eXpediency
New Member
If you do not have a filter electrolyte C16 half-wave rectifier (-31.3V) in the Led Driver, then you get the same effect with ripple at the mains frequency.
With proper power supply +5 for logic.
Compare with diagram in #33
Technics SH 8066 display problem
- Thread starter Gigiga
- Start date
With proper power supply +5 for logic.
Compare with diagram in #33
Have you checked for a cold solder on the crystal oscillator X1 for the main microprocessor IC 60. Because they vibrate, they can develop a cold solder. It maybe okay if the functions like the pink noise generator is working and other functions are working correctly, but one has to rule that out first.
Gigiga
New Member
I visually checked the solder joints under the motherboard and didn't see any cracks with the naked eye, but now that you've pointed this out, I'll double-check with a magnifying glass
The only equipment you need is a resistor of 100k and a little dexterity in your fingers to hold it between two solder pads. Or use a alligator clip wire to attach one end to the -31 V line (D17 is a good spot) and hold the other to a segment pin of the VFD. For instance to pin#1 of J7 on the FL board. You seem to be able to replace zener diodes, surely you can manage an easy task like this?
Gigiga
New Member
I'm completely self-taught: what I know how to do I learned by following these forums and some tutorials on YouTube.
Touching the same free end to any of the other pins on J7 greatly attenuated the ghosting effect, leaving it only slightly visible at the top of the segments.
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Thanks for the tip (I didn't know this). I didn't have a 100kΩ resistor at home, only a 100Ω/2W one and a 2.2Ω/1W one. I tried both by attaching an alligator clip to the anode of D17 and the other end to one side of the resistors. Touching the free end of the resistor to pin 1 of J7 turned off all the segments of the spectrum analyzer at the bottom of the display (I tested this without passing an audio signal through the equalizer) and the ghosting remained.
Touching the same free end to any of the other pins on J7 greatly attenuated the ghosting effect, leaving it only slightly visible at the top of the segments.
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Gigiga
New Member
I checked the solder joints of X1 next to IC60 with a magnifying glass: I didn't see any signs of cracks, but I took advantage of the open board to reinforce the solder joints and replace the D17 zener diode again (removing the 8.2 V one and replacing it with a new 6.8 V one as specified in the service manual). Naturally...no changes.
eXpediency
New Member
100kΩ resistor is like 100 x 100Ω resistor.
You unnecessarily risk damaging something that is still functioning.
Especially using a 2.2Ω resistor.
Gigiga
New Member
Unfortunately, I don't have the right resistor at home (but I still wanted to try it to get a feel for what you suggested). As soon as I can get a 100K resistor, I'll try again and post the results.
eXpediency
New Member
Trying with a difference of 100 units is reckless, etc.
This is commensurate with a short circuit in the circuit.
eXpediency
New Member
As an option, use an additional electrolytic capacitor in the -31.3V circuit.
Somewhere there or in another convenient place.
Or borrow an oscilloscope from someone to really clarify the picture of the ripple level.
Somewhere there or in another convenient place.
Or borrow an oscilloscope from someone to really clarify the picture of the ripple level.
Gigiga
New Member
Dear friends, I sincerely thank everyone on this thread (past and present) for their invaluable advice and remote collaboration. However, over a year after my first post, I've come to the conclusion that I won't be able to solve the problem alone, with my limited knowledge and equipment. My obvious technical incompetence will prevent me from achieving success. I'll keep the device as is (also to avoid further damage). Thanks again, everyone.
eXpediency
New Member
It's very unfortunate that your problem has not been resolved. 
At least the solution was out there somewhere.
At least the solution was out there somewhere.
Sometimes you need to walk away for a while. Then you can come back at it fresh again, sometimes with a new idea. Giving up for a while is a good thing. Cold solders are the number one fault in electronics, second by capacitor failure, third failed power supplies and then the trouble others. You learn nothing if you don't try.
eXpediency
New Member
Gigiga wanted a quick solution to the problem and without minimal skills in this field of electronics.
Some of which can still be repaired somehow, unlike the current one (disposable).
Some of which can still be repaired somehow, unlike the current one (disposable).
It actually is 1000 times (1k, metric). It seems the micro survived. Let's wait until TS finds a 100k resistor.
eXpediency
New Member
Or an oscilloscope, which will be more informative.
Looks like the 100k test was not successful. That means that I've exhausted my capabilities for distance repairing. Without the unit in front of me (or with a replacement microcontroller) the ghosting is not going away. The only way to get it going again (lacking a replacement controller) is a custom output driver for the segments. Again, without the unit on my workbench there's no way this will be realized. By myself, that is.
eXpediency
New Member
If the situation is similar to what was on my SH-8066 and presented here, then the controller is functioning.
Since all the logic of work is present.
The background is given by the lack of filtering on the -31V circuit.
But since the user’s competence and lack of equipment do not allow remote identification and solution of the problem.
I disagree. TS did performed actions that exonerated the -31 V line. I've seen more micros go phut this way. Getting it going again requires electronics skills that TS lacks.
eXpediency
New Member
We talk about this when we independently solve such problems.