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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Thu 10, 2017 2:47 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4919
Location: Indianapolis, IN
Heck---forgot to mention what I did this evening !

Don't worry WH---as you probably know by now, the dial cord and pointer come off in one piece when you remove the tensioner spring.

Installed a heavy-duty 9V battery clip to existing wiring since I plan to use either a 9V or 6-"AA" holder to power this set.

Unfastened the aluminum antenna rods support to gain access to tuning cap and found that the far right rotor blade of antenna gang was slightly bent causing the scratchiness and shorting during tuning---after straightening, all okay. Reception & selectivity improved tremendously after tweaking the ANT & RF trimmers---what a performer ! The IF's seemed close to dead-on as they were...
Still need to replace remainder of original electrolytics, but it works & sounds excellent with only the audio coupling cap bridged with new part !

What amazes me is the very low noise floor---almost silent between stations (even at full volume), but even when a very weak or fading signal is tuned, it is clearly heard (at lower volume of course).
How is your "properly working" radio in this aspect, WH ? Am wondering if that transistor I'm using for the audio driver is making the difference---it came out of an early Zenith color TV ultra-sonic R/C receiver I scrapped many years ago and imagine it must be an extremely low-noise part for that function. The sound quality is great with the "inverse feedback" circuit---even with chassis out of the cabinet ! Looking forward to comparing it to the Royal 97 when complete...

Getting there !

John


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Thu 10, 2017 9:40 pm 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
Your description of the low noise floor seems to apply here equally. Not having both radios side by side I can't say if your output transistor mod is better or worse.

As I said earlier, these radios are constructed with the same design parameters as the best flagship Zeniths of the same time period. Dialed-in and restored we should expect them to be on par with the Royal 3000 and the 500H. My good set performs equally in reception qualities to either. Tone is better on the 500H and much better on the 3000. But that's to be expected with their superior speakers. These are definitely "poor man's AM-only Transoceanics".

It would be fun to put a longwire and ground on one of these to see just how DX one can be. Wonder how easy it would be to post-engineer a set of terminals...


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Fri 11, 2017 1:55 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4919
Location: Indianapolis, IN
Hey WH,

Only replaced the missing audio driver transistor with one salvaged from that Zenith ultra-sonic receiver---made no mods. to circuit and it still has the original matched P-P output transistors. Since you also have the low "inter-station" noise level, probably sounds very similar...

I realize that these were constructed to the best Zenith standards---one reason being that they were designed for rugged service on-board a boat and needed superior performance/reliability since they were intended to assist in navigation if necessary...

I would put the 500H & 3000 into their own categories due to size and speaker differences (I have both)---but comparing this set (by memory) so far with others in collection of similar design like the 750, 755, 755M & 97, think the sound quality is somewhat better so far (with chassis out of cabinet), but need to do side-by-sides when it's completed...

Shouldn't be difficult at all to add connectors for external antenna with all the extra room and steel chassis (especially if you use a 6-"AA" holder instead of original "battery box")---would you add a few windings on ferrite or simply add a capacitor for coupling ? You could make a small plastic or metal panel for a couple banana jacks and attach it to side of chassis by volume control using existing holes...

Am hoping to get this one completed this weekend !

John


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Fri 11, 2017 2:29 am 
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Joined: Mar Mon 27, 2017 4:29 pm
Posts: 51
The "junker" 780 I got was modified and added two external ports, one for ground and one for a LW antenna. It looks like inside it was also re-soldered to connect the LW antenna to the external port. I can post pictures if you want. In fact I tried sticking a long wire in the lW port but still didn't find an european LW stations (although< I did not unwind the wire...too lazy!)


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Fri 11, 2017 3:40 am 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
I'd like to see the pix. Guess my idea wasn't very original... My plan would have been to study the Royal 3000 schematic and replicate the A and G terminal wiring exactly into the Navigator. Perhaps even try to locate the exact strip from a parts 3000. Perhaps that's just what your previous owner did to his.

I can't compare those other models -- this navigator is my only Zenith leather lunchbox. I also have a 500H and both Transoceanics (1000 and 3000). All 4 have very nice silence between stations -- the 500 being worst and the 1000 being best. The 3000 has by far the best audio. It gets heavy use daily in the living room. Playing now as I type.

