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Hi,
My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
Thanks in advance, David
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Sag from an electrolytic going out on that voice?
James
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On Nov 28, 2018, at 5:01 PM, David Cumming david.cumming@... [xpantastic] < xpantastic@...> wrote:
?
Hi,
My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
Thanks in advance, David
|
Depending on age of the Xpander, recap
PSU and electrolytic caps on voiceboard,- at least for that "voice
#1" and when swapping OSC chips made no difference.
It can be there are other reasons, but thats what Id do 1st and
see what happens then.
P.
Am 29.11.2018 um 00:52 schrieb 'James R. Coplin' james@...
[xpantastic]:
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Sag from an electrolytic going out on that
voice?
James
Hi,
My Xpander reliably passes all tuning functions
but voice 1 goes out of tune (flat) within a few
minutes afterwards while the rest stay in tune.
I've tried swapping voice chips but don't know
where to go from there. Any ideas?
Thanks in advance, David
|
Yeah I guess so. My soldering skills could stretch to replacing a few capacitors but I’m not exactly sure how to decide which.
I use a multimeter to find ones near the CEM 3374 that don’t hold charge compared to ones on a working voice board??
?
Sag from an electrolytic going out on that voice?
James
?
Hi,
My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
Thanks in advance, David
|
sounds like a cap problem...? did you change op amp chips around too?
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From: xpantastic@... on behalf of David Cumming david.cumming@... [xpantastic]
Sent: 29 November 2018 12:01 AM
To: xpantastic@...
Subject: [xpantastic] Xpander tuning issue
?
?
Hi,
My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
Thanks in advance, David
|
I'd check the poly timing cap for that voice;
after that, there are 4051 CV demultiplexers associated with each
voice which should be checked. The CVs from those go to opamp
buffers across smoothing caps to ground -- all should be checked
out with a scope (comparing them to the signals from a working
voice).
sounds
like a cap problem... did you change op amp chips around
too?
Hi,
My Xpander reliably passes all tuning
functions but voice 1 goes out of tune (flat)
within a few minutes afterwards while the rest
stay in tune. I've tried swapping voice chips
but don't know where to go from there. Any
ideas?
Thanks in advance, David
|
|
This email has been checked for viruses by Avast antivirus software.
|
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I would just change all of them for that channel.?
James
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Show quoted text
On Nov 28, 2018, at 6:54 PM, David Cumming david.cumming@... [xpantastic] < xpantastic@...> wrote:
?
Yeah I guess so. My soldering skills could stretch to replacing a few capacitors but I’m not exactly sure how to decide which.
I use a multimeter to find ones near the CEM 3374 that don’t hold charge compared to ones on a working voice board??
?
Sag from an electrolytic going out on that voice?
James
?
Hi,
My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
Thanks in advance, David
|
I 'd change not only all capacitors, but the whole XPander and
move to another neighborhood - just to make sure.
Change all capacitors, is not a good advice to a laymen. It can
do more much more damage than the defect currently observed.
My advice would be to put more effort into locating the defect
first, than just start some tedious solder work. IMHO the
capacitor swapping thing is very fashy but often to no avail.
Capacitors may break indeed, but no as often as indicated in these
nice forums here. In fact, in the way over hundred of 80ies synths
I had to repair, the capacitors only rarely had a problem.
I've seen lots of broken CMOS (40XX- and 45XX-type), OP-Amps
(TL-type) and even resistors and ceramic capacitors (I've never
read in a thread to change resistors or ceramic capacitors, but,
yes the tend to break, in particular in California made Synths ;-)
I also note that electrolytics of that era are of much better
quality as the material sold today.? Why would you swap a
electronic element, known to last more than 50 years, for a new
part calculated be clever engineers to last ten years at most.
There are weak points in the Xpander VoiceBoard though:
the CMOS ICs and
the Styroflex S/H-charge capacitors.
Those components weren't build so well those days and tend to
break quite often, that is, to become short, open or some? state
of random switching in between (funny).
Soldering of Styroflex caps is difficult and requires some
experience. The must not get hot! There is no need to use
Styroflex type again. You may use modern cap types here.
With you tunig problem, I'd first try to locate the tuning
circuit in the schematics? (or ask s.o. here) and then
change/swap? only t the parts for that functional instance. I'd
start swapping the CMOS, then checking the S/H caps there, then
the OP-Amps involved, then the electrolytics there.?
Soldering of Styroflex caps is difficult and requires some
experience. The must not get hot! There is no need to use
Styroflex type again. You may use modern cap types here.
GOOD LUCK
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klosmon, I've overlooked your advice, but I fully aggre from my experience with XPander Voice board.
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PS. Please, you need to login, because non-members are not allowed to post messages!
