Potato Cakes

One more question for now:

Where is the meter board and switch supposed mount? I can't seem to see these things on the photos of the originals or Martin's build.

Thanks!

Paul


And here is how the original power 18 gauge wires are twisted around.....I am doing my unit exact 100% original.....
Wire bends,color, wire gauge and all...They use a lot of 26 gauge and even 28 gauge. Besides the 24 gauge.
The reason being is to keep the wiring clean and the wire looms from being to big! They only used the bigger wire gauge where needed.
I have learned a lot on how these units where built...They are very detailed they way they did things.
Also I put a arrow where I will be installing the metal single line clamp they are called. This keeps the wires firm when door opens and shuts.
John
« Last Edit: April 29, 2019, 04:14:12 PM by jslstudio »

Also suppose to be a extra turret board that the output goes to first. On 175b you will see the mounting holes on floor of chassis,s.
I have to make this. Arrows show meter board and output turret board. Keeps it all nice and clean wiring wise....
Front facelate wires go through 1/4"gray and clear  pcv tubing.......
John
« Last Edit: April 29, 2019, 04:27:31 PM by jslstudio »

Potato Cakes

The early Originals where a gourmet. The extra hole you see below the choke is for a small C wire loom clamp.
That is also where the power cable was strain relieved from pulling out.
The power bulb is 5/16" Jewel lamp. A couple on eBay now. You need the #47 bulb holder.
The Drake Lamp assembly that will work is the 5-B .
Don't put a big fender power jewel......Unless you are doing the first version 175..;-))) They used that giant Fender amp size....
John

I didn't think about using clamps. The clamps will make that part a little easier.

I found the ones on eBay and I think I'll wind up getting those. It's unfortunate because I was going to use these:

https://reverb.com/item/4481370-invisible-sound-guitar-amplifier-jewel-lamp-indicator-amp-jewel-model-370-for-pilot-light

I ordered a pair and I'll use them for something else, but was hoping to do something unique for the jewel light.

Thanks!

Paul

Potato Cakes

Also suppose to be a extra turret board that the output goes to first. On 175b you will see the mounting holes on floor of chassis,s.
I have to make this. Arrows show meter board and output turret board. Keeps it all nice and clean wiring wise....
Front facelate wires go through 1/4"gray and clear  pcv tubing.......
John

Thanks for the additional photos.

I think I'm going to do mine without the meter selection as for me there is no need for one as I don't plan on opening this up once it's done. And it will simplify things for me a little. I just need to verify which resistor gets connected.

Thanks!

Paul

Potato Cakes

I'm using the newer switches which don't have the screws in the back to mount the ratio board, so I used some JB Weld to fasten some #4-40 threaded L-brackets to the side of the switch.

Potato Cakes

Doing one on each side makes the contact points too wide for the holes already drilled in the ratio board, so I had to add two more that were on the opposite ends length wise (perpendicular to the original holes). Seems to work great and it will still fit inside the chassis.

Thanks!

Paul

Potato Cakes

Finally wrapped the power section on the first one. I drilled a hole below the opening for the AC cable and made that my star ground connection, making it as close as possible the power coming into the unit.

The hold up now is the output transformers. I don't want to mount and wire the PCBs then have to move them and to attach and connect the transformer windings. Good news is Don Audio has them in stock. Bad news is I'm still waiting on payment for some things.

Thanks!

Paul

Potato Cakes

For the barrier strips, I should let everyone know that the solder terminals needed are on the BOM. I was thrown into disarray because when I checked the data sheet for the part, I only seemed to see terminals for joining adjacent connections. In the middle there is a tiny drawing that is the part which is listed in the BOM. The drawings also didn't have part numbers next to them, so I had to look at the measurements to decipher which part number was which drawing. Add that to the fact that I kept skipping over the really small one which was the one I needed seemed to put me in a state of uncontrollable fits of crying, anger, depression, and bowel irritation... things that normally take place when I build gear.

I added some shrink tubing on the terminals to protect from unintended contact with the chassis as it passes to the inside.

Thanks!

Paul
« Last Edit: May 03, 2019, 01:08:12 AM by Potato Cakes »

Potato Cakes

Since I decided to not use the meter select function (GR only), I was wondering if the external meter connections could be repurposed for some like a side chain link to my other 176 I'm building or external SC in. Or something else?

Thanks!

Paul


Potato Cakes

I'm using the USA power transformers that are found on eBay. They have a lead that is 55VAC referenced to the center tap and is labeled bias. I don't see this connection on the 176 schematic, so I wanted to confirm this is not being used. If it is I might need some help pointing out where it goes.

Thanks!

Paul
« Last Edit: July 06, 2019, 01:16:30 PM by Potato Cakes »

I asked owner..He said clip it. Shrink it and push back in the case!
John

Potato Cakes

I asked owner..He said clip it. Shrink it and push back in the case!
John
Copy that.

Potato Cakes

This is as far as I'm wanting to go until I get my hands on the output transformers. I'm tempted to start assembling the second one but I want to make sure this one works correctly first so as to not build both in correctly and double the troubleshooting fun.

The 1/4" connectors I have on the front are for balanced connections, so I think they are a little longer and the originals. I had to use some shorter stand offs so the PCBs will fit behind them and not create any shorts.

I think I might just use the Bourns 600 ohm T-Pad for the time being. I bought nice rotary switches to build stepped attenuators, but I don't know it will be worth the effort. Maybe this will be something I do after the fact, but chances are once it's in my rack and being put to use I won't think about it any more.

Thanks!

Paul

Hopefully next week I'll be able to resume this guy. I'm not too far from having it completed

Potato Cakes

Also, and last one for the night, I thought I saw information on calibrating this guy within this thread, but I think I was mistaken. Where can I find this information?

Edit: I there is a UA175 manual on the Sowter website, and it requires going back and forth between GR and output metering. Since I'm planning on not using the meter select function, I wonder if I can just connect a VU Meter to the output connection and proceed that way.

Thanks!

Paul
« Last Edit: May 03, 2019, 02:03:51 AM by Potato Cakes »

Phrazemaster

Hopefully next week I'll be able to resume this guy. I'm not too far from having it completed
Looks like you’re doing a beautiful job Paul!

Thanks for sharing your journey with us in all your posts.
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** * Kablooie!

Le Roux

I may be wrong but, would this not calibrate the same way as a rev d?
Mnats & Hairball have great info for calibration on their sites.
I’ll update once I’m there. 3/4 finished my unit

Potato Cakes

If it's similar to the 175 procedure then it is quite a bit different as you are balancing the tubes and not solid state components. For the 1176 you're setting the inductance for the FETs and adjusting things like distortion (which is sometimes optional).

Thanks!

Paul
« Last Edit: May 08, 2019, 04:26:43 AM by Potato Cakes »

Wire lace and a few more parts And I will have this thing done! sh*t load of work copying the original...But well worth it......
Original wire color codes ,wire bends route etc.....
Wire lacing next. Rock!!! :-)))
John

Potato Cakes

That is looking pretty nice.

I finally bit the bullet and ordered a pair of Sowter output transformers from Don Audio who happens to have them in stock. I was holding out to see if CJ was going to be able to make some but he's usually really busy and I think work has his full attention at the moment. So when those arrive I'll be able to get at least one up and running.

John, if you beat me to it, can to share how you went about calibrating/balancing your 176 build?

Also, I'm still halfway looking for the appropriate sized 0.5uF oil can caps that are working correctly. Right now I'm proceeding with the film caps I have soldered on the PSU board unless I do find some of the other type that are of the correct mounting position and terminal spacing dimensions.

Thanks!

Paul


 

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