GROUP BUY: Universal Audio 176 - a 100% faithful recreation of a legend! CLOSED!

[BramK]

Very helpful! Thanks for the general walkthrough Paul, and the PSU mounting tip, Molten. I'll post progress pics and any questions that come up along the way, aiming to get started next week.

 

[core13]

I would like to know if the 2 psu resistor value must be changed when using the 370bx because it deliver less voltage.

also if someone know what are the original radiall film capacitor C3 and C4?

thank you

 

[Phrazemaster]

Are these capacitors OK for the build?

I'm not sure the quality of Sprague paper in oil - I read somewhere the paper breaks down and that can degrade/damage the capacitor...

Thx all

PS having trouble finding the right lamp holder...does anyone have a part number or know what exactly was used? Thx!

 

[Potato Cakes]

Are these capacitors OK for the build?

I'm not sure the quality of Sprague paper in oil - I read somewhere the paper breaks down and that can degrade/damage the capacitor...

Thx all

PS having trouble finding the right lamp holder...does anyone have a part number or know what exactly was used? Thx!

If the can is sealed, it measures correctly, and fits the chassis you should be fine. I believe what you are referring to is when the paper is exposed, like I have on some old Colins modules. When the paper is exposed the material can form holes/become porous, and then the oil dries out.

The correct lamp holder is posted earlier in this thread.

Nice find, by the way. I had searched for quite a bit before I gave up and went with some nice film capacitors.

Thanks!

Paul

 

[Phrazemaster]

Thank you Paul. I think if you keep looking those caps pop up from time to time.

As far as the lamp holder - yes I saw that link (I read this whole thread) - but that link doesn’t work.

I tried taking just the text from the link and doing a search for that, but no go.

If anyone has extras I’m looking for two lamp holders and jewels.

Thanks everyone!

Mike

 

[BramK]

Alright, first setback going through my parts inventory. Looks like I had ordered the wrong Sowter 1285e and I'll need to drill some holes in the chassis to fit this one.

Does anyone foresee any hum/noise issues with either of these orientations? If so perhaps I should see if it's possible to replace it with the numetal can.

 

[Phrazemaster]

Hey Bram,

There is only one Sowter 1285e.

The one you bight looks like the “k” version.

I bet you could contact them and exchange it. There’s a price difference maybe $50-60.

Good luck,

Mike

 

[BramK]

Hey Paul, I've been trying to decipher from your build photos how you mounted your Hayseed can caps to the chassis, but it's unclear. Any insights there?

How are folks mounting the API Meter?

And thanks Phraze... Looking back through my emails from last year, it looks like I ordered and paid for the numetal version but was sent the open frame by mistake. I've contacted Sowter to see if they'll exchange it.

 

[Phrazemaster]

And thanks Phraze... Looking back through my emails from last year, it looks like I ordered and paid for the numetal version but was sent the open frame by mistake. I've contacted Sowter to see if they'll exchange it.

WOOT!  ;D

 

[Phrazemaster]

Hey Paul, I've been trying to decipher from your build photos how you mounted your Hayseed can caps to the chassis, but it's unclear. Any insights there?

Kosi posted a link to a mounting plate awhile back; not sure if it's for the right capacitor (sorry), but may this helps...

you need a mounting plate inside
https://www.tubesandmore.com/products/mounting-plate-metal-1-can-capacitor

you can also use one for the other cap with 4 "slits"

 

[Potato Cakes]

Hey Paul, I've been trying to decipher from your build photos how you mounted your Hayseed can caps to the chassis, but it's unclear. Any insights there?

How are folks mounting the API Meter?

And thanks Phraze... Looking back through my emails from last year, it looks like I ordered and paid for the numetal version but was sent the open frame by mistake. I've contacted Sowter to see if they'll exchange it.

The mounting plate are indeed how those caps are mounted. Be sure to get the appropriate sized ones as each cap needs a different one.

There is mounting hardware included with the API meter. It fastens to the front panel similar to how the Hairball meter is installed on their FET rack builds. I think you can see how it's done on some of the photos posted on this thread.

Thanks!

Paul

 

[Potato Cakes]

I would like to know if the 2 psu resistor value must be changed when using the 370bx because it deliver less voltage.

also if someone know what are the original radiall film capacitor C3 and C4?

thank you

The wiring guide prescribes either the 372 or 370x with no correction to the PSU, so I would imagine you would probably be fine. However, if you are looking to modify the PSU resistor values to accommodate the power transformer, you can simply do some good ol' Ohm's law as you know the target voltage drop per resistor based off of the UA176 schematic to calculate amperage then use that and plug in the voltage based on the 370x (370x voltage from the GZ34 minus the target voltage).

Thanks!

Paul

 

[moltenwok]

Here's a side shot of the mounting

 

[BramK]

Here's a side shot of the mounting

Ahah! That's what that random baggie of hardware I had floating around was for.  ;D Thanks for the capacitor mounting plate reference, I had missed Kosi's response.

 

[core13]

The wiring guide prescribes either the 372 or 370x with no correction to the PSU, so I would imagine you would probably be fine. However, if you are looking to modify the PSU resistor values to accommodate the power transformer, you can simply do some good ol' Ohm's law as you know the target voltage drop per resistor based off of the UA176 schematic to calculate amperage then use that and plug in the voltage based on the 370x (370x voltage from the GZ34 minus the target voltage).

Thanks!

