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2 issues & I need guidance from the experts please

Discussion in 'General Audio Discussion' started by Squirrel!, Oct 12, 2018.

  1. Squirrel!

    Squirrel! New Member

    Messages:
    24
    As many MAY recall, I refurbed [cleaned up and replaced burned out light fuses, belts & needle] on my fathers old Kenwood KS-4000R receiver & MCS turntable for my daughters b-day. I bought Yamaha speakers and the system sounds 'o.k.', but not with clarity that I remember it having back in the 70's. I am thinking a recapping [after reading about many of you who did this] will rejuvenate and restore the audio quality of the Kenwood. It seems the bass is bloated and the treble is more of a tone control. No crisp highs or clear bass, just a treble and bass control the tone, if that makes any sense. It sounds the same no matter the speakers I try.

    What I am seeking are suggestions on where I would find a QUALITY place to do the work. Someplace that can actually provide some guidance if a recap would improve [or not] the SQ, and for a fair [not trying to get something for nothing] fee. Hoping I could get some guidance here.

    The next issue I have is my subwoofer plate amp fried [I guess I had it too loud for too long] and instead of getting an expensive replacement, I bought a Behringer KM-750 amp instead. I love the new amp, tons of power but the cooling fan runs non-stop and is rather annoying since it is in the same room I am in [no place else to go with it]. I tried just unplugging the fan and the temps stay cool enough that I'm not too concerned with shorting its life span. However, when watching a movie like 'Hot Fuzz', the KM-750 goes into protect mode, due to the heat. What I would like to do is not disconnect the fan but rather lower its RPM to reduce the noise level and still provide some cooling.

    It was suggested to me to try and insert a 240 ohm, 20 watt resistor in-line with the fan. The fan is only a 2 wire connection so I would place it in the positive line. My issue is 2 fold; 1) is this the right resistor to use & 2) where do I find such a resistor. Parts Express [who made the suggestion to me] had none in stock and I cannot locate a resistor with those specs online. So I would appreciate it if anyone has any advice. As is, I'm only running 1 of my 2 subs and the difference in SQ is noticeable.

    Thanks so much in advance for any suggestions/recommendations you might provide.
     

     

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  2. JoeESP9

    JoeESP9 ESL's & tubes since 83

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    There are quiet fans available. I replaced the cooling fans on two Crown XLS-402's. The original fans were audible across the room. The replacements are inaudible a foot away. The ones I bought were drop in replacements.
     
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  3. Squirrel!

    Squirrel! New Member

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    24
    Thank you for your reply. How would I go about finding one of these "quiet fans" and how do I know which to get? I like this idea better than having to add components.
     
  4. JoeESP9

    JoeESP9 ESL's & tubes since 83

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  5. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    I was wondering what voltage the OP's fan actually requires.

    As for the receiver, :lurk:
     
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  6. JoeESP9

    JoeESP9 ESL's & tubes since 83

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    With a DC fan a lower voltage means slower operation. I seriously doubt if the current fan is driven by more than 12VDC. If the OP wants to know specifically what the voltage is a simple measurement using a meter will do.
     
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  7. Squirrel!

    Squirrel! New Member

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    Thanks for the replies. I just now checked the voltage and I am now confuzzled more now than before. Please see pics and advise.
     

    Attached Files:

