Picked up a non-working Yamaha t-85

[amr2]

Hello

I have just picked up this tuner. The seller stated that the problem is only the screen that doesn't light up, but It doesn't work at all. When it powers on, only memory leds lights up (B1-B10). The rest of leds and the display lights up for a fraction of second when the unit is powered on or off. Power supply voltages are OK. Any suggestions are greatly appreciated...

 

[amr2]

I'm testing the signals that goes from IC213 (CSL Controller) to the front board (CN2). IC213 uses a ceramic resonator (labeled as FCR800K). Anybody knows the frequency?

 

[amr2]

IC213 resonator

IC214 XTAL

 

[Lesterbest]

If you're serious about this tuner, you should get a pro alignment which can't be done with no knowledge & no pricey test gear.

 

[DRecovery]

I'm testing the signals that goes from IC213 (CSL Controller) to the front board (CN2). IC213 uses a ceramic resonator (labeled as FCR800K). Anybody knows the frequency?

Can you see any kind of oscillation with the scope?

As a quick guess, I would say it's 800kHz (800K) because newer FCR parts seem to be labeled similarly, e.g. FCR4.0M for 4MHz.

 

[amr2]

Solved. The problem was a faulty capacitor in the reset circuit. I think that is time to recap this unit.

As a quick guess, I would say it's 800kHz (800K) because newer FCR parts seem to be labeled similarly, e.g. FCR4.0M for 4MHz.

Yes, it's 800KHz. Checked with the scope.

 

[amr2]

Do you have any suggestion for the yellow NCC 5.5V 4.7mF capacitor? It's used for the memory backup.

 

[DRecovery]

Do you have any suggestion for the yellow NCC 5.5V 4.7mF capacitor? It's used for the memory backup.

View attachment 865991

I would try putting a SuperCap in there. You know you want to!

I might look at something like this:
http://www.digikey.com/product-detail/en/elna-america/DH-5R5D474T/604-1011-ND/970172

I would put a 1,000uF or so standard cap in that location and then add the SuperCap in parallel in a convenient location. Maybe use a 100 ohm resistor in series with the SuperCap to buffer the supply a bit.

Of course, something like this might just drop in:
http://www.digikey.com/product-detail/en/nichicon/UKL1C472MHD/493-10524-ND/2598405

 

[DRecovery]

Which cap was bad in the reset circuit? I'll bet it was the 1uF.

 

[amr2]

The faulty cap was C343 100u/16v. This makes Q287 and Q288 to be always in saturation mode, and the reset line = 0 volts

 

[amr2]

Of course, something like this might just drop in:
http://www.digikey.com/product-detail/en/nichicon/UKL1C472MHD/493-10524-ND/2598405

This is what I had in mind, a low leakage type. But I like the idea of a Supercap

 

[amr2]

If you're serious about this tuner, you should get a pro alignment which can't be done with no knowledge & no pricey test gear.

Thank you. I will try to find someone that can do the job.

 

[amr2]

About the capacitors, anybody has a recomendation for each section? I don't have too much experience with tuners.
For the power supply, Nichicon HE, PW or Panasonic FM could do the trick, and Nichicon BP for bipolars.

 

[dr*audio]

I use Panasonic FC caps or Nichicon 105 C high frequency caps, BP where required.

 

[amr2]

I use Panasonic FC caps or Nichicon 105 C high frequency caps, BP where required.

Thank you! What do you think about using FM instead FC caps?

 

[dr*audio]

Thank you! What do you think about using FM instead FC caps?

I was not aware of the FM caps. Should be good, I will have to try them myself. Lower ESR and higher ripple current, same specs otherwise.

 

[amr2]

Yes, and I think that the life time is longer as well. I have used them a few times. I think I'm going to use the FM's where I could, FC's if value/voltage is not available. For the main filter cap, Nichicon PW or UCC KYB.

 

[dr*audio]

Replace the caps in one section at a time, then test. That way if you screw something up, you will have an idea what section it is in. Always check the polarity marked on the board vs the marking on the cap before you remove it. Sometimes there are silk screen errors. A common problem in Yamaha tuners is the sensitivity drops off with age. Often this is caused by bad ceramic caps in the front end. Check the sensitivity when you are done and if it's poor, you might want to replace the ceramic caps in the front end. Use NPO / COG caps. Panasonic or Murata should be fine.

 

[amr2]

Perfect. Thank you very much!

 

[ConradH]

I've always thought the sensitivity of my T-85 sucked. Interesting about the caps- I've never seen ceramics go bad. Any particular caps you can point out? I haven't done an alignment yet and doing such when things aren't working correctly is usually a recipe for trouble. amr2, how does the sensitivity of yours compare with other tuners/receivers?