Problem with Octavia board from general guitar gadgets.

deviltone · March 12, 2006, 10:55:01 AM

I'm trying to start soldering the board for the Octavia, but the transformer I have has six leads coming off of it, but where it mounts on the board, there's only 5 holes? What do I do? Can post pics. Thanks in advance.

guitar_199 · March 12, 2006, 01:24:17 PM

Went and had a look at the schemo..... here's my take....

As delivered, it appears that tranny has center taps on both the primary and secondary windings.

In this application, the transformer is being used flipped around from it's intended direction. This design uses the secondary as primary then uses the center tapped primary as secondary to feed the rectifier.

On the data sheet it did not show a "color code" for the leads but it did identify the pin number scheme:

http://www.mouser.com/catalog/specsheets/164267.pdf

1 - Pri
2 - Pri CT (center tap)
3 - Pri
4 - Sec
5 - Sec CT
6 - Sec

So, since you are needing to use the secondary as YOUR PRIMARY you would need to leave pin 5 disconnected. You might try just bending it up at first if you can.... or bench test it "in circuit with jumper leads first just to make sure that you are indeed using the right pins as primary before cutting it off.
But, from the above data sheet ... it looks like you need to get rid of pin 5 and solder that puppy in.

Good luck.

deviltone · March 12, 2006, 01:34:48 PM

That's correct... The center pin on the secondary is the one not used. I think... So you're saying I'm supposed to install it backwards or am I not getting what you're saying.

I looked at some pictures from the GGG site and they show the sixth pin soldered on there.... I don't know what to do. I wrote JD Sleep over a week ago, but he hasn't responded.... Here's the pics from the site

here's the diagram...

deviltone · March 12, 2006, 10:11:04 PM

Here's my wiring job... The wires are a little long so I can take out the board and work with it.... I had the unit working with a DPDT switch, but I wanted an LED on it, so I wired it to GGG's specifications and the LED will light, but no sound when the effect is supposed to be on. Bypassed works... I've even tried a different 3PDT switch, but no luck. I don't know what I'm doing wrong....

burnt fingers · March 13, 2006, 01:30:46 AM

Dude you and me are in the same places at teh same time aren't we. I go by scottywompas on TGP and just replied to your post there.

Again, Nice work man.

Scott

guitar_199 · March 13, 2006, 08:58:02 AM

Yeah, once you identify and remove pin 5 ( the transformer's secondary center tap...) it goes in backwards from what you would normally do.....NOT backwards from the drawing! The drawing is marked for what it wants. When you are done with the removal of pin 5 it should be soldered on the board so that the NORMAL primary ( pins 1,2, and 3 ) go towards the diodes that rectify the audio. That ought to get it put in correctly.

deviltone · March 13, 2006, 12:46:40 PM

Thanks - I did a little research on it.... But I have a new problem now... I can't get it to work with a 3PDT switch. The LED lights up, the bypass works, but when the effect is on - nothing... Worked fine with a DPDT switch.... I don't know what happened... I need some help!

Thanks again.

Mark Hammer · March 13, 2006, 01:20:40 PM

If I've understood all the info correctly, it is the set of transformer leads with the lesser DC resistance that "faces" the diodes?

guitar_199 · March 13, 2006, 01:37:21 PM

Mark,
I went back to the data sheet just to make sure and it is the higher that goes to the diodes.

Per spec. the tranny has 1.5K primary with 500 Secondary for a ratio of 3:1. But then this design turns it around which feeds the secondary and sends the primary to the diodes. Looks like they may be using this as a "step up" to bring the signal level up by three p-p before they whack it in half with the rectification. This way the recified "double harmonic" should have a little extra oomph in the mix. Of course, this is just my speculation which makes it immediately suspect.

burnt fingers · March 13, 2006, 03:23:55 PM

Deviltone,

I just had a switching problem with an overdrive I finished last night. I just rewired everything on the switch after I eliminated anything on the board as being the culprit. I had the wires going to the led and ground mixed up. If yours worked with a dpdt then you probably can eliminate any errors on the board. I rewired the switch checking of the connections as I went. I used the GGG diagram too.

Hope this helps
Scott

deviltone · March 14, 2006, 02:45:46 AM

So no one has an idea? Hmmmm.... I'm still stumped about it.

guitar_199 · March 14, 2006, 11:53:16 AM

Well...... assuming that it worked before on a DPDT..... but doesnt when the switch is 3PDT......
I guess I would....

1) use a few clipleads from guitar cords and verify that the effect PCB itself still works.

2) If you did anything else and didn't mention is...like... doing a power switch in the ground switching of one of the instrument jacks, make sure that you still have power and ground on the PCB.

There's just not a lot of room for it to be much......... other than a wiring "oops". They do happen.

burnt fingers · March 14, 2006, 03:41:06 PM

The pic you posted on TGP looks like you have your input jack tip going to one of the outer lugs on the switch, According to the GGG diagram the input jack tip should go to the center lug.

Scott

hubble · June 08, 2006, 02:23:36 PM

are those caps reversed? also i was wondering if you ever got yours to work because im having the same problem

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Problem with Octavia board from general guitar gadgets.