    Last edited: Oct 12, 2018
  8. Racingh11

    Racingh11 Active Member

    Messages:
    153
    First, a recap will probably get it sounding good again. I've had some amazing before and after results lately on some MCS 3233 receivers from recap.
    Second, the fan question is very similar to a job I just did. I rebuilt a Ashly FET500 for someone. They are actual theater amps and the fan runs at full speed all the time and is too noisy to be in the listening room. The first thing I did was replace the 20 watt fan with a low noise fan from ebay with a noise rating of 35-40 dB. It was still way too loud for my ear. So what I did was add a 20 watt, 400 ohm resistor in series with the fan. This brought the speed down to about 1/4 - 1/3 if I remember right. It all can be figured out by using ohm's law. Yours may take a higher value resistor if the fan is less than 20 watt and might be able to use a 10 watt rated resistor instead of 20 watt like I used. The second thing I did was wire a normally open thermal switch in parallel with the resistor and attached it to the heat-sink. The temperature value I used was 55C, which is around 132F. So when the heat-sink reached 132F(about 145F at the transistors), the switch closes and bypasses the resistor turning the fan on full power. Worked great when done and the noisy fan only turns on high when the the amp is cranked so loud you would never hear it.
    Here's the type I bought. : https://www.ebay.com/itm/KSD9700-Te...rotector-Normally-Closed-Open-C0/202303501365
    It might be possible to use only the switch and no resistor, but I used both because the FET500 idle current would heat up the heat-sink and I didn't want it to cycle on and off all the time.
     
    Last edited: Oct 13, 2018
  9. Racingh11

    Racingh11 Active Member

    Messages:
    153
    Look
    Looking at your pics, my guess is that it is a 12v fan that is rectified and regulated poorly and has voltage spikes on top of the dc voltage. If you have an oscilloscope it could be found out. Those fans usually have ratings on the case side of them and could be used to figure a resistor size. The one I worked on was a 120v ac fan. Resistors aren't really that expensive, you could get a 200, 400, and 600 ohm and see what noise and speed you are comfortable with. The one I built had specs of around 22 watt, 120v, .18A. So, 120/.18=667 ohm running resistance. 667/(667+400ohm)=.625, 120v*0.625=75v, .18A*.625=.1125A, .1125A*75v=8.4w, 8.4w/22w=.38. The fan I had with the 400 ohm resistor ran at 38% power when thermal switch was below 55C. If you could get the fan specs or measure the amperage and voltage, a power level and resistor could be chosen.
     
  10. Squirrel!

    Squirrel! New Member

    Messages:
    24
    I wish I was smart enough to know what you are talking about. As is, I do not have an oscilloscope, I know what they are, just not how to read one. I find it odd that I have stable voltages in both AC & DC when checked, as well as such a voltage drop when the fan is connected vs. unconnected. This is what confuzzles me so. Also, it seems from the link provided to Newegg, shows only 3 wire fans and this is a 2 wire fan. I would naturally ASSume that 3 wire is AC and 2 wire would be DC? I'm not good at electronics measuring/interpretation, as one might have surmised thus far. ;)
     
  11. toxcrusadr

    toxcrusadr AK Subscriber Subscriber

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    Central Missouri
    Haven't looked at the Newegg fans but either AC or DC would have two wires. Probably set up for two speeds using longer and shorter motor windings.'

    If the power supply for the fan is current limited, the voltage will drrop under load, compared to static no load conditions. The voltage when the fan is on is the one to watch.

    If the fan is emovable, look at all sides and the bottom fo a tag.
     

     

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  12. blhagstrom

    blhagstrom Mad Scientist, fixer. Subscriber

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    The fan should have a label on it with voltage rating. Probably on the “other side” where you can’t see it. Somehow, it always works out that way.

    Voltage readings can be weird when the circuit is unloaded, as in things are unplugged.

    Most fans I see are 12v but once in a while I see a 120v.


    The receiver may have quite a bit of SQ improvement with new e-caps but the cost is not trivial and that receiver is not worth the investment to hire the job done. A recap on a receiver is in the multiple hundred dollar range if done completely.

    If you just desire clear clean sound and want good sound from the turntable, I suggest a newer Yamaha. You can pick up a good working black face Yamaha cheap and they do an excellent job on Phono. I’m talking something like 15-20 years old, stereo. You should be able to pick one up for $100 or less shipped off eBay.

    It would be tough to get the Kenwood tuned up for that price.
     
