Transformer for NeoVibe ? (Univibe Clone)

[mark.carline]

I am building a NeoVibe (UniVibe clone) using the RTS PCB from GGG, as per:

http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=121&Itemid=26

and the instructions below:
http://www.generalguitargadgets.com/pdf/neovibeupdate.pdf

mention that the transformer should be :

14-16VAC or 20-24VDC

I am going to site the transformer inside the unit which will be a aluminum diecast case (when I find one the correct size) and so I am going to use a "torodial" type.

I have managed to find a source of the following three different types of torodial transformers which maybe suitable:

(1) 12v-0v-12v at 25VA and 8V-0V-8V at 3VA
(2) 24v-0v-24v at 25VA (WOULD GIVE 25V AT 1A OR 50V AT 1/2A)
(3) 7v-0v-7v at 500mA

With each of these three transformers the voltage output could be combined to give a single supply of double the voltage (ie 7v-0v-7v could become 0v-14v).

Can somebody recommend if any of the above three transformers would be any use ?

My gut feeling is that transformer (3) will be ok as I will be able to get 0v-14v at 500ma which is only one less volt ac than the one that RC recommends here:
http://www.diystompboxes.com/smfforum/index.php?topic=56319.0
and that PDF on mouser mentions "Output: 15VAC 400mA"

Will I be ok at 14v ? (its at the lower end of the range originally mentioned - "14-16VAC").

I am using the recommended voltage regulator in this circuit which is a 78L15.

Alternatively can anyone recommend a UK 240v torodial mains transformer and supplier that would be suitable for this circuit ?

Thanks

Mark

[mark.carline]

:BUMP:

Anyone any ideas ?

Was this circuit designed by R.G. - Does he know ?#

I have found a UK supplier of TOROIDAL transformers here:

http://www.rapidonline.com/productinfo.aspx?&tier1=Electronic+Components&tier2=Transformers&tier3=Toroidal&tier4=Miniature+open+style+toroidal+transformers&moduleno=72687&catRef=88-3388

and these are the ones I was thinking about if (3) is no good in my original post above:

MINI OPEN TOROID 5.0VA 7V+7V 0.357A(RC)   88-3400         £8.13
MINI OPEN TOROID 7.0VA 7V+7V 0.500A(RC)   88-3406         £8.56

I am assuming that I need more than 300mA as per this post here:
http://www.diystompboxes.com/smfforum/index.php?topic=64364.0

Thanks inadvance !

Mark

[yeeshkul]

i use 10VA / 15VAC HAHN transformer

[R.G.]

(1) 12v-0v-12v at 25VA and 8V-0V-8V at 3VA
(2) 24v-0v-24v at 25VA (WOULD GIVE 25V AT 1A OR 50V AT 1/2A)
(3) 7v-0v-7v at 500mA

My gut feeling is that transformer (3) will be ok as I will be able to get 0v-14v at 500ma

You should be OK with (3).

14Vac will translate to about 19Vdc, which will work. It is important that it is not lower than that under load. Most transformers are specified for voltage at maximum load and go higher under less load. Look at the no-load or open-circuit voltage specification for the transformer, and if it's more than 14V total, it should be fine.

(1) could be OK, using the 8-0-8 winding. However, I worry that the voltage could sag too low under load.
(2) would definitely work, but would provide nearly 30Vdc and would cause much higher dissipation in the regulator and lamp driver.

[mark.carline]

thanks for your comments - I managed to get the (3) transformer so i'll try it when I build it and let you guys know:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&rd=1&item=360099271144&ssPageName=STRK:MEWN:IT&ih=023