Need Help With My Rockola 484
sbiceps77
I just picked up a Rock-Ola 484 from guy a guy that told me that the
machine was tempermental after you moved it and that for him over the
years, after it was moved, it would make a loud humming sound for about
5 minutes or so after the first plug in. I moved it all in to my house
and it did do that loud humming sound the first time I plugged it in and
it went away. The problem is that it is still sporadically making this
loud humming sound when it's truned on and a lot of times, right in the
middle of playing a song from one of the 45's. Any ideas of what the
problem is or how to stop this? Thanks...
--
sbiceps77
Rob in NYC
wrote:
Where does the hum come from? Speakers? Or is it mechanical.
Rob
sbiceps77
It seems to be coming from the speakers...
'Rob in NYC[_2_ Wrote:
> ;663015']On Nov 26, 9:25*pm, sbiceps77
> sbiceps77.80e7...@collectingbanter.com
> wrote:-
> I just picked up a Rock-Ola 484 from guy a guy that told me that the
> machine was tempermental after you moved it and that for him over the
> years, after it was moved, it would make a loud humming sound for
> about
> 5 minutes or so after the first plug in. *I moved it all in to my
> house
> and it did do that loud humming sound the first time I plugged it in
> and
> it went away. *The problem is that it is still sporadically making
> this
> loud humming sound when it's truned on and a lot of times, right in
> the
> middle of playing a song from one of the 45's. *Any ideas of what the
> problem is or how to stop this? *Thanks...
>
> --
> sbiceps77-
>
> Where does the hum come from? Speakers? Or is it mechanical.
>
> Rob
--
sbiceps77
Rob in NYC
wrote:
Ok, if the hum is coming from the speakers it points to either power
supply filtering or poor ground connections.
Is the hum a deep bass note -same as when you touch the center
connection of an RCA cable that is connected to an amp. 60hz. If so
you might try wiggling the various connectors that go into the amp
chassis and see is that causes any change. Does this type of hum
occur if you unplug the pickup or move it's wire.
Or is it a somewhat nasal higher pitch, this would be 120Hz From
your description it seems that the hum can occur even when the machine
is just sitting there, plugged in but no playing. That points to amp
power supply. Again, try moving wires and bumping the chassis of the
amp to reveal a loose connection
If there are any filter capacitor cans on the amp, try tapping
those. We are looking for a loose connection or poor solder joint.
If nothing definitive comes of this you will have to remove the amp
and, depending on your comfort in dealing with electronics, secure a
schematic and trouble shoot or find someone willing to take it on.
I don't have a schematic for Any R-o's but Vern Tisdale has one for
the 478-481 series and they may be the same or "close enough".
http://www.verntisdale.com/schem/478-81.JPG Part 1
http://www.verntisdale.com/schem/478-81a.JPG Part 2 with power
supply section. If this is the same in yours, I notice an edge
connector on the "Power supply P C Board assembly" These connectors
are often the cause of problems. If you are able to open the amp, you
might try removing this boards and cleaning the copper edge connector
with either contact cleaner or just rubbing alcohol then reseating
it..
But It sounds like a simple change of filter caps is in order.
Rob
sbiceps77
Thanks for the help, I will give it a go. Also, it is a dull, deep bass
hum, not high-pitched at all...
'Rob in NYC[_2_ Wrote:
> ;663175']On Nov 27, 2:13*pm, sbiceps77
> sbiceps77.80f7...@collectingbanter.com
> wrote:-
> It seems to be coming from the speakers...
>
> 'Rob in NYC[_2_ Wrote:
>
>
> -
> ;663015']On Nov 26, 9:25*pm, sbiceps77
> sbiceps77.80e7...@collectingbanter.com
> wrote:-
> I just picked up a Rock-Ola 484 from guy a guy that told me that the
> machine was tempermental after you moved it and that for him over the
> years, after it was moved, it would make a loud humming sound for
> about
> 5 minutes or so after the first plug in. *I moved it all in to my
> house
> and it did do that loud humming sound the first time I plugged it in
> and
> it went away. *The problem is that it is still sporadically making
> this
> loud humming sound when it's truned on and a lot of times, right in
> the
> middle of playing a song from one of the 45's. *Any ideas of what the
> problem is or how to stop this? *Thanks...-
> -
> --
> sbiceps77--
> -
> Where does the hum come from? Speakers? Or is it mechanical.-
> -
> Rob-
>
> --
> sbiceps77-
--
sbiceps77