Original Specs for Radioshack DX-398/Sangean ATS-909 Speaker?

[cc333]

I received the DX-398 I ordered, but the speaker is completely blown (it puts out no sound). The headphone jack also only puts out audio on the left, so the audio amplifier circuit might be partially blown, or maybe the jack itself is damaged somehow. I'm not sure. I do get both channels out of the line out jack, however, so most of the circuit, it would seem, is intact.

Nevertheless, I've been researching replacement speakers, and this one seems like it might work: https://www.digikey.com/en/products/detail/cui-devices/GF0771/304442

I would like to know what the specs are on the original speaker, however, so I can compare. As long as any replacement has the same or similar dimensions and has the same impedance, it should work, but I want to be sure.

c

 

[Boilermaker]

The folks at www.radiolabs.com might be able to give you that information. They used to modify the DX-398/Sangean ATS-909 receivers and part of the modification was replacing the OEM speaker with a better sounding one.

 

[cc333]

I tried looking there, but there was no mention of the 398/909?

Maybe I should look harder....

c

 

[bearcatrp]

Are you sure you input the jack all the way? I still have mine that I brought to Desert Storm back in the early 90's. When I used it last winter, the head phone jack was a little finicky but still works when plugged in all the way.

 

[Boilermaker]

I tried looking there, but there was no mention of the 398/909?

I don't think they do the mods anymore but, there is a "contact us" tab at the bottom of the page. Someone there may have the answer you're looking for.

 

[cc333]

Are you sure you input the jack all the way?

Yes. I also tried another, known good cable that is connected to my computer's input, and I still only get sound coming from the left. The right is completely dead.

c

 

[cc333]

I don't think they do the mods anymore but, there is a "contact us" tab at the bottom of the page. Someone there may have the answer you're looking for.

Ah, I see. Thanks!

c

 

[cc333]

OK, I dug around a little, and instead of searching for the DX-398, I searched for the Sangean equivalent, the ATS-909, and had better luck!

It seems, the ATS-909X (and I assume also the recently released 909X2) uses the same speaker as the upgrade part RadioLabs used for its Super 909 modification package, and they sell them a la carte for about $22. Link.

So with that, I think I'll just not bother looking for the 909's OEM speaker, which was apparently junk anyway, and simply save up and buy the much nicer upgraded part. Seems easier!

Now that that mystery is solved, I can get to diagnosing and fixing the headphone jack's missing right channel.

Does the jack itself ever go bad on these?

Perhaps there's a cracked solder joint. I'll have to open up the radio anyway to replace the speaker, so perhaps I can take a look around the PCB.

c

 

[bearcatrp]

If you decide to get another radio, consider the newer version of the Belka radio. One hell of a HF little radio. You won’t regret getting it.

 

[Boombox]

I would spray the inside of the jack with contact cleaner, before attempting surgery on the radio. The headphone jack to my Sony ICF-38 decided to cut the speaker off. A shot of tuner cleaner inside the jack fixed it. It's been normal for about 5 months since, so far.

The specs for the 398's speaker may be on the speaker. Most speakers have the wattage printed on the frame somewhere. The Sangean ATS505 / Radio Shack 200629 speaker is 8 ohms, 3W max. Probably fairly standard for Sangeans of that era. I don't think the output chips on Sangean radios exceeded 700mw - 1W or so. I haven't taken apart my DX-398 in a while, but the only pic I can find of it with the back off (that I took) has the printing on the speaker frame illegible.

You could find a datasheet on the DX-398/909's AF chip and get the audio output specs, but like I said, most of these Sangean portable SW AM FM radios didn't even put out a watt, and the speaker was probably capable of more than the AF chip would put out.

I just found my schematic, the AF "chip" is actually two of them, two AN7117's. The speaker rating is .5W, 8 ohms.

 

[cc333]

I would spray the inside of the jack with contact cleaner, before attempting surgery on the radio. The headphone jack to my Sony ICF-38 decided to cut the speaker off. A shot of tuner cleaner inside the jack fixed it. It's been normal for about 5 months since, so far.

OK, I did that, and then exercised it a bit, but the problem's still the same. I'm beginning to think the jack itself is fine, and maybe there's some damage to one of the two AF ICs.

And the OEM speaker's reading says 8Ω, 3W. It's so cheap looking, with such a tiny magnet, that I doubt it could handle even 1/4 of that power for very long. No wonder these things blow out so much!

Anyway, bach to the AF circuits. I just downloaded and studied the schematic, and it looks like one of the two AN7117's are connected to both the speaker and the headphone jack's ring contact (which I believe is where the right channel lives), so as best as I can surmise, something caused the speaker to short, which overloaded and blew that AN7117. It also appears to be the last stage in the audio circuit, which explains why the line output is unaffected.

Looks like I'll need to replace that AN7117 to test my theory. Fortunately they're still relatively common and cheap, so getting one shouldn't be hard.

c

 

[cc333]

OK, update time.

I replaced both AN7117's, with no change.

I'm waiting on a replacement speaker, but in the meantime, I've been working on a DX-399 for a friend that has a blown sounding, but working speaker.

I have a theory that perhaps the circuitry is designed such that the right channel won't work without a working speaker. So, I put the iffy speaker in the 398, and the right channel is now working!

So the AN7117's were a red herring, it seems, and all it needed was a speaker.

Ok, well. Once I install the proper replacement, I'll have to align it (the BFO seems off, and when I tune, it seems like most of the time, I need to be off frequency by about 1 kHz for things to sound right (for example, 5000 kHz sounds in tune at 5001 kHz)).

c

 

[cc333]

Good news!

The new speaker came today, and it works!

However, it now seems that I can't get the volume to go completely to zero. Even with the knob turned all the way down, I get sound. Out the headphone jack, the right is a bit louder than the left as well.

I suspect the new AN7117's have something to do with it. I suppose I could stick an extra resistor somewhere in the right channel audio circuit to equalize it, but where?

I'll have to check the schematic.

c

 

[Scan125]

Looking at the AN7117 spec. sheet there is no volume change/adjustment capability with the chip itself. i.e. no feedback / closed loop gain ability other than phase correction. Looking at the ATS-909 schematics Volume looks like it is determined by the VR2 potentiometer acting as a divider.

When I look a the audio paths this is a fairly complex setup. If the record output volumes are the same? then probably you can only change the headphone output series resistors (R137 / R136 both 47 Ohms) but this will only work for one particular headphone impedance.

 

[cc333]

Yeah, maybe.

When I looked at the schematic, it seems there are a couple extra resistors in the right channel circuit, and since said circuit seems to require a functional speaker be installed to function, perhaps the speaker's impedance affects it somehow?

Output on both channels is equal on the line out jack, so this definitely seems to be happening somewhere past the AN7117s.

Could it be like a faulty VR2?

I'll have to check it and see.

c

 

[MWDXer249]

For what it's worth - I had an original ATS-909 back in the day - for me back then it was a lot of dough. Nice rig, used for several years - Long gone now. Anyways - my memory is that the volume never went to zero. Very faint at lowest level.