The relay delay section works by attenuating and rectifying a small level of a.c. from the transformer secondary using diodes and an RC network - the output of which is sufficient to bring a sense transistor to the threshold of conduction. There is a 47k resistor in part of the input to this set up which also provides dc protection.
The resistance in the new relay coil is less than the original so the combination with the 560 Ohm series resistor will divert more signal current away from the sense transistor along with an increased element of mains frequency a.c. passing to the relay coil.
The resistance in the new relay coil is less than the original so the combination with the 560 Ohm series resistor will divert more signal current away from the sense transistor along with an increased element of mains frequency a.c. passing to the relay coil.
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Just a little question, Has anybody experience or had an idea why is my TA 4650 that is being restored has a problem of not working when dual channel (stereo) have the vfets. If i removed the vfets on one channel the channel sings with good measurements on voltage reading with respect to the service manual. If both channel vfets are in, the voltages collapsed but the supply is stable for output and predriver. I had already done replacement of the death diodes and additional diode in the psu doublre area. also replaced 1.5k res to 3.3k.
I'm just puzzled why if they are in mono they work and sing but in stereo not, what causes the problem? I had isolated the amp section alone.
I'm just puzzled why if they are in mono they work and sing but in stereo not, what causes the problem? I had isolated the amp section alone.
an other try!
My next try to solve this issue of popping speakers in Sony 4650 (which also happens in the 5650 serie), is the power button itself. Spraying some heavy cleaner in the power switch solves the issue for a while. I cut of exactly the same switch from an old TA-2650 and opened it. The contacts are totally black. I have cleaned the switch and managed to put it back together (which is not easy with big hands and thick fingers). No I am going to change the switch in the TA-4650 with the cleaned one... fingers crossed guys.
My next try to solve this issue of popping speakers in Sony 4650 (which also happens in the 5650 serie), is the power button itself. Spraying some heavy cleaner in the power switch solves the issue for a while. I cut of exactly the same switch from an old TA-2650 and opened it. The contacts are totally black. I have cleaned the switch and managed to put it back together (which is not easy with big hands and thick fingers). No I am going to change the switch in the TA-4650 with the cleaned one... fingers crossed guys.
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Clean off switches with a liquid cleaner like Carbon Tetrachloride (hard to get) or perchloroethylene, to remove the black oxidized stuff. I use an old tooth brush.
When reassembling, align contacts as they were, they tend to make male - female matching peaks and lows as they wear, so in contactors I used to do one set at a time, so that they matched.
Then I used CRC 2-26 contact cleaner, excellent.
It quenches the spark, contact life is greatly enhanced, and I used MOVs too to reduce arcs further.
Not needed in low watt stuff, but if the switch is hard to obtain, put one MOV live to neutral on load side.
Saves you trouble later on.
When reassembling, align contacts as they were, they tend to make male - female matching peaks and lows as they wear, so in contactors I used to do one set at a time, so that they matched.
Then I used CRC 2-26 contact cleaner, excellent.
It quenches the spark, contact life is greatly enhanced, and I used MOVs too to reduce arcs further.
Not needed in low watt stuff, but if the switch is hard to obtain, put one MOV live to neutral on load side.
Saves you trouble later on.
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FIXED!
Hi Guys,
Well... often problems are more simple than we can guess... The issue of popping speakers in the Sony TA-4650 / 5650 is solved! Carefully opening and cleaning the very dirty contacts inside the power switcht solved the issue!
Putting the power switch back together is quite a challenge. There are two bent contact bridges and two tini springs and plasic pieces that switch the bridges... Don't drop them!!
If I do a next one this weekend, I can post some more pics from inside the power switch. I will be looking for a replacement switch, but they will probably be hard to find.
Most important: The trick works!
Hi Guys,
Well... often problems are more simple than we can guess... The issue of popping speakers in the Sony TA-4650 / 5650 is solved! Carefully opening and cleaning the very dirty contacts inside the power switcht solved the issue!
Putting the power switch back together is quite a challenge. There are two bent contact bridges and two tini springs and plasic pieces that switch the bridges... Don't drop them!!
If I do a next one this weekend, I can post some more pics from inside the power switch. I will be looking for a replacement switch, but they will probably be hard to find.
