Ceriatone Forum

Good evening all,

Thanks in advance to Sion for replying to my last thread. I proceeded with this build based on what he said, and just finally finished up. The amp sounds GREAT! Really happy with it.

Now that I've gotten most of the worst operational gremlins out of the way, there's one nagging issue I have yet to settle.

The impedance selector, when set to 4 ohms, works just fine (although it's a mismatch with my speakers, so a little think... hence the issue and hence this thread) but neither 8ohm or 16ohm setting works. Both just send out white noise at full volume, the 8ohm setting fairly loud, and the 16ohm BLISTERING loud... both totally ignore changes to any volume knob on the amp... they just blast full volume and they transmit NO guitar signal at all.

The main part of it that confuses me is the fact that obviously all three settings are originating from the same place and being sent to the same jack, so I'm having a hard time understanding why I'd be getting a varied response from each? I thought I might've wired the selector switch wrong, so I desoldered everything, rotated it to the next group of pins and got the same result.

One thing I noticed was the fact there's a line that runs from the board to just one pin on the impedance selector switch... which just so happens to be the only one that's working for me, the 4 ohm pin. Being the type to do my due diligence, I looked at some other Ceriatone layouts and noticed that same lead wire is attached to different pins of the selector on different amps. There's some degree of continuity between all the secondary wires on the OT, so the design makes sense to me logically but I'm not sure why I'm getting the result I am? Real head scratcher.

Anyway, any advice would be a big help. For reference, here's the area in question... you can see what I'm talking about re: the green lead into the 4ohm pin.

(http://www.jcedricguitars.com/images/gear/otsminibuild/otsimped.JPG)

White noise might not be the best description because it's not so much electrical buzzing noise or hissing, it actually sounds like a solid test tone being sent through the amp at FULL volume... it sounds like all the knobs on the amp turned up all the way but it's sort of 'musical' in that you're actually hearing amp tone, not just electrical buzzing.

Quick update, incase I'm not the only person reading this thread.

As I was messing around with this today, tried a few experiments and made a couple observations.

My cabinet is 8ohms. If you're following from the first post, the 4ohm position is the only one working, and it's also the one that the green lead from the PCB is wired to. I decided to wire the green lead to the 8ohm lug, and I was able to get guitar to come out of that, the 4ohm AND the 16ohm but all of it was accompanied by LOTS of noise and that same "everything turned up all the way" sound I was getting before. Since I went from "no guitar signal" on two lugs, to "guitar signal through all of them" by soldering it a different impedance setting, does that implicate the rotary switch itself?

Two other observations:

I decided to try running the effects loop 'send' to a different amp to check and see if that was working correctly and to see if the preamp was in full working order.

When I plugged the external amp into 'send', I was getting sound out of both the second amplifier AND the speaker connected to the OTS. That's obviously not right.

When I plugged the external amp into 'return', I was getting signal just through the second amplifier, and it responded to knob adjustments just like it should, with no extra noise.

So is there some potential the impedance selector is originating from something wrong with either the jack(s) or somewhere in the connection between them and the power tube section?

The wire from the board to the 4 ohm pin is for negative feed back. Don't disconnect it. Yes it can be on one of the other pins, but go by your layout.

You need to build a current limiter first before you blow your stuff up.
This is too fancy;

http://www.tdpri.com/forum/shock-brothers-diy-amps/527023-light-bulb-current-limiter-build.html

I would just butcher an extension cord and put a porcelain socket with a bulb in it in series on the black wire.

**I think you may need to reverse the leads to the output transformer from the power tubes.**

Make sure your output transformer is wired to the speaker jacks, not the send/return jacks.

good luck.