Yamaha CS80

If I plug in the main wire loom into the psu and turn it on, the middle fuse blows immediately 
and I lose the +8.5 and -6.5. If I unplug the main socket into the PSU and turn it on (after 
replacing the fuse it doesn't blow)

Heath Finnie wrote:
> If I plug in the main wire loom into the psu and turn it on, the middle fuse blows immediately 
> and I lose the +8.5 and -6.5. If I unplug the main socket into the PSU and turn it on (after 
> replacing the fuse it doesn't blow)
>   
Well, this isn't surprising.  Almost all the digital chips in the CS80 
want to run on 15 volts. However, since they want these chips to 
interface to analog voltages, mostly through the 4016/4051 analog muxes 
and switches, they changed +15v/gnd to +8.5v/-6.5v. Therefore, almost 
every part that uses one of these supplies also uses the other.

I guess you have to start disconnecting the +8.5/-6.5v wires from 
various boards to isolate which one has a short. You could disconnect 
from boards one at a time and check the resistance across the two to 
look for hard shorts.

Good luck,

 David

*Middle* fuse? - there are only two fuses in my 80's... the slot
nearest the PSU circuit board is empty..!?!

Is that normal or am I missing one...?

Cheers,
TOM



--- In yamahacs80@yahoogroups.com, "Heath Finnie" <heathfinnie@...> wrote:
>
> If I plug in the main wire loom into the psu and turn it on, the
middle fuse blows immediately 
> and I lose the +8.5 and -6.5. If I unplug the main socket into the
PSU and turn it on (after 
> replacing the fuse it doesn't blow)
>

I am having the same problem... even worse some idiot had even put a 2.5A fuse instead of the 500mA and it still blows! Did you find out where it shorted, is there a particular place I should start at? I would appreciate any help I can get!!!

Martin

Hey,

I haven´t serviced a CS-80 yet, but on the CS-50 the +8,5 and -6,5 power the
KAS and SH board. Are your CS-80´s recapped and have all new logic installed ?

It should not be a big problem to find which board has the short, desolder the
E, +8,5 and -6,5 set a DVM to continuity test (diode mode) and probe E and +8,5
if there is resistance between these tracks try E and -6,5 if the DVM beeps or gives
a very low reading you will have found your shorted board and the rails that have
a short. Do this test without the power on.

Best of luck,
/RL


-----Originalmeddelande-----
Från: martinjboisvert@...
Till: yamahacs80@yahoogroups.com
Datum: 2013-10-02 09:29
Ämne: [yamahacs80] RE: the continuing saga of my CS-80 repair.. blowing fuse

       
I am having the same problem... even worse some idiot had even put a 2.5A fuse instead of the 500mA and it still blows! Did you find out where it shorted, is there a particular place I should start at?  I would appreciate any help I can get!!!


Martin
 

---In yamahacs80@yahoogroups.com, <noddyspuncture@...> wrote:

*Middle* fuse? - there are only two fuses in my 80's... the slot
nearest the PSU circuit board is empty..!?!

Is that normal or am I missing one...?

Cheers,
TOM



--- In yamahacs80@yahoogroups.com, "Heath Finnie" <heathfinnie@...> wrote:
>
> If I plug in the main wire loom into the psu and turn it on, the
middle fuse blows immediately
> and I lose the +8.5 and -6.5. If I unplug the main socket into the
PSU and turn it on (after
> replacing the fuse it doesn't blow)
>

3 fuses in mine

-----Original Message-----
From: martinjboisvert@gmail.com
To: yamahacs80@yahoogroups.com
Date: 10/02/13 02:29
Subject: [POSSIBLE SPAM] [yamahacs80] RE: the continuing saga of my CS-80 repair.. blowing fuse

         
I am having the same problem... even worse some idiot had even put a 2.5A fuse instead of the 500mA and it still blows! Did you find out where it shorted, is there a particular place I should start at?  I would appreciate any help I can get!!!


Martin


---In yamahacs80@yahoogroups.com, <noddyspuncture@...> wrote:

*Middle* fuse? - there are only two fuses in my 80's... the slot
nearest the PSU circuit board is empty..!?!

Is that normal or am I missing one...?

Cheers,
TOM



--- In yamahacs80@yahoogroups.com, "Heath Finnie" <heathfinnie@...> wrote:
>
> If I plug in the main wire loom into the psu and turn it on, the
middle fuse blows immediately
> and I lose the +8.5 and -6.5. If I unplug the main socket into the
PSU and turn it on (after
> replacing the fuse it doesn't blow)
>

Thank you very much for the swift response,

I am currently in the process of recapping the sensitive parts of my CS80... I will follow your instructions and see where it leads me!  Will let you know what I find.

Thanks Rikard