How to change a digital tuner's stepping?

[Thumpy]

I have an SAE Two T14 digital tuner and the readout for the stepping isn't correct. For FM, it reads on even tenths (e.g. 97.8, 99.4, 102.2) and it should be odd tenths (e.g. 97.9, 99.5, 102.3). I haven't used this tuner for awhile and I honestly don't remember it doing this before. Any idea how to change it?

 

[OvenMaster]

Well, I can't find any switches for that specific item. Yet.
Any switches on the back panel?

Here's a schematic: http://www.fmtunerinfo.com/T-14schematic.pdf

 

[Thumpy]

Any switches on the back panel?

No, just a knob to set the muting threshhold.

 

[JBL GUY]

How about the "Set" button? Does that only get you access to setting the clock?

Maybe the "set" button in combination with the "fm" button?

Or maybe holding in one of the buttons when you power it up...

Like maybe the "Set" or "fm" buttons...

Just a bunch of wild guesses...:yes:

Good luck...

 

[Punker X]

I've seen alignment throw off the digital read out as described.

 

[Thumpy]

I've seen alignment though off the digital read out as described.

That might be it. I just checked AM and it's consistently 1 kHz low, e.g. 829, 839, 849 instead of 830, 840, 850. However, the 10 kHz stepping is correct.

 

[Hokieman]

On my HK TU915 tuner it has a switch on the bottom for odd/even stepping for the FM tuning . I think it has to do with some old European or Asian standard. Maybe this is your issue.

 

[jdurbin1]

I sold an SA5ES Sony recently that had a boot-up process where you could change the tuning increment by holding down specific button or buttons during power-up. Only worked for AM, they left the FM with the additional increments,

Could be that type of programmable design rather than a hidden switch, depending on age. Also could be designed for non-US operation and not be switchable.

John

 

[w1jim]

...Also could be designed for non-US operation and not be switchable.

That's not likely the situation. USA market uses 200khz steps with odd spacing whereas other markets use 50 khz spacing (which will work in the USA). Am uses 10khz in the USA and 9khz in other markets.
I think PunkerX had it, it's slightly out of alignment - I had a similar problem with my SX-D7000 until I tweaked it.
JimB

 

[Thumpy]

I think PunkerX had it, it's slightly out of alignment

I'm thinking the same thing...
It's rated 120V and the stepping increments are correct (for the USA) on both AM and FM (10 kHz and 200 kHz, respectively). I looked underneath, on the back and even inside for a switch. There may be a mystery sequence of buttons to push, but I could spend quite some time trying to guess something that may not even exist. I found a schematic at fmtunerinfo, but I didn't see anything obvious (I'm not a tech).

 

[Bob@FM]

On digital tuners, there are two things you can adjust when the digital tuning is off -
see http://www.fmtunerinfo.com/T-14schematic.pdf
1) the detector zero - The Quad detector is built into the HA11225 chip (top middle of schematic), and is adjusted by either T1 or T2 shown above it. Usually there are two test posts sticking up nearby, you put a DC voltmeter on these, and adjust for 0V. Mark them first, so you can return them to where they were if this does not work.

2) The main crystal oscillator for the PLL tuning - on board PLL-265 (top right of schematic), this is adjusted by the cap TC901, which adjusts the crystal X901

I usually use instruments to verify what is going on, but if you mark the positions first, you may be able to fix it "by ear". As you can see, this stuff is different for every tuner, and sometimes 1) works, sometimes you need to do 2). Crystals age with time and drift, so it's not uncommon for older units to need this. If there is no adjustment cap on other tuners, you can add one, but fortunately this model has one.
Bob

 

[Thumpy]

Thanks, Bob! I'll see about getting the time to try this in the next few days. I assume I should use non-metallic screwdriver.

 

[Bob@FM]

Thanks, Bob! I'll see about getting the time to try this in the next few days. I assume I should use non-metallic screwdriver.

On the transformers - yes, you must use non-metallic tools. Many need a square tool head, you can make one with a plastic or hardwood stick and a knife. Cut to fit - it must be tight with no slop. Using a metal tool is bad for 2 reasons - it throws off the reading when in contact with the ferrite, and it can also easily break/crack the ferrite core.

For some reason I still don't understand, one crusty old engineer used to argue to death that it was fine to use metal tools to adjust the ferrite slugs in transformers. It's not - once you break a ferrite core on a vintage tuner, you may not ever find another exact replacement. The same guy advocated using WD-40 to clean switches - go figure - false economy, and not in my gear!

For the cap, it does not matter, I use a plastic isolated scope probe adjust tool with a metal tip, but a small metal screwdriver will also work.

Bob