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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 16th Apr 2021, 1:56 am   #1
Entangler
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Default Replacing Capacitors on Akai GX210D

I have an Akai GX 210-D, very infrequently used, that just lost audio in the right channel. Heads are clean, happens in forward and reverse, no signal to VU meter either direction.
It worked ok, then a loud hum-pop and it went out. I gather that the likely cause is failed electrolytic capacitors...but not completely sure.
I have the service manual, and am really good at de-soldering and re-soldering components, but I have no knowledge of actual electronics repair.
Sooo, I decided to replace all of the capacitors on the playback amp pc board...

So I looked at the board and the schematic and parts listing, and the first one on the board didn't match the paperwork. 1uF, 25WV (presume 25volt...not sure about the W) is actually 50V.

What should I do? Replace with the 25V, which are available...or look for 50V to match those on the board?
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Old 16th Apr 2021, 3:27 pm   #2
Grubhead
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Default Re: Replacing Capacitors on Akai GX210D

As with all capacitors, you can either match the ratings or go higher. A working voltage of 25 volts, can be replaced by anything at the level or higher. It doesn't effect the outcome. On some you have to watch the temperature shown in degrees. You couldn't replace a 100 degrees with an 85 one. But you could do it the other way around.
With capacitors it more or less down to space, since some 50V are bigger than a 25V, but if you have the space to fit it then it's fine. The voltage levels on the capacitors is sometimes near to the voltages in the circuit. But sometimes even the makers of the parts fit capacitors that have voltage ratings way in access of the volts in the circuit. So you will see 100V ones where the power supply is a 9 volt battery!
If the circuit says 25 volts you should get away with it. It's possible that when the board was made the maker had loads of 50V capacitors in stock so fitted them even though it specified 25V.

Last edited by Grubhead; 16th Apr 2021 at 3:34 pm.
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Old 16th Apr 2021, 4:31 pm   #3
Uncle Bulgaria
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Default Re: Replacing Capacitors on Akai GX210D

I think the worst thing you could do is replace capacitors willy nilly. You vastly increase the chance of creating a problem, without knowing if you've fixed the original one.

I'd recommend taking it slowly and being methodical.

Do you have a multimeter? Checking the DC voltages would be a first step that would narrow down the problem greatly, as you can see whether there is the right voltage at different parts of the amplifier chain.

You will likely find someone able to offer step-by-step assistance here, especially if you have the manual and/or circuit diagram as you appear to do. It's likely the part you mention as being a different voltage rating was either replaced previously, or the diagram you have is for a slightly different but basically similar revision of the unit.

A 'pop' implies something has blown, which should be obvious - the failed component should be visually distressed, perhaps cracked or burned.
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Old 16th Apr 2021, 5:08 pm   #4
TIMTAPE
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Default Re: Replacing Capacitors on Akai GX210D

I agree it's better to trace to the actual fault. The fault could be anywhere between the preamp's input and the line output. Why not check you have a signal from line input to line output on that channel?
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Old 16th Apr 2021, 9:04 pm   #5
DMcMahon
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Default Re: Replacing Capacitors on Akai GX210D

WV on a capacitor means "Working Voltage", the 1uF looks to be C23 which as you say is shown on the schematic as 1/25 and listed on the parts list as 1uF/25WV.

The DC supply to the PB amp board is +23.3V, C23 would see a lower voltage than this, so 25V rating would be OK, the 50WV one may be there for various reasons as already previously stated.

Agree with the others that just replacing all the capacitors is not a good idea in this case, you may do more harm than good, especially if you are not familiar with this type of work. I would first do a good visual of all the components looking for anything obviously damaged/overheated.

DC voltage checks as suggested by Uncle Bulgaria is a good place to start if no damaged components found, first establish if the +23.3V supply is reaching the PB amp board.

David

Update - the capacitor could also be C21.

Last edited by DMcMahon; 16th Apr 2021 at 9:10 pm. Reason: Update
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Old 17th Apr 2021, 5:56 am   #6
Entangler
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Default Re: Replacing Capacitors on Akai GX210D

Thanks all. This is extremely helpful! Comments and advice is exactly what I'd hoped for. I need to figure out next steps, but now know what to do and more importantly what I should probably NOT do.
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Old 17th Apr 2021, 4:34 pm   #7
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Default Re: Replacing Capacitors on Akai GX210D

1uF is such a small value for an electrolytic that these days it's pointless for cap manufacturers to make them in the lower voltage ratings, hence most are 63V and sometimes 50V. Even with a 63V rating a modern cap will likely be half the size of the original 25V rated part.
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