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 Post subject: Zenith TransOceanic 3000-1 problem.
PostPosted: Nov Fri 15, 2019 12:17 pm 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
Hi all.

This is my very first post in this forum so bear with me if I'm doing something wrong :oops:

I've just inherited a very good looking Zenith Trans-Oceanic Royal 3000-1 that's not working at all. It is missing the battery box (must be somehwere in my father-in-law's house). The radio has been resting unused for 20+ years. I've been told that "the last time they used it worked OK".

I've been reading a lot here and there about this radios and their usual problems. So far I've done these steps:

-Powered the radio with the "External Power" 2.5mm minijack, with very clean 12V DC, tip negative and sleeve positive, but I got no signal at all in any of the bands. Once powered on, it draws about 20mA.

- Tested all transistors: They all seem to be OK -> PNP Ge transistors. My PEAK Atlas DCA55 semiconductor tester show that all four legged trannies have a "shunt between Collector and Emitter". The other semiconductor tester I've got, pure chinesium, detects a diode between Collector and Emitter in every four terminal transistors. Otherwise, all measurements seem OK.

- Measured the Test Points:

For FM:
1: -0.080V (-0.08V in the Service Manual)
2: -0.920V (-0.88V in the Service Manual)
3: -0.921V (-0.88V in the Service Manual)
4: 0V (0V in the Service Manual)
5: -0.420V (-0.38V in the Service Manual)
6: -0.447V (-0.41V in the Service Manual)
7: -0.584V (-0.55V in the Service Manual)

For AM:
1: -0.797V (-1.06V in the Service Manual)
2: 0V (0V in the Service Manual)
3: -0.506V (-0.78V in the Service Manual)
4: -0.086V (-0.05V in the Service Manual)
5: -10.67V (-10.2V in the Service Manual)
6: -8.00V (-6.9V in the Service Manual)
7: -7.88V (-6.7V in the Service Manual)

- Tested the output stage: I've injected a 1KHz line level signal in the RCA connector in the chassis and there was indeed a powerful and crisp sound out of the speaker. The output stage works fairly well. The volume and tone pots work albeit a bit scratchy as expected for such an old radio (12/4/66 labeled in the chassis).

- Cleaned the transistor sockets: sprayed with no-residue contact cleaner and then reset all the trannies several times.

- Disconnected the ground leg from all four legged transistors. This is a typical step when troubleshooting this radios because of the infamous "whiskers".

- Actioned the band selector back and forth several times to clean the contacts.


After all these steps I've managed to hear a couple of AM stations but with very-very low output... almost inaudible but existent nonetheless. Antenna deployed, of course, but absolutely no output in either FM, LW and SW.

What else can I do?... recap? intensive cleaning of the band selector wafers? So far I have not yet extracted the chasis.

Please, any help will be welcomed.
Thanks a lot in advance.


Last edited by Calambres on Jun Wed 17, 2020 8:58 am, edited 1 time in total.

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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Nov Fri 15, 2019 5:49 pm 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
Corrected typo :oops:


Last edited by Calambres on Jun Wed 17, 2020 8:59 am, edited 1 time in total.

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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Nov Sat 16, 2019 6:00 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 740
Location: dayton oh usa
all the lytics are probably gone by now.
they did not last very long.
i remember replacing them in 10 year old at the time sets.


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Nov Sat 16, 2019 8:34 pm 
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Joined: Mar Mon 17, 2008 5:05 am
Posts: 5332
Location: Ashhurst, New Zealand
Two larger electrolytic on the front of the chassis will definitely need changing. The 3000-1 runs on 12 volts and these caps are only rated at 12 volts! C61 and C62. Modern caps are much smaller so getting higher voltage shouldn't be a problem. There are two others, C52 and C58 which are pigs to get to under the tone/volume control panel that you should change while your'e at it. Be careful with your soldering iron anywhere near the dial scale! The service manual is easily downloaded from various web sites.

Attachment:
Amplifier.jpg
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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Nov Sun 17, 2019 9:49 am 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
Thanks a lot for your answers. I'm planning to remove the chassis on next week and change all the lytics.
I'll keep you posted.

Thanks again.


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Tue 16, 2020 5:51 pm 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
Well, it's been quite some months since my last post here. I've managed to repair the radio and now it works quite well.