Cheers, Tiitu
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Hello David, ????????I've helped quite a few people fix their Xpanders/ matrix 12 over the years ( look in the history of this forum). I have never seen the Poly S/H caps fail.? The caps used ?in the?American made Matrix 12/ Xpanders are military grade and poly caps tend to repair themselves anyway. This is good news because you can't get audio poly caps anymore. ( when analog equalizers?ceased being manufactured the relevant companies stopped making them)? I agree with other posters that the CMOS 4051 chips used to demux the control voltages to the voice circuits can fail. These would be? U706? and U707 for voice?one on the xpander.? A relatively easy fix because all the chips are socketed on these synths. Which brings up another point. Over time chips can come loose in their sockets. If it were me I would ( carefully ) pull all the chips for the voice one circuit and?push them back?in ( re-seat? them) this is also an easy fix.??You can use a chip puller or a small straight edge screwdriver can also be used. You may also try replacing C749 and C747. These are 2.2 uF???(note the decimal point) electrolytic capacitors. While not directly related to the tuning of the synth the are the most common failure by far on this particular synth.
Best Luck Karl Schmeer?
On Wednesday, November 28, 2018 5:22 PM, "David Cumming david.cumming@... [xpantastic]" wrote:
?
Hi,
My Xpander reliably passes all tuning functions but voice 1 goes out of tune (flat) within a few minutes afterwards while the rest stay in tune. I've tried swapping voice chips but don't know where to go from there. Any ideas?
Thanks in advance, David
|
Thanks for all the advice guys. I decided to send the synth to a technician and it came back running perfectly. Dry joints were it’s only problem.
Thanks, David?
?
I 'd change not only all capacitors, but the whole XPander and
move to another neighborhood - just to make sure.
Change all capacitors, is not a good advice to a laymen. It can
do more much more damage than the defect currently observed.
My advice would be to put more effort into locating the defect
first, than just start some tedious solder work. IMHO the
capacitor swapping thing is very fashy but often to no avail.
Capacitors may break indeed, but no as often as indicated in these
nice forums here. In fact, in the way over hundred of 80ies synths
I had to repair, the capacitors only rarely had a problem.
I've seen lots of broken CMOS (40XX- and 45XX-type), OP-Amps
(TL-type) and even resistors and ceramic capacitors (I've never
read in a thread to change resistors or ceramic capacitors, but,
yes the tend to break, in particular in California made Synths ;-)
I also note that electrolytics of that era are of much better
quality as the material sold today.? Why would you swap a
electronic element, known to last more than 50 years, for a new
part calculated be clever engineers to last ten years at most.
There are weak points in the Xpander VoiceBoard though:
the CMOS ICs and
the Styroflex S/H-charge capacitors.
Those components weren't build so well those days and tend to
break quite often, that is, to become short, open or some? state
of random switching in between (funny).
Soldering of Styroflex caps is difficult and requires some
experience. The must not get hot! There is no need to use
Styroflex type again. You may use modern cap types here.
With you tunig problem, I'd first try to locate the tuning
circuit in the schematics? (or ask s.o. here) and then
change/swap? only t the parts for that functional instance. I'd
start swapping the CMOS, then checking the S/H caps there, then
the OP-Amps involved, then the electrolytics there.?
Soldering of Styroflex caps is difficult and requires some
experience. The must not get hot! There is no need to use
Styroflex type again. You may use modern cap types here.
GOOD LUCK
|
Hi
Frequently, fails like this are caused by open coupling caps at the output of each voice. Part # would be Cx49 on the voice board a 2.2 uF electrolytic.
Look in the resources on this site for an Xpander service manual. I think there is a simple DAC testing routine you can access from
the Xpander's service page.
- Karl
--------------------------------------------
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On Wed, 5/8/19, pa7500@... [xpantastic] <xpantastic@...> wrote:
Subject: [xpantastic] Re: Xpander tuning issue
To: xpantastic@...
Date: Wednesday, May 8, 2019, 4:17 PM
?
Hello there!
I just bought a Xpander but the voices are all messy .. the
tune test fails on every voices and there is no bass sound.
The notes are the same below C3... vcf is OK but I don't
know how to test the DAC..?
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Thanks Karl for your kind help,
I read on the conversations this thing about the capacitor's failure but I didn't think that all of them would fail at the same time... Anyway I will change the capacitors and will be back here soon.. Fred
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Dont replace parts just on suspicion. Unreflected activism may lead to more trouble than intended to resolve.
Think thrice before igniting the blowtorch and touching the system.
I urge you to get comfortable with an Oscilloscope and to try to understand the schematics which BTW are good to read. Use colors to mark signal flows, CV and audio.
If there is a problem with a whole group of parallel circuits voices, the problem most likely is located upstream thereof.
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Hi there,
Just to let you know that I replaced? cd4053 (ic 904 if I remember well) and the tune is now working...
Thanks for your help there are loads of good advice to read here...
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Mondovermona