New Vintage Audio Restoration HQ

atmasphere said:
I hope you get to testing some vintage tubes in that soon...
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Thanks Ralph. I'm going to be replacing the main capacitor in it this weekend and go from there. I have a beautiful pair of 1945 National Union in original box type 45 tubes on their way to me. I'd love to be able to test them in it.

I'm waiting to get this beauty back. I currently have a friend who is an amp builder trying to bring it back to life. It's unique in that the top part is completely isolated from the bottom half which means you set it for the right tube using manual patch cords.

This one took 25+ hours just to strip of the almost 85 years of military grade lacquer being brushed on year after year. I've got the wood case ready to go for when I get the unit back (hopefully working). It's 2.5 feet tall.

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Going to try starting my internal modifications and learning as I go.

This is a pic of my super mint 1947 NRI model 70 tester. Honestly it looks to me both inside and out like it has never been used.

It works great, but I'm going to be replacing the giant cap with a new one. At 78 years old it's probably safe to say it needs to be updated.

From there I'll run some checks as I found a page that walks me through testing and updating this exact tester. So I'll see how the other parts of it test.

But I seriously think this has never been used.

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Michaels HiFi said:
Thanks Ralph. I'm going to be replacing the main capacitor in it this weekend and go from there. I have a beautiful pair of 1945 National Union in original box type 45 tubes on their way to me. I'd love to be able to test them in it.

I'm waiting to get this beauty back. I currently have a friend who is an amp builder trying to bring it back to life. It's unique in that the top part is completely isolated from the bottom half which means you set it for the right tube using manual patch cords.

This one took 25+ hours just to strip of the almost 85 years of military grade lacquer being brushed on year after year. I've got the wood case ready to go for when I get the unit back (hopefully working). It's 2.5 feet tall.

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Make sure you get those connections right!
Before you start testing tubes from the wild, test a few known good ones so you know if the tester is working.
Michaels HiFi said:
It works great, but I'm going to be replacing the giant cap with a new one. At 78 years old it's probably safe to say it needs to be updated.
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This is a case where just putting in a competent film cap, but nothing exotic, will work great, like these.
 
atmasphere said:
Make sure you get those connections right!
Before you start testing tubes from the wild, test a few known good ones so you know if the tester is working.

This is a case where just putting in a competent film cap, but nothing exotic, will work great, like these.
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Thanks for the link.

I agree - I want to do as few changes as possible so I don't create any new issues.

I figure light cleaning and lubing of the pots with the appropriate products, testing the tube to ensure it is good (I bet it will be), replace the power cable with a new one, and change out the cap and then see how it is at that point.
 
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I've still got 7 more wood finishes to try, however on this one I'm trying Osmo Matte.

I previously tried Osmo and didn't really care for the look. However this time I'm trying the matte finish as I've changed in the last few month from like a more glossy look to instead preferring a more matte / flat finish so it looks like a nice aged piece rather than a museum piece (with the gloss) BUT it still needs to highlight the grain nicely.

My hypothesis is that it will give a similar look to my personal favorite tri-blend of products I mixed up that is beautiful, though Osmo won't be quite as much perceived depth in the grain. This one step product will be an easier mix to use rather than always having to mix up my concoction.

Here it is still wet after coat one.

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Michaels HiFi said:
I've still got 7 more wood finishes to try, however on this one I'm trying Osmo Matte.

I previously tried Osmo and didn't really care for the look. However this time I'm trying the matte finish as I've changed in the last few month from like a more glossy look to instead preferring a more matte / flat finish so it looks like a nice aged piece rather than a museum piece (with the gloss) BUT it still needs to highlight the grain nicely.

My hypothesis is that it will give a similar look to my personal favorite tri-blend of products I mixed up that is beautiful, though Osmo won't be quite as much perceived depth in the grain. This one step product will be an easier mix to use rather than always having to mix up my concoction.

Here it is still wet after coat one.

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You are putting quite a lot more time into the idea of the finish than the OEM did, that's for sure. They likely just built it to be practical. Most of the prewar test equipment I've seen has had a darker finish, but that might well be simply because of the age rather than the original appearance.
 
atmasphere said:
You are putting quite a lot more time into the idea of the finish than the OEM did, that's for sure. They likely just built it to be practical. Most of the prewar test equipment I've seen has had a darker finish, but that might well be simply because of the age rather than the original appearance.
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Hey Ralph - yeah many of the ones I've received so far are usually white oak with oil yellow lacquer finish. The lacquer has heavily ambered over the 90 years along with embedded grime. Part of the way to tell their original color is when I take them out of the case I can see the original color (or a cleaner version of the original color) on the inside. A simple lacquer finish over white oak would have kept the wood relatively light in color.

To me these are pieces of history that represent the best of the art deco period. There were nearly constant innovations on new tube types, new ways to test them, and electrical products of all kinds. I find that so exciting to go back to that time in this way.

I've think my journey in terms of the look I like is complete: I'd like to clean up the wood and bring back its beautiful grain and charm, while having a finish that looks like it's a nice aged used look for an item that is meant to be used, and not merely put on a shelf like a museum piece.

So I've gone from satin, to semi-gloss, to gloss and now to a matte finish and mixes to find that ideal finish. I also think each piece kinda tells its own story and has its own character that will dictate what finish is appropriate for it. Some may be French Polished with Shellac, some may be my trifecta mix based on tung oil, and some may be a piece that is simply waxed. I think it's fun to have each one have their own personality.
 
