Klark Teknik DN36 Analogue Time Processor

[thomasdf]

Hello everyone

I am trying to fix my DN36 Analogue Time Processor (read : phaser, flanger, chorus, short delays). Channel A seems appears to be working (correctly ? I don't know, never head the unit in working conditions but it makes all sorts of modulation), channel B has no output. It's a quite complex unit, with LOTS of BBD chips, obsolete chips and other joys like that

Here's where I am as of today :

The PSU has new regulators and recapped, I get a clean +/- 15VDC
All the electrolytics of the unit have been changed. I haven't changed the tantalums (yet ? aaaaaarrrg)

Channel A seem to be working correctly. Channel B output is silent, but the LED meter is working.

I am feeding a 1Khz signal in the unit's input and following it with my scope, making comparisons between channel A and channel B. The signal stops after the first rows of TDA1022 chips (all of them). They are IC 7, 8, 9 and 10. I can track the sinewave before them, not after. I am surprised that all of theses 4 chips would have died so I took a closer look at the power supply. From what I read in the datasheet, TDA1022 needs -15VDC on pin 9...
All of my TDA1022's pin 9 are linked in the unit, but when powered I measure them at around 0 and Pin 16 that's supposed to be GND is around 14VDC, so I have a ground elevation, obv.

Any clue where this could come from ? Any pointers is welcome !

 

[Bo Deadly]

Running a TDA1022 from 0V to -15V is the same as 14V to 0V. So it could be that the circuit is really being powered from +14V to 0V. Although that would make the schematic very misleading because it clearly shows the same 0V symbol being used for other things that are pretty clearly 0V (meaning the whole thing is not running positive ground).

However, it's not clear how you could get +14V across the chip from a broken solder joint. So I must conclude that you are actually not measuring things quite right. Like your connecting your meter ground to the negative supply.

When you measure the same way on the working channel, what voltages do you see on pins 16 and 9?

Connect the ground probe to 0V at the power supply. If that has a solid connection to the chassis, try connecting it to the chassis. Test resistance between different ground points throughout the board to 0V at the supply to verify there are no bad ground connects.

Apply gentle varying pressure to the board as you probe. If there's a broken solder joint, you might see the connection restored momentarily.

Finally, be VERY careful probing around in this unit. Make sure you ground yourself by touching the chassis to discharge any static electricity. Touch the probe to the chassis momentarily before you start poking around. When you turn the unit off, wait a few seconds before touching PS stuff. It's not high voltage but if you bridge something you could send power to the wrong place and destroy something.

 

[thomasdf]

Thanks for your message !

I've measured voltages with ground reference at IEC's inlet ground (power ground). It's the same as the ground of the unit at audio connectors, ground plane on the PCB and the chassis etc. 0 resistance between these points. I'll call that ground in the following.

Resistance :
Between ground and TDA's pin 16 (supposed to be grounded) I get around 800 ohms.
Between ground and TDA's pin 9 (supposed to be -15VDC) I get 0 ohms.

Voltages :
Ground - Pin 9 = 0V
Ground - Pin 16 = 14V

All of TDA's pins 9 are linked to each other's and same goes for the pins 16, so these values are common to the working and non working channel. It makes sense, and apparently ground is elevated to around 14V. Since it's the same for A and B I suppose this is not the source of my problem.

I'll probe around and test ground at various places around the circuit and will look at the TDA's control circuit and voltages... I am a bit puzzled and knowing how rare and expensive a real TDA1022 is kind of freaks me out haha

EDIT : NEW BULLETIN : On both channel the delay pot is fed + 15 and -15 on each side and the center lug is going to IC 26. I have output on B when the pot CCW. When I turn it CW my signal disapears around IC 7,8,9 and 10.

