The Much Anticipated (?) Bluesmaster Build Thread

[Raoul Duke]

It’s time…

First I need to thank the many TAG members who have helped me narrow down and research my next build. I truly appreciate the expertise, patience, and plain old kindness and generosity you all show when I ask questions. I try to do my best to figure things out before bothering you guys; but sometimes I need a “lesson” from the many experts here. Much appreciated!

Next, I hope my build threads are helpful to those who want to try but have no background in this. With the resources I’ve been able to find here to include the references to the Blencowe, Aiken, Livesey, and Hoffman websites (and many others like them) - I’ve really learned a lot compared to where I was when I started lurking here and talking myself out of trying this. Great hobby and a great community here!

Here’s my two previous builds and the 102 wrap-up for any prospective builders (or anyone really) looking for reference material:

102: https://ampgarage.com/forum/viewtopic.php?f=4&t=36689
102 After Action Report: https://ampgarage.com/forum/viewtopic.php?f=4&t=36859
2nd Gen: https://ampgarage.com/forum/viewtopic.php?f=4&t=36895


On to this project:

- Bluesmaster HRM as drawn by Tony A. and mdroberts1234
- 50w - and unlike my 2nd gen build - all modern components
- home made boards (with Hoffman relay boards)
- Precision Power Supply to include snap in reservoir caps as drawn by Martin
- keeping with the Koa resistor theme, but using CF (vs MF) because I had more than half the needed values on hand
- caps are modern 715 and 6PS with Panasonic ECQ in place of the three NTEs
- Hammond 290DX PT and Heyboer APD8025B-H OT (choke yet TBD)
- All housed in one of Taylor’s super high quality chassis produced about 50 miles north of Plymouth Rock and 12 miles west of the “shot heard ‘round the world” (give or take, lol) inside a home made head cab (aesthetics TBD)

Let’s get started:

[Raoul Duke]

Built the PS board a couple of weeks ago just to get familiar with the new (to me) design. Worked out great and makes the PS “future proof” regarding parts selection.

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Also put together the HRM board and pre-set the trimmers to the values Tony shared in Ian’s BM build thread.

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Did these a little early because I planned to use them no matter what I settled on. Same can mostly be said for the other small boards as well. Martin’s plans are so versatile and easy to use and implement! Can’t thank him enough! Awesome tech support too, lol!

[martin manning]

I hope my build threads are helpful to those who want to try but have no background in this...

The Q&A leading up to this (six pages) is useful too, and it will get lost if it's not linked: https://ampgarage.com/forum/viewtopic.p ... 13#p464413

The main filter board looks great! I think this is the first all-radial one from that drawing I've seen. Still has the classic look.

[Raoul Duke]

Thanks Martin!

I’m pretty happy with how the PS worked out and it wasn’t difficult to do at all. Your plans were easy to follow and everything fit perfectly. It’s pretty amazing how there’s so much more selection for way less cost in radial and snap in components; and I agree that it still has the Dumble look.

Thanks also for linking the questions thread. It didn’t occur to me that my (sometimes) inane questions might actually be helpful, lol.

[martin manning]

You might consider adding a link in your 102 build thread to its follow-up impressions thread too.

[Raoul Duke]

I’ll do that Martin

Question about the layout: it looks to me like the relay system is not wired the same way your boards are; but it seems like the mdroberts schematic is closer to yours (from what I can tell - can’t figure out the relay board Com points on the schem). Am I correct or am I misinterpreting?

[martin manning]

HAD used different relay PCB's for the OD and PAB, which seems silly when a generic board can be used for either. The connections in the boards .pdf use the universal relay PCB shown there, or you can use the C/NC/NO references to use any other DPDT relay board.

[Raoul Duke]

Understood. I’ve got a conversion “map” for the Hoffman boards that makes using your plans easy. Just thinking through the differences to try and anticipate any traffic jams.

Just to be sure; I’m using the “Separate Masters HRM, Bluesmaster” connections, correct?

Every time I look at the layout then the board plans, then the schem - I get turned around - so now I’ve thoroughly confused myself, lol.

Thanks Martin!

[martin manning]

UJust to be sure; I’m using the “Separate Masters HRM, Bluesmaster” connections, correct?

Correct.

One of these 25-turn Bourns trimmers https://www.mouser.com/ProductDetail/Bo ... 2Fqg%3D%3D soldered to your PAB relay board would work for the variable lift. Bend the center pin over to one of the outside pins and put both in the same hole.

[Raoul Duke]

Hey, that’s helpful Martin! Been searching on and off today and had a few “maybes” - but this saves me some energy, lol.

How does the 25 turn thing work? Just better fine tuning due to the multiple turns?

Thanks and very much appreciated!

[martin manning]

I’ve never opened one up, but it looks like the brass screw is a worm drive gear. In this case it’s very compact and makes the adjustment easy to access.

[GAStan]

Martin got it right, it's a linear (physical) resistive element with the wiper on a screw (worm drive). 25 turns covers full range, in this case 500k. Doing the math 1 turn equals 20k, 1/2 turn equals 10k, etc... As you can see very fine adjustments can be made-much finer control than with a single turn.

This adjustment tool works great, stays on the screw head. Alternative is carve a chopstick end to a screwdriver-its really easy to slip off and a nonconductive tool is highly recommended.

[Raoul Duke]

Glenn,
That chopstick trick is actually what I’ve been using as a trimmer adjuster. I have a long one and a short one. They work great, and I can say I made them myself. I make sure anything I stick in the chassis when it’s running is non-conductive. Learned that one at about age 5 when I plugged a fork into a wall outlet and it blew me backwards about 6 feet. I don’t really remember it, but apparently everyone else did for the first 30 years of my life, lol.

Been doin’ dumb shit all my life - but I’m trying to cut back on that now…

Thanks for the clarification on the pot. I’m eager to see how this mod turns out. Seems pretty practical.

[Raoul Duke]

Got a Mouser box Friday evening and kind of just went bananas since then. That Triad 12v transformer dropped right in, got my small boards buttoned up and installed and got the tube sockets “decorated”.

And I still managed to get about 4 hours of yard work done yesterday as well, so my better half can’t sayI spent all my time on the amp, lol.

Quick clarification: I went with the 3 position R/J switch for the PAB center. Is there any modification I need to make there or at the rear panel relay switches for this to work either with the footswitch or without?

It’s interesting to see how familiar everything is even though it’s only my third build. Less stressful and more enjoyable.

Should have transformers tomorrow or Tuesday - not that I’m at that stage yet - just want to check fit so that if I need to drill, I’m doing it before there’s anything else inside the chassis.

[martin manning]

Quick clarification: I went with the 3 position R/J switch for the PAB center. Is there any modification I need to make there or at the rear panel relay switches for this to work either with the footswitch or without?

Dumble did not always wire the Manual PAB switch lugs on the back panel (see #102 layout, e.g.), leaving it to the mid position on the R/J for manual, and the Pedal position on the back panel for pedal control. IMO there is no reason not to connect it up and have two ways to turn the OD on. The mid R/J position will switch PAB on without the relay, regardless of the back panel switch position, and lock out the normal mode.