Re: [AH] Fwd: Moog Voyager elusive problem, asking for your advice

From cheater00 .
Sent Fri, May 10th 2013, 16:17

Well, as I said, first swap it for a known-working PSU and see if the
synth still exhibits the problem. If not, then the issue is in the PSU
which is currently not connected. Start bringing in the single rails,
one by one, and see which one of them is erroneous. Then get a can of
freezing spray (special spray for solder joint inspection) and go
crazy with it.

On Fri, May 10, 2013 at 2:50 PM, System 100 <system100m@gmail.com> wrote:
> Yes, I do synth repairs. The problem with finding a cold solder joint is
> that there are way too many parts to resolder...
> I can try starting with the power supply first. Somehow I have the feeling
> that it starts there... but not sure (I know these chinese PS from other
> product which have failed more than once). It there any trick finding a cold
> solder without resoldering a suspicious area ? when I tap the components I
> can't recreate the problem, it just comes and goes.
>
> How do I check for it's correct operation, other than just monitoring the
> output DC voltages ? I have a friend who is an engineer so I can use his
> help monitoring it...
>
> Thanks!
>
>
> 2013/5/10 cheater00 . <cheater00@gmail.com>
>>
>> sounds like a cold solder. are you a tech?
>> try disconnecting the power supply and connect a soupy linear bench
>> power supply.
>>
>> try to trigger the bug while observing the voltage rails on the scope
>> with the original psu.
>>
>> On Fri, May 10, 2013 at 2:11 PM, System 100 <system100m@gmail.com> wrote:
>> > Hi all !
>> >
>> > I bought a second hand Voyager a while ago and just found it has a
>> > severe
>> > issue... Once I power it on, after a few minutes the overall pitch can
>> > change dramatically and intermittently for a fraction of a moment and
>> > than
>> > return to normal. I can happen after a few minutes or after half an
>> > hours
>> > after powering it, and it can come and go spontaneously. It can be heard
>> > when using MIDI or the keyboard, and it happens also when the pitch
>> > wheel is
>> > disabled.
>> >
>> > Please take a look at this video, of an RME acting exactly the same as
>> > mine:
>> >
>> > http://www.youtube.com/watch?v=Ew5DQXc-xko
>> >
>> > The guy there says it was sent to moog for repair a few times and it
>> > still
>> > acts the same... Can anyone think of any idea what causes it ?
>> >
>> > The voltages are stable and when the pitch changes no change in the main
>> > voltages is observed. All connectors and ICs are tightened in place...
>> > All
>> > functions performs well and all pots are in good contact...
>> >
>> > The only irregular thing I notices was that the 4 transistors on the
>> > small
>> > powersupply board (not the main PS board) are very (very) hot. No
>> > heatsink
>> > was built around them, just thought one of them might have gone bad but
>> > again, all voltages are pretty accurate.
>> >
>> > Will appreciate any help.
>
>