 

[thomasdf]

I've copied trimpot settings P21, 22 and 23 on channel B instead of the calibration I had made by the manual, and I have some sound output now. For some reason the modulations depth and behaviour are very different, as are the tensions in the clock section ... Sometimes the mod is deeper if the pot is a 50 / 75% than 100%... It's weird and makes it hard to dial some "stereo" settings, but at least it's making some sounds now... Chorus, flanger, weird metallicy oscillations ... you name it ! It doesn't phase well, and that's a shame haha... I'll keep on tweaking / sniffing around one of these days.
Overall, channel A controls behave in a normal way but the effect is little bit shy, and channel B controls are weird but the effect is more extreme.

to be continued ... !

 

[Bo Deadly]

Resistance :
Between ground and TDA's pin 16 (supposed to be grounded) I get around 800 ohms.
Between ground and TDA's pin 9 (supposed to be -15VDC) I get 0 ohms.

Voltages :
Ground - Pin 9 = 0V
Ground - Pin 16 = 14V

All of TDA's pins 9 are linked to each other's and same goes for the pins 16, so these values are common to the working and non working channel. It makes sense, and apparently ground is elevated to around 14V. Since it's the same for A and B I suppose this is not the source of my problem.

It sounds like they're running positive ground. Instead of 0V to -15V it's +15V to 0V. Same difference. This is contrary to the schematic on the Internet but there could be different versions of the circuit. The change would be pretty simple and isolated. So the ground is not elevated. They just move it from running on the neg rail to the pos rail.

Either that or you're misinterpreting something.

Note that the ideal 0V reference point is going to be the spot where all grounds converge which should be 0V of the last filter cap at the PS (and not earth ground which in some gear might not even be connected to 0V at the PS or have some resistance between).

 

[zhuparty]

I've copied trimpot settings P21, 22 and 23 on channel B instead of the calibration I had made by the manual, and I have some sound output now. For some reason the modulations depth and behaviour are very different, as are the tensions in the clock section ... Sometimes the mod is deeper if the pot is a 50 / 75% than 100%... It's weird and makes it hard to dial some "stereo" settings, but at least it's making some sounds now... Chorus, flanger, weird metallicy oscillations ... you name it ! It doesn't phase well, and that's a shame haha... I'll keep on tweaking / sniffing around one of these days.
Overall, channel A controls behave in a normal way but the effect is little bit shy, and channel B controls are weird but the effect is more extreme.

to be continued ... !

Hi thomasdf did you ever get the unit working? If not would you be keen to sell it.... been trying to find one for ages... kind of joined group diy since i saw how recently you posted about it. What's also weird to me is that although it's a KT effect a lot of dn36's are in france...

i'd love to get one for my fx rack build: space echo re-150, peavey 1310 (poorman's primetime), Maxon/ ibanez ad230, DN36, possibly a dynacord DRS78, and two SPX90's...

 

[thomasdf]

Well you joined GDIY to contact me, what an honor
Feel free to DM me so we can talk about this. At the moment the unit is working, but not perfectly. It sounds interesting tho, but when I hear demos online I know it still needs some care.

 

[zhuparty]

hey there

Well you joined GDIY to contact me, what an honor
Feel free to DM me so we can talk about this. At the moment the unit is working, but not perfectly. It sounds interesting tho, but when I hear demos online I know it still needs some care.

hey there!!! oh my gosh i can't believe you actually replied. i'd love to try to get it working at my studio... i have an old tweed console that needs some yummy BBD outboard... i really really want to pair it with my ibanez ad230.

 

[zhuparty]

Well you joined GDIY to contact me, what an honor
Feel free to DM me so we can talk about this. At the moment the unit is working, but not perfectly. It sounds interesting tho, but when I hear demos online I know it still needs some care.

sorry to spam thomasdf but i just realized since i'm such a new member you will have to pm me to start a private conversation about the dn36. those things are so insane with the number of 512 chips in it. i've restored my AD230 which has 16 MN3004 chips. i'd love love to have the DN36 in the studio and bring it back into working order.

 

[zhuparty]

Last question thomasdf... what's working and what's not working is it the same symptoms you posted back in feb?

 

[thomasdf]

I DMd you, let's not spam the thread

 

[thomasdf]

I received some DMs regarding the DN36, please know that I sold it a while ago to @zhuparty