Tom,
That hum could also be caused by a bad voltage regulator, which would
explain why you don't hear it when the mic is unplugged. If the VR is bad,
the voltage will vary more as you draw more power, which will make the hum
increase.
Steve
----- Original Message -----
From: "Colin McDonald" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, April 18, 2013 20:00
Subject: Re: Mike hum
> hey tom, you did say it's a home brew power supply right?
> could the filter caps be going bad in the power supply? When they begin
> to
> go bad you do get hum on the tx signal because there is ac coming through
> to
> the radio.
> Do you have another supply you could try?
> Also, turn on the tx monitor on the ts2000 to hear if the hum is coming
> through the audio path.
> It's function plus the RF power key to adjust the tx monitor level. Use
> the
> multi-select knob to adjust the level etc.
> I used a home brew supply for several years and had to replace the big
> main
> filter cap once for precisely the same problem.
> The hum will tend to get worse as you increase the load on the supply,
> that
> is, when you increase current draw with higher power. However, if the cap
> has really gone south, even 5W output will have a hum.
> I presume you have tested for the hum on all bands including VHF/UHF and
> on
> FM as well?
> I'm not posative the hum will be heard via the tx monitor if it's a power
> supply hum though. Also, you won't hear hum on the receive if the cap is
> still healthy enough to supply enough smoothing capacity for the low
> current
> draw on receive.
> A further question on the home brew supply, does it utilize a 3 pin power
> plug, or a two? if a two pin, try flipping it around to see if the hum
> and
> shock go away.
>
> We'll narrow this down yet.
>
> 73
> Colin, V A6BKX
> ----- Original Message -----
> From: "Tom Brennan" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, April 18, 2013 4:26 PM
> Subject: Re: Mike hum
>
>
>> I'm not really hearing any hum myself. Its being reported to me as an rf
>> hum by
>> other hams.
>>
>> I can disconnect the mic cord from the mic itself. I've replaced the
>> cord
>> but
>> no joy. Heil has looked at the mic and says its fine.
>>
>> Tom
>>
>>
>> Tom Brennan KD5VIJ, CCC-A/SLP
>> web page http://titan.sfasu.edu/~g_brennantg/sonicpage.html
>
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