Probably all of them aren't maximum tweaked to optimum factory settings though. I imagine the 3000 could be brought to perfect inter-channel silence. Maybe the 500H too.

Note to self: learn how to factory align these things...

My 3000 is a workhorse and isn't detailed or particularly nice cosmetics. The 500 is pretty restored and sees little use. Turned on today several times though, still loud and clear.


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Fri 11, 2017 4:14 am 
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Joined: Mar Mon 27, 2017 4:29 pm
Posts: 51
Ok, hope this picture makes sense. There are 2 nonstock jacks going to the outside of the leather cabinet on the side opposite from the headphone jack.
What this picture shows is the 2 jacks from the inside.
The ground jack is shown with a red wire that goes to the metal chassis.
The upper jack is connected by a green wire to the LW antenna (I haven't taken it out of the case yet to see exactly where that wire terminates but I assume it connects to the LW antenna which is one of the dual ferrite rods.

Concerning reception, I think the 790 and 97 outperform the 780, but it might just be the ones I have. The 760 is pretty good, too. I have heard (JayAllen) that the 755s are good too but I dont have one yet. The Zenith 1000s are outstanding. The quietest AM reception I have is an old analog Grundig Satellit 5000. On AM
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LW ant and ground jacks 780.jpg
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it seems like the set is off until you tune a station.


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sat 12, 2017 3:16 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4919
Location: Indianapolis, IN
Hello All,

Chassis complete ! All electrolytics replaced, tuning pointer guide cleaned, reassembled and "tweaked"... Both AM & LW (unknown beacon broadcasting Morse code boomed in) work great---the band switch is a bit noisy when rotated, but contacts fine when in position. Noticeable difference in NAV position compared to NOR when AGC is functioning...

Need to give all leather wrapped cabinet parts a "sunbath" inside & out mid-day tomorrow to help get rid of remaining strong "musty" odor before chassis can "go home"...

May need to drill & tap hole in compass dial shaft for screw since the "plastic melt" which retained it originally had to be cut off for removal, but will see if there is enough "stub" left to re-melt first...

Almost there !

Chassis pics below.

Looking forward to seeing WH's external ant & gnd connection solution...

John


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1ARF 780 BAT BOX CLN.jpg
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2ARF 780 OLD CAPS.jpg
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3ARF 780 SPKR BACK.jpg
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4ARF 780 TUNING POINTER GUIDE CLEAN.jpg
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5ARF 780 CHS BOT BEFORE.jpg
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6ARF 780 CHS FRT W-O SPKR BEFORE.jpg
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7ARF 780 CHS FRT AFTER RECAP.jpg
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8ARF CHS COMPLETE FRT.jpg
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9ARF CHS COMPLETE REAR.jpg
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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sat 12, 2017 9:37 pm 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
Got #3 playing loud and clear.

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After removing the speaker, the problem is actually visibIly apparent. See it?

As it stands now:

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All spaghetti and alligators but room-filling static-free hiss-free sound.

Will put it all back together in the next day or two. Outside work to do now.

Happy.


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 1:46 am 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 3822
Location: Sunnyvale CA
WeekendHacker wrote:

After removing the speaker, the problem is actually visibIly apparent. See it?


Not for sure, , pretty fuzzy and small, but I see at least 8 potential issues - "brown sludge" capacitors, IEI/Nashville ceramic tube electrolytic capacitors, one IEI plastic (dual, I think) electrolytic capacitor, but I imagine that the issue is probably that the headphone jack is clocked where it can touch the speaker magnet bracket.

Brett


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 2:37 am 
Member

Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
Nope. The caps were all bad but that wasnt the deal breaker. Thought maybe John would see it. Actually the problem was visible in the 2 pix I posted 4 days ago. See it yet? Compare and contrast:


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 5:11 am 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4919
Location: Indianapolis, IN
Hey WH---Guess I should have looked here before checking PM's ! Surprised I didn't notice the other day, but didn't look at the polarity, just that they were older Nichicons... Sure glad it was an easy fix ! Looking forward to seeing it all back together...

