EDP Wasp Repair

EDP Wasp e1300143082416 EDP Wasp Repair I suspect this Wasp was bought of ebay here (at Matrixsynth) as it had the same crack and the cloth tape on the back. The drone is caused by a faulty AR (with broken CMOS IC’s) not capacitance. The wasp is deceptive, not only does it make really nice rich squelchy sounds for something that looks like a toy, it is also very hard to repair! The main problem is the low quality of the PCB combined with the fact that all the knobs are directly mounted to the PCB board and nothing else. So any excessive pressure on the knobs can cause havoc to the traces and components mounted around the control knobs. Another issue is that the wasp uses a lot of CD4xxx CMOS IC’s that are known to degrade as they get older. 1 The customer just wanted it to work so little was done to the cosmetic condition of the Wasp apart from cleaning.  The case is made from a 2 vacuum formed pieces of textured (I think its called ‘haircell’ ) ABS clammed around the PCB. Wasp crack EDP Wasp Repair A common problem is that the screws eventually shatter the plastic around the holes meaning a lot of them end up being held together with duck tape! You would be hard pressed find a wasp case without this problem today. The case and keyboard definitely have a lot of influence from another synth made in Britain … the Synthi AKS keyboard which was also touch sensitive and vacuum formed texture case. EDP Wasp IC2 EDP Wasp Repair All the IC’s I replaced were socketed, which prooved quite difficult as the PCB is double sided but not ‘through hole’ plated. The main failing IC’s were the D Flip Flops (4013) the analogue gates (4016) and the inverter buffers (4069.) Although ideally I would have replaced the lot.  The keyboard design is fascinating (if you like that kind of thing) the designer Chris Hugget used an array of analogue multiplexers to create a big scanning circuit that makes the single capacitance detecting circuit scan the keys and detect which key the finger is on and for how long, I could see a lot of potential in it for making it polyphonic and pressure sensitive. I did not manage to get a sound sample of it, but I have another Wasp on the go so more on wasps coming soon! But below is a video of me testing the keyboard Mid-repair ……  

About Clack

Technician at Clacktronics
This entry was posted in Repair, Synthesizer and tagged , , . Bookmark the permalink.

32 Responses to EDP Wasp Repair

  1. Amalia says:

    It is a thing I must find more information about, many thanks for the blog post.

  2. brian arthur says:

    hi, my wasp has a dead key, no luck in finding any info about repairing this. thanks

    • Clack says:

      Hey, it means the IC that it connects to is broken (it will be a CD4052) you need to replace it. Be careful though you can melt the keyboard decal very easily. To remove the IC you need a good de-soldering tool and you have to remove the solder on the top and bottom side. When it is removed, use a socket to replace it, I recommend using a turned pin socket as they are easier to solder in on the top side (you have to do this, there is no through hole plating) than cheaper sockets. I will be publishing a proper wasp help page soon.

  3. Maf says:

    Yeah mine has 8 dead keys (the middle 8). Would that be the same cause? The number of dead keys being a power of two seems significant. In the meantime I bought the Kenton interface box and just play it over MIDI.

  4. Clack says:

    Yes old CMOS chips are prone to failing. I recommend replacing the whole lot of gates that are used to scan the keyboard at the same time, its about 5 IC’s that are easy to get hold of HEF4xxxx work fine in place of CD4xxxx in the wasp.

  5. Laurence says:


    My wasp holds the lowest note on all the time and the lowest 7 or so notes are dead but slightly effects the note that is holding-any ideas?


    • Clack says:

      apart from the lowest note which is direct, each set of 8 keys are multiplexed by a 4052 analogue mux, which are then in turn multiplexed by 7 4016 gates. If it is stuck on the lowest note then this suggests that either the clock is dead (IC39 4069) , the counter is dead (IC32 & IC45) or the multiplex parts (IC38,39,42,43,46 and 47).

      • Laurence says:

        Thanks for the reply- Before I saw your response-I replaced IC 38 and 39 and now the upper notes which had nothing wrong with them are now not tuned properly- On my schematic IC39 is a 4052??
        I’ll replace 32 and 45 and see what happens.

  6. Laurence says:

    forgot to mention if I touch pin 6 or 7 of IC38 the lowest note does’nt hold anymore but eventually starts again..

  7. Laurence says:

    I’ve now replaced 38,39,42,43,45,32- before I replaced 42 all the keys were working but were all out of tune i.e they did not go up or down chromatically. When I replaced 42 the top half of IC43’s keys dont work and also the top half of IC47 keys dont work- Do you think replacing the majority of the IC’s associated with the keyboard scanning and tuning circuit would fix it? I’ll got to maplins again tomorrow and get the extra 4016’s and sockets to finish off replacing the multiplex parts.Do you know which IC’s are responsible for playing the correct note in the correct order? Thanks for your help!

    • Clack says:

      Reading this again suggests to me that the whole number is not getting through. You need a scope or some kind of digital probe to check if the binary number is getting through IC 30 and 31. Could also be that there is a lag on the trigger signal getting to 30 to hold the note in time and it plays the wrong note but I think the former is more right. IC30 is hard to get but you might find it at cricklewood electronics.

  8. Laurence says:

    I’ve managed to get all the keys working now,but the lowest still holds.Is IC 30 and 31 responsible for the keyboard “coding”?

