Ceriatone Forum

Hi all,

 After 20 and some hours, i finished the OTS... and the result is just static, to my desapointment  ???   So i did something wrong along the way :(

I had a lot of doubts during the build. If any of you can help or just tip, please type :)


I have doubts regarding the Transformers.... Mcinku was kind to send me a picture with the correct wiring for this PT. I've managed to copy it, but i don't know if it's still well connected. With the PT comes a colour code for the wires. I wrote it on "PT wire codes.jpg" (very small numbers, sorry).

The two wires from the choke are not differentiate?

The Primary of the OT has 3 wires, two wires for lug nº3 of each 6l6; The third goes to the 200uf Cap, with a choke wire? It's there on the schematic, but i'm not sure if im reading well...

Another thing about the schematic is the power amp in and preamp out jacks. The perspective of the schematic tells me wires N and T are on the lugs closer to chassis. But on Ceriatone OTS pics, you see the other way around... So i followed the pics.



 

Another thing about the PT; it has 3 red wires. 2 with 340v, 1 with 3,15v. I'm just guessing wich is wich...

I have double checked all the wiring, nothing i could spot wrong.

some more pics

First step is to pull all the tubes and measure all your voltages with a DMM.

Post the voltage measure at every pin on each tube socket...

If you built a lightbulb limiter to test for shorts at first start-up...and I advise you should have one...you should use it and check for any symptoms of a short-circuit.

Once we've determined if the voltages are correct throughout the amp, then we start tracing for breaks in the circuit. This is best done with a signal generator and a O'scope, but it's far cheaper to make a probe that can be run into another amp.

Building an amp is far, far easier than troubleshooting one.

I don't understand your comment on the effects loop...the layout looks exactly as the pictures show it wired (including your own pictures) Still, NEVER defer to the pictures, the were often taken of amps built with older layouts or different parts. On many of the Ceriatone models, the chassis in the pictures looks nothing like the current chassis/layout.

Last, what Ceriatone supplies is a layout, it is NOT a schematic. There is a big difference between the two, the layout shows the mechanical connections between the parts, but often leaves assumed details, that are the same across all tube amps, out (like filament wiring). But more importantly, if you use different parts, the connections can change as well.

Thanks Wyatt, gonna dig for those measures right now....

Sorry about the technical names, i lost most of my electronics knowledge. I've learned 4 years in electronics, but stopped around 1999....


BTW, how does these input jacks look to you?

Thanx

Already turned it on for a minute, the only sound i get is static....

I have it working with tubes and on standby, it measures the following:

V1

1 - 380mv
2 - 400mv
3 - 60mv
4 - 0
5 - 0
6 - 390mv
7 - 610mv
8 - 10mv
9 - 0

V2

1 - 490mv
2 - 550mv
3 - 30mv
4 - 0
5 - 0
6 - 430mv
7 - 630
8 - 1
9 - 0

V3

1 - 290mv
6 - 290mv
all other pins read 0


should i take the tubes and measure every pin?

First, pull all the tubes pout...you don't need them to check voltages and if you have the power tubes in and no speaker load hooked up, you'll fry the output transformer.

When you measure, connect the black probe to ground (alligator clip works best), and place the red probe on each pin. Keep the free hand in the pocket (for safety).

But those measurements aren't right...not at all.

First off...you don't have any filament voltage...that's pins 4/5 (connected) and 9 on the 12AX7's. The tube should be seeing 3.15VDC on pins 4/5 and 3.15VDC on pin 9. Are you measuring 3.15V with the PT hooks up to the terminal strip ebfore going to the tubes and pilot lamp?

According to this...
www.ceriatone.com/voltage/VoltageChart.xls

You should see...
~200 volts (NOT millivolts) on your plates of V1 and V2 (Pins 1 & 6) and ~300V on the plates of V3.

So, we have multiple issues going on, many may be related to PT wiring. Strat measuring the voltages were each PT lead makes it's first connection and make sure you have the right wires connected. If you don't, you may have damaged other parts.

This is going to get difficult to do online, eventually, you have to buck it up and see one of these...
http://ceriatone.com/tlbrBorderSub/tech_service.htm

Thanks wyatt, i'll try your advice before taking it to a tech...

Well, there is a lot of stuff we can work through. One winding at a time.

The first is the 3.15-3.15 filament winding. Make sure you get 3.15V (to ground) on both halves of the winding connected at the terminal strip. Does the pilot light come on? Make sure you are getting 3.15V (to ground) at the pilot light.

If the voltage is correct at the terminal strip...follow the next wires to V5 and measure at Pins 2 and 7. If it's correct here go to V4...if correct there...well we know V3 isn't seeing the filament voltage, so there has to be a short or an open circuit somewhere between the PT and V3. Let's track it down.

On a related note, do you know if one of those green wires is a center-tap for the 3.15-3.15 winding?

