[sdiy] Echolette Echo 400 / Dynacord EC-504:: Anyone have a varispeed mod figured out?

Kenny Balys kenny at beatkamp.com
Sat Sep 26 22:30:53 CEST 2020


I just received some vital information from an Echoplex expert in Germany.

Christian aus Ingolstadt sagt:
The motor inside is a 220V three phase motor which follows the 50 Hz phase of 
your power plant. To use the same motor you need a frequency converter which 
provides three rotating phases out of your 230V AC single phase. Then the 2uF 
capacitor at your motor is not needed anymore, actually it generates the 
additional phase for your motor. The frequency of the frequency converter is 
adjustable and with the frequency you control the speed of the motor. I have not 
tried this before myself but that is possible. If you buy such a frequency 
converter you should be able to easily reconnect the three motor phases and then 
you would have vary speed. Of course the motor was built for 50Hz but +/- 20 
percent variation (only estimation) should be possible as long the motor does 
not get too hot.

Of course you can also replace the motor by a DC motor and control the speed 
with the DC voltage. But that would also require some mechanical skills and a 
motor which fits to the Echo machine.

[(Christian's words posted with his permission)]

The information that Christian has provided over the Echo 400 / EC-504 does not seem
to be anywhere else on the net.

On 26.09.20 14:43 , Ben Stuyts wrote:
> Correcting myself, that example is for a 3-phase motor, and Kenny obviously has
> a single phase motor with a secondary winding for the capacitor we see in his
> photo. This generates the necessary 90 degrees phase shift. You might actually
> get away with using a dimmer-type circuit for this, relying on the larger losses
> at lower settings. But as Ritchie said, noise/EMC will be awful.
>
> Ben
>
>
>> On 26 Sep 2020, at 16:14, Ben Stuyts <ben at stuyts.nl <mailto:ben at stuyts.nl>> wrote:
>>
>> Correct, and there are ready made frequency inverters which can do this. I use
>> those at work. However, they usually chop up the output (PWM) at frequencies
>> of a few kHz. You would need to very heavily filter the output to make sure
>> that this won’t be audible. For example:
>>
>> https://nl.farnell.com/schneider-electric/atv12h018m2/drive-v-s-atv12-240v-0-18kw-1ph/dp/2042992
>>
>> Ben
>>
>>
>>> On 26 Sep 2020, at 13:27, Richie Burnett <rburnett at richieburnett.co.uk
>>> <mailto:rburnett at richieburnett.co.uk>> wrote:
>>>
>>> That AC motor with run capacitor attached looks like either an induction
>>> motor or a salient-pole synchronous motor. I suspect that you will have
>>> limited success trying to control the speed with a light dimmer. The Triac
>>> switching an inductive load will probably also generate a lot of switching
>>> noise and EMI.
>>>
>>> In order to properly control the running speed of the motor you'd need to
>>> alter the frequency of the AC supply to the motor. If you decrease the
>>> frequency you may also need to decrease the applied voltage in the same
>>> proportion to prevent it drawing too much magnetising current and saturating.
>>>
>>> Hope this info helps,
>>>
>>> -Richie,
>>>
>>>
>>> ---- Kenny Balys wrote ----
>>>
>>>>
>>>> Further info:
>>>>
>>>> This echo machine has a 220V AC motor, not a DC motor.
>>>>
>>>> What I think I might do is something like an AC light dimmer
>>>> triac thing. Like this:
>>>>
>>>> https://www.electroschematics.com/motor-speed-regulator-with-triac/
>>>>
>>>> The goal is to slow it down so that I can get longer delay times.
>>>>
>>>> The 75, 150, 225, 300ms delay times doubled would be just awesome.
>>>>
>>>> Hope this isn't OT. Thanks in advance for any input.
>>>>
>>>>
>>>> On 26.09.20 24:43 , Kenny Balys wrote:
>>>>>
>>>>> I am thinking about adding a varispeed control on my Echolette 400 tape delay.
>>>>>
>>>>> The partial schematics are available here: (look for Dynacord EC-504, its the
>>>>> same as Echo 400)
>>>>> http://peel.dk/Dynacord/index.html
>>>>>
>>>>> The details of the motor control seem to be missing.
>>>>>
>>>>> Has anyone done this?
>>>>>
>>>>> If so, I would love to hear how you did it.
>>>>>



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