Synth-DIY Yahoo! Groups Archives

Non-working attenuator

2014-12-23 by tuk88@rocketmail.com

Hi everyone,

at first thank you for all these topics and knowledge which are very important for every polysix user (and repairer). With all these messages, the polysix will still live in some years :)

I post this topic due to my non-working attenuator. I'm pissed of by this one because I check everything I can (following differents topics found here).

At first the KLM-367 was changed by a clone. I build everything and the attenuator never worked with the new card. I don't know if it worked with the old acid eaten card.

- So, I checked P10, P11, P12, P13 and D03 conductivity, between KLM-370 and KLM-367. Everything is OK.

- I checked the presence of D03 on the different chips on KLM367. It's OK too.

- I checked the conductivity of P10, P11, P12 and P13, between connector of KLM 367 and 8048 uC. OK.

- D03 and the others are presents on CN10 of KLM367.

- Every diode of attenuator swich are OK.

- D03 signal seems to be OK.

So, now I'm lost...

Has anybody and idea, where does this issue can come from ?

Thank you a lot !

Lucas

Re: [PolySix] Non-working attenuator

2014-12-23 by Bob Grieb

There is another switch that is also driven by P10 etc. does
That one work correctly? If so, then the problem should be with D3.
You can unplug the connector on the 367 bd that goes to the
Front panel and check between the different pins for the
Diode connection in each position of the atten switch.
That will confirm that everything in the cable and front
Panel is OK. Also check continuity from that connector to
The pins on the 8048. Go right to the pin of the chip,
Not the pin on the pcb, so that the chip itself is getting
The signal. You said the attenuator doesnt work.
Could you be more specific? Does any position of the
Switch make a difference?

Bob

From: tuk88@rocketmail.com [PolySix] <PolySix@yahoogroups.com>;
To: <PolySix@yahoogroups.com>;
Subject: [PolySix] Non-working attenuator
Sent: Tue, Dec 23, 2014 7:53:36 AM

Hi everyone,

at first thank you for all these topics and knowledge which are very important for every polysix user (and repairer). With all these messages, the polysix will still live in some years :)

I post this topic due to my non-working attenuator. I'm pissed of by this one because I check everything I can (following differents topics found here).

At first the KLM-367 was changed by a clone. I build everything and the attenuator never worked with the new card. I don't know if it worked with the old acid eaten card.

- So, I checked P10, P11, P12, P13 and D03 conductivity, between KLM-370 and KLM-367. Everything is OK.

- I checked the presence of D03 on the different chips on KLM367. It's OK too.

- I checked the conductivity of P10, P11, P12 and P13, between connector of KLM 367 and 8048 uC. OK.

- D03 and the others are presents on CN10 of KLM367.

- Every diode of attenuator swich are OK.

- D03 signal seems to be OK.

So, now I'm lost...

Has anybody and idea, where does this issue can come from ?

Thank you a lot !

Lucas

Re: [PolySix] Non-working attenuator

2014-12-23 by tuk88@rocketmail.com

Thank you for your answer Bob !

When I say attenuator doesn't work, that means that turning the knob has no effects on sound (no increasing or decreasing sound).

The differents functions driven by P10, P11, P12 and P13 work well (effects and an other one).

I check between the different pins of the connector and change the attenuator position. I've got a binary counting from 0 to 10 (considering 1 when short circuit done by diode, and 0 by open circuit). So I think the panel doesn't have any problem.

I check the presence of D03 on the different chip by directly touching the pin IC. D03 is present where it should be.

I'll try to find an oscilloscope to check the good signal of D03.

Maybe I've got a 4042 or 7408 out of service ? I think I'll try to change them.

What do you think ?

Lucas

Re: [PolySix] Non-working attenuator

2014-12-23 by Bob Grieb

Hi,

I think we have been looking in the wrong place. Probably the switch and sensing of

it are fine. As you mentioned, we should focus on IC35 outputs, and the circuitry that

they control on the chorus board. I think you should see the same values on IC35 as on the switch,

0-10 if that is what you found. Regardless, the voltage at point "I" should be changing

when you move the attenuator switch. Please check that, and if that is changing, tell us

what it is, then you need to see if that is getting to the chorus board. Then we can take it

from there.

What 7408 are you talking about?

Bob

From: "tuk88@rocketmail.com [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Tuesday, December 23, 2014 12:27 PM
Subject: Re: [PolySix] Non-working attenuator

Thank you for your answer Bob !

When I say attenuator doesn't work, that means that turning the knob has no effects on sound (no increasing or decreasing sound).

The differents functions driven by P10, P11, P12 and P13 work well (effects and an other one).

I check between the different pins of the connector and change the attenuator position. I've got a binary counting from 0 to 10 (considering 1 when short circuit done by diode, and 0 by open circuit). So I think the panel doesn't have any problem.

I check the presence of D03 on the different chip by directly touching the pin IC. D03 is present where it should be.

I'll try to find an oscilloscope to check the good signal of D03.

