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

Cut four large studs off. Drilled and installed proper  ( 6 ) #4-40 screws with small drive nuts.
Will bondo non used holes to simulate original.
John

Back side. #4-40 slotted pan heads like the original.

Filled holes. Gray primer ,1964 Silver Blue metallic....I guess nobody cares and is ok with 75% recreation...LOL..

First coat. Will let this dry a couple days. Then fine sand and do a final coat.
John

Just about done. As cool as Martins brackets are I am going to cut them off. And add the L shape brackets with U clip nuts. And the slotted thumb screws with point. I am going for all original look.

This pic shows how the color changes with light and angle. The rack ear on left looks gray. But its just
as silver blue as the rest.

Another shot.

Wow! John, great work. I want my 176’s  to be as accurate as yours. Thanks for all your informative posts.

Thank You Mike!
Here is the original 8/32" U clips for door hinge. These actually work better for alignment and adjustment
of front door holes. My kit did not line up that great.
The original holes drilled in the sides are also oval shaped so you can adjust up or down. Metal U clips are still used today for car door panels etc......
The 8/32" pointed thumb screws actually enable you to hit the hole quickly and turn in.
And it looks original.
Thank,s
John

sorry if this has been asked before, but do we have a replacement/source for the rectangular capcitors on the back?

They are on eBay all of the time.
And they are very good capacitors. Very low leakage on my peak capacitor tester!
John

jslstudio said:

They are on eBay all of the time.
And they are very good capacitors. Very low leakage on my peak capacitor tester!
John

Click to expand...

thanks. could you le me know what to search for specifically on ebay. i tried searching once and found nothing. guess im using the wrong key words..... cheers

Even though we've been in touch through email I can only repeat great work John!

If I only had an original unit at hands when I was starting all this. All I had were some pics from the web and schematics  ;D

Regarding the color - if John can provide a physical sample of the color I can try to find out if there's anything closer to that available as a solution for the powder coating service I use.
On the other hand - even though I still haven't had the chance to hold a vintage unit in my hands yet, the feedback I got in the meantime from several people who own one or more 175b/176 was they all vary in terms of color. Some are more like blueish grey metallic, some grey metallic and some are even just plain grey with no metallic effect at all.
Given the fact that the 175 and 176 was the first commercially available compressor by Bill Putnam back in the days, I guess they simply used what was available - so each batch is slightly different.

I experienced the same when I was doing the research for my Pultec EQP-1A project back then. I asked in a studio that has several units what color they were and they laughed at me saying "They are all different" Some blueish grey, some plain grey and some more like a greenish gray...

Anyway I'm extremely grateful for all the feedback you are mailing me on the details such as pcb dimensions etc. John - that's incredibly valuable in the mutual quest to get it right! And having a physical sample of the color of original units would be great to see how close we can get.

Yes,
Very true....On the color! BUT! You won't see much of the blue If they are not in direct sunlight! In a dark studio
they look completely gray. My 175B has a metallic blue chassis. But the transformer is plain gray. The 176 I am referencing has
the transformer painted the same metallic as chassis. But yes many variations.
And original units depending on how much sunlight exposure.  Have faded over the past 40 years. As metallics do.
The one I am copying is very blue. 
As is my 175b. And If  UA was having them sprayed in a auto shop ( more then likely ) And paints where being hand mixed.
Its a good explanation of the varying colors also.....
That is what I love about the old stuff.
Kits are great Martin! A lot of hard work getting these to people!
John

Here is how the GZ 34 is wired up on my original.
Pins 5/7 (unused )on the GZ 34 are used for the second set of 6.3v
heaters (green leads ).
No twisting of leads. The old school wire is left/right angles. Still waiting for my small pattern #6/32
nuts. So larger on for now.
The V4 tube is then hooked up via long thin 22 gauge wires to pins 5/7. This way you don't have large
mains leads going to the small tube (V4)
Thought this might be helpful to some..... Also on the original ALL of the mains leads come out of the left chassis hole. But I am using both. As that is how the leads come off my USA power supply.
John
*** I would also note that I have seen these units without the 2nd set of 6.3V heaters going to pins 5/7
on the GZ34 ***  But I am copying my own unit. And my bulb is also connected to these pins.
Original untouched mains I will add.

Thank you for all this info everyone! Tube monkey's pics were really helpful. Little request. Does anyone have more info on which type of components were used for the less obvious parts and would care to share? C1,2,3,4,5,10 for example. I assume the units in the pictures have been recapped at some point and caps aren't original?
Martin (amazing work btw!), I noticed you used two (three?) different colours for resistors. I assume brown means carbon composite. What types were the red ones?
Thanks!

The red/brown resistors most common that where used in these units where IRC and Aerovox.
1/2 watt 1% precision resistors. I have seen a coupe others but these where the most common!
Cinch made the Tube sockets,Terminal strips etc..... 
I am still searching for the red 180K half watt. If anybody bought a packed can spare two? Also the 1.1M.
I have also seen 1.21 M in these units.
Most hardware nuts are:
#4-40 slotted pan head screws with small pattern nuts except the two big caps use standard size #4-40 nuts.
Mounting bolts for mains transformer is #8/32 with small patter nuts.
GZ 34 uses #6/32 slotted pan heads with small pattern nuts.

Also after looking at my unit I was trying to find what they used for the center ground lug. Its actually one of the Cinch terminals
taken from a block and mounted upside down!

John

Here is the other way they hooked up the second set of (green ) 6.3V heaters. 
Actually four turrets on right side of pcb. The upper two are the green. Then attach the
heaters going to V4 to the rear of these turrets. Input power is below the 6.3V.
John

Thanks John! Also thanks for you mails

I was always wondering how they hooked up the heaters when I built my prototype.
Some 175b or 176 have 2 turrets on the right hand side of the PSU turret board while others have 4 - as shown in your pics.

My unit is modeled after the ones that only use 2 turrets, and in my wiring layout you can see what I came up with. But  hooking up the heaters via the unused pins of the GZ34 makes totally sense!

The only thing I find a little strange is that they used thin 24AWG wire for the further heater wiring as there's quite some current flow here.
Even though I use 24AWG in audio circuits, I mostly  go with AWG22 throughout the pretty much the entire circuit of a tube build I was taught to always use at least AWG 20 or 18 for the heaters as those thin wires otherwise might get pretty darn hot.

But obviously most unit made it through the last 60 years anyway 

Anyway - great info John - keep it coming!

Martin

Yes Railton,
***UPDATE ***Compared to my original small 26 gauge wire is correct for 90% of the wiring. ( even smaller 28 in some places ) Except heaters 22 gauge (brown/white ) Could also be 24 gauge on heaters. I bought a bunch of gauges to compare.
Most is very small gauge!
The only big gauge wire on these units  are mains transformer and the 18 gauge for bulb and on/off switch.
The turrets should have protruding back side pins. These are a bit hard to find off the shelf!

John        PS going for the original parts and details are very very painstaking.......))

Who has mounted the small 9 pin tube sockets to pcb yet?
New Old stock foot print is to big.....will have to try and bend legs in.....Martin what sockets did you use? Spec on these
pcb,s?  The holes for the original sockets are inward to small...
Thank,s
John