The Much Anticipated (?) Bluesmaster Build Thread

[martin manning]

Good to hear you figured it out. Note in the Bluesmaster layout the switches shown are slide types, but the lug connections are shown as they would be for toggle switches.

[Raoul Duke]

Thanks Martin, that’s exactly how I wired them (plus the caps).

I guess I’m clear to do the initial PI setting and continue wiring everything else in then. Looking forward to hearing how this circuit sounds as well as the unusual OT I’ve used. Hopefully I got the relays/board/pots right. Triple checked all that - hopefully it pays off.

Surprised at the initial B+1 though. I was expecting it to be a little lower considering the different PT specs. I think that’s interesting.

[Raoul Duke]

Balanced the PI and finished the wiring today:

IMG_0222.jpeg

Went through the initial power up with the limiter - all was good. Removed the limiter and everything was still good.

B+1: 473
B+2: 471
B+3: 441
B+4: 352
B+5: 312

V1a: 170 (1.9 cathode)
V1b: 178 (1.8 cathode)

V2a: 213 (1.9)
V2b: 222 (1.7)

V3a: 290
V3b: 281 (40.7)

FET Drain: 1.7 top, 10.1 bottom

Then the big moment - plug in. Nutshell: with the drive, volume, and master cranked - I get decent crunch sound and the volume by the jacks works. When I switch OD on manually, everything’s gone. Feels like PAB works - but it’s hard to say for sure. Mid and bright seem to work, J/R seems to work. Tone controls; hard to say. Seemed like they worked, but not as noticeable due to the distortion. Got out the signal tracer and went in circles trying to follow the schematic. I’ll try again tomorrow; but my hunch is the relay wiring. I wrote out what I did trying to reconcile the layout, schematic and board plans (bugging Martin, too, lol) - but that’s the area where I got turned around a few times.

Used an Amazon credit and got a small oscilloscope with a signal generator for nearly “0” dollars, then made a signal “funnel” for it, then put it to use:

IMG_0221.jpeg

Got a lot done today; but still more to do.

[martin manning]

Well, it looks great, anyway! Your lack of OD may be some wiring error in the relay switching, and it seems strange that you have to set the volume and master very high to get decent volume. DC voltages look good except for the FET, which needs a bias adjustment.

BTW, the "top" and "bottom" of the FET drain resistor you refer to are the physical locations, but that terminology is usually understood to be electrical, where the "top" is the (higher) supply voltage and the "bottom" is the (lower) drain voltage.

[Raoul Duke]

Thank you! I try to be as neat as possible when I put these together. And thanks for the terminology explanation Martin. I’m generally very literal, so I thought it was location-based. A big part of my knowledge gap is interpretation of what I read here. In other words: you guys know what you’re talking about and I don’t sometimes, lol.

I bench biased the FET, so I can’t be too far off. Easy enough to adjust.

Yesterday I traced the signal through V1 and back through the tone stack, but lost it before the OD entrance - just not certain where yet. Also had signal on the unused eyelets on the PAB relay board - which I thought was strange. Didn’t have any clean channel - which I also thought was odd given my signal tracing. Almost like I swapped one of the co-ax connections or something. I’ll verify everything again today. Hopefully I get it running by “Miller time” lol.

Raining here; so it’s the perfect reason for me to troubleshoot vs yard work, lol.

[dbharris]

Hey Raoul, this build is looking great! If you post some more pics of the relay board, effects loop jacks, and channel masters we may be able to help you spot something.

When signal tracing, I always start after the coupling cap of each stage. If you find signal at one but not the next, you know the problem is in between.

Good luck, I am sure you will get it sorted soon!

-Dan

[Raoul Duke]

Thanks Dan, I appreciate the offer and will put some up here soon. Right now I’m going through each run between components and verifying they are going where they’re supposed to. Once I have that figured - I’ll take a couple of pics and re-start the signal tracing.

Dumb question, but just to make sure I’m in the right place - is “after” the coupling cap on the pot side or tube side; or does it depend on which cap? My limited understanding thinks it’s the pot side - but I wanted to confirm.

Funny thing: with this build I wanted to use color coded shrink tubing on the co-ax to aid in tracking connections in case I had this problem; but completely forgot to. Everything is random based on whatever I pulled out of the bin at the time Yep, I’m a genius, lol.

Thanks again!

[dbharris]

Yes, the pot side or rather the opposite of the tube side. The coupling caps block DC so you can set a scope or meter to measure AC and check at that end of the coupling cap leg.