Maybe I've got a 4042 or 7408 out of service ? I think I'll try to change them.

What do you think ?

Lucas

Re: [PolySix] Non-working attenuator

2014-12-29 by Malte Rogacki

To add to what Bob has been saying:

The attenuator does not affects KLM366 (the voice board), it affects KLM368
(the effects board). The signal is called "P.VOL" (probably for
"Programmable Volume" in the schematic, and we can see that it travels on
CN03-6. That's the second pin from the bottom for the orange cable.

Now, you mentioned that you're using a clone now and that the old board had
acid damage. I've found it more than once that this damage had spread to
the KLM368 which is directly next to it; and especially to the area where
the connector between KLM367 and KLM368 is located. Remove KLM368 and check
the bottom of it for damage.

Re: Non-working attenuator

2014-12-30 by tuk88@rocketmail.com

Thank you both, for these answers.

I test at the output of the IC35, I've got the counting as at the panel board.

I check the voltage at the output, and I've got a variation from 3.6mV (0 binary) to 15.6mV (10 binary). I think it's to few.

So, I'll check the KLM-368 board.

Howether, what is the signal "VCA Mod" for ? Because, when I check the "P.Vol" signal on KLM 368 board, this one goes on a 2SA798 which is a kind of double transistor, where the signal comes too, through an inverting amplifier.

I expected either the LM13600 or the 2SA798.

I keep you in touch

Lucas

[PolySix] Re: Non-working attenuator

2014-12-30 by Malte Rogacki

VCA Mod is the LFO signal if the switch in the LFO section is in the VCA
position.

You might also want to check the cable itself. Sometimes the battery acid
has affected the cable or the connectors. While I have seen this most
commonly with the Poly 61 I have also seen at least one case where the acid
had move partially inside the cable isolation.

Re: [PolySix] Re: Non-working attenuator

2014-12-31 by tuk88@rocketmail.com

Thank you Malte,

I checked the cable they are OK. I test the continuity between the KLM368 and the KLM367, it's OK. I will focus at first on the transistor Q24 by changing it. The second way is to change the LM13600N by a LM13700N.

I'll keep you in touch if I have good (or bad) news.

Lucas

Re: [PolySix] Re: Non-working attenuator

2014-12-31 by Bob Grieb

I see a capacitor from the base of one transistor in the dual fed by p vol.
If that was shorted, it could stop the p vol from working.
Also check the comparator fed by the reset circuit.
It would short p vol signal to gnd and stop it from working.
I think it is a mute circuit for the output to prevent
Clicks etc when turning on or off.

Bob

From: tuk88@rocketmail.com [PolySix] <PolySix@yahoogroups.com>;
To: <PolySix@yahoogroups.com>;
Subject: Re: [PolySix] Re: Non-working attenuator
Sent: Wed, Dec 31, 2014 10:54:59 AM

Thank you Malte,

I checked the cable they are OK. I test the continuity between the KLM368 and the KLM367, it's OK. I will focus at first on the transistor Q24 by changing it. The second way is to change the LM13600N by a LM13700N.

I'll keep you in touch if I have good (or bad) news.

Lucas

Re: Non-working attenuator

2014-12-31 by tuk88@rocketmail.com

Hey Bob,

I already change the capacitor on the base, but no change on the attenuator...

What are you talking about the reset circuit ?

Re: [PolySix] Re: Non-working attenuator

2014-12-31 by Bob Grieb

On the klm 367 board, there is a comparator output hooked into
The resistors driven by u35 outputs. I think this comparator
Will short the control voltage to gnd to mute the audio. So
Maybe this circuit is interfering with your volume control
Voltage.

From: tuk88@rocketmail.com [PolySix] <PolySix@yahoogroups.com>;
To: <PolySix@yahoogroups.com>;
Subject: [PolySix] Re: Non-working attenuator
Sent: Wed, Dec 31, 2014 3:46:18 PM

Hey Bob,

I already change the capacitor on the base, but no change on the attenuator...

What are you talking about the reset circuit ?

Re: [PolySix] Re: Non-working attenuator

2015-01-02 by tuk88@rocketmail.com

I confirm that the problem come from the IC5. I disconnect the output 1 and everything works fine. I will adjust the reset circuit and try again. If it doesn't work, i'll check the different signal which fed this AOP.

I'll keep you in touch

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-02 by Bob Grieb

What voltages are on the two comparator inputs in normal operating mode?
The plus input should be more positive than the minus input to turn off the output transistor.
If the voltages are not like that, then the comparator could be working properly.

Bob

From: tuk88@rocketmail.com [PolySix] <PolySix@yahoogroups.com>;
To: <PolySix@yahoogroups.com>;
Subject: Re: [PolySix] Re: Non-working attenuator
Sent: Fri, Jan 2, 2015 4:31:14 PM

I confirm that the problem come from the IC5. I disconnect the output 1 and everything works fine. I will adjust the reset circuit and try again. If it doesn't work, i'll check the different signal which fed this AOP.