I changed each and every electrolytic capacitors in the radio. A total of 8:

C19 20uF 3V
C31 5uF 12V
C35 10uF 6V
C56 5uF 12V
C57 5uF 15V
C58 5uF 15V
C61 500uF 12V
C62 50uF 15V

All of them were substituted for modern replacements with at least 35V of working voltage:

Image

Besides this, all transistors were tested. They were all in good condition except for one RF transistor: the "A.M. RF" four legged one which suffered the infamous "internal tin whisker" syndrome. The ground lead was electrically connected to the Collector. I bent the lead out of the way and all of a sudden everything worked OK, loud and crisp. This is the failing transistor in a red circle:

Image

But there's something strange here. My radio has a couple of marks on it's chassis side stating the date of manufacture: 2-3-66 and another marking for the type of chassis used: 12KT40Z8.

Image


This is precisely the chassis type the Service Manual refers to but I have found something odd. The failing transistor is referred in the 12KT40Z8 Service Manual as a 121-44 (2N2089) but it is not what it was there, a 121-349, the same reference displayed in the sticker glued to the inside of the back door:

Image

I suppose there were different revisions of that chassis number...

This radio came to me without the original battery box. I have to use it with external power which is a bit of a nuisance but useable nonetheless. Unfortunately, there's one thing not working in this configuration: the dial lamps cannot work because they rely on a single 1.5V battery from the pack (see the schematic in a previous post) and there is no provision for this feature when the battery box is not present. I'm planning to add a 1 D cell battery holder inside the back of the radio just for this... there's plenty of room there now!


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Tue 16, 2020 7:18 pm 
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Joined: Aug Wed 24, 2011 4:35 am
Posts: 4967
Location: Sunnyvale CA
Calambres wrote:
This radio came to me without the original battery box. I have to use it with external power which is a bit of a nuisance but useable nonetheless. Unfortunately, there's one thing not working in this configuration: the dial lamps cannot work because they rely on a single 1.5V battery from the pack (see the schematic in a previous post) and there is no provision for this feature when the battery box is not present. I'm planning to add a 1 D cell battery holder inside the back of the radio just for this... there's plenty of room there now!
\

It is also very easy to add 2 4-cell C or D battery holders, and a single for the dial light. The draw is so small that even AAs will run it for a long time, and are very cheap. The original battery boxes are nothing to write home about, even the cheapie Philmore types you can get anywhere hold them better.

Brett


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Tue 16, 2020 7:47 pm 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
Good idea.

Do you know of any source for the battery connector?

At least its name or reference so I can find it on the web...


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Thu 18, 2020 11:35 am 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
More on this...

The radio sounds quite good and punchy but with a bit too much noise and not that sensitive as it is supposed to be. I think it needs realignment.
Is there any web, youtube, etc. with a procedure tutorial on how to align this radio? Better than the Service Manual itself, naturally.
I own all that's supposed to be needed (RF signal generator, Scope, etc.)

Some data...

Here is a table with the values of the seven Test Points in both AM and FM with the radio powered with an external laboratory power supply at exactly 12.0V and no signal, measured with an Amprobe 37XR-A True RMS multimeter:
Code:
AM:   Radio     Service Manual
1     -0.920V   -1.06V
2      0.000V    0V
3     -0.627V   -0.78V
4     -0.084V   -0.05V
5    -10.580V  -10.2V
6     -7.833V   -6.9V
7     -7.675V   -6.7V

FM:   Radio     Service Manual
1     -0.076V   -0.08V
2     -0.911V   -0.88V
3     -0.912V   -0.88V
4      0.000V    0V
5     -0.419V   -0.38V
6     -0.444V   -0.41V
7     -0.580V   -0.55V

Transistor data obtained with a PEAK DCA-55 taking care not to heat the trannies with my fingers:
Code:
TRANSISTOR MODEL#     Hfe        LEAKAGE    COMMENTS
AM RF      121-349     93(*)     0.08mA     Shunt between B-E Whisker between Collector and Shield (bent lead)
AM OSC     121-350    163(*)     0.15mA     Shunt between B-E   
AM MIX     121-351    100(*)     0.06mA     Shunt between B-E   
FM OSC MIX 121-295    121(*)     0.00mA     Shunt between B-E   
FM RF      121-294     97(*)     0.00mA     Shunt between B-E   
1ST IF     121-352    111(*)     0.00mA     Shunt between B-E   
2ND IF     121-352    132(*)     0.00mA     Shunt between B-E   
3RD IF     121-352    104(*)     0.00mA     Shunt between B-E   
DRIVER     121-375     75        0.17mA     "E" on top
1ST AUDIO  121-374    173        0.45mA     "A" on top
OUT LEFT   121-373     48        0.06mA     "N" on top Matched
OUT RIGHT  121-373     45        0.06mA     "N" on top Matched

(*)Hfe not accurate due to B-E res.


What's your advice on all this?
Thanks a lot in advance.


