Zenith G2952 "St Regis" porthole restoration

[bandersen]

A customer dropped this off last year and I'm finally getting around to it. Apparently, it had been rented out as a prop for years and is a little rough.


Worse issue cosmetically is brown enamel paint was slopped on the top and upper sides.

Also need to track down the inner power/volume knob. It came with an Admiral knob stock on!








29G20 chassis with power supply down below.
Partial recap on the power supply. Main chassis appears to be 100% original.
Curious that is has the tuner on the left.

[bandersen]

I expected the 16EP4 to have gone to air and secured an all glass 16DP4. However, after letting it cook a while, the EP4 came to life.


The chassis is absolutely pristine under a thick layer of dust.


A few original tubes still in the set.


Every single power resistor is open! Dropped $25 for 7 new ones.


Very roomy under the chassis and easy to recap.


I'll finish detailing the chassis later. Next up, first power up attempt! I love that Zenith used a snap conector on the HV lead that works with a conventional CRT.

[bandersen]

First light!
It took a while to realize there's a, RCA jack in the back for a pilot lamp interlock. It needs to be shorted for the lamps to illuminate. I assume it can get annoying while watching the set to have those on.


At full power with 5U4s installed, I got a raster!


Height increased


After a lot of control tweaking, a stable image was achieved


Hmm. I think the huge focus coil is messing up my little 5AXP4 CRT.


Here it is with focus coil unmounted. Rather washed out even with brightness turned all the way down. Still have 10 electrolytics to replace on the main chassis.

[Chris K]

Congrats!

[Yamamaya42]

Since you mention “5U4s”, I have always wondered, is there really a big dif in the 5U4/5U4G/5U4GB, and so on.

This site seems to list differences, but does it matter in a TV?
https://300guitars.com/articles/rect...ge-drop-chart/

My set has the OEM RCA 5U4-Gs, they still work but are old and a bit worn, I can see a bit of the heater material has come off and is floating around in the tube, to get EXACT replacements will hurt a lot cause of the insane prices they want for them, thanks to the audiophile market.

$170 for a NOS RCA 5U4-G is insane!
The GB has a larger voltage drop, 6-7 volts and has a much less crazy price, will that drop of 6-7 volts in the G vs the GB really matter much?

The GZ37 has an even better voltage drop rate at 37v, but it's price is even MORE insane for NOS, WTF!

And there is also the 5AR4 / GZ-34 , not so over priced, but with a voltage drop rate of 10v, may be too harsh.
So it seems is is 5U4-G and pay, and pay A LOT for them, or 5U4-GB, and have slightly lower voltages.
To me it makes no sense for the prices to be so damn high.

[bandersen]

No, it will not make any difference in a TV.

You can throw sense out the window when it comes to tubes used in audio gear.

Pretty much all of the components (caps, resistors, tubes etc.) have a wide operating window. Plus, there's no voltage regulation so all the voltages vary with what's coming out of your outlet. That's why you have so many controls to compensate.

[Chris K]

Originally Posted by bandersen

You can throw sense out the window when it comes to tubes used in audio gear.

Absolutely! Vintage and new tube amp audio have gone off the charts in the past couple of years. The turntables and tuner/amplifiers we were so proud to have in the 1970s are commanding outrageous prices on auction sites. A basic, entry level Marantz tuner in good shape will fetch anywhere from $1,500 to $2,500. The higher end Sansui and Pioneer stuff is more insanely priced. I know they were all solid state and not tube gear but it is an indication of how all old audio platforms have rocketed up in price.

[jr_tech]

“The GB has a larger voltage drop, 6-7 volts and has a much less crazy price, will that drop of 6-7 volts in the G vs the GB really matter much?”

But the drop through the GB was measured at a higher current! I suspect the drops are nearly the same @ the same current.

jr

[Kevin Kuehn]

findatube.com shows new 5U4G for $24, used $10. Who knows if they're in stock. Ebay or any audio/guitar amp site is about the last place I'd look for a NOS tube.

[Yamamaya42]

If there really is no difference that matters then, I do have a pair of NIB NOS Raytheon 5U4GBs that I was keeping for other newer sets, I just find it nuts that they have such a markup for what is more or less the same tube 5U4G/5U4GB.

And insane that my Sansui 9090 amp would go for over $4000 now!

[Electronic M]

Anything 5U4 based will replace a 5U4G, but the opposite isn't always true. A set that specs a high current rated 5U4 variant may not be happy with a lower current G... At least long term.

[Chris K]

Originally Posted by Yamamaya42

If there really is no difference that matters then, I do have a pair of NIB NOS Raytheon 5U4GBs that I was keeping for other newer sets, I just find it nuts that they have such a markup for what is more or less the same tube 5U4G/5U4GB.

And insane that my Sansui 9090 amp would go for over $4000 now!

Did you do an eBay search and find that price? The prices are crazy. Vintage electronics repair businesses are overwhelmed with restoration work.

[Yamamaya42]

Originally Posted by Chris K

Did you do an eBay search and find that price? The prices are crazy. Vintage electronics repair businesses are overwhelmed with restoration work.

Exactly, I took a peek on evil-bay for what restored amps like mine were going for, and it's crazy, mine is not “ restored” but is working, could use a rebuild, it too is something I saved from destruction when I saw it in my HS electronics class. Weighs a ton, so you know it's built well!

[bandersen]

Started work on the cabinet. Plan is to refinish the top and touch up the rest.



Underneath all the crud, the veneer is in good condition.

[John Marinello]

The button below Zenith is what operates the dial lights.
You won the lottery on the 16EP4! Those are very difficult to find.
Curious if you determined that there is enough room for the 16DP4?