Klark Teknik DN27A - Replacing Faders?

[smilan]

Hi,
I got a 27A with few broken faders.
I would like to find a replacement, but cant find any info or part number.
Does someone have experience with finding a direct replacement for those faders?

 

[radardoug]

Its old and I presume you have no documentation. Open it up, pull a fader. Look for numbers on it. Measure the travel etc. You are on your own....

 

[smilan]

Its old and I presume you have no documentation. Open it up, pull a fader. Look for numbers on it. Measure the travel etc. You are on your own....

Thanks, I'll do that.

 

[Michael Tibes]

The manual including the schematic is easily found on the net in case you didn’t check yet. But that probably doesn’t include part numbers. You might also be able to open and clean / fix the fader - running the risk of final destruction. But if it’s already not working, then there’s nothing to loose ;-)

 

[smilan]

The manual including the schematic is easily found on the net in case you didn’t check yet. But that probably doesn’t include part numbers. You might also be able to open and clean / fix the fader - running the risk of final destruction. But if it’s already not working, then there’s nothing to loose ;-)

Actually I did search the net and even found two versions of the service manual, one operates at +/- 15V and the other (like the one I have) at +/- 20V/In both versions there is no info about the faders, not even their Ohmic values.Anyhow I got this unit in a non working condition with a faulty relay that stock at bypass.The voltage and the transistor seem to be good, so I'm waiting for a new relay to arrive and if the unit will work and I'll not find a direct replacement I'm planning to repair those faders, maybe to print with a 3D printer an extension to the broken handle or maybe converting them to rotary potentiometers. As soon as it will work I'm thinking to add a spring reverb circuit after the EQ like I've done in the past with DN360.

 

[Rob Flinn]

I have had quite a few DN27(a)'s over the years. IMHO these are the absolute best sounding graphics. They only have 3 op amps & every band is inductor based unlike the later models which had gyrators for some of the bands. Very simple & peachy sounding, I still have a pair in the studio.

I had one with some broken fader shafts and I was able to somehow bolt & glue a metal extension on to what was left of the original shaft. The bolts were tiny & I think I had to slightly bend the existing shaft to one side to allow for the extra thickness of it with the extension to smoothy move in the slot.

Some DN27 use standard op amps & others have black potted ones which may be DOA's.

The relay you have maybe a fail safe thing. I was using mine for live & one DN27 came so that the relay got energised when you turned the box on, but in the event that the unit failed & popped the fuse then the box would go into bypass (because the relay switched off due to lack of power) so you still had sound & I used thos pair for FOH. Not all the DN27's I owned had this & I added it to some of them.

There was another one I had where the PSU was missing, but it was quite easy to reinstate.

I think you only need about 4 caps to recap the box too.

Also they are pin 3 hot, so don't let that catch you out.

 

[smilan]

The new relay was installed and it seems like everything works well.
For now I'll try to make a 3D print of this fader extension.
If I'll be able to glue it it will be the easiest solution.

 

[kags]

What kind of glue do you think will work? I have a similar situation with some API graphic EQ faders

 

[smilan]

I'm thinking about a generic epoxy glue from the local hardware store.
But if someone have good experience with something else please let us know.

 

[kags]

I tried some 2-part epoxy (JB Weld) and it didn't hold for me. I think there is too much lever (cantilever?) force for the epoxy to hold. Maybe your faders have more surface area to glue?

 

[smilan]

I tried some 2-part epoxy (JB Weld) and it didn't hold for me. I think there is too much lever (cantilever?) force for the epoxy to hold. Maybe your faders have more surface area to glue?

I'll try it and report as soon as I'll print this part and glue it.

 

[Rob Flinn]

When I repaired the DN27 fader years ago. I made a scarf joint with a piece of metal, & would have used araldite 2 part epoxy. But I also used at least one very small nut and bolt. They were something like M2 sized.

 

[Rob Flinn]

@smilan I like your spring reverb in the vid you posted. It's a clever idea & sounds really good.

Have you ever herad one of the KT spring reverbs ? I had one in for repair a couple of years ago. I was very impressed by the sound of it.
This is the one Klark Teknik DN-50 Dual Channel Reverberation System - Stereo spring reverb | Reverb UK

 

[smilan]

@smilan I like your spring reverb in the vid you posted. It's a clever idea & sounds really good.

Have you ever herad one of the KT spring reverbs ? I had one in for repair a couple of years ago. I was very impressed by the sound of it.
This is the one Klark Teknik DN-50 Dual Channel Reverberation System - Stereo spring reverb | Reverb UK

Thanks Rob, I've never worked with a KT spring reverb.

 

[gar381]

If memory serves me these faders are custom tracked. If you can fix these its probably best. Maybe
ebone a junker. the DN22 used the same fader. I owned a bunch of 27 and 27A over the years
in my monitor mix days and still have a pair on my studio monitors. The "27A" have a slightly higher
PSU voltage and have a transformer daughter card. The NON "A" the transformers were bolted
to the case otherwise they are the same and as Rob says these are the best sounded graphics
ever made along with the DN22. Hope you get it fixed

Gary

 

[smilan]

The new relay was installed and it seems like everything works well.
For now I'll try to make a 3D print of this fader extension.
If I'll be able to glue it it will be the easiest solution.

I was thinking of making a 3D printing of the extension part, but my friend with the 3D printer told me that he is thinking it won't be strong enough and he can build this part from "German silver". So I tried to glue it with two different types of epoxy and it was not strong enough, I tried to solder it with soldering iron which did not worked so I came up with the idea of wrapping it up with a thin copper wire from an electric cable and than solder it with soldering iron which worked great for me. I made this short video showing what I've done + a sound demonstration of the spring reverb.

 

[Rob Flinn]

Intersting solution. Does the solder adhere to the fader shaft now ? You can get adhesive lined heatshrink which would probably make your repair even stronger.

 

[smilan]

Intersting solution. Does the solder adhere to the fader shaft now ? You can get adhesive lined heatshrink which would probably make your repair even stronger.

I don't sure if the solder adhere to the fader shaft or it's just the tension of the copper wire holding the two parts together with the solder acting as a "glue" that keeps the tension of the wire and hold everything together.
If it won't be strong enough I'll try a adhesive lined heat shrink, but so far it seems to be strong enough.

 

[Disco Volante]

That shaft would be made of mild steel with a super thin electrocoat of zink. Which is why you might be able to get some solder adhesion (maybe with some fluid flux), but epoxy wont get sufficient adhesion.
The strongest solution would be a brass solder, but that's significantly higher temperature (800 C), so you'd have to remove the shaft. OR while you've dismantled the fader and freed the shaft, I could make you a few spare shafts...

I'm glad you've got it solved for now!
Cheers, V!