SLO 100 full clone cause I'm a glutton for punishment...

A few months ago this project started with me looking at parts to do a Soldano SLO 100 build and I realized that there's a company that sells the boards, chassis and transformers (albeit the most expensive transformers I've ever bought). C3 amps out of somewhere in Texas is the supplier I found and over the last few weeks I've been acquiring parts.

This is by far the most complicated amp I've ever assembled so I'm taking a while to get it done. As it sits right now the power supply is wired up and I just have some board jumpers to add that to between the power board and the preamp board.

Preamp board is assembled and the every thing is mounted in the chassis. I think next up will be the preamp socket jumpers and resistors, then I'll get the pots buss wire in.

Slow and steady with this one but I'm really excited to do this build.

 

Honestly, this is the only way I was ever going to get one too. $3-4k is quite a bit above the area I can justify, so if I can get reasonably close with this then I'll be happy. All in, I think I have about 1k into it and quite a few hours so it probably works out in the end.

 

I got a little more work done and wired up the input and some of the switch stack along with the pot buses.

I'm certainly no Mike Soldano but it's turning out pretty good. I may spend a little more time trying to straighten things up a bit once I get all the jumpers in place to the pots and sockets and board.

I am short a few small parts, so I got another order in for some resistor values that I am out of as well as a few 470pF caps.

More to come once those come in, but I should be able to button this up within the next few weeks. Hoping the mail gods are in my favor on this one.

 

Got the slave out, footswitch and effects loop all wired up at the jacks. I also did a little wire management but unfortunately that's about all I can do until my last few things come in.

Home stretch sucks when you don't have everything you need...

 

The company mentioned above who was the source for the transformers, boards and chassis called C3 Amplifiers has a website with a pictorial build log on it. It's not complete, but using schematics and pictures of other SLO amps online has helped me piece the missing bits together.

The link to their website is: C3 Amps - Soldano Kits, Transfomers, Chassis, Boards, Head Cabinets and Components

(no affiliation)

I have been doing a lot of studying to make sure I get this right and I think that has been paying off. Just looking at pictures and then studying my build to make sure everything is in its place. Reviewing the schematics to make sure everything is still accounted for has been key as there were already a few things I almost looked over.

As far as I know, there are not any build manuals for these amps. It has been challenging working on something that has so much less documentation, but I am enjoying the heck out of it and I am learning a little more than the previous amps I have done. I have only ever done fender style clones, be it tweed, brown or black I have built a few of each... but this is in a whole other league.

 

Well, this week has been an interesting week for this project... I got the last few parts in the mail so I got to finishing up the soldering job and then the startup procedure.

Upon first start up, my dim bulb tester shined brighter than I have ever seen it. Unfortunately, I had some kind of short, but after a ton of testing and pulling this lead and that, I finally decided to test the PT by itself outside of the circuit... and there was a dead short with the PT hooked up by itself.

I assumed this was somehow my fault and ordered another PT... but after thinking on it for a few days, I figured I may as well pull the transformer apart and see if I can see what's going on. Upon removing the bell covers, I find that the primary wiring code has been setup wrong on this particular transformer. White and Brown happened to be reversed where White was supposed to be the end of the winding and Brown the beginning (in comparisson to the other winding). When I followed the parallel steps for the windings (for 120V operation) I was hooking the beginning of one winding up to the end of the other.

I figured at this point I already have another PT on the way, I may as well try this one again with the wires hooked up the way I think they should be... and now it works. Voltages are all seemingly correct and I put the transformer back into the amp to restart the startup procedure.

After fiddling with the bias resistor a bit I managed to get things dialed in to about 75mA per pair of power tubes. The only other thing I am particularly unsure of is there is a massive volume drop between high gain and clean. This may just be a quark of the amp because of the way the channels are attenuated, but I wanted to bring it up to see if anyone else has any experience with a SLO and switching between clean and overdrive.

 

Thanks a lot mooncat, that helps a lot.

I am still doing some troubleshooting with this since the B+ is quite low and v1 has some odd voltages.

I am going to wait until I get the new transformer in to do any more testing. This project has been testing my patience a bit, so I am taking it slow through the finish line.

 

Spent some time going back and forth with Rob at C3 and he explained that the voltages are fine where they are. I was expecting B+ of around 500V, but in reality I am getting around 450V. I am living with it for now but may revisit it later...

I also figured out why the clean channel sounded so bad... On the board the cathode resistor for v1A was printed as 220k ohm and so that's what I populated... but in my efforts to double check everything I was looking over the schematic and noticed that it's actually supposed to be 2.2k ohm.

Fixing that made the amp sound much better between the clean and crunch settings, and now I think I can call it electronically complete. Saving up some dough to get a cabinet made so I can start taking it places, but for now it's home is my living room rig.

 

Thanks Robrob! I'm excited to play through it and compare to the naked slo 6l6 that I built a few months ago.

This thing is indeed a monster. I can't wait to get it on my 4x12.