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Old 5th December 2011, 02:35 PM   #1
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Default 1960 Zenith TV/Stereo Combo-WOW!

Okay, here's one for the old-timers who remember the days of vacuum tube hi-fi & TV sets.

I own a gorgeous 1960 Zenith TV/stereo combo that amazingly, still works. Well, almost. The only thing that doesn't work is the phonograph. On one occassion, it did work so I know the turntable motor is fine. Problem is something trickier...I suspect selector switch.

On this model, you turn selector switch from "Off" to either "Radio" or "Phono." If you select "Phono" then you open the other cabinet lid and turn the turntable "On." Usually, nothing happens; the amps don't fire up and the motor doesn't turn.

The one occassion where phono did inexplicably work, the sound was strange and tinny (unlike the radio which shakes the foundation of the house). The left channel barely came in at all, even when amps were switched to "monoraul" setting. This is not an issue at all with radio.

Bad tone arm cartridge or loose wiring would explain some of this except for the fact that it's the same even when amps set to "monoraul" setting.

I replaced the 5Y3GT rectifier and pre-am/amp tubes, partly why radio sounds so good...please tell me what I should do about the phono problem! Thanks!
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File Type: jpg Zen-combo-stereo.jpg (52.3 KB, 147 views)
File Type: jpg Zen-combo-phono.jpg (48.1 KB, 147 views)
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Old 5th December 2011, 03:28 PM   #2
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Phono can be more affected by corrosion of the tin and brass connectors and switches because the voltage is so low. Pink eraser, rub rub, and alcohol wash.
It is a shame you replaced the tubes without measuring, usually on hifi equipment they don't wear out much. Rectifiers are the worst to go, followed by power output tubes at 5-10000 hours. My signal tubes in my 1961 dynakit equipment are original, as are all the signal tubes in my 1968-69 organs.

What does go based on the calender, is the electrolytic capacitors. These are tall cans with triangles, squares, moons for plus, or aluminum cans with cardboard wrappers with a plus on one end. They are full of water and sealed with rubber. How are the tires on your 64 mustang? Oxygen attacks rubber, powered on or not. You may get a brief second life before the water boils out past the bad seals. I replaced 70 caps in my 1968 organ, which hextupled the volume, added bass & treble, and made functions work that were dead. I've recapped the ST70 power amp 3 times since 1971 when I bought it with bad caps. You can buy 3000 hour up rated radial lead caps now, maybe get off the cap replacement treadmill. I put them on solder terminal strips from tubesandmore.com under the deck. Remove the old cans from the circuit, they tend to short out when dry. Read tube learning and high voltage for newbies sticky threads at the top of the tube amp section before touching any metal under the deck. Electrolytic capacitors can kill, there are simple rules that must be followed. I survived my encounter with a 20 uf 400 VDC capacitor in 1966 in a 6V car radio before silly things like HV safety were covered in the Ford Car manual.
The TV may need tubes, they tended to burn them up more than stereos, which is why every corner grocery had a tube tester/sale point. Color TV's may also need alignment, they were always fuzzy which is why my parents didn't buy color until 1970. The 1954 Philco also had only one electrolytic capacitor to go bad.
In the end you might have to get a new phono cartridge.R**** S***** internet still carries phono cartridges I think. I'd test the wiring with a sine wave generator at 25 mv AC for magnetic or 1 VAC for ceramic before buying one. I'm building one out of two transistors from the GE transistor manual edition 7, I'm into build 5 today, I'll post something if it ever works. I Tried an XR2206 IC sine wave generator last week, the solder prefers to stick to the pcb rather than to those tiny IC socket pins. Never could get all 12 wires connected at the same time.
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Last edited by indianajo; 5th December 2011 at 03:38 PM.
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Old 6th December 2011, 01:36 PM   #3
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Thanks, that is helpful. I tried again last night and found that if I gently massage the "Selector" switch right and left when it's on the "Phono" setting the turntable powers right up! So I think you're right, years of oxidation or whatever on the contacts there.