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  13. Racingh11

    Racingh11 Active Member

    Messages:
    153
    Those should be DC fans, but I don't know why they use a 3 pin connector. AC fans only use 2 wires unless they are a huge 3 phase unit, which these are not. Maybe they have a speed output for PC use? Or maybe it's just the standard connector. The ac voltage on your meter will only show what voltage is alternating and the dc what is steady dc voltage. So it seems like you have 12 volts steady with voltage varying with it. AC "rides" on dc. So if you looked at a scope you would have the ac form positioned above or belove 0v by how much dc you have. I'm thinking the ac is just noise either from the dc supply or from the fan itself as it turns.
    What I was trying to show with the numbers above is that installing a resistor changes both the voltage and amperage at the fan and how it worked out on my project. Voltage divided by amperage equals resistance. If you used one of the 12v 0.12A fans listed on newegg, it would give you a running impedance of 100 ohms (12v/.12a). If you added a 100 ohm resistor to it, then you would have 1/4 power. 100/200total=1/2, 12v/2=6, 0.12A/2=.06. So your voltage and amperage would be cut in half. Volts multiplied by amps equals watts(power) So, 6v*.06A=.36W. Originally it was 12V*.12A=1.44watt. So .36watt is 1/4 of the original 1.44watts. I hope that makes sense. Basically I'm saying that if you can get the specs from the fan, you can pick a resistor. Or if you get one of those fans it may be quiet enough on its own without slowing it down. I would remove the fan and see if it has a label on the other side and start there.
     
    Last edited: Oct 13, 2018
  14. JoeESP9

    JoeESP9 ESL's & tubes since 83

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    Location:
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    What does the lose two conductor plug (red and black wires) come from and go to?
     
  15. wmgwizard

    wmgwizard AK Subscriber Subscriber

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    Location:
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    While I appreciate your desire to use the Bheringer amp you have, perhaps you should consider purchasing a replacement plate amp from PartsExpress. They are fairly inexpensive and designed for the sub with crossover and level controls.

    Is the "unimpressive sound" you describe on all sources, or just the TT ?

    Have you tried different speakers ?

    While a recapping of your receiver MAY alter the sound, there are vastly different experiences reported by many an AKer after performing similar repairs/upgrades/updates.

    A recap probably won't make a silk purse out of a sows ear....

    You may have better results with different speakers, a different cartridge or even just a new stylus.
     
  16. Squirrel!

    Squirrel! New Member

    Messages:
    24
    I agree. As much as I would like to have it done, I just can't justify paying $200 or more for a recap when I can get a sweet new[er] receiver for less. It's just that my daughter REALLY likes the thought of it being her grandfathers.
     

     

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  17. Squirrel!

    Squirrel! New Member

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    Yeah...I think I need to pull the fan and see exactly what I'm working with.
     
  18. Squirrel!

    Squirrel! New Member

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    Just the female end on the PCB.
     
  19. Squirrel!

    Squirrel! New Member

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    Yeah. I'm replacing a PE plate amp [SPA-500] which costs considerably more. I never used the parametric controls because I have the subs connected to my Denon w/Audyssey XT32 which does all the EQing needed. Crossover is handled by the AVR and the Behringer [of course] has level controls. Not to mention more power when bridged and an extra amp when not bridged, should the other PE plate amp fries.

    As for the sound, it is all sources and yes, I have tried different speakers, with the best sound coming from my MartinLogan's [of course] but still not close to what it should be.

    The Kenwood, while old and a lower tier of Kenwood, is [or more aptly, 'was'] no sows ear. The thing cranks for being 14 watts/ch. And I remember the sound being vastly superior back when I was a kid.

    The TT does have a new stylus and new belt, Deoxit used and honestly, sounds just like what a decent TT sounded like back in the day.

    I think I am leaning towards just replacing the receiver, just trying to look into all options before I break the news to the daughter.
     
  20. wmgwizard

    wmgwizard AK Subscriber Subscriber

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    Sadly our sonic memories can be some of the most jaded of all, perhaps it wasn't all you remember it was.

    As far as the sentimental aspect, many of us here have spent waaaay to much time and money keeping something alive well past it's monitary value for the sake of a memory.
     
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