[Raoul Duke]

Ok, hopefully I can get this thought out in some sensible fashion. After comparing the layout, schematic, board plans, and re-reading my questions about the changes - I think I might see where I went wrong. Bear with me because I still struggle with how these things flow from a theory POV - so I may be way off. Here goes:

I currently have the OD relay wired as such:
Coil -: to switch
Coil +: to/from 12v
Com1: Power Amp In
Com2: OD entrance 470k on main board
NC1: co-ax to OD volume wiper
NC2: ground
NO1: master volume wiper
NO2: co-ax to master volume CW

I’m thinking I need to switch NO1 and NC1 because I mixed up the “Cl Vol” designation even after Martin explained it to me.

Does this make sense?

[dbharris]

Ok, hopefully I can get this thought out in some sensible fashion. After comparing the layout, schematic, board plans, and re-reading my questions about the changes - I think I might see where I went wrong. Bear with me because I still struggle with how these things flow from a theory POV - so I may be way off. Here goes:

I currently have the OD relay wired as such:
Coil -: to switch
Coil +: to/from 12v
Com1: Power Amp In
Com2: OD entrance 470k on main board
NC1: co-ax to OD volume wiper
NC2: ground
NO1: master volume wiper
NO2: co-ax to master volume CW

I’m thinking I need to switch NO1 and NC1 because I mixed up the “Cl Vol” designation even after Martin explained it to me.

Does this make sense?

Yes, that sounds like the appropriate fix.

[Raoul Duke]

Thanks Dan, that certainly helped!

Now the OD switches in and out as it should, as does the PAB. Confirmed all tone controls/switches function as they should as well. Still weak with weird behavior though:

Pre-amp volume goes off in the middle of its rotation (call it “5”) with weak volume from 1-4 and stronger volume from 6-10.

Master volume has little effect - mainly either “on” at 10 and “off” from 1-7 with a sharp increase from 8-10.

The OD section volume acts more like a master and the Drive like a pre-amp volume; but even cranked all the way up - still weak. If I dime the master, OD volume, and drive (and pre-amp volume) then switch on PAB - I get a high-pitched whistle (oscillation?).

I must be losing signal somewhere, right? Or a drastic wiring error?
I’ll keep verifying everything and hopefully find something obvious. If not - back to signal tracing.

I’ll get there…

[martin manning]

The OD section volume acts more like a master and the Drive like a pre-amp volume; but even cranked all the way up - still weak. If I dime the master, OD volume, and drive (and pre-amp volume) then switch on PAB - I get a high-pitched whistle (oscillation?).

The strange preamp behavior could be an ultrasonic oscillation. Does it happen in both Clean and OD?

Does the power amp work properly with your 102 driving it? I'd be nice to confirm that and isolate the issue to the preamp.

[Raoul Duke]

Just OD; and with everything maxed out and PAB on.

How would I drive the power amp with 102? Preamp out from 102 plugged into power amp in on BM? Would I use regular cables or speaker cables? Any risk involved that I need to pay attention to?

On the power amp master volume - is the identified V1b coupler connection at NC2, or should it go directly to the .02 coupler on the board?

Thanks!

[martin manning]

Just OD; and with everything maxed out and PAB on.

Worst (or best) case for starting an oscillation. Try chopsticking and see if you can make anything change.

How would I drive the power amp with 102? Preamp out from 102 plugged into power amp in on BM? Would I use regular cables or speaker cables? Any risk involved that I need to pay attention to?

Probably doesn't matter if you are just testing the BM power amp.

On the power amp master volume - is the identified V1b coupler connection at NC2, or should it go directly to the .02 coupler on the board?

On the layout, the lead from the Clean Master says "V1b .02 coupler," which to me would mean on the board.

[Raoul Duke]

On the power amp master volume - is the identified V1b coupler connection at NC2, or should it go directly to the .02 coupler on the board?

[/quote]
On the layout, the lead from the Clean Master says "V1b .02 coupler," which to me would mean on the board.
[/quote]

Thanks for the info Martin!

That’s what I’m now thinking as well. I currently have it going to the OD relay NO2 per the board plans - but nothing connecting to that cap on the board. I think I’m going to try a jumper from OD relay NO2 to that cap. I’ve looked at a couple of builds and I see that. Only question is: should the co-ax go to the board first, then jump to the relay - or can the co-ax go to the relay and then jump to the board at the cap? My limited understanding tells me it probably doesn’t matter.

Going to try the simplest way first and jump relay to board.