Sound was a shade better but still very tinny compared to everything else. I pulled the needle out of the cartridge, seems newer and sounds clean, not worn or chipped. Wires in cartridge appeared clean and soldered in tightly, though left channel still weak and muffled while right is way too treble.

I found the schematics for this unit can be bought online for $15...might not be a bad investment. I ordered some NOS tubes for the TV also, even though it fires up. Picture tube is very bright and high contrast so original owners must not have watched it much. I'm told you can play video tapes on these sets if you use a 400ohm to 75ohm adapter. Surprising because when I was young the word on the street was that solid state gadgets were totally incompatible with tube TV sets.

I'm beginning to suspect there may be one of those "RIAA curve" circuits built into the selector switch "Phono" option and that is what's not working now, leading to tinny phono audio.
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Old 6th December 2011, 02:50 PM   #4
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Treble doesn't drain the electrolytic caps like the bass does. It takes full current for 1/64 of a second to reproduce a low bass note. Your power amp cap is probably empty before a bass note is 1/2 done. Back to post 2- electrolytic caps. If only the record player is tinny, then an electrolytic coupling cap (small) in the signal path might be blocking the bass. I replaced 8 each 10 uf 50v caps in my organ preamps with film caps where they would fit, and 50v ceramic caps (Z5U) where the film wouldn't fit. Really added bass.
A WP25 iron is good enough to put the wires on them, but it takes a 130 W pistol iron or a butane torch to get the can tabs out. Newark.com is having a sale on 10000 hour 350-400-450 V caps right now. Click passive components, click capacitors, click aluminum electrolytic. For P.S. caps set minimum of 350V and 10 uf, click show results. Get some before they are gone, 1000 hour caps like 90% of stock might wear out in a year or two. Your coupler caps will be smaller, read the value on the print or can, get something close. Exact match won't be possible, stocked values now are 10,22,33,47,68,82 etc. Go a little up on size or voltage as necessary to buy something in stock. Radial lead, axial lead, snap in package caps will all fit on t&m solder terminal strips. 600V wire from t&m might be necessary to replace too-short wire for re-routing. triodeelectronic.com is another tube specialty supplier that has this stuff, good service, but their 600v wire is fabric insulated. Newark teflon wire at 600V is $60/100 ft, too high because of ROHS.
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Last edited by indianajo; 6th December 2011 at 02:58 PM.
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Old 6th December 2011, 03:01 PM   #5
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Glad the hear that it is almost functional. My family owned a couple of Zenith TVs and a console (no TV) in the 60s and 70s. I always liked them, but none were as pretty as this. Some of the old repair guys I knew said they enjoyed working in Zenith as they were designed for easy service.

You can watch just about anything on the TV with the right adapter. Yes, you'll need a "Balun" to go from the 75 ohm coax on the VCR to to the 300 ohm twin lead on the set.
You can buy an RF modulator if you want to play DVDs or Blu Ray. They don't cost much. They take the audio and composite video out of the back of the disc player and put it on channel 3 or 4. Works well.

You can also get one of the HDTV converter boxes that will pick up digital broadcasts and convert them to an RF signal your set can use. Standard cable TV should connect up just fine, with the Balun. I just got rid of an old Magnavox console here that we ran that way. The picture tube was very dim

Enjoy it, she's a beauty!
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Old 6th December 2011, 03:25 PM   #6
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Thanks Indianajo, sounds like you've really got a handle on what the problem is. Wish it were something easier to fix, I never "operated" on one of these in my life so no experience with caps, etc. I'll just have to live with tinny phono.

