Quantcast Panasonic S-VHS power supply, bigger caps on UNREG_V? - digitalFAQ Forum
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  #1  
02-24-2016, 01:23 PM
AdamEurope AdamEurope is offline
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I can see that there are many lines labeled UNREG_*V in the power supply section (Panasonic S-VHS VCRs). They are after the main transformer.

My question is: is it OK to put bigger caps (1.5-2 times bigger) to these lines?
Or will it cause overvoltage?
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  #2  
02-24-2016, 05:07 PM
jawasmell jawasmell is offline
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Are talking about higher voltage caps or higher values, it is always safe to go a bit higher voltage, but I believe to be sure you should use the same value. Also try to use 105c caps and higher quality caps, such as nichicon pw or Panasonic fc,fr and fm, like I would, no point in doing that amount of work if you are just going to replace them with any no name cap.
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  #3  
02-24-2016, 08:37 PM
AdamEurope AdamEurope is offline
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Thanks. Yes, I have not clarified what does it mean "a bigger capacitor".

So I am talking about slightly bigger capacity, eg. putting 3300uF instead of 2200uF. Nothing more than adding 30-100% additional capacity. Voltage not less than original.
And an important thing. I am talking only about those big stabilizing capacitors in power supply that are right after the main transformer and silicon diode.

In an example Panasonic NV-HS1000 power schematic diagram (section 4.1.) i saw the UNREG_14V line. So I was curious if bigger capacity overvoltages latter circuit.
Now I can see that the UNREG_*V is simply "regulated" by a Zener diode in each case.


But my question was if it is OK to play using bigger capacity with that fancy switching supply?
Will it cause any problems like overvoltage, shutting down the switching power supply driver or homemade fireworks?
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  #4  
02-28-2016, 05:07 PM
dpalomaki dpalomaki is offline
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Consider that larger mfd means lower impedance, and potentially larger inrush current, especially those caps immediately after the diodes. While some modest increase would not likely be an issue, significant increase (e.g., 2x) might be depending on the overall circuit design. Note also that some power supply components are labeled a safety items calling for exact replacement.

I would stick with the values and tolerances used by the OEM - if the gear was a quality performer when new. A higher temp and/or voltage rating may be OK, but can mean a physically larger component that might not fit in all applications.
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  #5  
02-29-2016, 06:52 AM
AdamEurope AdamEurope is offline
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@dpalomaki: Thank you for the considered answer.
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  #6  
03-01-2016, 02:24 AM
ShemSeto ShemSeto is offline
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As per my experience it is always safe to go a bit higher voltage, but I believe to be sure you should use the same value.
Also try to use 105c caps and higher quality caps, such as nichicon pw or Panasonic fc,fr and fm, like I would, no point in doing that amount of work if you are just going to replace them with any no name cap.
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  #7  
03-01-2016, 08:04 PM
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lordsmurf lordsmurf is online now
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We always defer to TGrant on things of this nature.

The best place to get JVC/Panasonic S-VHS VCRs repaired!

http://www.tgrantphoto.com/sales/ind...epair-services
http://www.tgrantphoto.com/sales/ind...talFAQ-coupons

- Did my advice help you? Then become a Premium Member and support this site.
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