Comparison of two finishes I tried this week. I like them both equally and out of the 15-20 I've tried so far, these are in the top 3 spots for sure.

I like finishes that add depth to the grain (vs looking like a flat painted finish), have a matte finish to accentuate the wood and not hide behind a fake looking gloss, and do not look like a plastic layer sitting on top of the wood (most finishes have that cheap plastic look).

First one is my custom mix - 1/3 Liberon (from the UK) Finishing oil which is primarily tung oil with driers to help it dry faster, 1/3 matte Zar oil based poly, 1/3 citrus solvent, mixed and applied in 3 super thin coats.

Second one was slightly darker wood to begin with than the first one, and I applied Tried & True Original finish (oil & wax mix). This one was harder to apply thin as it is a much thicker consistency, but if not applied super thin it will stay sticky forever.

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That's very nice work, and beautiful boxes, worth the time to take care of them.
I just got three cheapie wine boxes to hold my overflowing stacks of CDs, but I don't think I'll refinish them. Eh, maybe for the hell of it someday (if I get a round tuit). I need one of those..

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JDC said:
That's very nice work, and beautiful boxes, worth the time to take care of them.
I just got three cheapie wine boxes to hold my overflowing stacks of CDs, but I don't think I'll refinish them. Eh, maybe for the hell of it someday (if I get a round tuit). I need one of those..

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Those are great looking boxes. You could have fun trying different finishes on those!
 
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Michaels HiFi said:
Thanks! It's been a lot of fun through trial and error and learning as I go along.
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Hey Michael, just wondering how long before you do an in depth assessment of the Alan Eaton type 45 SET amps, you mentioned about doing it months ago and I’m patiently waiting all that time. I’m sure others are waiting also. Hate to say I can’t wait, but I can’t wait!
 
Dr Morbius said:
Hey Michael, just wondering how long before you do an in depth assessment of the Alan Eaton type 45 SET amps, you mentioned about doing it months ago and I’m patiently waiting all that time. I’m sure others are waiting also. Hate to say I can’t wait, but I can’t wait!
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Review on the stereo 45 hopefully next week. The mono block 45's are currently burning in. Lockwood speakers just finished burn in and I moved them to the main room today.
 
Michaels HiFi said:
Review on the stereo 45 hopefully next week. The mono block 45's are currently burning in. Lockwood speakers just finished burn in and I moved them to the main room today.
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The Lockwood looks like an excellent speaker but if you want to hear what the 45s really do you'll want a speaker about 10dB more efficient. The one in the photo you just put up is good to 30Hz. You if your plan is to use this speaker with the 45s, you might consider putting a small capacitor in series with the input to limit bass below 30Hz. I can work the math out for you if interested; if the amp's input impedance is 100K, the cap needed would be about 0.05uf or slightly larger.

Its obvious from the sheer size of the output transformers in the 45s that they use a gapped output transformer (so are not a parafeed circuit). The size is so large (what you might expect to see in a 15 Watt PP amp) because gapped transformers lose their inductance at low frequencies. This causes the impedance of the transformer at those frequencies to drop dramatically, which puts an excessive load on the power tube (IOW, hard on the tube, not a good thing to do to an expensive or rare DHT).

The 'gap' is required to prevent the DC current flowing thru the transformer from turning the transformer into a magnet and thus saturating the core- so this move vastly reduces distortion.

The larger size of the output transformer is an attempt to get around this problem. The good news, the reason why type 45 SETs are often the best sounding SETs, is that the larger transformer isn't so large that you don't get good high frequency bandwidth; I'd not be surprised if it has bandwidth past 100KHz. That reduces high frequency phase shift quite a lot. The ear perceives phase shift as a tonal coloration and it can affect the presentation of the sound stage. So I expect to hear good things about this amp in that regard.
 
atmasphere said:
The Lockwood looks like an excellent speaker but if you want to hear what the 45s really do you'll want a speaker about 10dB more efficient. The one in the photo you just put up is good to 30Hz. You if your plan is to use this speaker with the 45s, you might consider putting a small capacitor in series with the input to limit bass below 30Hz. I can work the math out for you if interested; if the amp's input impedance is 100K, the cap needed would be about 0.05uf or slightly larger.

Its obvious from the sheer size of the output transformers in the 45s that they use a gapped output transformer (so are not a parafeed circuit). The size is so large (what you might expect to see in a 15 Watt PP amp) because gapped transformers lose their inductance at low frequencies. This causes the impedance of the transformer at those frequencies to drop dramatically, which puts an excessive load on the power tube (IOW, hard on the tube, not a good thing to do to an expensive or rare DHT).

The 'gap' is required to prevent the DC current flowing thru the transformer from turning the transformer into a magnet and thus saturating the core- so this move vastly reduces distortion.

The larger size of the output transformer is an attempt to get around this problem. The good news, the reason why type 45 SETs are often the best sounding SETs, is that the larger transformer isn't so large that you don't get good high frequency bandwidth; I'd not be surprised if it has bandwidth past 100KHz. That reduces high frequency phase shift quite a lot. The ear perceives phase shift as a tonal coloration and it can affect the presentation of the sound stage. So I expect to hear good things about this amp in that regard.
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Hi Ralph - great info. Thanks for sharing.

I agree 45's aren't ideal for these speakers. That's why I keep telling my wife I need a restored pair of Altec's or better yet giant Western Electric's. :)

I'm thinking more inline with my 25 to 60 watt amps. For instance I'm sure the BAT integrated will have no problem driving the Lockwoods.
 
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