Morley / Award JD10 problems - any help appreciated

[bajaman]

Hi
Has anyone built this - I found the schematic on this site - I built one but it doesn't seem to be working right - is the schematic correct???
The tone controls have minimal effect and the sound is very scratchy and thin - and it whistles high frequency oscillation etc.
Any help with verifying Rob Strand's schematic appreciated.
Cheers
Steve

[Rob Strand]

I don't have the schematic with me and I can't find it on this site any more - got a link?

That circuit was straight forward.  I'm pretty sure the circuit should work.  The part values and structure of the circuit makes sense.  The tone control wasn't anything new so it should work as good as any.

I'm not writing off the fact there could be a silly mistake on the schematic that causes the problems you are seeing, if there is it will be something obvious.

I suspect you have made a build error.  Bypass each part of the circuit with wires and confirm which parts of the circuit are working and which are not.  Perhaps make sure you have made all the ground connections on the parts, pots and input & output sockets.

[bajaman]

Hi Rob
Many thanks for your reply - schematic can be found easily by searching for Morley JD-10 on this site!!!
I have triple checked my tone control wiring, and simulated in microcap, but the bass and middle controls have very very miniscule effect when built as per schematic.
I suspect there is an error on the schematic regarding the connections of the 4n7 and 47n capacitors.
Any gut shots still available?? The whisling only occurs on power up - easy to fix this, but tone control is the real problem area.
Cheers
Steve

[bajaman]

Hi
Problem solved - turned out to be a faulty potentiometer - the treble pot bottom lug was not connected to the carbon track properly! - and it was a brand new pot too!!!
Anyway the controls now work correctly at last - although the bass and middle controls could benefit being logarithmic law types - better control at low to mid settings.
The tone stack is rather unusual, although I have seen a DUMB*E schematic with something similar in topology. How does it sound??? I'll let you know when I'm finished tweaking it to my tastes, but the LM1458 surely overloads very smoooooooooooooooothly - heaps of smooth sustain on some settings. The schematic shows a very interesting power input schematic - it will accept any polarity dc AND ac voltage between 9 and 30 volts - it works okay too. No more burnouts when using the wrong polarity power pack - why is no other manufacturer using this - does Steward Ward hold the patent?? hehe.
Anyway, it is worth building one, if only for the simple but very effective speaker emulation.
Thanks Rob - great job done here - thanks for all your help too.
Cheers
Steve

[aron]

Great job! Thank Rob for the schematic. Unfortunately since then, mine has broken. I need to take the time to debug it. rrrrrrr!

[Rob Strand]

> Problem solved

OK good!

Incidently I managed to find the schematic on this site.  I haven't played with the search much on this site, and when I do it's usually a half hearted attempt.

> The tone stack is rather unusual, although I have seen a DUMB*E schematic with something similar in topology.

You will see variations of this in many places.  Dumb*e, Red Hat, Later Marshalls, Peavey, and others.  Depending on the values it has a bit more mids than say a Fender stack.

> why is no other manufacturer using this

It's not new and is used in many commercial devices (not only effects).   If provides polarity indpendent DC input and it will even cope with an AC plug pack (provided the voltage isn't too high) .  With AC the 470uF cap acts as a filter.    It doesn't come for free, you lose 2 voltage drops on the rails ie. about 1.4V - that's the penalty.  Using Schottky diodes will lower the drop.

[Rob Strand]

> Great job! Thank Rob for the schematic. Unfortunately since then, mine has broken. I need to take the time to debug it. rrrrrrr!

Hey no problem - you helped a lot too you know!

That one shouldn't be too hard to debug.  I've got a few broken things around the place myself - never seem to get around to fixing them.

Aron, hope things are going OK with you these days.