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Sat 20, 2020 4:19 pm 
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Joined: Feb Wed 17, 2016 2:38 pm
Posts: 284
Location: Cottage Grove, Minnesota
Quote:
Besides this, all transistors were tested. They were all in good condition except for one RF transistor: the "A.M. RF" four legged one which suffered the infamous "internal tin whisker" syndrome. The ground lead was electrically connected to the Collector. I bent the lead out of the way and all of a sudden everything worked OK, loud and crisp.


Tin whiskers can be removed easily and you won't damage the transistor. All you need is a 9v battery and some leads. Connect leads to battery and touch one lead to the transistor can and the other to (in your case) the collector, for a couple seconds. This will clear the tin whisker and the transistor can be inserted normally and should function properly. I have done this to many dead ZTO transistors and have had only a few that I could not resurrect. Since yours is not dead it will work fine after the procedure.

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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Sat 20, 2020 8:43 pm 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
Yes, I've also read about the charged electrolytic capacitor in place of the battery. An alternative way of vaporizing the whiskers.
I may do it as I have a spare AF116 that should work in case I break anything.

Now I'm gathering the "guts" to perform an alignment of the radio :roll:


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Thu 25, 2020 12:54 pm 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
More on this topic.

I have changed all paper capacitors:

C5: 100nF
C32: 100nF
C59: 220nF
C60: 330nF

Upon later inspection, all of them were perfectly functional with correct capacitance, no leakage at all and good Q factor. Go figure!


I have realigned the radio as much as I could (see later) but have found a strange thing in the original Service Manual. It seems a typo in the AM alignment instructions. Look at the indications for aligning the 2.1MHz in the 2-4MHz SW band: L17 in the red square:

Image

L17 is a double coil in the same coil form, labeled as both 17A and 17B in the coil map, but both are for bands other than SW, that is, L17A is for Broadcast (BC) and L17B is for LW (look in the previous image). There is no "single" L17 coil. As I just said, I think it is a typo and must be meaning L7 instead which is an "Antenna Loading Coil" for, I think, all SW bands. Here in a red square too:

Image


Anyone with experience aligning these radios can confirm this?. After all this will not be the only typo I have found in the Service Manual, as it indicates a voltage of 10.2V for test point 5 in AM and there are no positive voltages in this radio anywhere (except fot the two light bulbs: +1.5V) and should say -10.2V

Besides, I've found two other problems:

- The double coils in the same coil form need a special tool that can "dive" past the top slug into the second bottom slug and I cannot find one that suits this task... I can only adjust the top slugs :(

- The FM aligning instructions are very confusing, indicating coils that are not located anywhere in the coil map, etc. Again, if anyone with experience on this can lend me a hand I'll be more than thankful.


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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Mon 29, 2020 6:16 pm 
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Joined: Feb Wed 17, 2016 2:38 pm
Posts: 284
Location: Cottage Grove, Minnesota
I have only ever replaced the electrolytic capacitors, I don't see any paper caps included in the parts list. Rarely have I needed to align the radio for decent performance. I suspect that you have an under-performing transistor. I have seen transistors that check out OK in multiple transistor checkers, but does not perform well in the radio. Replacing with another transistor solved the poor radio performance issue.

You need a tool with this type of end to adjust the upper and lower coils, this is the smaller of this type.
Attachment:
20200627_072332.jpg
20200627_072332.jpg [ 1.58 MiB | Viewed 77 times ]


The typos you suggest seem reasonable, L7 makes sense since L17 is adjusted in a previous step. Looking at the schematic shows that TP5 should be negative. I see that L101, L102 and L103 are not listed on the coil map, however they are the antenna, detector and oscillator coils and are adjusted from the front of the chassis.

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 Post subject: Re: Zenith TransOceanic 3000-1 problem.
PostPosted: Jun Mon 29, 2020 6:45 pm 
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Joined: Nov Fri 15, 2019 11:25 am
Posts: 9
I modified a tool I had to make it more or less like the one you show above and I managed to (almost) align all bands until the tool definitely broke in the very last band alignment :evil:

Now the radio is MUCH more sensitive:

- FM and BC ("normal" AM) sound very well and get many stations. Output is very clear and powerful.
- LW is mostly empty save for noise induced, I presume, by the many switched power supplies we all have permanently connected at home. Sometimes I get a very faint station but it is rare.
- SW is full of stations here and there and many are quite powerful depending on the band and the hour. There's a constant, albeit not identical, background noise through all bands.

Couriously, the less sensitive band (other than LW) is the last band I could not fully align. Where can I buy a proper tool like yours to finish the alignment?

One side note: the infamous L7 coil apparently have no effect in alignment. I couldn't see any difference when fiddling with it. I returned it to its original position.
I still don't know what the Service Manual means with "Coil L17" :(


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