    • Clack says:

      30 and 31 controls what is sent to the encoding. 31 is like a gate to let the note that is pressed on the keyboard to be sent to the encoder. 30 is sequentially triggered and holds the note that is pressed, this also allows for an external control to be sent through too which feeds in between 30 and 31. If it is holding this suggests that 31 is being triggered every time it passes the lowest note. The lowest note has a little less resistance as it doesn’t go through a 4052 mux and only through 1 4016 gate, have you played at all with the sensitivity pot? I found that if you replace one you generally have to replace them all as even the same CMOS chip but on a different manufacturer has different resistance. I am not quite sure but I think C43 is put there to balance the fact the lowest note does not pass through a 4052, try increasing it. Play around with it a bit and then I would suggest attempting to replace IC 38, 42 and 36 (thats all the 4016’s)

      • Laurence says:

        Thanks for the reply once again, I have adjusted the sensitivity pot but it makes no difference I will change the value of the cap first and then replace 30 and 31. Any ideas on the keyboard coding? i.e it not being in semi tone up and down etc?
        Would it be possible to send it to you to repair if I can’t get it working?


        • Clack says:

          There might be something wrong in the encoding part or more likely in the oscillation bit but I have never had that problem so not much experience with it. Yes that’s fine it’s Ben@clacktronics. Co.UK to organise a repair , ideally you should be in London and it will take some time because I don’t get much time these days.

          • Laurence says:

            Do you know which IC’s are responsible for the encoding?
            If I can’t fix it and you have some time I’ll send it to you.

  9. Laurence says:

    Dont suppose you know of a link to a schematic for the wasp? The one I have is quite difficult to read. When do you think you will be able to repair the wasp if I do send it to you?


  10. Pedro says:

    Hello Everyone !
    Please help me , my wasp edp was working fine until this afternoon ,
    the first Oscilator from panel does not output any sound ,
    only works the above oscilator from the panel .

    what can be the problem ? Thanks !!

  11. pedro says:

    i will try to replace the

    is that a good idea ?
    Thanks in advance :)

  12. pedro says:

    ( my WASP EDP had a failure on oscillator 1 no output )

    Today i went to buy the LM3900N , replaced just this one and now the Oscillator 1 is
    working !!!! great day :)) now i have the 2 oscillators working just fine .


  13. Atombrew says:

    My Wasps Control Osc Freq no longer functions but the Pitch Mod still operates. Any ideas?

    • Clack says:

      This means the oscillator is broken probably latching high so this explains why the pitch is changing. Check IC18 ( its not labelled its a 4069 ) 40xx CMOS from the 70s is quit susceptible to degradation. Luckily modern 40xx IC’s work quite when if you swap them in.

      • Atom brew says:

        Had a good look at the circuit diagram and have purchased the 4069 CMOS chips from RS and hope to be making the repair this weekend. I’ll let you know how I get on cheers.

        • Atombrew says:

          I finally managed to change IC18 which didn’t resolve this problem. Whislt the wasp was open I changed IC11 as I had some spare 4069s to hand. Never mind it was a good exercise. Have you any other ideas or suggestions as how I could resolve my osc freq problem many thanks Atombrew.

          • Atombrew says:

            I finally managed to change IC18 which didn’t resolve this problem. Whislt the wasp was open I changed IC11 as I had some spare 4069s to hand. Never mind it was a good exercise. Have you any other ideas or suggestions as how I could resolve my osc freq problem many thanks Atombrew.

  14. VIAL says:

    HI.. I have a Wasp that generally plays fine. Except sometimes when touching knobs/pots the signal volume either drops off or behaves strangly, there is some play in the pots, eg excessive movement….Knobs that seem affected are in the Control Osc and Filter sections.
    Is there anyway to repair/clean /or tighten these, or do you think they need replacing?
    I am based in New Zealand and have not been able to find anyone with experience to help.

  15. Peter says:

    Hi Clack (and everybody else),
    I have a Wasp where the pitch tracking on oscillator 2 is not working correct (oscillator 1 is fine).
    Bottom C and middle C on oscillator 2 is in pitch but the rest of the notes are all over the place.
    Any ideas?
    Kind regards

  16. davee says:

    Hi Clack, just wondering if you can suggest anything for my Wasp’s fault … only half the keyboard seems to work, but only for one of the oscillators (both oscillators work on top half of keyboard, only one oscillator works for bottom half). When you play a high note then a low note with glide ON, the ‘broken’ oscillator seems to sweep down to a very low, inaudible note, it seems. Any suggestions hugely appreciated!

    Also I don’t suppose you know where to get replacement Wasp knobs from? Or a suitable alternative?
    many thanks!

  17. Dennis Matana says:


    Thanks for your blog. Im the proud owner of my precious Wasp and since yesterday suddenly the output dropped dramaticly. Sound was still heard and everything else still functioned fine but i really needed to crank up the volume on my mixer. Like way out of proportion compared to my other synths.
    So something was (read was) wrong.
    My first thought was the output amp (LM386). Swapped that to no avail. Looked at the schematic and decided to swap out C14 (4.7uF electrolyctic) in the VCA circuit and swap out C28 (220uF electrolyctic) in the output circuit.
    That was the solution to my problem. The volume is back again in full effect so fixed.
    Thought i would share this with you all if you ever run into the same problem.
    Those electrolyctics are really on the end of their lifespan and im concidering a total recap for the electrolyctics. I also noticed some tantalums which i will also replace in the near future.

    Anyway im happy again and im buzzing along now.

    br, Dennis

    • Clack says:

      Hey, I am glad you found the problem! its most likely your VCA circuit was being held low but still partially operating.

Leave a Reply

Your email address will not be published. Required fields are marked *

* Copy This Password *

* Type Or Paste Password Here *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>