Fryette Effects - SAS EF86 Overdrive  [traced]

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diagrammatiks
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Post by diagrammatiks »

hey where did you buy that transformer?

who makes it?

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mat
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Post by mat »


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mat
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Post by mat »

Ok, so the bridge diodes will drop the voltage almost 2V's.. What about using the second (cascade) voltage doubler instead of the bridge rectifier and using a bigger resistor to drop the voltage to 9V and leave the regulator out ? I'll draw something later today.

Thanks again,
mat
ppluis0 wrote:Hi Mat,

I think that you can replace the 1 ohm resistor to another one of 56 or 68 ohms rated at 1/4 watt, and increase the size of the 47uF cap, maybe, to another 1000uF in order to have low ripple.

Considering that a single TL071 draws only 2.5 mA from the supply, the 56 or 68 ohm resistor of the RC cell result in almost 7.2 Vdc to feed this IC. In the datasheets I can`t find what is the lowest value reccommended to make this IC work reliably.

Perhaps any forum member can tell us about how to supply a TL0xx family chip.

Cheers,
Jose

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diagrammatiks
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Post by diagrammatiks »

man they have some nice toroids. wish there was something like those over here in the states.


for your power supply. you only need 8vdc for the op-amp.

just run a bridge rectifier and a big cap.

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mat
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Post by mat »

diagrammatiks wrote:man they have some nice toroids. wish there was something like those over here in the states.


for your power supply. you only need 8vdc for the op-amp.

just run a bridge rectifier and a big cap.
Ok, bridge it will be then. Thanks !

mat

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mat
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Post by mat »

Does the screen grid (pin1)100uF cap really have to be rated for 400V ? There is a 1M resistor between the 330V supply and the cap..

mat

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mat
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Post by mat »

Anyone looked under the hood of the Boostassio yet ? How different it might be. I was thinking of adding a DPDT to bypass the IC.

mat

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mat
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Post by mat »

mat wrote:Does the screen grid (pin1)100uF cap really have to be rated for 400V ? There is a 1M resistor between the 330V supply and the cap..

mat
Jose, I think I misread the value of the screen grid cap. Is it 100nF/400V instead 100uF/400V as I suggested ?

Thanks,
mat

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Post by mat »

questions questions :oops: Would the http://www.datasheetdir.com/RB154+download be suitable for the rectifier for the 9V supply ? How about the HV rectifier ? Is it to small for that (rates from 50V to 1000V) ? Just want to be sure.

mat

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mat
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Post by mat »

Coming up:

http://mattitee.kuvat.fi/kuvat/IMG_0564.jpg (seems I cannot get the pic to be seen on the post..

mat

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Post by ppluis0 »

mat wrote:Jose, I think I misread the value of the screen grid cap. Is it 100nF/400V instead 100uF/400V as I suggested ?
Yes. Is effectively a poly cap of 100 nF/400V, same as the coupling cap that connect pin 6 with the hot side of the volume pot.

Forgive me for having such poor handwriting ... :oops:

Cheers,
Jose

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Post by ppluis0 »

Hi Mat,

You need a bridge rectifier rated at 100 V/1 Amp for the low voltage supply, and another of 1000 V/1 Amp from the high voltage secondary.

Just think that the original unit have 4 x 1N4001 and 4 x 1N4007 at these positions.

Cheers again,
Jose

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mat
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Post by mat »

Thanks again Jose! One more (maybe the last) question is the voltage rate
of the 47uF cathode cap ? I only have a 47uF/25V and HUGE 47uF/450V ones..

mat
ppluis0 wrote:Hi Mat,

You need a bridge rectifier rated at 100 V/1 Amp for the low voltage supply, and another of 1000 V/1 Amp from the high voltage secondary.

Just think that the original unit have 4 x 1N4001 and 4 x 1N4007 at these positions.

Cheers again,
Jose

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Post by ppluis0 »

47 uF rated at 25 volts is fine.

Go ahead with this project !!!!!!!!!

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mat
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Post by mat »

ppluis0 wrote:47 uF rated at 25 volts is fine.

Go ahead with this project !!!!!!!!!
Thanks ppluis0 for confirming the cathode cap.

Added today power switch + power light indicator and added also glue under and behind of the transformer. It is also kept in place with metal belt, so that is the last part to fall of from the box :mrgreen: Two new pics:http://mattitee.kuvat.fi/kuvat/EF86over ... G_0566.jpg

Hope to finnish the main board tomorrow. Then I will make a small board for the IC and a bigger one for the power filter section. After that all it needs is wire :D

Thanks all !

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mat
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Post by mat »

Could someone confirm the power section pic (lacks the 100k after last 22uF/450V) ?

http://mattitee.kuvat.fi/kuvat/EF86over ... sasPWR.png

Thanks,
mat

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Post by ppluis0 »

mat wrote:Could someone confirm the power section pic (lacks the 100k after last 22uF/450V) ?
Looks good to me, but the 1000 uF filter cap at the low voltage section must be of 2200 or more microfarads depending if you hear residual hum when you test this pedal.

In any case assign some space on the board if were neccesary increase the value of this filter.

Cheers,
Jose

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mat
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Post by mat »

Thanks Jose :D

Updated pic: http://mattitee.kuvat.fi/kuvat/EF86over ... sasPWR.png

mat

ppluis0 wrote:
mat wrote:Could someone confirm the power section pic (lacks the 100k after last 22uF/450V) ?
Looks good to me, but the 1000 uF filter cap at the low voltage section must be of 2200 or more microfarads depending if you hear residual hum when you test this pedal.

In any case assign some space on the board if were neccesary increase the value of this filter.

Cheers,
Jose

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mat
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Post by mat »

The main circuit board is ready. Power supply board almost ready and the IC board is not ready yet.

One thing that came to my mind was that if the bias pot is 25k and not 20k is there a chance to outwear the tube too quickly for it to be biased too hot ?

mat

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Post by ppluis0 »

Hi Mat,

Bear in mind that the values of these 3 pots were an guesstimate due we never seen the original ones.

Nevertheless you can put a resistor across the extreme terminals of the bias potentiometer, say 100 K and you will have the same bias voltage range as if you use a 20 K pot.

Perhaps is a better idea start paralleling your 25 K pot with a lower value (56 or 68 K ?), to see what bias range you have and avoid the risk of damage an expensive EF86... :hmmm:

Cheers,
Jose

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