I put in a new 4011UBP today but the problem is still there. From initial voltage measurement's (measuring at collector of Q15 & 16) it looks as though the schmitt trigger stays high/constant no matter what happens with button presses in write mode (but maybe this is not the best way to test this part of the circuit?). Also in play mode the flip flop does seem to work as does the clock gen as it starts & stops ok & tempo is good. Ill have to get myself a logic probe so i can understand this circuit a little better. Nick ________________________________ From: Nick Bell <mckenzie126@yahoo.co.uk> To: "vintagesynthrepair@yahoogroups.com" <vintagesynthrepair@yahoogroups.com> Sent: Tuesday, 2 July 2013, 12:43 Subject: Re: [vintagesynthrepair] Boss DR-55 write mode problem Thanks guys, I had a few 4011BE's lying around & so used that - so ill order some unbuffered ones & see how I go. Will get/make myself a logic probe as well! Really appreciate your help Nick ________________________________ From: Dennis Matana <connect2techno@...> To: vintagesynthrepair@yahoogroups.com Sent: Monday, 1 July 2013, 22:51 Subject: Re: [vintagesynthrepair] Boss DR-55 write mode problem you must use 4011UB or UBE and not 4011B, so use the unbuffered version, the buffered one doesnt work in this machine... 2013/7/1 Paul Rak <paul.rak@...> > >I've had two different codes (can't remember what they were..) both from maplins and sold as 4011s - one worked 100%, the other didn't. It was as if it's initial state was wrong? Best way I can describe it. Good thing is they are pennies. >On 1 Jul 2013 19:37, "Christian Oncken" <concken@...> wrote: > > >> >>two tips.. >> >> >>1) if you drop by your local electronics shop and ask for 4011s make sure they give you 4011s and NOT 4001s. Having to drive 30+ miles to exchange a < $1 part will screw up your whole day. >> >> >>2) get yourself a logic probe. Cheap and invaluable in this kind of work. I repaired my 606 with the help of a logic probe before I got my scope, picked one up on ebay for like $8. Its much more useful for this type of work than a scope IMHO. Plus, if you're the trusting type and tend to not double check part numbers on chips it can also help you sort out problem 1)... :) >> >> >>Paul, what's the "right" kind of 4011? The one's they gave me (after they gave me the right ones) worked just fine.. did I just get lucky? >> >> >>Christian >> >> >> >> >> >>On Mon, Jul 1, 2013 at 1:10 PM, Paul Rak <paul.rak@...> wrote: >> >> >>> >>>Start with the 4011 I've repaired a LOT of these machines where that's all it needed. Needs to be the "right" kind of 4011 though. >>>On 1 Jul 2013 17:37, "Nick" <mckenzie126@...> wrote: >>> >>> >>>> >>>>Hi, I wonder if anyone could give me some help with this little drum machine. Play mode seems to work fine & it will start & stop ok & everything sounds ok. Problem is with write mode, the LED stays on & pressing either of the start (S5) or stop (S6) buttons wont advance the sequence & so LED stays on & nothing is written. >>>> >>>>I thought id found the problem initially as Q18 was bad but this has been changed now & the problem persists. 4011,C45,C43,C41 have all been replaced & Q15 & Q16 have been checked out of circuit & appear to be working fine. Any hints on what to look for would be great & oh, I have no scope unfortunately. >>>> >>>>thanks all >>>> >>>> >>
Message
Re: [vintagesynthrepair] Boss DR-55 write mode problem
2013-07-04 by Nick Bell