IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

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w-u-2-o
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IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby w-u-2-o » Thu Dec 28, 2017 2:43 pm

UPDATE: please see the post from Sunday, 31 Dec, below. There is some danger in using this circuit, it is not recommended at this time.

John, KB1YD, recently came up with a brilliant method to fix the fan noise on the 7000DLE and gave me permission to post it here.

As you may know, the root cause of the problem is reported to be the PWM controller waveform. John reasoned that the old trick of using a snubber circuit to soften the edge rates on the PWM waveform might help. According to John, this makes his fan "as quiet as a mouse".

John very graciously provided this schematic:

Image

Conveniently, the fan control circuit on the 7000DLE is arranged such that you can actually install this circuit without opening the case, as the external fan connector is wired in parallel with the internal fan:

Image

If you try this and find that it works for you, please post here and let us all know.

Disclaimers: I don't have a 7000 and have not tried this for myself. There are no oscilloscope measurements of the resulting waveform nor any fan speed measurements either (yet). Do this at your own risk.

73,

Scott
dl4zbg
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Re: 7000DLE fan noise fix

Postby dl4zbg » Sat Dec 30, 2017 7:54 am

Hello Scott,

just tried this mod "on the fly" (did not manage to get the right pins for the fan plug - they will arrive in within a few days). Reduces the "rattling" noise A LOT. Will report next year.

Thanks again

73

Volker

DL4ZBG
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w-u-2-o
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Re: 7000DLE fan noise fix

Postby w-u-2-o » Sat Dec 30, 2017 2:59 pm

That's great, Volker!

If you are able to capture any waveform or fan speed/performance data associated with this modification, I'm certain everyone would find that invaluable. Right now there is not enough data to know if it is reliable and safe.

Thanks,

Scott
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w-u-2-o
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Re: 7000DLE fan noise fix

Postby w-u-2-o » Sun Dec 31, 2017 4:44 pm

John has just reported to me that the snubber circuit is not fully compatible with the TC652 fan controller IC. It turns out that the TC652 implements a fan sensing circuit that will cause the fan to shut down until power is cycled on the radio if it thinks the fan is not turning. Refer to Sections 3.0 and 3.3 of the TC652 datasheet.

It would appear that the softening of the current pulses is on the edge of tripping the fault detection in the TC652. John reports that this is happening to him every few hours. This can be a dangerous condition as you may not hear or notice that the TC652 has stopped the fan and the radio could overheat. Use of this circuit is therefore not recommended at this time.

Looking at the TC652 datasheet more closely, it can be seen in Section 4.1 a method that the TC652 manufacturer recommends for reducing acoustic noise. It also refers to this application note.

Unfortunately, looking at the Apache Labs implementation, it can be seen that they attempted to implement this noise reduction method, but defeated the entire method by using a FET instead of a BJT as the switching circuit element. This also explains why the base resistor is shown as a 0 ohm resistor. Most unfortunate.

The question now is can a set of snubber characteristics be identified that reliably satisfies the TC652 sensing circuit while still providing enough softening of the PWM waveform to achieve a useful amount of noise reduction in a safe manner.

The other alternative is to replace Q7 with a suitable BJT and R77 with a suitable resistor in accordance with this application note.

73,

Scott
dl4zbg
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby dl4zbg » Mon Jan 01, 2018 5:04 pm

Thanks for the warning, Scott......

Please excuse me for not replying earlier but we weren't celebrating New Year's at home....
I have been using John's "rattlesnake taming circuit" for a few hours without problems, just after I have finished the connection of the 7000 to my MicroHam MK2R+. Just made a few QSOs on 80... However, the level of noise was greatly reduced, but the rattle is still audible.

I call in question whether Apache Labs will ever fix this (NPN transitor instead of FET). So as a true coward I will wait for the first volunteers to make the mod with the BJT HIHI.

Thanks again and Happy New Year to you and all Hams reading this post reply.

Volker

DL4ZBG

BTW: If you want to use DIG2 input for an external keyer (e.g. MicroHam), you have to enable DSP>CW> Checkbox IAMBIC. Took me some time to figure this out...
K9RX
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby K9RX » Mon Jan 01, 2018 11:27 pm

Volker,

Not sure if Scott is going to want to move this but - use DIG2 as an external keyer? Why would you put the radio in DIG mode to use it in CW? What am I missing? I DO have a microHAM Keyer II and I was not able to get N1MM+ to work driving the radio on CW ... not sure if this applies or not.

Gary
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w-u-2-o
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby w-u-2-o » Tue Jan 02, 2018 12:17 am

Gent's,

Moving individual posts is a pain ;)

It's a great topic, though. It would be beneficial to all if you made a new topic in the keys and keyers sub-forum where future seekers of the same information would logically look for it.

Thanks,

Scott
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David G
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby David G » Tue Jan 02, 2018 1:51 am

Man, what is it with Apache Labs and fans? :lol:
dl4zbg
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby dl4zbg » Tue Jan 02, 2018 4:17 pm

K9RX wrote:Volker,

Not sure if Scott is going to want to move this but - use DIG2 as an external keyer? Why would you put the radio in DIG mode to use it in CW? What am I missing? I DO have a microHAM Keyer II and I was not able to get N1MM+ to work driving the radio on CW ... not sure if this applies or not.

Gary


Gary,

Scott is right. I will post the info in the keyer index.

I'm shure you know this:
http://www.microham.com/Downloads/MK2_N ... _Setup.pdf

I am using both the MK2R+ and the micro keyer II (for contest operation with our local team). Winkey operation works flawlessly with Win-Test and UCXLog. There are two ways of connecting an external keyer (like a straight key):

1) Front panel Keyer jack "Tip and Sleeve" : Checkbox DSP>CW "IAMBIC" OFF
2) Rear Panel RCA jack DIG In 2 : Checkbox DSP>CW "IAMBIC" ON (not mentioned in the User's Guide- I was a little surprised....)

Sorry for causing confusion

Volker
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w-u-2-o
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby w-u-2-o » Tue Jan 02, 2018 9:25 pm

Has anyone tried their fan simply hooked up to 12VDC and running full speed? It might be quieter that way...
dl4zbg
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby dl4zbg » Thu Jan 04, 2018 7:14 am

Yes, Scott.

No rattle but the fan is loud at full speed. Abt. 7-8 Volts should be ok while using an external controlled fan. I will check this next time.

Volker
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w-u-2-o
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby w-u-2-o » Thu Jan 04, 2018 12:32 pm

Good to know, Volker, thank you.
W2PHL
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby W2PHL » Mon Jan 22, 2018 3:48 pm

After experimenting with different values, I settled on 10 ohms with 68uf. I haven't had the fan shutdown with these values. The circuit is pig-tailed on the external fan connector. Since the snubber components are located farther away from the fan, it's possible there is some inductance also affecting the timing. I'm using the original fan.

Phil
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w-u-2-o
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby w-u-2-o » Mon Jan 22, 2018 8:26 pm

Keep a careful eye on that, Phil!

How's it sound? Much quieter?
W2PHL
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby W2PHL » Tue Jan 23, 2018 7:31 pm

I'd say most of the rattle sound is gone. It is noticeably quieter but not silent.
dl4zbg
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Re: IMPORTANT UPDATE/DO NOT USE: 7000DLE fan noise fix

Postby dl4zbg » Thu Jan 25, 2018 3:53 pm

Installed the new snubber circuit today. I agree with Phil. It works just like the one described previously.

The Indian Rattlesnake is not tamed but somehow appeased...... :D

Hopefully I have a little more time in the near future to try the internal fan on fixed speed.

73

Volker

DL4ZBG

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