#124 Build Started! (Progress and Questions)

[michaelwwesbrook]

After months of research and prep/parts ordering I’ve finally started the build process! I’ve built a couple of kits as well as numerous mods on those and other amps but this is by far the most difficult of anything I’ve done. I’ve learned a ton already but still have a lot of questions. I’ll use this thread to document the process and post any questions I have. Also, thank you to everyone here at TAG for their knowledge and openness to help and share!

Going fairly traditional #124 using a chassis and boards I got from Taylor at Amplified Nation. Other than the Dales I’ve gone with “fancy” resistors where I’ve been able to find the values. I do like the thicker, stiffer leads for sure. Hammond PT, Mojo (Heyboer) OT and choke.

Current stage -
- Most hard ware is installed, Boards are built with most wires attached. (Photo’s just have the boards set in as a mock up) I’m following Funk’s build order as a lot of people seems to think that makes good sense.
- Relay power board is installed, regulator installed, footswitch and switches (although I did wire them upside down) are wired and installed.

Next up is the Rec/Bias Supply board. I do have a few questions here - the DIY eyelet boards have spots for 2 bias pots. I’ve found a bit of info about having 2 separate bias controls for each pair but nothing is very clear on how this should be wired up? Also, are any changes needed to just go with the standard single Bias pot while still using the DIY eyelet board?

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[martin manning]

Next up is the Rec/Bias Supply board. I do have a few questions here - the DIY eyelet boards have spots for 2 bias pots. I’ve found a bit of info about having 2 separate bias controls for each pair but nothing is very clear on how this should be wired up?

The DIY HV Rect/Bias board is designed to be used with a single bias pot, which is the one in the photo you posted. The 1 and 2 refer to the pot terminals, where 1 is the ground end of the pot's element, and 2 is the wiper.

[michaelwwesbrook]

Wow… of course it is. I feel like an idiot. Thanks!

[Stephen1966]

Install the transformers as soon as practicable. I made that mistake and had to undo a lot of work to make it work. Think of layers and work from the bottom up - you've already made some progress here. The boards and components on the chassis sides, front and back are easier when you install those first. Also, install any under-board wire runs before you set the boards in place. I believe MrD sometimes did this after the boards were installed but it's a lot easier to do it before the main chassis boards go in and you route them more precisely this way. Think lead dress, keep looking at the photos and try to observe the phase relationships of the signal wires. Always double check your solder joints - don't ask me how I know that one

Stephen

[michaelwwesbrook]

Following Funk’s build process so far though it’s been slow going. Got a few hours in last night finally. There are still a few things loose but it’s moving forward!

Questions:

On the half power switch:
The chassis I have doesn’t have spot for a half power switch. I know a lot of folks think they are unnecessary but I would like the option. How does this location look for a half power switch (between V4/5) ?

Also unsure of best lead dress for pin 1 (ultimately the control grid)? How is looking correctly? I don’t love how it’s elevated over the center tap resistors on V4/5 but also trying to make it as short as possible. Any thoughts?

Thanks guys!

[ijedouglas]

On the half power switch:
The chassis I have doesn’t have spot for a half power switch. I know a lot of folks think they are unnecessary but I would like the option. How does this location look for a half power switch (between V4/5) ?

I think that's fine.

Also unsure of best lead dress for pin 1 (ultimately the control grid)? How is looking correctly? I don’t love how it’s elevated over the center tap resistors on V4/5 but also trying to make it as short as possible. Any thoughts?

I don't think you need to worry too much with the length of the run. HAD ran the lead to the back of the chassis:

Screenshot 2022-10-05 072143.png

This is how I do it:

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[michaelwwesbrook]

Lots of progress here! Nearing the end and learning a ton. My process has been work until I don’t know what to do and then read a bunch here to try to understand and sense of it.

The last steps are wiring up the PT, wiring the filaments, and doing all my last checks.

My questions are about the PT and some of the wires. I’m using the Hammond 290fx (diagram attached) I want to check on what to do with the Orange, red/blue, and red/yellow wires. I feel like I should be able to figure it out easily but because it’s the power section I want to be extra sure.

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[martin manning]

Orange is connected to an internal shield. Connect that to the reservoir ground, along with the Red/Yellow (HV center tap). The two Red's (HV) and Red/Blue (bias) go to the rectifier board.

[martin manning]

I suggest you reroute your reservoir ground like this. That will keep all the high current pulses on the Red/Yellow wire and the under-board wire going to the reservoir cap ground. There won't be much on the long green wire, but in any case I would not run it in with the other wires at the back of the chassis. You should have a dedicated bolt and ground lug for the earth safety ground too.

[michaelwwesbrook]

Thanks Martin!

I almost ran the green wire that way but didn’t…

Noted on the red/yellow reroute and the separate bolt on the earth ground. With those in mind, where is the best place for the orange (internal shield) wire now?

[ijedouglas]

Thanks Martin!

I almost ran the green wire that way but didn’t…

Noted on the red/yellow reroute and the separate bolt on the earth ground. With those in mind, where is the best place for the orange (internal shield) wire now?

If you take a look at pics of 124, you will see he has another ground point between the rectifier board and the pilot LED diode and dropper tag strip. You can run the red/yellow + orange shield + reservoir ground + rectifier ground to this ground lug .

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[Stephen1966]

Thanks Martin!

I almost ran the green wire that way but didn’t…

Noted on the red/yellow reroute and the separate bolt on the earth ground. With those in mind, where is the best place for the orange (internal shield) wire now?

If you take a look at pics of 124, you will see he has another ground point between the rectifier board and the pilot LED diode and dropper tag strip. You can run the red/yellow + orange shield + reservoir ground + rectifier ground to this ground lug .

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Yeah! Same here. I used the Euro version of this transformer and routed the orange shield wire to GND 4 as per Tony's layout. No issues there. Best in my opinion not to use the mains GND tag for anything other than that.

[michaelwwesbrook]

It lives!!

Went through the start up process today. No smoke or issues thankfully. Huge thanks to everyone here.

Initial impressions are great and I’m really impressed by the variety of tones. Lots of different ways to go about shaping things. I did originally change the cap across the master to a 47uf (as recommend by someone around here) but have gone back to the stock value as it seems more even from low volume to higher volume in terms of top end.

At this point I’m not sure I see myself changing much and will just let it keep breaking in and opening up. Even from the first time of playing it to now, a few hours later, it’s noticeably different (and I’m also learning it I suppose). The only thing that doesn’t seem super useful for me is the bright switch. Even with humbuckers it feels like it’s a bit too much. What values do you all recommend?

The other thing I’m in need of is a cab. Any recommendations in the states? I don’t have the space or tools to take that on right now.

[ijedouglas]

The only thing that doesn’t seem super useful for me is the bright switch. Even with humbuckers it feels like it’s a bit too much. What values do you all recommend?

The other thing I’m in need of is a cab. Any recommendations in the states? I don’t have the same or tools to take that on right now.

Congrats!!

I don't use the bright switch either. My 124 is already pretty bright so no need for it.

[rccolgan]

On other Dumble-style amps I've built with rock/jazz, the bright switch seemed to work best with "jazz".