Tuner problem any ideas?

I've completed the tuner kit and installed it today.

After setting up the tuner section of the Empeg to Europe and left hand stalk, the Empeg detects it OK and all functions including the stalk work fine.

The problem is that although the signal strength is at maximum, the reception is very poor and all stations sound very weak. AM is marginally better than FM which only rarely has the stereo symbol displayed and gives no RDS data at all.

I have treble-checked that the connectors are in the correct positions in both the connector body and at the PCB and the coax connection at the PCB looks fine.

I have tested it the whole thing with the car-dock on the bench (with a spare car aerial connected) as well as in the car and I have the same problem.

Does the fact that I get maximum signal strength rule out an aerial/coax connection problem?

Any ideas as to what I should be looking for or anything else I can check?

What year is your Golf? Do you have the "bee-sting" antenna?

If so, do you have the power adapter that allows you to feed power (+12V) down the antenna lead to the antenna amp?

/Michael

The Golf is a 2002 and it does have the bee-sting aerial, but I already had the "amplifier adaptor" for the aerial as I already had an aftermarket Blaupunkt head-unit.

I did wonder if that was the problem, which was why I bench-tested it all with a normal aerial, but that gave the same problem.

The AGC (signal strength) and the MPX signal are on separate wires, therefore you could have full scale deflection on the signal strength display but no audio.

The AGC (signal strength) and the MPX signal are on separate wires, therefore you could have full scale deflection on the signal strength display but no audio.

Yup. There's a FAQ entry specifically on this. Although that FAQ entry describes the factory supplied tuner module and extension cable, perhaps it's a similar problem. Check the pinouts on your connector and double check the wires themselves and how they're soldered to the module's circuit board.

Edit: I see that you say you've treble-checked this stuff already. Ah well, then, I don't know what to tell you.

Hmm. I'm in uncannily similar situation. Signal strength at full, but the reception is terrible, and very quiet.

Can anyone offer any hints on how to debug this problem? What do the different wires on the tuner connector actually do? Is there a schematic for the circuit, so I can start narrowing down where to look? I have access to an oscilloscope - are there any points on the board to check for a particular signal?

I've also got a MkIV Golf (yes, I've got the amplifier), but it doesn't work on the test bench either :-(

Silly question, but what does the SSM show without any aerial attached?

Well, I can't detach the aerial amplifier (I soldered it on), but it's pretty much the same. The signal strength does vary, if you tune/detune to a station.

The AGC (signal strength) and the MPX signal are on separate wires, therefore you could have full scale deflection on the signal strength display but no audio.

Which is the MPX wire so that I can quadruple check the connections on it?

The MPX wire is called Signal, it's the second wire from the top on the tuner board and should be grey, it then mates to pin 2 on the molex connector which is on the bottom row, first from the left.

Thanks marria01.

I have pulled the system out of the car and have it back on the bench now. With the tuner module plugged in, I have just checked continuity from the tuner PCB to the sled connector and everything checks out fine, all of the pin numbers and wire colours are as per the instructions and match the tuner connector colours and pins from the Empeg itself.

The only thing I can see at the moment that could be a problem is that the dual op amp shown as LM258N on pca's list is marked KA258 on the component. I presumed, when I was going down the checklist, that this was just a generic part with different codes from different manufacturers - is this right or has a rogue part slipped through?

The KA258 is an equivalent of the LM258

Here's one that could cause it;

Different areas of the world use different increments for tuner frequency stepping. If you have your tuner set up to the wrong area then it will probably never get a perfect lock on the signal, even though the SSM will be strong. Check your config.ini


[tuner]
region=us

or;

[tuner]
region=uk

the signal strength is at maximum, the reception is very poor and all stations sound very weak. .... no RDS data at all.

I have found that the signal strength often shows 7/7 but the reception is sketchy and the RDS is intermittent. If I can keep my eyes on the display long enough when this happens I sometimes notice the signal fluctuating between 6/7 - 7/7. I can get perfect reception and RDS data but it depends where I'm driving and what station I'm tuned into.

Silly question but have you tried driving about to see if you can get a good reception somewhere other than where you live?

In my case it's like the empeg needs a stronger signal than most HU's for the same performance and also the signal strength display is out of calibration.

My (15 yr old telescopic) antenna is worn out and doesn't stay up too well. I'm replacing it in a short while and hopefully that might improve reception, I'll post the outcome in here.

genixia

I have set region to Europe (UK is not listed as a seperate option)

Tuner section of config.ini is as below

[tuner]
region=europe
[controls]
stalk_side=left

I'm pretty sure that I am tuned in correctly because the signal strength meter only goes to max when it's on the frequency of a known station i.e 97.9 FM for BBC Radio 1.

