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UserXP
Badcaps Veteran
Last Activity: 01-19-2024, 03:47 PM
Joined: 04-14-2012
Location: Niš, Serbia
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  • UserXP
    replied to Mackie CR4 amplifier no sound
    in Troubleshooting Audio Equipment
    Re: Mackie CR4 amplifier no sound



    You are welcome, it can be an interesting learning experience - and, you may actually fix your speakers.

    Yes, don't worry, the mains power is completely isolated. It goes through the cord, then through the black switch on the back and then to the power transformer through a fuse. Plus, all the soldering is covered by that black resin glue. So nowhere on the PCB is there a 120-240V power. The only voltage going through the board is that provided by the transformer, which is dual 14V (~20V total). We need the speaker...
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  • UserXP
    replied to Mackie CR4 amplifier no sound
    in Troubleshooting Audio Equipment
    Re: Mackie CR4 amplifier no sound

    The re-soldered diode looks fine, good job on that. Did you completely take out C39? In you image, it still soldered on.

    The black area is the burned PCB where Z3 and Z4 are. They are 12V, but receive about 20V. So, the remaining ~8V are disipated as heat. The two big resistors help do that. However, the diodes permit only 12V and get super hot in the process. It is possible that they burned out so there is nothing to produce the required 12V. Also, inspect the traces at the burned area. Intense heat can cause the PCB to crack. If the...
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    Last edited by UserXP; 06-08-2022, 05:25 PM.

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  • UserXP
    replied to Mackie CR4 amplifier no sound
    in Troubleshooting Audio Equipment
    Re: Mackie CR4 amplifier no sound

    You see, the no sound occurs when to much voltage is being apply to the TDA7265 amplifier chip on Pin5 - which is the Play/Mute pin. When there is voltage difference betwen the input voltage and the voltage on that pin (which is like 6-7V difference), the amplifier enters the Play Mode and you can hear the sound. When the voltage is equal to the input voltage (around 20), the amplifier chip goes into the Mute mode - that is why cutting Pin5 re-enables the sound, but then you lose its intended pourpose: to mute the speakers when you plug in headphones,...
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    Last edited by UserXP; 05-30-2022, 09:59 AM.

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  • UserXP
    replied to Mackie CR4 amplifier no sound
    in Troubleshooting Audio Equipment
    Re: Mackie CR4 amplifier no sound



    Great! Like you said, you have nothing to lose - but, since the [I]no sound[/I] issue with these CRx speakers is quite widespread, it is likely that you will be able to fix them. If you haven't done so already, take a look look at my other topic about the CR4s, there you will find how I implemented the LM7x12 daughter board:

    [URL="https://www.badcaps.net/forum/showpost.php?p=960666&postcount=62"]Mackie CR3 monitors - Page 4[/URL]Re: Mackie CR4 amplifier no sound



    Great! Like you    ...
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  • UserXP
    replied to Mackie CR4 amplifier no sound
    in Troubleshooting Audio Equipment
    Re: Mackie CR4 amplifier no sound



    Hello. Thank you for reading and finding this thread useful. Don't worry about not having experience, I was in the same shoes and have learned a lot from the people on this great forum.
    Since CR3s and CR4 use practically the same PCB, what you read in this thread will likely be applicable to your CR3 set as well.

    Now, you needn't worry about discharging anything. When the speakers are plugged into the mains, they immediately start converting power even if they are turned OFF on the volume knob switch (kind of...
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    Last edited by UserXP; 05-30-2022, 01:22 AM.

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  • UserXP
    replied to Mackie CR4 monitors
    in Troubleshooting Audio Equipment
    Re: Mackie CR4 monitors



    Great work! I am glad my topic has helped you fix your Mackies. As all the good people here on this forum directed me towards me fixing mine.

    Now, I haven't replaced all the capacitors like you did. But the TDA7265 puts out a lot of heat and the mute problem should be at bay with quality capacitors like the Japanese ones.

    I also don't understand the manufacturers. Instead of those two zener diodes and two resistors, they should have used two LM7x12 regulators and made a PCB that wouldn't have been a fire hazard....
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)



    OK, that sounds great. I didn't observe any overheating or bad voltages. I checked the line that powers the OKI chip, the voltage is about the same or slightly lower than it was with the original power transformer which was run on a 220 to 110 volts power converter. The clock is operational, it shows quite an aqurate time, the radio sounds clear, no crackling, buzzing, humming or any other unwanted noise, the reception is great, so it seems it will work OK.
    I also measured some of the filtering capacitors in there....
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    After a couple of hours of testing, I think this may turn out to be a good conversion. For reference, here are the previous readings with the original PT.

