[sdiy] Internal clock issue (Roland)

[Nicholas Keller]

Thanks, Tom.   Hopefully I can get my hands on it soon, or my friend can get it back and have a go.  I've managed to fix my own 101 and 303, so I'm a bit more eager to DIY than he is. 

I will report back whatever issue I discover, but it may be a few weeks 

Nick 

Sent from the future

> On May 23, 2014, at 7:46 PM, Tom Wiltshire <tom at electricdruid.net> wrote:
> 
> A cracked track still sounds like the most likely culprit to me. I've been over circuits several times and until I'd eliminated everything else, I didn't see the hairline crack that was *clearly* evident after the fact!
> 
> On 23 May 2014, at 20:31, Nicholas Keller <niroke at tampabay.rr.com> wrote:
> 
>> Dave, 
>> 
>> Thank you for your response.  
>> 
>> First, this isn't my synth and it is in another state, so I've only been able to remotely diagnose the problem via phone chats.  But, those are the first things I had him check weeks ago, before he took it to be serviced.  The socket was good, solder pads good, and I tried to have my friend verify the clock signal at different points with his meter, whatever it was, nothing fancy.  
>> 
>> The LED did in fact respond to the rate slider.  It seemed to me that the LFO clock signal was not getting to the CPU, but was present elsewhere. 
>> 
>> Someone else has suggested a fried trace may be the culprit.  I'm sure if I had it in front of me, and since I have my own working 101 to compare it to, I could figure out what is wrong.  
>> 
>> I guess I'm hoping to rule out a known/common failure with the 101 CPU.  At least then I can tell him that it should be a more simple fix.  
>> 
>> Thanks again
>> Nick
>> 
>> 
>> 
>>> On May 23, 2014, at 2:04 PM, "Dave Magnuson" <abide at dmdrafting.com> wrote:
>>> 
>>> Hi Nick,
>>> 
>>> First thing I would check is the 1/4" jack.   Maybe it's dirty or has a
>>> cracked solder joint on the normally closed connection?   Sorry if this is
>>> obvious, but it's the first place I'd start.  
>>> 
>>> Then start following components backwards until you hit the LFO.   Since
>>> it's a square wave, a simple logic probe would probably be sufficient to
>>> diagnose it.
>>> 
>>> Does the LFO light flash and respond to the rate knob?   Does it work for
>>> modulating VCF, etc?
>>> 
>>> Dave
>>> 
>>> -----Original Message-----
>>> From: synth-diy-bounces at dropmix.xs4all.nl
>>> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Nicholas Keller
>>> Sent: Friday, May 23, 2014 1:39 PM
>>> To: AH; synth-diy
>>> Subject: [sdiy] Internal clock issue (Roland)
>>> 
>>> Apologies for the cloak and dagger, but I was afraid to mention SH-101 in
>>> the subject line...
>>> 
>>> My friend has an SH-101 which stopped responding to the internal clock.
>>> Arp, seq, random generator ... None work from internal clock.  All work from
>>> external clock.   
>>> 
>>> He has taken it to a tech but reports that they seem stumped about the
>>> clock.   
>>> 
>>> Has anyone here fixed a similar issue?  After looking at the schematics, and
>>> while I admit I am no expert, I think that if it works via external clock,
>>> the CPU must be working.  I question transistor TR8, but again, I'm just
>>> following the signal path and don't fully understand the circuit.  Seems to
>>> me that the LFO generates the clock and TR8 is one of the only parts between
>>> the Clock source and the CPU. 
>>> 
>>> Any help or suggestions are appreciated, and your patience too as I don't
>>> have the synth here.  
>>> 
>>> Nick
>>> 
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