I was just using the set night before last. Last night, turned it on and got almost nothing on AM and SW. FM and weather are fine. I can barely hear a few strong AM and SW stations, but volume is very low. Before I have to open it up again (I just got this up and running a little while ago and have been using it a few days a week until last night), any ideas?




AM readings are pretty close to normal, but FM voltages are way off. Doesn't make sense to me. FM works fine.


Jay

Before I took the chassis out of the case, I figured that I would shotgun some transistors. When the mixer was replaced, the set came alive. Checked the mixer transistor, Q102, with an ohmmeter. Strangest thing that I have ever seen. B-E and B-C shows no connections at all. Got out a DMM and set to 20M range. Infinite readings between any pin. It is like there is nothing inside the transistor.

Jay

Most DMM's won't test a transistor or diode unless it has a special function for that purpose. Try testing your transistor using a VOM.

Dave

I wonder if he even reversed the leads

Real nice Mbird97x.

My first choice for continuity is always a VOM. Got no reading on Rx1, RX10 or RX100. That is why I then tried the DMM. This is the strangest thing.

When I said ohmmeter, a VOM is what I meant. I have been in the electronics profession since the late 60s.

No kidding, that was a bit much.



I would certainly think that "open" is a valid failure mode. Just imagine the junction burned out.

Brett

Brett,

I should have know better about the DMM. It's just that I have never come across a transistor with both junctions open before. Just for kicks, I checked the DMM voltage at the test leads on the 20M scale and it was only .25v. On the diode test (200 ohms) scale, it puts out 2,5 volts.

Needless to say, it was pretty upsetting to find that set not working again after all we went through getting it running recently. I guess those high freq small signal transistors are more fragile than run of the mill audio types. It turned out to be a good thing that I after I first got it running, I tested a batch of high freq transistors to stash sway as replacements. Who knew that I would ever need to use one.


Jay

Hey Jay1028:

Before your radio failed Was it an outstanding performer on SW ? My D7000Y radio is a mediocre performer (compared to a Sony ICF-5900 and Panasonics) regardless what transistor I put in instead of the originals. Are all radios of this model the same ?
Bests
Ali

I have two examples of this model series, a Royal 7000 and a 7000-1. I would not classify either as having mediocre performance but they do seem a bit lower in sensitivity on all bands compared to my Sony ICF-5900W. On the other hand, my next generation R7000-2 is equal or better than the Sony in most respects except for undistorted audio power where the Sony has all of them beat. That's hard to understand because the Zeniths use 12 volts as the supply voltage while the Sony uses only 4.5 volts. I think maybe the Sony's speaker is just more efficient.

Dave

No doubt that there are off shore portables that can out perform the Zenith D7000Y. I don't see how they can compare in the aesthetics area or ruggedness of hand wiring. I have various 1000s,3000s and a G500 and this 7000 has a hotter front end and better selectivity.

Huesby,
I had this radio sitting around for about 10 years and was a little shy about getting into it. After locating a schematic, I had it running and aligned in a few days. It worked great with all the original transistors intact. It is strange why the mixer failed. Luckily, after replacing it, the alignment hasn't changed.


Jay

My R7000-2 isn't as good as some folks. It works OK, but what a dog to rip into. I don't find it as good on SW as others I have.