Yamaha CS80

After long days of patient work, the Aftertouch problem was eventually solved:
1)  a SMALL  piece of  solder shorting two pins in IC 6 of TKC
2) the trace leading the output of a 4051 (pin 3)  to the in of 4558   in the TSB 2.
Both of the problems were not detectable by eye, although I had used the magnification loupes by Zeiss that I usually have in my dental practice. Just by the DVM I was able to identify the fault!  Hope this helps for the future...
Thanks for your precious suggestions, my friends.
NOW THE SEQUEL:
The CS  worked fine for three days, before I had the damned idea of checking the PSU before calibrating the voice boards.
I only replaced 4 caps, in the correct way. When I reconnected the PSU to the CS,  A NEW DRAMA:
+ - 15   become + - 21 V
-6,5    become - 8  V
+8,5  become  +11 V  .

...and a low frequency  hum was the only thing coming from the machine.   Naturally, I switched it off immediately. 
Then, I checked the PSU alone,  after connecting the jumpers between  + 15 and + 15s  and  - 15 and - 15s : the voltages are normal.

I replaced both the 4558s (I have a bunch of new ones in stock) but nothing.   As soon as I connect the PSU to the synth connector, the voltages raise. 

My question:  can this be a problem internal to the PSU? I mean,  is it possible that  with no charge it works and after connecting to the synth boards all of its voltages raise?

I had done nothing inside the boards, when it stopped working.

I am upset again now.     






Il giorno 21/apr/2011, alle ore 12.37, Andrew Kirkby ha scritto:

> Fernando,
> 
> Check that you have the right supply voltages at the points at the 
> board (where you installed the decoupling caps) and check continuity 
> from point to point for each wire attached to those boards (Fluke on 
> "beep" mode :P )
> 
> Let me know how you go.
> 
> AK
> On 21/04/2011, at 8:30 PM, Fernando Zarone wrote:
> 
> > Probably, it could be.
> > But I checked the solder points, refreshed them... seem ok.
> > Moreover: could a broken wire "lock" the output (pin 3) of 4051s ? 
> > shouldn't it be an internal processing, between the inputs (other IC 
> > pins) and pin 3?
> >
> >
> >
> > Il giorno 21/apr/2011, alle ore 11.32, Quazimodo ha scritto:
> >
> >> If you've been working on the TSB and/or TKC boards then I would 
> >> suspect broken wires...!?!
> >>
> >> --- In yamahacs80@yahoogroups.com, Fernando Zarone 
> >> <fernandozarone@...> wrote:
> >>>
> >>> Thank you Mike.
> >>> Some progress has been done.
> >>> I replaced all of the 1uF electro caps and all of the tantalium 
> >>> ones (the latter with polystyrene ones) in the TSB1 and 2. 
> >>> Decoupling caps were added to all of the CMOS ICs.
> >>> The problem is still there: last octave (from C5# to C6) exhibit a 
> >>> working AT, the others no.
> >>> News: I checked all of the voltages from the AT sensors of the 
> >>> keys, all of them are present at the single input pins of the 
> >>> 4051's corresponding to the single keys, I mean the stronger I 
> >>> press the key, the higher the voltage comes out, e.g. at the pin 2 
> >>> of IC5 /TSB2 when I press C6, pin 5 when B5 etc. This means that 
> >>> the problem is not before the 4051s. When I check at the sum 
> >>> terminal (pin 3 of the 4051s) , the voltage is OK in the last 2 
> >>> (IC 4 and 5 of TSB2), corresponding to the WORKING last octave) 
> >>> but it's missing at the other IC's pins 3, as expected.
> >>> I thought: the ICs are faulty. No, in that in the TSB2 I swapped 
> >>> IC 3 with the IC5 (working): the same - last octave keys / IC4 and 
> >>> IC5 = AT OK, the others no. This means that it cannot be blamed to 
> >>> faulty ICs!
> >>> I would like to understand whether the fault is in both TSBs 
> >>> (except at the level of the last two ICs of TSB2 - not that 
> >>> likely...) or somewhere outside, locking these voltages in both 
> >>> boards...
> >>>
> >>> I think this is an important clue.
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>>
> >>> Il giorno 20/apr/2011, alle ore 23.34, Mike ha scritto:
> >>>
> >>>> I don't understand your question and can't help you until you 
> >>>> tell me which pins you checked. What pin on the 4051 on the TSB 
> >>>> boards did you check? I wouldn't even bother trying to 
> >>>> troubleshoot the aftertouch and velocity unless it was working OK 
> >>>> before you replaced the 1uf Caps on the TSB1 &TSB2 boards.
> >>>>
> >>>> It could be a lot of things. I would start by checking Pin 3 of 
> >>>> the 4051 on the TSB1 & TSB2 boards. Each 4051 on the TSB1 & TSB2 
> >>>> boards is responsible for the the aftertouch and velocity for a 
> >>>> group of notes on the keyboard. Pin three of each 4051 will sum 
> >>>> the output of whatever notes are playing that the 4051 is 
> >>>> responsible for. Try playing one note at a time corresponding to 
> >>>> each of the 4051's and press down to engage the aftertouch. You 
> >>>> will see the aftertouch voltage for the corresponding note if the 
> >>>> 4051 is working properly and the N1, N2, N3 lines are working 
> >>>> properly for the entire keyboard.
> >>>>
> >>>> -Mike
> >>>>
> >>>> --- In yamahacs80@yahoogroups.com, Fernando Zarone 
> >>>> <fernandozarone@> wrote:
> >>>>>
> >>>>> I replaced ALL of the ICs in the KAS, TKC, SH and ALL of the 
> >>>>> electrolytic 1uF caps in TSBs. Going to replace the tantalium 
> >>>>> with polystyrene ones.
> >>>>> The Aftertouch and Initial touch only work in the last octave 
> >>>>> from C5# to C6 . Backwards from C5 to C1, nothing.
> >>>>> On the 4051 pins after the key pressure the relative tension 
> >>>>> raises from 0 - -0,20 to 6 and more, so it should not be a 
> >>>>> matter of keyboard sensors.
> >>>>> Could you please indicate how and where to check, considering 
> >>>>> that it seems to be a "global" problem. Any specific test? Which 
> >>>>> boards could be involved?
> >>>>>
> >>>>> Any help strongly appreciated...
> >>>>>
> >>>>> F
> >>>>>


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