My 77D(x) had sat for many years unused when it came to me, it’s a very early
s/n but still a great amp. Initially the blower was horrendously noisy.
Finally I pulled it out and stripped it down. Low and behold proper ball
bearing races at each end. I forget the number now but they are a standard off
the shelf bearing.
I used a windscreen wiper blade puller to extract the old bearings and a
suitable sleeve to drive home the new bearings. Awesome result and the only
noise now is air movement. Other than that a failed capacitor would seem the
only likely failure so it’s hard to imagine a need to replace the motor.
Replacing the bearings is easy and straightforward just work methodically and
clean.
Martin, HS0ZED
Sent from my iPhone
> On 26 Aug 2018, at 23:44, MU 4CX250B <4cx250b@miamioh.edu> wrote:
>
> Gary, I doubt you will find a drop-in replacement blower for the
> original rotron blower in your amplifier. It's a wonderful blower, and
> extremely reliable, but hasn't been made for years. Mine is thirty
> years old and still going strong. Of course, there would never be a
> need to replace the squirrel cage, and it should be possible to find
> an equivalent motor if the need arises.
> 73,
> Jim w8zr
> Sent from my iPhone
>
>> On Aug 25, 2018, at 7:06 AM, Gary Smith <Gary@ka1j.com> wrote:
>>
>> Folks,
>>
>> For years I've turned on the amp when
>> needed or when anticipated I will likely
>> use it as trying to work a DXpedetion or
>> sked. Turning off the amp, I've waited
>> till the tubes (pair of 8877 & another amp
>> with a pair of 3-500) are cooled down &
>> then turned off when done. Sometimes I
>> plan to use the amp later in the day &
>> wonder if I should turn it off & restart
>> later or better to leave it running.
>>
>> I've been concerned that frequent
>> cool-down & warm-up will cause future
>> leaks from excessive contraction/expansion
>> of the tubes. At the same time I have
>> concerns for leaving the fan on
>> un-necessarily.
>>
>> A replacement blower for the old Alpha SX
>> will be less expensive than replacing
>> tubes but replacement blowers for it I
>> understand, are difficult to obtain.
>>
>> I'm interested in thoughts about when it's
>> best to shut down an amp vs better to
>> leave it running. Other than the obvious
>> mechanical wear on the fan, is there an
>> issue on the tubes or PS by leaving the
>> amp on but unused for hours at a time.
>>
>> What's a practical rule of thumb?
>>
>> 73,
>>
>> Gary
>> KA1J
>>
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