    A for [B]black[/B] (center tap)
    C for one [B][COLOR="red"]red[/COLOR][/B] wire
    D for the other [COLOR="red"][B]red[/B][/COLOR] wire.

    The voltage between A and C is 5.7V.
    The voltage between A and D is 5.9V.
    The voltage between C and D is 11.7V

    New readings with the replaced PT are:

    A...
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    Here are the results. The replaced transformer provides ~0.2 lower voltage now that it is loaded than the original one did.

    I used a replacement cable clip as the original one was broken.

    I connected the input power to the PT with a joint. It is neatly fixed with an M3 screw which conveniently is placed in the hole next to the 220-240V marking - excellent as an input voltage indicator on the back.

    I reattached all the wires. The little grey flat cable was especially challenging to solder without...
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    Last edited by UserXP; 01-06-2022, 10:35 AM.

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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    Update:
    I found a 230VAC transformer that outputs dual 5.5V, it arrived today. It is also shielded, so it could have come from some audio equipment, which is a plus (it's used, but in good shape). Upon measuring its terminals without load applied, it actually outputs 5.7V on center tap and 11.4V total. So it seems to be within the measurements taken from the radio clock unit. Hopefully, it will help converting the unit to work with 220V mains.
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    This is measured exactly at the point the three output wires are soldered onto the PCB. The rotary switch was set to OFF, only the display switched on.
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    I measured it.

    On the diagram, these wires are labelled:
    A for black
    C for one red wire
    D for the other red wire.

    The voltage between A and C is 5.7V.
    The voltage between A and D is 5.9V.
    The voltage between C and D is 11.7V.

    This is with load applied as the device turns the display on immediatelly after powering on.

    I suppose we need to achieve the 5.7 and 11.7 values (although, according to schematics, they should be slightly lower). But...
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)



    Thanks. If that's the case, then teplacing it wil be "go to eBay and search", which would bring Chinese sellers whose pictures of the products are usually generic/stock, plus the 50 day long shipping.
    The lowest dual output PTs I can find in a local electronics shop is 6-0-6. :/...
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)



    Could the marking T6-13CH on the original mean something like [B]T[/B]ransformer, center tap [B]6[/B]V, total voltage [B]13[/B]V, [B]CH[/B]ina? Maybe it's a 6-0-7, but Sony marked the two output voltages on it. In that case, a 6-0-6 12V transformer would provide the correct voltage for the 6V center tap, but slightly lower overall voltage (12V instead of 13V)?

    The schematics also show the pin setup for the 24 hour mode. Pins 41 and 42 indeed need to go to different pins of the display, plus Pin18 to 11V...
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    I will check with my multimeter. I followed the traces, black wire is A, red wires are C (half voltage) and D (full voltage). I see that black goes through a resistor to the first pin of the display marked as F. Is that the filament (heater) contact you were referring to?
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    It is small. Maybe 2.5x2.5x4cm roughly. The longest dimension is the base with holes for being fixed to the casing with two screws. Based on its small size, it is probably a 5W, 2x0.125A or so. I'm just guessing.
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)



    Bell transformers are what I looked for and found. The original PT is also of that type. It's the proper rating that needs to be selected. ...
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    I didn't know there is a heating element inside. A heater?
    So, could a resistor be inserted between the center tap 6V output to drop the voltage to the required 5.2V?
    I guess the output voltage of the PT would also drop a bit after load is applied.

    I found several PTs at a local shop which are dual 6-0-6 volts, a total of 12V of various VA, power and current. They are all 220VAC 50Hz input.
    I tried leaving the clock radio running for almost six hours to test the clock. It works flawlessly after the...
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    Last edited by UserXP; 12-25-2021, 02:43 PM.

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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)



    So finding a suitable 220-240VAC transformer with that specific output will be next to impossible?

    I found a 6-0-6 transformer which gives a total of 12V, so I hoped it would work. But it would be off-center, right? Would it work or would it over/undervolt some of the components and damage them?...
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  • UserXP
    replied to Sony ICF-C12W Radio Clock schematics (power)
    in Troubleshooting Audio Equipment
    Re: Sony ICF-C12W Radio Clock schematics (power)

    One more question. Is the transformet in this unit a center tap one, and would it be designated as 13V, 6,5-0-6,5?
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