Rue

Yes I tried driving around, but it did not improve. I have had no signal problem in my area before and I was able to pick up all the stations clearly on the Blaupunkt HU I have just removed.

The only other things that I can think of is to go and re-sweat all the solder joints just to make sure. I'd also try and double check all the resistor values.

My (15 yr old telescopic) antenna is worn out and doesn't stay up too well. I'm replacing it in a short while and hopefully that might improve reception

I've just replaced the antenna and it's a heck of a lot better now. The old antenna's chassis ground was very corroded as was the earth braid (which was hanging on by a few wires).

Any further joy on this, Geoff? I'm still having the same trouble with mine. I've spent quite some time re-inspecting, soldering, and testing joints, but still no progress. It would be very helpful to have some more information on how the circuit works so that I could narrow where to look for faults - presumably there are some components that are involved in generating the MPX line, but no the signal strength.

I have exactly the same problem with an original Empeg Tuner, I've had it back to Empeg twice and they can't find any fault. I also don't get any AM reception, signal strength shows full when tuned to "known" frequencies but no audio. Checked and replaced wiring looms etc.

Mark.

Check that R2 is definitely 220R. This is in the path of the FM MPX signal. Also check that R16 on the lower board was jumpered across with a wire. This links the MPX signal to the max4544 switch IC. Check that there is 9V on pin 7 of IC7, the CA3140. Check that R14, R15, and R24 are 200K, 100K, and 10K respectively.

If there is no problem with any of the above, I'm thinking it might be an antenna mismatch/impedance problem. Car aeriels are a compromise at best, and are never very good from an RF standpoint. The one in my Civic (quite an old one) actually made the reception worse when plugged into the tuner prototype. This was traced to a faulty earth on the antenna, which screwed up the ground plane. Replacing it fixed the problem.

pca

I will check all of those this evening, although I pretty confident that they're right, only because I would have had to make a pair of matching errors in order to not end up with a missing / extra component at the end. I'll double check the actual values with a multimeter just to be sure.

With the antenna mismatch possibility - I'd be surprised because (a) that aerial + amplifier works really well with other radios and (b) the noises that the tuner makes are completely unrelated to what antenna is attached. Also, reception in this area (Oxford) is pretty decent normally. Would you expect the signal strength level to be high if reception was the problem?

A further data point - when the tuner is scanning frequencies it makes a fairly loud clicking noise as it passes each frequency. I don't know if this is normal, but it doesn't sound right to me. The noise that the radio makes when "tuned" isn't what I'd normally associate with poor reception - it's very quiet, as well as distorted, but in a different way to a poorly tuned FM radio. What is the format of the MPX signal - presumably it's digital audio, but is it multiplexed with other data? I'm just trying to understand what might cause what I am hearing.

I believe that the problem is most likely poor soldering on my part, but I'd be interested to know if Geoff is seeing exactly the same symptoms - that is quiet, poor reception, and clicking when changing frequency.

Paul

Patrick,

Check that R2 is definitely 220R. This is in the path of the FM MPX signal


I am just about to check all that you suggest, but have noticed that the above contradicts the tuner instructions that give R2 as the 22K resistor (R13 is the 220). Is this just a typo above or is this the problem?

Paul,

I would say that we have the same problem - quiet, poor reception more like a distorted signal rather than just a weak one. I don't know if mine clicks when changing frequency as I tuned it in to known stations on the bench before I had any speakers connected and have left it tuned in ever since.

Geoff

Something else y'all should check for: loose wires on the sled connector... Maybe the problem isn't in the tuner at all.

Also, has anyone ever heard of the pinouts being wrong on the connector on the sled itself? These symptoms sound like the problem that existed in a miswired extension cable, perhaps it's a miswired sled connector?

OK - just checked all that pca suggested.

R2 is 22K as per instructions not 220 (see earlier post)
R14 is definitely the 200K according to the colour bands but measures 155K in situ.
R15 is 100K
R24 is 10K

Pin 7 of the IC7 CA3140 has only got 0.07V on it not 9V.

Does this help narrow down the problem?

Geoff

Eureka !!!!!!

I've just realised my mistake- I've put the CA3140 in the wrong way round.

I looked at the notch on the PCB layout for IC4 and thought it applied to IC7. I can now see the smaller notch applting to IC7 at the other end. Doh !!!!!!!!!!!!!

Will I have damaged it by doing this ?

I'll now try out my de-soldering skills !

Paul, perhaps you should check if you've fallen into the same trap. (might be a Golf owners thing).


Geoff

Yes, there is a type, but it's in my post not the instructions I meant, of course, check that R13 is 220 ohms.

pca

Paul, perhaps you should check if you've fallen into the same trap. (might be a Golf owners thing).


God, I hope not...

In reply to:

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I've just realised my mistake- I've put the CA3140 in the wrong way round.

