Creative T10 Speaker Standby Issue Solved!

KD0RC

I bought some Creative T10 speakers for my Flex 6400 a few years ago. I have been really happy with them - they sound good, have plenty of volume, are reasonably RF-proof and were pretty inexpensive. I power them from the main station 13.8 supply (no noisy wall-wart) and feed the audio through a 1:1 audio transformer (ground loop isolator). I also pass all the wires through a mix 31 snap on ferrite.

What I don't like about them is that there is a circuit that puts the audio amp into standby mode if it doesn't get enough audio volume for a while (this may only be for units meant for the UK). What a PITA!! If I mute the speakers to take a phone call or something, then un-mute to get back to operating, it takes several seconds for the audio to come back on. If the band is quiet, it might not come back on until I tune onto a loud signal, then I still have to wait.

I finally opened the case and discovered that the audio amp is an STA540 from STMicroelectronics. Looking up the specs, I discovered that keeping more that 3.5 volts on the standby control pin allows amplification and less than 1.5 volts puts it in standby mode.

I used my o'scope to watch the action as it went into and out of standby mode. They put input power supply voltage on the pin for normal operation, then when it doesn't get enough audio, the voltage slowly decays to a few hundred millivolts. I think they just use the audio to charge up a big capacitor to keep it out of standby.

To fix this unpleasantness, I hung a 10 K ohm resistor from the standby pin to VCC.

Now it stays on, even if I mute the rig for an extended period of time or have it on a squelched repeater freq. If enough time elapses, sometimes the LED extinguishes, just as if it was going into standby mode, but in fact the audio amplification stays alive. I made no effort to change this quirky behavior.

I hope this helps anyone else who has these otherwise great speakers.

KT0AM - Mark

This is an interesting and innovative solution, Len. Thanks for sharing!

KD0RC

Thanks Mark, I appreciate it! This has driven me crazy ever since I got the speakers.

Ted VE3TRQ

I have T10 speakers, and figured I’d retrofit it with this change. However, although I’ve removed the six screws, the face just won’t come off. The top separates, but the bottom seems pretty thoroughly stuck or glued to the case.

How much prying is necessary to get the case apart?

Thanks for any guidance.

KD0RC

Hi Ted, I don't remember having to pry much. I can't find my uber-long screwdriver right now, but I think I might have had to pull off the knobs and retaining nuts.

If that does not do it, I will try to find the screwdriver and open it back up. I bought the screwdriver just for this speaker...

EDIT: Found the screwdriver... Once the six screws are out, pull off the two front panel knobs and remove the retaining nuts and washers. The front panel will now wiggle off. Don't pull too hard or you risk breaking the wires.

The circuit board is hot-glued in there, but I was able to reach in with a small soldering iron and solder the resistor in place.

Ted VE3TRQ

Thanks, Len. I was not able to determine of the knobs were part of a circuit on the fron panel. Retaining nuts would explain the added resistance! I'll need to pry off the knobs (which are REALLY tight).

Ted VE3TRQ

Wow - were those knobs tight! Not enough room for a screwdriver, and I don't have a puller that is small enough, but a silicone sheet I had gave my two hands together enough leverage. Then in addition to the extra long Philips scewdriver, all I needed was a deep 10mm socket for the **** nuts. Nothing the right tools won't fix :-)

And as luck would have it, the #3 and #7 pins are the easy to get at ones, better for soldering. No way that board comes out with all that hot melt goop.

KD0RC

Yep, pretty much how mine looks! Once you get the resistor installed, the looking around to see what is causing the audio loss completely goes away!

Mark777

Re. the LED going out - does it eventually light up again?

Useful mod, I just acquired a set to improve on the craptastic sound of a Panasonic LCD TV (for a relative), didn't realise they have this standby function which is frankly worse than useless - the speakers probably use about a watt while silent and in my experience electronics are more likely to die with constant power-cycling than being left on 24/365 (which I always do with low-current devices).

KD0RC

Hi Mark, yes, once it gets enough audio, the LED comes back on. I didn't feel like fiddling with it further, so I just left this little "feature" alone.

Mark777

Hi Len - the example I got hold of don't seem to go into standby. They were bought (used) in the UK, tested them for a day, couldn't get them to mute, and my aunt reports no such occurrence either, so maybe they've, er, gone wrong?! Or perhaps they're really old and the 'feature' hadn't been introduced at the time? Whatever, I can't say I'm disappointed!

KD0RC

Hi Mark, most likely old enough that the feature hadn't been implemented yet.