Got this one done today (except for attaching rear cover) !

Gave it a 5+ hour "sunbath" on deck table from around noon to 5:30 PM---moving pieces periodically to give all good exposure to the UV inside and out... Seems like most of odor is now gone, but time will tell... Buffed it once more with clean towel and blew off before assembly.

Forgot to mention yesterday that someone had worked on this previously as some of the hardware was missing---the two bottom speaker mounting screws and the one for the right side of aluminum support for antenna rods. Fortunately, had enough plastic left in compass dial plastic mounting stud to re-melt it... Still need to figure a way to reattach rear cover---Jim (Brownie45) offered strip of pig-skin for the Royal 97, but neither that set nor this one have enough clearance to attach anything that thick. Have seen some flexible, sturdy, thin plastic used for parts cases where it also functions as the hinge for lid---maybe this could be tucked/glued between leather & fiberboard on both case and cover ???

Radio looks much better and works great as mentioned before. Sound is very good, but after reassembly decided my previous assessment was a bit exaggerated...

Pics below including one with Royal 755 of same vintage and another with the newer/superior Royal 97 "Super" Navigator...

Thanks again, WH !

John


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ARF 780 NAV CASE ASSMBLD INS CLN.jpg
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ARF 780 NAV CMPLT INS.jpg
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ARF 780 NAV CMPLT FRT.jpg
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ARF 780 NAV 755.jpg
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ARF 780 NAV 97 SUPR NAV.jpg
ARF 780 NAV 97 SUPR NAV.jpg [ 221.32 KiB | Viewed 820 times ]
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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 6:19 am 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
No sweat. Got me off my lazy behind to fix mine as well. My #3 is now functionally way #1. I'm very happy with its performance level now. Very hot set. Too hot, makes me think the royal 200's driver transistor may not be a perfect replacement. Might be overgaining it a little bit. Not that that's a bad thing...

Wonder if a spritz of Febreeze would finish off the basement smell.

I Elmer's Glued the hinge on my daily driver and FWIW it looks pretty respectable and has held up for over a decade. I wouldn't want to use it as a daily hinge but once every few years to install new batteries doesn't stress it much.

Awhile back somebody posted about a chrome-paint marker pen that looked great on his plastic grille. Wonder if this would be a good solution for the knobs. The yellow plastic looks bad next to your 755. 3 of my 4 are as bad or worse. One has enough chrome left to let me know they should all be chrome.

Otherwise your 780 looks sweet! Great job on it. I hope mine turns out half as well.


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 2:29 pm 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 3822
Location: Sunnyvale CA
WeekendHacker wrote:
Nope. The caps were all bad but that wasnt the deal breaker. Thought maybe John would see it. Actually the problem was visible in the 2 pix I posted 4 days ago. See it yet? Compare and contrast:


That clears it up, it was quite unobvious which parts were the old and which were the new. And where did you get the new caps? They look gigantic and ancient, too. The 100 mfd axials I get are much smaller than the originals, these look bigger or much bigger. And you left the little (maybe 16 mfd) IEI cap? That one is almost certain to be bad.

Brett


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 2:56 pm 
Member

Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4919
Location: Indianapolis, IN
Thanks WH---am glad you were motivated to put the time in #3 as these are too good of radios to just sit in a box ! Will be watching for "complete" pics... Considering that the chrome plating wore off the knob plastic so easily, don't think paint of any kind would hold up well to frequent "fingering"---at least they're thoroughly clean ! Some of the 755's knobs used black base plastic as you can see on the tuning knob of mine---would be great to find a set of these for the 780 as the black looks good when all traces of old chrome is removed...

Tried NAV mode today with several stations and the radio has a very sharp null as expected when pointed toward locations...

Listening to favorite DX oldies station right now in family room now while on-line...

John


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 4:13 pm 
Member

Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
Brett_Buck wrote:
WeekendHacker wrote:
Nope. The caps were all bad but that wasnt the deal breaker. Thought maybe John would see it. Actually the problem was visible in the 2 pix I posted 4 days ago. See it yet? Compare and contrast:


That clears it up, it was quite unobvious which parts were the old and which were the new. And where did you get the new caps? They look gigantic and ancient, too. The 100 mfd axials I get are much smaller than the originals, these look bigger or much bigger. And you left the little (maybe 16 mfd) IEI cap? That one is almost certain to be bad.

