Coron - Over Drive  [schematic]

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Coron - Over Drive

Postby Dingleberry » 05 Sep 2014, 11:31

Hi.
I got a Coron Over Drive pedal for maintenance from my friend. It's a quite nice sounding low gain overdrive. One fet (k86A), two tant. caps (100nf, 3,3uf) one film cap (47nf) and three resistors (10K, 22K, 510K).
At the input there is a 1MC pot wired as a variable resistor (gain control, labeled "emphasis") and output vol pot is 50KA. Beautiful, simple, classic.
I will document it and post pics and schematics when I get into it, although there is some pics and one schematic floating in the net. The funniest part is that it runs on one AA-battery (1,5Vdc.)
I always thought that Maestro FZ1-A was the only one that runs on 1,5Vdc until I opened the Coron.

My friend wants to hook it up to his existing pedalboard and he only has 9Vdc outlets. My question is: What is the best way to drop the voltage to 1,5Vdc? Should I use lm317 regulator?
Should a simple voltage divider do the trick? Zeners?

-T
Simplify before you amplify.

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Re: Coron Over Drive

Postby phatt » 05 Sep 2014, 13:51

This is often missed;
Unlike a lot of later pedals which draw insane amounts of electrons to run,,,
This unit (with only one active element) likely has such a low power draw the battery will last a very long time, which was the whole idea of pedals when I Wus young.
So running from a supply is hardly worth the trouble and add needless complexity.

A wise man would simplify,,,Just buy a battery and go play the guitar. 8)
Phil.
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Re: Coron Over Drive

Postby ggedamed » 05 Sep 2014, 16:23

You should measure the current drawn by the pedal. Then it'll be easier to choose:
- if the drawn current does not vary a lot, you could use a single resistor with a value big enough to cause the needed voltage drop.
- there are no 1.5V Zenners that I know of, you could use a green LED or 3 1N4148s.
- a LM317L (TO-92 case) circuit should be almost as small as any of the other variants and provides more voltage regulation and more curent capability.
- if your friend does not care that much for the overdriven sound, you could also have him try the pedal at 9V; I couldn't find the datasheet for K86A (the Toshiba 2SK series?), but I seriously doubt that it cannot stand 9V.
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Re: Coron Over Drive

Postby Dingleberry » 09 Sep 2014, 15:47

phatt wrote:This is often missed;
Unlike a lot of later pedals which draw insane amounts of electrons to run,,,
This unit (with only one active element) likely has such a low power draw the battery will last a very long time, which was the whole idea of pedals when I Wus young.
So running from a supply is hardly worth the trouble and add needless complexity.

A wise man would simplify,,,Just buy a battery and go play the guitar. 8)
Phil.


That is totally true my friend, but you missed the whole point of my question... My friend wants to hook it up to his existing pedalboard and 9Vdc is the only voltage his pedal board power supply delivers so my goal is to make it happen.

The current draw for that fet will be nearly nothing but I decided to go with the LM317 route, mostly because I've never fiddled with one before. Only have experience with LM78- and LM79-series regulartors. I already made a tiny board for it and probably get the pedal done this evening. Got to change the jacks too because they are broken and install DC jack and make it true bypass with led. It's gonna probably be a little pita because he had already tried to "mod" it and drilled hole without thinking it any further and regular dc jack is probably not going to fit between input and output jacks... we'll see how's it gonna turn out.
Lm317 being variable voltage regulator it will be interesting to try it with higher voltages also and see how it changes the character of the the pedal.

-T
Simplify before you amplify.
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Re: Coron Over Drive

Postby fuzzbunny » 15 Sep 2014, 07:25

I look forward to seeing a schematic for this!
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Re: Coron Over Drive

Postby Nocentelli » 16 Sep 2014, 20:03

fuzzbunny wrote:I look forward to seeing a schematic for this!


Dingleberry wrote:One fet (k86A), two tant. caps (100nf, 3,3uf) one film cap (47nf) and three resistors (10K, 22K, 510K).
At the input there is a 1MC pot wired as a variable resistor (gain control, labeled "emphasis") and output vol pot is 50KA. Beautiful, simple, classic.... The funniest part is that it runs on one AA-battery (1,5Vdc.)


With so few parts, there are a fairly limited number of different ways of connecting them that would produce overdrive: This is my best guess until dingleberry gets around to tracing it -

coron OD perhaps.bmp
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mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.

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Re: Coron Over Drive

Postby fuzzbunny » 20 Sep 2014, 18:49

Thanks for your fine help Nocentelli!
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Re: Coron Over Drive

Postby Dingleberry » 19 Nov 2014, 22:00

Just switch the input and output caps Nocentelli and it's correct.
Mild overdrive/pre amp booster, good Texas tone with strat and didn't sound bad with humbuckers either.
Simplify before you amplify.

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Re: Coron - Over Drive  [schematic]

Postby Dingleberry » 20 Nov 2014, 20:58

This is the schematic. 100nf and 3,3uf are tantals. 47nf is film cap.
All resistors carbon film. And only 2 lugs of the 1Mc pots were used (actually mislabeled in the scheme... should be lugs 2 and 3 connected)
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Simplify before you amplify.

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Re: Coron - Over Drive

Postby johnk » 26 Nov 2014, 01:05

I drew up a pcb for this one, etched it, built it, and tested it and IMO, it's a decent low gainer.
I used an LM317LZ and an NTE458 since I couldn't find a K68.
layout:
Image

PCB:
Image

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Re: Coron - Over Drive

Postby Bill_Mountain » 26 Nov 2014, 15:31

Are there any other FETs that would work? MPF102? 2N5457?
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Re: Coron - Over Drive

Postby johnk » 26 Nov 2014, 17:27

probably a J201 but mind the pinout.
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