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Aha! An Anti-Notchist!

We in the Pro-Notchist camp feel it is a basic ruile of tuner kit design that all the chips face the same way!

With a little luck, you may have gotten away with it. Carefully desolder and remove the chip, and put it back the way nature intended.

pca

To coin a phrase... Eureka!!!!

I've just realised my mistake- I've put the MAX4544 in the wrong way round.

I have absolutely no excuse, except that it was quite close to the end of the instructions, and I was obviously getting careless.

Flipped it round and it works perfectly, even with no aerial plugged in.

Thanks for all the suggestions - and to Patrick for a great kit, and the patience to listen to us lot whinging about our inability to follow simple instructions :-)

I'm glad you guys are sorted now, we can all enjoy the monotonous, boring programming that only radio can bring!

Woohoo!!

Well I've now got IC7 in the right way round, but it's not quite the unqualified success that Paul seems to have had.

The AM reception is now good and clear but the signal strength on FM is now not registering more than one or two bars and I can't hear anything. This is still set up on the bench with a spare (but new) car aerial so maybe it will be OK in the car. However I think, to be on the safe side, I'll get a new CA3140 from Maplins tomorrow (they're only 60p) just in case I've fried part of the chip. Oh well I should have paid more attention in the first place !

Is it possible that I have damaged any other parts by having IC7 in the wrong way round?

Geoff

OK if anyone is still interested after all this, here's the latest !

Got a new CA3140 from Maplins (2 actually just in case !) and replaced the one that I had put in the wrong way round and desoldered/soldered.

Connected it all up and ...................still no FM

It seemed that connecting the aerial made no difference, which made me suspicious, and on inspection, the RF lead, having been removed so many times from the case had broken where it joins the PCB.

I resoldered the RF lead and (at last) I had full FM reception including RDS

I've just re-installed it in the car and have still got excellent FM although the AM is a bit flaky. It was fine on the bench so maybe the VW amplified aerial is causing the problem. I'd be interested to know if any other VW owners have the same problem with AM.

Anyway FM is now 100% and, apart from the odd football match on Radio 5, I can't see me needing AM anyway, so I'm 99% happy

Thanks for the help on this, and thanks to Patrick for a great product - my problems in no way reflect badly on your instructions - I'm just an idiot !

Geoff

Hi Geoff,
I own aLuipo, but we do have the same antenna. I don't have an empeg, but I'm not too happy about that antenna VW puts on our cars. While it's okay if you have an original VW HeadUnit, it just doesn't work well even with Blaupunkts, at least on my two Lupo's I've owned; and before someone asks: I used the adapter...so what I'm trying to say (in my not-so-good english..) is that I?m going to change the antenna for a non-VW one, one that has a normal lead coming out where you have to connect 12v + . Maybe this could "solve" your AM problem? But it's probably not an easy job to change the antenna in a Golf; as it's not quite easy on a Lupo.

In reply to:

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I resoldered the RF lead and (at last) I had full FM reception including RDS

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Yay, glad you finally got your tuner working!

Yeah, I'd suspect the antenna too. My VW Golfs reception (AM or FM) with it's 'amplified' antenna is not as good as the bog standard non-amplifed antenna in my wife's '93 Mazda.

>I've just realised my mistake- I've put the MAX4544 in the wrong way round.

Now that I have a couple of kits here, I can see how easy it is to make that specific mistake: The writing on the chip is "upside down" compared to the silk-screened writing on the circuit board.. so naturally we want to flip it around..

-ml

I PMed Patrick about this, but maybe i'll get an answer here faster.

Can someone tell me if the left hand leads of R10 and R30 and the right hand leads of R30 and R29 have traces connecting them on the board? I think i might have scraped of the traces thinking it was a joined solder joint....

I don't have my tuner kit with me at the moment but I may be able to help. Patrick posted a link to the screen grab of the PCB layout which is here and from squinting at the correct position it looks like you've chopped out two traces by accident...

If you mean that R10 and R30 are connected together on the left hand side then yes.
And R30 and R29 are connected on their right hand side.

- Trevor

DOH! No problem... a little solder to bridge the gap and i'll be fine. Heh...

mental note: don't solder tiny components at 2:30am

since we have been speaking of chips backwards and so forth, quick question...having trouble so far having success (although only had about 2 minutes to attempt installing in car) with the tuner kit. I do remember one of my chips, can't remember if it was max or ca, did not have a notch out of either end, am I to assume that the recessed dot on the corner also specifies direction? I installed the chip assuming the recessed dot stood for the missing notch.
thanks

In reply to:

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am I to assume that the recessed dot on the corner also specifies direction?

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Manufacturers put the "dot" next to pin 1, so yes. Some even have both a notch and a dot.

Stu