Brett


Sorry for throwin' you a curveball, Brett. None of the capacitors shown are in the set anymore. I spent a few days chasing wild geese because I wasn't observant enough to notice a previous repair job placed the black capacitors in backwards, and just wanted to see if I was alone in this respect. So I re-posted a pic of the capacitors just before removal. The new replacement caps are tiny in comparison and are jumpered into circuit in the 2nd pic. Will detail them clearly in a future post.

The black capacitors were installed so professionally and were of a vintage that made me believe they were factory. Obviously not. John and I theorize that the mistake/oversight cost the long-lost serviceman a couple of output driver transistors, and he must have purchased two "parts radios" chasing the problem before giving up and tossing the whole lot. It nicely explains the as-found condition and pricetag of all 3 sets pretty reasonably.


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Sun 13, 2017 4:57 pm 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
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Fell asleep with it playing oldies station thru the larger speaker. With the additional bass response its tone rivals the TO-3000.

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The caps going in are 105C Xicons from Mouser. My hobby is antique TV sets where electrolytic caps are in the 450-Volt region. The majority of my stock of new caps is way too huge, but was lucky to have a bag of 25V 47uFs as well. The two black Nichicons will be replaced by a pair each in parallel (pictured in alligator clips), the 16uF and 50uF Nashvilles by one each, and the tiny 3uF by a tiny 5uF I scavenged from the pc board of an old lightning-struck dish receiver. All replacement parts will be less than half the physical size of what came out (even after paralleling).

And to avoid confusion:
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The remaining IEI is clipped out of circuit (as shown). The green alligator above it is supplying its function at the moment. The negative lead is not currently reachable by wire cutters.


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Tue 15, 2017 3:23 am 
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Joined: Jul Wed 08, 2009 12:17 am
Posts: 904
Location: Wyoming, Michigan
#3 is off life support.
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No surprises. Re-used spaghetti tubing from old caps. New 105C Xicon installed here.
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Doubled-up Xicons still smaller than the black Nichicons. Had a pair of vintage 100uF caps that still test good, almost used them but opted for new.
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Didn't have heatshrink tubing but they fit tight in a section of plastic drinking straw. Gave me something to write on. Installed:
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Volume-control shaft was sloppy. A brass bushing is soldered to the chassis to stabilize it. It somehow broke off at the solder joint. Re-flowed that as well:
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Radio still plays perfectly. Did the NAV test as well and observed the sharp null at the expected orientation. The NAV function functions perfectly. Chassis complete.

Both my cases are more rough than John's. Will start working on them shortly...


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Aug Tue 15, 2017 7:25 pm 
Member

Joined: Nov Fri 14, 2014 12:22 am
Posts: 108
Location: Howell Michigan
xrhonda91 wrote:
Hey Wold,

Did you get all the tear spliced together ? Any other damaged areas on speaker ? I've used both water diluted Elmer's wood glue and Superglue to repair tears if edges of damage still come together well and they worked fine...

That top mounted "compass dial" is cheaply mounted by the tip of plastic shaft being melted on inside of case---had to cut off the "melt" to remove. Am thinking of drilling and tapping to accept a 2-56 screw if possible to reattach.

John


A long time ago I had a 12" (IIRC) in a RCA Hi-Fi that had a tear in the cone. I repaired it by using clear fingernail polish and multiple layers of Kleenix. One layer at a time on both sides of the cone. Took a few days but it worked. Just an FYI to try out.


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 Post subject: Re: Zenith Royal 780 Super Navigator "gift" project...
PostPosted: Sep Mon 04, 2017 3:11 pm 
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Joined: Oct Mon 26, 2009 10:02 pm
Posts: 4919
Location: Indianapolis, IN
Just wonder if the fingernail polish would do better if thinned a bit with acetone ?

Forgot to post several days ago that after viewing the inside of a Royal 760 that the chassis appears nearly identical to this one...

Any further progress W.H. ?

John


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