Most important: The trick works!
Open it inside a box turned on its side, the parts that fly off will stay in the box.
Or try to put another switch if you can, more life, especially if you put one with a higher rating.
Stick to Japanese, German or Indian, the ones from China may not be what the label says in terms of current rating.
Given there are different plastics inside, I would not advise a dip in solvent as an alternate way to clean it, you must open it.
Or try to put another switch if you can, more life, especially if you put one with a higher rating.
Stick to Japanese, German or Indian, the ones from China may not be what the label says in terms of current rating.
Given there are different plastics inside, I would not advise a dip in solvent as an alternate way to clean it, you must open it.
In most countries, nasties like carbon tetrachloride and perchlorethylene have been banned from use and public sale for decades - that makes it hard to get. It was once widely available - yes, my father often used carbon tet. for cleaning delicate instruments but thankfully, they are no longer since chlorinated hydrocarbons and similar dry cleaning solvents, have bad effects. In in acute cases, they do permanent damage to lungs, liver and kidneys.
These days, isopropyl alcohol is considered much safer for home use, even if not as fast and effective in all situations. After all, the solvent action is less important here than just having a quick drying, flushing medium to aid with removing accumulated dirt and debris.
After several tests, the popping is not completely gone, but it has improved a lot!
I have done several powerswitches now and they all are very dirty. some of the contacts are really worn out. To see if the wearing causes the left over minimal popping, I have ordered some replacements to see if this makes the popping go away completely.
If anyone has any advice on matching replacements... please let me know. The ones I found will probably not fit very well in the amplifier.
I have done several powerswitches now and they all are very dirty. some of the contacts are really worn out. To see if the wearing causes the left over minimal popping, I have ordered some replacements to see if this makes the popping go away completely.
If anyone has any advice on matching replacements... please let me know. The ones I found will probably not fit very well in the amplifier.
@Ian, Carbon Tet was used to extract diacetyl morphine from solution, dehydrated acetic acid, or acetic anhydride, was reacted with morphine.
Acetic anhydride is used to make synthetic vinegar, for example.
Diacetyl morphine is a potent and addictive painkiller, it was named Heroin by Bayer...
These - Carbon Tet and dehydrated acetic acid - were being used in the production of narcotic substances, India is one of the largest producers of opium.
In an attempt to control the illegal production of narcotics, these substances are highly controlled, and are not available except to users with permits who must account for the use of the material.
Here white petrol (benzene?) is used as a dry cleaning solvent.
Iso propyl alcohol disintegrates poly carbonate, and acetone is dangerous to many plastics, also it can damage paint.
Hence during use bear this in mind.
I just found my stocks of acetone and chloroform have evaporated, I got them in 2005.
Now to see if I can get them from the chemical dealer, I had only 500 ml each....
Acetic anhydride is used to make synthetic vinegar, for example.
Diacetyl morphine is a potent and addictive painkiller, it was named Heroin by Bayer...
These - Carbon Tet and dehydrated acetic acid - were being used in the production of narcotic substances, India is one of the largest producers of opium.
In an attempt to control the illegal production of narcotics, these substances are highly controlled, and are not available except to users with permits who must account for the use of the material.
Here white petrol (benzene?) is used as a dry cleaning solvent.
Iso propyl alcohol disintegrates poly carbonate, and acetone is dangerous to many plastics, also it can damage paint.
Hence during use bear this in mind.
I just found my stocks of acetone and chloroform have evaporated, I got them in 2005.
Now to see if I can get them from the chemical dealer, I had only 500 ml each....
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Oh and another thing, the MOV acts as an arc quencher, so the pops will reduce.
For testing, use another switch next to the fitted one, or outside in series, leaving the original one fitted and in circuit.
Then put the MOV and see. it should help a lot.
Another trick from sodium lamps is to put a 2.2 or 3.3M resistor across the main caps as a bleed resistor.
You gave output caps in series with the speakers?
Those may work too...
For testing, use another switch next to the fitted one, or outside in series, leaving the original one fitted and in circuit.
Then put the MOV and see. it should help a lot.
Another trick from sodium lamps is to put a 2.2 or 3.3M resistor across the main caps as a bleed resistor.
You gave output caps in series with the speakers?
Those may work too...