adjusting analog tuners!!!

[baddboybill]

I looked through archives about adjusting tuners and really could not find anything I already know how to adjust the tuner so the scale readout and tuner match using 1 of the four screws located on tuner. But every once in a while I will be adjusting and it seems like I am adjusting wrong screw and then it really gets out of adjustment and its a b---ch to get right. So I need to know if there is a secret to this and also is one of the screws(out of 4 screws) to fine adjust fm

 

[Fatdog]

...So I need to know if there is a secret to this and also is one of the screws(out of 4 screws) to fine adjust fm

It's called a service manual.



As far as I know, there is an order in which the screws on a variable capacitor have to be tuned. You can't just get all willy nilly in there.

 

[oldskool69]

...So I need to know if there is a secret to this and also is one of the screws(out of 4 screws) to fine adjust fm

It's called a service manual.



As far as I know, there is an order in which the screws on a variable capacitor have to be tuned. You can't just get all willy nilly in there.

And an ocsilloscope goes a loooooooooonggggg way.....

 

[Superduper]

Don't forget the millivolt meter, an MPX stereo generator, an RF signal generator, and an instrument to inject markers into the injected signal too.

And an ocsilloscope goes a loooooooooonggggg way.....

 

[oldskool69]

Don't forget the millivolt meter, an MPX stereo generator, an RF signal generator, and an instrument to inject markers into the injected signal too.

And an ocsilloscope goes a loooooooooonggggg way.....

Absolutely.

 

[Fatdog]

Just out of curiosity...

Can you "transplant" a working/tuned variable capacitor into another of the same boombox that has a bad varcap?

 

[MasterBlaster84]

Just out of curiosity...

Can you "transplant" a working/tuned variable capacitor into another of the same boombox that has a bad varcap?

I would say no because of all the other variables, that's why you have to tune it to the circuit it's in.

 

[Superduper]

Yes and No. You can transplant it but the system is tuned as a unit so the entire tuner will have to be re-tuned.

 

[baddboybill]

So my question has not really been answered I am not talking about out of tune I am saying that when I adjust the station on the scale to the tuner, twice out of the 40 or so bbx's I did seemed to get out of range... example... the station plating is 93.9 but the scale reads 105, and when I try to readjust it is a b-tch!!!!!!

 

[Fatdog]

So my question has not really been answered I am not talking about out of tune I am saying that when I adjust the station on the scale to the tuner, twice out of the 40 or so bbx's I did seemed to get out of range... example... the station plating is 93.9 but the scale reads 105, and when I try to readjust it is a b-tch!!!!!!

If you are talking about adjusting screws on a variable capacitor, your question has been answered.

If you just want the needle to point to the correct, just readjust the needle on the string and call it a day.

 

[MasterBlaster84]

the station plating is 93.9 but the scale reads 105

If you just want the needle to point to the correct, just readjust the needle on the string and call it a day.

If the pointer is off that far I would want to know why, that's an extreme deviation for the pointer unless it has simply moved that much on the string. In that case I'd fix it quickly since it would obviously be moving to much and possibly ruin your tuner string.

 

[Fatdog]

If the pointer is off that far I would want to know why, that's an extreme deviation for the pointer unless it has simply moved that much on the string. In that case I'd fix it quickly since it would obviously be moving to much and possibly ruin your tuner string.

Badboybill has said he was messing with the screws on the varcap. Doing so without the proper measuring tools and specifications guarantees a messed up tuner.

 

[MasterBlaster84]

If the pointer is off that far I would want to know why, that's an extreme deviation for the pointer unless it has simply moved that much on the string. In that case I'd fix it quickly since it would obviously be moving to much and possibly ruin your tuner string.

Badboybill has said he was messing with the screws on the varcap. Doing so without the proper measuring tools and specifications guarantees a messed up tuner.

Ahh that's right.
I won't say I don't experiment but I make note of what I did and don't do to much at one time so I can return to where I started so this doesn't happen, well hopefully it doesn't happen.

 

[baddboybill]

I use to adjust the scale by moving the pointer but was told by a member who works on bbx's that I could do this with one of the 4 screws on tuner (by checking all 4 carefully). I have been succesful 38 out of 40. One time I was able to readjust it taking quite a bit of time but the last time on a walkman I was able to tune it to the scale but it seems to be hard to keep in stereo on some stations I had read in another forum on s2g something about 19 khz centered. But its not a big deal with a $5 walkman I got for my daughter. I just dont want to mess up an expensive bbx :'-( Like I said I know one of the screws is for adjusting but Just wanted to know if there was a fine adjustment screw

 

[monchito]

tuner are a bit complicated and most of the time if you dont have proper equipment and knowledge of the circuit most of the time it will get screwey ,, i have done a few with good results but i have a few that i just left it alone because trying to get them to tune perfectly has been a pain and a half :annoyed: , some tuners are so sensitive that trying to adjust takes them off and to get them back is mostly a pain , sometimes if you can find a donor then you can do a swap if the radio board is not part of the mainboard,, if it is then if its off then the real best way is to shift the dial needle to the correct station without harming or adjusting anything,, on some tuners overtime they may drift out of sync, i have found that without touching the tuner with moving just the dial needle you will correct the problem as long as its working i would not worry unless it will not pick up stations or its not locking in correctly causing a lot of unwanted noise or lost signal..

 

[Fatdog]

There are 38 steps in aligning the tuner on an M90. That's definitely not a "1-screw" kind of job.

 

[Superduper]

There are 38 steps in aligning the tuner on an M90. That's definitely not a "1-screw" kind of job.

EGGZACTLY.

I did not know a nice way of saying it so I have been mostly avoiding posting here. But as far as I'm concerned, let's just say there is the right way, and the NO-WAY. If I don't have a service manual with adjustment procedures, sequences and specifications, I don't touch. Even WITH the service manual and schematic, sucess is not nearly at the ratio that I'd like to see which is why I basically don't like to take those jobs. AND yes, I do have oscilloscopes, signal generator, stereo modulator, marker injector, etc.

If I knew that a boombox tuner was messed with before, I WOULD AVOID THAT BOOMBOX LIKE THE PLAGUE. The tuner is the most difficult circuitry to work on, on any receiver. Even many technicians that have no problem working on audio issues will have their tuner specialist do the tuner. It's a very difficult art/science to master.

Whoever suggested to play around with 4 screws to adjust the tuner is way off base and flat out WRONG. Nothing can be further from the truth. Even with the proper equipment (already discussed), it is very difficult. Without the equipment and tuning blind -- that's just a big no no. Can you make it better? Maybe. Can you make it worse? Absolutely. Can you screw it up totally? Very possibly. There can be 4 adjustments -- there could be 14 adjustments. How many, and whether you will be adjusting the varicap, the variable pot, the RF tuning coil, transformer, inductor coil, etc -- all depends on the tuner and layout. The fact that you mentioned 4 screws without even saying what type of componentry you are adjusting just tells me you don't know the difference betwen a L101 or a T101 or a CT101, or a VR101.

The answer therefore is NO, there is no secret -- just years of education, training and tons of experience. Tuner adjustment is DEFINITELY NOT a novice project. Any adjustment that seemingly made things better at one location of the tuner dial probably messed something up at another area or another band. My suggestion? If you can live with it, by all means leave it alone. If you can't live with it and it's a cheapie that you can toss/replace, then go ahead and play with it. You already decided that you can't live with it. If it's a big $$ irreplaceable job -- do it right and farm it out. Just My 2 cents.

 

[baddboybill]

Thanks for all the info guys