't forget to experiment with the main volume knob - it makes a huge difference in how the od channel works. I have mine set at 7, which just pushes the clean channel into light drive if you play hard on my strat. Also don't forget the volume control on your guitar - at these settings it can make a huge difference in your sound.

Edit: forgot to add - keep in mind that the drive circuit has it's own tone stack, and that engaging PAB cuts out the front panel tone stack, so for best results always use overdrive with the PAB on with your amp. Otherwise you're running through 2 tone stacks, which can have an adverse effect on your tone.

Finally got around to finishing this up - it's green -


Green Amp front by sduck409, on Flickr


Green Amp back by sduck409, on Flickr

Did I mention that it's green? 

Something around your speaker wiring is way wrong - the sleeve of these jacks should connect to ground, and hence the chassis.

Yay! And good work. Now play that thing til it's gold...

I wish I hadn't read that ampgarage thread. I haven't messed with my PI trimmer yet, and was just going to use Nik's method to set it, maybe next week or whenever I can find the time. But now... do I just follow Nik's method, or do I worry about injecting a signal, testing the AC current, etc??? Hmmm...

BTW, I just grabbed a bunch of tubes from the local music store when I was building my Bluesmaster 50w - JJ 6L6GC's and new TungSol 12AX7's. Figured they'd get it going, and I can mess with the tubes later. However, these tubes sound great! Absolutely no problem with the tungsols. Although admittedly I haven't tried other tubes yet - can it be even better???!?

I don't see a manual online for this variant of the ots. There are 2 trimmers in the layout - the FET one and the phase inverter one. The FET one you set to taste I think - start out with it in the middle. The Phase inverter one is set with a DMM once you have everything else running, and it isn't critical where it is when you power up the thing, so set it in the middle for now. Email Nik for specific instructions about how to set the phase inverter for this amp, although I suspect it's pretty much the same as the other amps - look at the standard ots manuals.

Yes, that's one of the things that can be confusing about the layouts - the stuff on the back panel is kind of backwards in relation to how it's depicted on the front panel. I found it easiest to use common sense as a guide - know which connections are supposed to go to ground and work from there.

About continuity checking - set your dmm for that - so that when you touch the 2 probes, they beep (or give some kind of indication on screen, depending on how yours works). Then you just start checking connections - like in the input section, you might want to plug a cord in the high input jack, and put one probe on the unplugged tip end of the cord, and then poke the 2 resistors on the terminal block near v1 with the other probe - you should get beeps on both resistor leads (on the sides closer to the terminal block). Switch the cord into the lo input, you should only get a beep on one resistor - A2. Basically, you want to check the integrity of all your solders; so anything you soldered should get checked. There are a lot of them, so take your time; be thorough. From what I've heard, problem areas to start with are all the ground connections - it can be hard to get a good solder on these, especially if you've bolted down the connections before soldering - the bolt acts as a heat sink, so it takes longer for the solder to really heat up enough to make a good connection. Likewise with the bus bar over the knobs. If you have a way to attach an alligator clip to one probe of your dmm it'll make testing all the ground connections a bit faster. I'd also recommend triple checking everything around the main controls - there's a lot of detail stuff there, and just one wrong connection and it won't work. And don't forget to test stuff that looks obviously connected - like in the picture I posted, that green wire that connects the 2 jacks - put your probes on the lugs of the jacks and check that both those solders actually work - cold solders can fool you - they can look fine but won't be making a good connection. (btw there are a few less than good solders in that picture - I think I went back and redid some of them after taking that)

Oh, and make sure you've drained all the caps before doing any of this! And obviously disconnected the power.

It sounds like you have the right idea about the input jacks. Maybe that's not the problem.

Here's how i did mine - I flipped them to the outside of the chassis to have better access but still have the spacing correct - mine's a bluesmaster, but it's probably close enough -

Did you build this amp yourself?

What I do for troubleshooting, which almost always finds the problems, is first - take some time off. Get some rest. Attack the problem with a clear head, well rested. Then, take your DMM and put it in continuity testing mode, and just start going over every single connection that you soldered. Test from component to component, not just solder to solder - if there's problems outside of the solders you want to find them. Also check that connections aren't being made to nearby things that aren't supposed to be connected! Use the layout while doing this, perhaps a new printout of it, checking off connections after you've cleared them. Hopefully you'll turn up a cold solder or a solder that you forgot to make - this is the kind of thing that plagues even experienced builders. Be patient doing this - and allow hours to go over everything.

Oh, and if you built this yourself, double (triple!) check the input jack wiring - the way it's shown on the layout can be a bit confusing. Likewise for the output jacks.

The coax that came with my kit a few months ago was particularly hard to unwind - there was some sort of goo in and around the ground sheathing that made it really hard to unwind. I had some belden coax of the same specs here that I ended up using for a lot of my coax instead. Unwinding the ground braid is a pita even without that goo in there - just be patient and try to be neat doing it.

A drill?

I ordered Mercury PT/OT/choke from Nik - he's a dealer, and can get a good price - you pay him via paypal, Mercury ships the stuff domestically (I'm in the USA, your mileage may vary in other countries).

The mercury PT fit the existing holes perfectly. The OT however didn't, but it only took a few minutes to drill holes that worked.