Explain the problem:
After a long trip with a horrible jet lag I decided to replace the el. capacitors in the last boards. Big mistake. I did not noticed that in the OE2 (chorus etc) a droplet of soldering material had made a short-circuit between two terminals of IC9, pins 5 and 6. At least I guess that was the reason why, later, the machine didn't work anymore but its power light!
The PSU doesn't give any of the + - 15 and 10,5 voltages, while both the accessory ones (8,5 -6,5) are present.
After bridging the voltages as suggested in the manual p.59 and by some of you, friends, I replaced the 4558s and tested the transistors on the Board. In particular, I found the following transistors, some had been replaced (but the machine used to work great):
R703 = 2SA424
TR704 = CBC639
TR705 = 2SD234
TR706 = 2SA561
All of them are OK with the EBC test (DVM)
At the P1 and P2 terminals, + - 28 are present (think it's ok)
I did not check the four large metallic transistors, connected to the heat sinkers, , in that I would not desolder the robust cables. Is it worth measuring tensions on their pin? How much would they be?
Any clue ? Your suggestions are highly appreciated. BTW, no puff, bang, burning plastic smell, burned fuses...
Fernando
Il giorno 02/mar/2011, alle ore 22.02, Quazimodo ha scritto:
> That isn't exactly true I don't think.
>
> In a situation where you have just serviced the PSU - like I have done to both my CS80's, replaced all caps and the IC's etc... you don't really want to be switching on not knowing if there are any over-voltages. So therefore the 'on-the-bench' setting up is vital!
>
> This allows you to check to see the PSU is indeed still functioning - and to set all voltages accurately.
>
> Once happy - then it is time to re-install the PSU, remove those jumpers - and then monitor the voltages with all circuit boards connected (as you say) and again adjust voltages but this time measuring at the points specified in the service manual. ie: not on the PSU itself but a certian key positions that take into account distances from the PSU and also cabling etc.
>
> Please service tech's, do correct me if am wrong here. I am no tech as such, just picked up what I know from either here or other sites I follow.
>
> Cheers,
> TOM
>
> --- In yamahacs80@yahoogroups.com, Csaba Zvekan <czvekan@...> wrote:
> >
> > Hi Fernando,
> >
> > The PSU should and can only be calibrated/troubleshooted under load meaning connected with all other boards. What exactly is your problem ? What voltages do you read ? And compare them with the service manual . If something is off and can not be adjusted we can see further down.
> >
> > Kind Regards
> >
> > Csaba
> >
> >
> > On Mar 2, 2011, at 9:40 AM, Fernando Zarone wrote:
> >
> > > A question.
> > > If something is wrong in the PSU of CS-80, how to check why all of the CC voltages are faulty from the origin? Usually one separates the PSU unit from the machine and checks where it is bad. In the service manual (p. 59 if I don't get wrong) it is alerted not to detach the connectors from the PSU, for the risk of damaging the whole.
> > > So, how to check the PSU unit?
> > > Moreover, if both two fuses are ok, is there any other component protecting the system ?
> > >
> > > Thanks
> > > Fernando
> > >
>
>
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