Synth-DIY Yahoo! Groups Archives

Thread

KLM-367 Clone D/A Adjustment impossible

2018-09-13 by golbicali@yahoo.com

Hi,

i've just completed a Klm-367 clone board ( from https://sites.google.com/site/jedjorgensen/ )

I'm not able to complete the D/A adjustment. Programmer led "4" and "5" stay on. Turning VR7 or VR6 has no effect.

What could be the parts involved in this D/A adjustment?

Where could be the fault?

Is it a knows fault ?

A few years ago i've successfully built the same clone board for a other Polysix. I don't understand why i'm not successful this time.

Please help me.

Thank you.

Re: [PolySix] KLM-367 Clone D/A Adjustment impossible

2018-09-13 by <backshall1@bellsouth.net>

I think I saw this a couple of times about 5 or 6 years ago. One time I forgot to add the missing ground wire between C22 and C23 so there was a clock stability problem. The other time it seemed to happen when I forgot to set all the knobs and switches to the “normal setting” as shown in the picture in the service manual.

Don Backshall

From: golbicali@yahoo.com [PolySix]

Sent: Thursday, September 13, 2018 5:27 AM

To: PolySix@yahoogroups.com

Subject: [PolySix] KLM-367 Clone D/A Adjustment impossible

Hi,

i've just completed a Klm-367 clone board ( from https://sites.google.com/site/jedjorgensen/ )

I'm not able to complete the D/A adjustment. Programmer led "4" and "5" stay on. Turning VR7 or VR6 has no effect.

What could be the parts involved in this D/A adjustment?

Where could be the fault?

Is it a knows fault ?

A few years ago i've successfully built the same clone board for a other Polysix. I don't understand why i'm not successful this time.

Please help me.

Thank you.

Re: [PolySix] KLM-367 Clone D/A Adjustment impossible

2018-09-14 by golbicali@yahoo.com

Thanks a lot for the help.

-I have double checked, the C23 C22 ground mod has been done

-I have triple checked to set Manual and "normal settings"

C23 is already a 10pf in staid of 22pf.

Unfortunately problem is still the same.

Any other clue?

Thanks

Re: KLM-367 Clone D/A Adjustment impossible

2018-09-14 by golbicali@yahoo.com

I've replaced the IC27 ( TL072 ) by the original ( 4560 ). Problem is still the same.

I've replaced the X1 Clock by the original clock, problem is still the same.

The only thing is strange is that IC27 is a bit hot.

I'm lost this time. Hope someone has the solution?

Thanks

Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible

2018-09-15 by <backshall1@bellsouth.net>

Back before we knew the ground was missing between C22 and C23, the workaround was to use 10pf for C23 instead of 22pf. With the correct ground connection, C23 should be the original 22pf, not 10pf. Maybe try that.

Don B.

From: golbicali@yahoo.com [PolySix]

Sent: Friday, September 14, 2018 1:48 PM

To: PolySix@yahoogroups.com

Subject: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible

I've replaced the IC27 ( TL072 ) by the original ( 4560 ). Problem is still the same.

I've replaced the X1 Clock by the original clock, problem is still the same.

The only thing is strange is that IC27 is a bit hot.

I'm lost this time. Hope someone has the solution?

Thanks

Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible

2018-09-17 by golbicali@yahoo.com

I did it ( original 22uf value with ground mod ) , and unfortunately results are the same.

This fault is hard to find.

If nobody has the solution or other idea to find the fault, maybe if understand how the D/A adjustment works exactly i will maybe able to find the fault and repair it. But i don't exactly understand how the D/A adjustment works. I understand that is the DAC calibrating but how it is done exactly?

Any ideas are welcome.

thanks to all.

Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible

2018-09-17 by Bob Grieb

I uploaded a commented copy of the MCU code to the files section.
The calibration code is at the end of the program IIRC. If you really
want to understand what it is doing, I suggest you look at the code
and my comments.

Bob

--------------------------------------------

On Mon, 9/17/18, golbicali@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:

Subject: Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible
To: PolySix@yahoogroups.com
Date: Monday, September 17, 2018, 6:34 AM

Re: KLM-367 Clone D/A Adjustment impossible

2018-09-17 by golbicali@yahoo.com

Thank you Bob.

I attentivlaly read your code comments, but unfortunately it do not help me to find the fault.

When i'm trying to process D/A adjustment it is stuck on "4" and "5" led ON, but VR6 and VR7 have no effect.

I'm going to double-check everything everything on that clone board.

Any other ideas welcome.

Thanks for the hlep.

Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible

2018-09-17 by Jed Jorgensen

You may have a bad solder joint somewhere. I remember on one of the prototype boards I was having all kinds of problems. Turned out a little blob of solder was bridging the legs on an IC. The fact that you've got a warm/hot IC may be worth investigating -- that was one of the symptoms I found too.

Jed

On Mon, Sep 17, 2018 at 11:40 AM Bob Grieb bobgrieb@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:

I uploaded a commented copy of the MCU code to the files section.
The calibration code is at the end of the program IIRC. If you really
want to understand what it is doing, I suggest you look at the code
and my comments.

Bob

--------------------------------------------
On Mon, 9/17/18, golbicali@yahoo.com [PolySix] <PolySix@yahoogroups.com> wrote:

Subject: Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible
To: PolySix@yahoogroups.com
Date: Monday, September 17, 2018, 6:34 AM

Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible

2018-09-18 by Bob Grieb

If you have an oscilloscope, monitor pins 1, 2 and 3 of IC6 when calibrating the DAC
Show us the waveforms. This is the comparator
that compares the DAC voltage to the voltage of the selected pot for ADC conversion.

If that chip is socketed, you might try replacing it. Also, maybe replace the one you
said was hot to the touch.

Re: [PolySix] Re: KLM-367 Clone D/A Adjustment impossible

2018-09-20 by golbicali@yahoo.com

Thanks a lot you've helped me.

By comparing the DAC section of the clone boards with the original boards ( by luck i have a few old boards and a few clone boards).

I found an error on the clone board:

IC33 pin 1 et pin 2 are linked on the clone where there is no link on the original boards.

That is why the D/A adjustment was impossible.

Now D/A adjustment has been done OK.

Now I've got a new problem, I'm going to open a new topic for this new problem in order not to confuse readers.

Again, thanks to all of you.

Re: KLM-367 Clone D/A Adjustment impossible

2018-09-27 by golbicali@yahoo.com

Thanks to Bob in the other topic I've opened ( MG adjustment on KLM-367a Clone topic )

In fact I've discovered that the D/A has not been done well. All the pots that are from 0 to 10 do not make any changes after the 5 middle position. I think the D/A adjustment is half done; This is certainly why i am not able to get a 50Hz LFO when doing MG adjustment.

When i discover the dac error on the clone board ( on the clone board IC33 DAC has a link between pin 1 and 2, these link is not present on the original board ), I've replaced a few components that have been damaged, I've replaced IC33, IC27 and now IC6. D/A adjustment is better but not complete. Like if only half of the pot course is working. This is certainly why i am not able to get a 50Hz LFO when doing MG adjustment.

Where should i look if the D/A adjustment is made at half ?

With a normal D/A adjustment, what signal should i get on IC6 Pins 1,2,3 ?

What other component may have been destroyed with the IC33 pins 1 and 2 short?

Thanks a lot for the help, it help me a lot.