Paul

Thank you paul
I think I will use the 370bx
I will do my math and see

edit.

the 370bx deliver 2x275v instead of 2X325v
on the schematic going from ac to dc with GZ34+Choke 10HY add 40v
maybe with the 370bx it will add also 40v or maybe less like 35v
so 275+35v=310v

310V is the voltage needed after the first dropping 1,5k resistor (R44).
too much resistance is going to reduce  the voltage on the 12BH7 plate.

so do I need to remove completely the first resistor?
put only 300ohm or something and lower the second resistor (R43)?

 

[Phrazemaster]

Some little things.

Question about the large resistors, 1.5K and 10K:

I found an Ohmite wire wound for the 1.5K 20W; it is not "non-inductive." I'm a little concerned if this matters? I know when current stops in an inductor, there's a large spike/kickback...usually this is handled with diodes. Maybe I'm being paranoid but somehow I doubt the originals were non-inductive.

Anyway this is what I found. Are these all right?

1.5K:

https://www.alliedelec.com/product/ohmite/b20j1k5e/70022623/?gclid=CjwKCAjwnMTqBRAzEiwAEF3ndnh7BY-Z6EbyxBlVzrzvmh5S1WDv3yUOskEy7S2d0_JFY998KYlM-xoCriQQAvD_BwE

10K:
https://www.alliedelec.com/product/ohmite/b12j10ke/70022596/

Also, being somewhat of a purist, I'd love to use NOS parts where possible. Martin's build guide so far is marvelous - an outstanding achievement! I'd love to also know what actual parts were used. I've gleaned some tips from John (jlstudios) in some threads (thanks mate!) - but I'd love to know more precisely which exact parts were used where.

For example, the resistors R36, R37, R38 all look like carbon comp to me. Is that true? What was used - AB? This is the kind of info I'd love to have. I'm not that great at just looking at a picture and instantly knowing what the part is.

Thanks for any insights into any of these questions.

Mike

 

[Phrazemaster]

Another Question about the CE cap (C11). There's 2 listed at tubesandmore.com

https://www.tubesandmore.com/products/capacitor-ce-mfg-475v-20202020-f-electrolytic-25-height

https://www.tubesandmore.com/products/capacitor-ce-mfg-475v-20202020-f-electrolytic

They both have same electrical specs, but one is shorter and fatter and the other longer and skinnier. Or so the pictures seem. But they both claim to have bottom diameter of 1.375".

Anyone has bought this cap (C11) and knows which is the right one?

Thanks,

Mike

 

[Potato Cakes]

Another Question about the CE cap (C11). There's 2 listed at tubesandmore.com

https://www.tubesandmore.com/products/capacitor-ce-mfg-475v-20202020-f-electrolytic-25-height

https://www.tubesandmore.com/products/capacitor-ce-mfg-475v-20202020-f-electrolytic

They both have same electrical specs, but one is shorter and fatter and the other longer and skinnier. Or so the pictures seem. But they both claim to have bottom diameter of 1.375".

Anyone has bought this cap (C11) and knows which is the right one?

Thanks,

Mike

Regarding the externally mounted capacitors, you have plenty of room in relation to adjacent components that it wouldn't matter if you go with the fatter ones. For the one that mounts to the PCB, you will probably want to get the skinnier version to ensure it fits through the opening in the back of the chassis.

If you're really uncertain then go here:

https://hayseedhamfest.com/products/ua-176

This is what I used and it works great. I believe this is where Martin got his caps for his prototype.

Thanks!

Paul

 

[Potato Cakes]

Thank you paul
I think I will use the 370bx
I will do my math and see

edit.

the 370bx deliver 2x275v instead of 2X325v
on the schematic going from ac to dc with GZ34+Choke 10HY add 40v
maybe with the 370bx it will add also 40v or maybe less like 35v
so 275+35v=310v

310V is the voltage needed after the first dropping 1,5k resistor (R44).
too much resistance is going to reduce  the voltage on the 12BH7 plate.

so do I need to remove completely the first resistor?
put only 300ohm or something and lower the second resistor (R43)?

On the spec sheet for Electro Harmonix branded 12BH7 it shows maximum plate voltage for class A circuits listed at 300V and for typical applications 250V. With all things being equal and you do end up with with 310V after AC to DC conversion with the 370bx transformer and you also get the 50V drop across R44 as shown on the schematic, that will still put you at 260V, which is above the typical plate voltage from the 12BH7 spec sheet. If the voltage does indeed prove to be too low, you can try using something like 1k for R44 and see if that satisfies the power requirements.

I would not recommend or condone leaving off any resistors from this PSU for safety purposes.

Thanks!

Paul

 

[Phrazemaster]

Regarding the externally mounted capacitors, you have plenty of room in relation to adjacent components that it wouldn't matter if you go with the fatter ones. For the one that mounts to the PCB, you will probably want to get the skinnier version to ensure it fits through the opening in the back of the chassis.

If you're really uncertain then go here:

https://hayseedhamfest.com/products/ua-176

This is what I used and it works great. I believe this is where Martin got his caps for his prototype.

Thanks!

Paul

Thank-you Paul. It's strange they have two nearly identical - and also fail to put the dimensional differences on their site...

Edit: my real concern is I don’t know the quality of the hamfest caps. I trust in the CE Mallory name more than off-label generics...although the CE’s are only rated to 65C and the hamfest to 105C...