That's a great tip, Pano! It would be great to watch some of the old black & white shows on this vintage set..."What's My Line," "One Step Beyond," "I've Got a Secret," etc. :-)

Great forum and awesome input from everybody...really helpful. Thanks!!!
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Old 6th December 2011, 05:08 PM   #7
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Well, if you don't want to do it yourself, you're in the wrong place. I started soldering with the $5 RS meter and the 1959 Ford Car manual. I haven't designed and scratch built an amp yet, but am working up to it.
If you can't disassemble the dirty phono switch to clean the contacts, you can spray De-Oxit into it to eat off the oxide. It has a corrosive chemical in it, so you will probably have to do it again in a year or so. I won't use the stuff on anything I can reach with an eraser.
I watch TV on a DTV converter, using a roof UHF Yagi antenna. I'm too cheap to pay for commercials on cable or satellite. The only place you'll see those shows besides pay TV is the -2 and -3 channels above the broadcast stations. They tend more to sit-coms, though, like Car 54, Mr. Ed etc.
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Last edited by indianajo; 6th December 2011 at 05:11 PM.
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Old 6th December 2011, 05:37 PM   #8
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Yeah, I'm afraid I'd do more harm than good if I really operated on it. On this unit, the radio is built into the same metal box that houses the selector switch. With all those fine tuning wires and so many plugs & leads coming in and out...plus just trying to reach the screws...I'm afraid if I did get it taken apart I'd never figure out how it all goes back in again. Oh well!

I have a 1958 Grundig Majestic too, which I got in 1999. After replacing all the tubes it worked like new until a crappy Radio Shack tape player I had plugged into the auxiliary jacks started sporadically blasting pre-amp volume. Ever since the Grundig has a low "buzz" whenever it's on.

You mentioned the old cars so I thought you'd get a kick out of seeing my 1960 Plymouth Fury! A lot of rust in the usual places but looks great if you don't get too close. This particular one originally had the optional RCA Hi-Way Hi-Fi 45rpm record player under the dash. The previous owner took it out and sold it separately...I could kill him for that! Sigh.
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Old 7th December 2011, 12:47 AM   #9
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Wow, tail fins bigger than mine! I'm still driving the ugliest 59 Ford, have 3 of them. Put floor pans & rocker panels on it a couple of years ago. The radio works, pity about the 45 rpm player. I most often get accused of driving "Christine" from the movie, which was in fact a Plymouth. I suspect the Grundig buzz is electrolytic caps also. They work a while when first reactivated because they still have water in them , but the rubber seal is cracked so after a few hours the capacitance goes away with the water vapor. Maybe you would feel more comfortable learning to solder on that. With cameras with close up lenses to take "before" pictures, and the internet to talk on, it is hard to get so messed up that you can't back up.
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Old 7th December 2011, 01:02 AM   #10
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Quote:
Originally Posted by indianajo View Post
Wow, tail fins bigger than mine! I'm still driving the ugliest 59 Ford, have 3 of them. Put floor pans & rocker panels on it a couple of years ago. The radio works, pity about the 45 rpm player. I most often get accused of driving "Christine" from the movie, which was in fact a Plymouth. I suspect the Grundig buzz is electrolytic caps also. They work a while when first reactivated because they still have water in them , but the rubber seal is cracked so after a few hours the capacitance goes away with the water vapor. Maybe you would feel more comfortable learning to solder on that. With cameras with close up lenses to take "before" pictures, and the internet to talk on, it is hard to get so messed up that you can't back up.
Ditto on this! I bought a Crown Comtech 400 and I thought I wouldn't ever get it working. I just kept diagnosing the amplifier with a schematic and after a week I found the problem! The solution involved 4 new resistors and about 12 new capacitors (the previous owner had likely connected another amplifier to the inputs of this amp and cranked the volume up). FYI, these amplifiers have something like 1200 parts.

If you know that the capacitors are bad, it should be a piece of cake to repair! I don't know if your model uses a pcb or direct wiring, however just make sure to completely remove the solder from the joints before pulling on the capacitors. It shouldn't take more than a day to get the caps replaced and the unit working perfectly again!

I would actually be more worried about disassembling the cabinet than working on the electronics lol.
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