I'll keep you in touch

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-02 by Bob Grieb

If you look at the circuit, you can see that the reset adjustment only

affects the other half of the comparator. It should not affect pins 1,2,3

Looks like you should have about 1.1V on pin 2 (5V-3.9V)

On pin 3 you would have about 5V unless the tape enable switch is closed.

So closing tape enable switch will mute the audio.

Bob

From: "tuk88@rocketmail.com [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Friday, January 2, 2015 11:31 AM
Subject: Re: [PolySix] Re: Non-working attenuator

I confirm that the problem come from the IC5. I disconnect the output 1 and everything works fine. I will adjust the reset circuit and try again. If it doesn't work, i'll check the different signal which fed this AOP.

I'll keep you in touch

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-02 by tuk88@rocketmail.com

I've got 3.35 V on pin 2 and 5V on pin 3. Normally, that works fine. But at the output, 0V. So I think that the LM393 is brown.

Howether, I'm looking for this strange voltage on the input 2 of IC5. I think there is a mistake on the Clone PCB. Because the voltage divider looks like to works fine.

I will contact the PCB maker to have the layout picture to check where the trouble come from.

I'll keep you in touch

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-02 by Bob Grieb

The layouts are available on the web. You should be able to

see what's happening with just a voltmeter.

With a 3.9V zener and 120 ohm to ground, you should get

3.9V across the zener, roughly, and 1.1V to ground.

Bob

From: "tuk88@rocketmail.com [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Friday, January 2, 2015 12:35 PM
Subject: Re: [PolySix] Re: Non-working attenuator

I've got 3.35 V on pin 2 and 5V on pin 3. Normally, that works fine. But at the output, 0V. So I think that the LM393 is brown.

Howether, I'm looking for this strange voltage on the input 2 of IC5. I think there is a mistake on the Clone PCB. Because the voltage divider looks like to works fine.

I will contact the PCB maker to have the layout picture to check where the trouble come from.

I'll keep you in touch

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-02 by tuk88@rocketmail.com

Hey Bob, I've got thee two measurements, and they are OK. But it seems like the point R41 - D2 doesn't reach directly IC5 (measurement show a resistance of ~5k between R41-D2 and IC5 pin 3)

The definition of the bottom layer isn't enough to see were the pin goes. I'm waiting on the picture of Jed.

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-02 by Bob Grieb

Do you mean pin 2? It doesn't hook to pin 3.

What do you measure for voltage at the jcn of R41 D2 to ground?

Is D2 a zener diode? If so what part number is it?

Did you buy a new one or re-use the old part?

R41 should be 120 ohms. brown red brown gold

Right?

Bob

From: "tuk88@rocketmail.com [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Friday, January 2, 2015 4:42 PM
Subject: Re: [PolySix] Re: Non-working attenuator

Hey Bob, I've got thee two measurements, and they are OK. But it seems like the point R41 - D2 doesn't reach directly IC5 (measurement show a resistance of ~5k between R41-D2 and IC5 pin 3)

The definition of the bottom layer isn't enough to see were the pin goes. I'm waiting on the picture of Jed.

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-03 by <backshall1@bellsouth.net>

Like Bob said, the point between R41-D2 connects to IC5 pin 2 not pin 3. Pin 3 is Tape Enable (inverted). IC 5 pin 2 should be about 1.1V unless the zener D2 or resistor R41 are not connected properly or are the wrong parts inserted.

Don B

From: mailto:PolySix@yahoogroups.com

Sent: Friday, January 2, 2015 4:42 PM

To: PolySix@yahoogroups.com

Subject: Re: [PolySix] Re: Non-working attenuator

Hey Bob, I've got thee two measurements, and they are OK. But it seems like the point R41 - D2 doesn't reach directly IC5 (measurement show a resistance of ~5k between R41-D2 and IC5 pin 3)

The definition of the bottom layer isn't enough to see were the pin goes. I'm waiting on the picture of Jed.

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-03 by tuk88@rocketmail.com

Sorry, it was of pin 2 which I was talking about.

I just find the problem. There is a broken trace on the PCB. I'll make a bridge and I think everything will be OK !

Thank you a lot for this debugging :)

I keep you in touch if it's working

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-04 by tuk88@rocketmail.com

Hey everyone !

Everything works fine. It was due to a broken trace on the PCB ( I think I broke it when I solder the PCB)

Thank you a lot for you help ! :)

Lucas

Re: [PolySix] Re: Non-working attenuator

2015-01-04 by Bob Grieb

Glad you got it going.

From: "tuk88@rocketmail.com [PolySix]" <PolySix@yahoogroups.com>
To: PolySix@yahoogroups.com
Sent: Sunday, January 4, 2015 9:05 AM
Subject: Re: [PolySix] Re: Non-working attenuator

Hey everyone !

Everything works fine. It was due to a broken trace on the PCB ( I think I broke it when I solder the PCB)

Thank you a lot for you help ! :)

Lucas