Vintage Synth Repair

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@....uk> 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

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

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 I9;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