Once we have the filaments working, we'll move to the high voltage wiring.

this is what i've got without tubes:

PT secondary taps:
55VAC
374VAC x2
3,4VAC x2
15VAC x2
0V x2

OT Primary taps:
507VDC x3

I've re-checked the connections from these taps on my build, and they seem to be according to the layout...

Measured some connections :  3,4V at pilot light wires and heaters, 6L6's pin3 with 507VDC; 30V to voltage regulator and 25,6V out...
Maybe i just misread the DMM  at the first time  :-[  im going to measure again with the tubes tomorrow and compare them with the chart.

Just receveid your reply, ill answer after....

So i've checked the 3.15V (3.4V in my DMM) taps: the pilot light comes on, heaters on V5 and V4 (pins 2 and 7) all see 3.15V.



.....  About the center tap, there is a sticker in the PT. reads as follows
- 2 x yellow = 6 V
- black 2,5 mm2 = 3,15
- green 2,5 mm2 = 0 V
- red 2,5 mm2 = 3,15 V
- 2 x red 1,5mm2 = 340 V
- green 1,5 mm2 = 0 V
- orange 1,5 mm2 = 60 V

 wich means i don't have it well connected in the picture, right? The thickest green wire on the bottom(3.15V center tap) goes to fuse instead of direct ground. I'll correct it tomorrow....

Not true.

The Filament CT (thick green) goes straight to ground.

The High Tension (high voltage) CT (thin green) goes to the  .5A HT fuse.

So, what is happening with the filament wired between V4 and V3 that you aren't seeing 3.15 on the 12AX7's?

Hi, i resoldered the two green wires. Heaters ground to ground and 340v center to fuse. My written english is not the best.... Hope the picture clarifies...

The pins 4,5 & 9 from v1, v2 and v3 read 3,4v now.

Im Göing to measure all v pins without tubes next... Or is there something else to test before?

...The diode (rectifier?) board reads 340v on each Red wire from PT secondary.
55v from another PT secondary wire to this board.
 The wire out from this board reads 507VDC.

Thanks for support onde again Wyatt !!

So, figured out wich Pins are AC/DC  :o that's why i had bad readings the first time....

values without tubes:

V1
1 - 334 DC
2 - 0
3 - 0
4 - 3.2 AC
5 - 3.2 AC
6 - 350 DC
7 - 0
8 - 0
9 - 3.2 AC

V2
1 - 340 DC
2 - 0
3 - 0
4 - 3.2 AC
5 - 3.2 AC
6 - 350 DC
7 - 0
8 - 0
9 - 3.2 AC

V3
1 - 434 DC
2 - 0
3 - 0
4 - 3.2 AC
5 - 3.2 AC
6 - 430 DC
7 - 0
8 - 0
9 - 3.2 AC

V4 and V5 measure pretty much the same, so:
1 - 0
2 - 3.2 AC
3 - 490 DC
4 - 490 DC
5    -37 DC
6 - 490 DC
7 - 3.2 AC
8 - 0

Comparing with the voltage chart ( www.ceriatone.com/voltage/VoltageChart.xls ), i have "expected" higher voltages on DC Pins.

Exceptions are
V4&5   Pins 1 and 8 are 0V instead of 37mV

V1 & 2 Pins 3 and 8 are 0V instead of ~1,5V

V3       Pins 3 and 8 are 0V instead of 54V

are these readings tolerable? What would be the next step? Still no burning smell, hope i'm on the right track :)

Pin 1 on V4/V5 does NOT matter, the pin isn't connected internally. Becuase 6V6 and 6L6 don't use Pin 1, Fender used Pin 1 on the socket as a handy lug for making connections to Ground. Personally, if I built the amp, I would not connected the bias probe contact and 1ohm resistor straight to Pin 8 and left Pin 1 unconnected to anything, allowing for use of EL34 if desired. But there is nothing wrong with it as is.

But I digress...Pin 1, as it stands, is unimportant. Since it's connected directly to Pin 8...it will always show whatever Pin 8 shows.

---

Pin 5 on V4 and V5 is showing your negative bias voltage. It's in the ballpark.

---

Pin 8 on V4/V5 and Pins 3 and 8 on V1/V2/V3 are all cathodes. Just make sure all their connections are right and we'll look at them again with tubes installed.

---

But I would say it's time to hook up a speaker load install the tubes and re-measure. If everything seems good, we can begin to look at the signal path for your "no sound" issue.

Thanks Wyatt!!!

Here are my readings, tubes loaded, speaker load in "operate" mode:

V1
1- 163   VDC
2- 0
3- 1.7   VDC
4- 3.15   VAC
5- 3.15   VAC
6- 185   VDC
7- 0
8 -1.65   VDC
9 - 3.15   VAC

V2
1- 174   VDC
2- 0
3- 1.7   VDC
4- 3.15   VAC
5- 3.15   VAC
6- 186   VDC
7- 0
8- 1.54   VDC
9- 3.15   VAC

V3
1- 270   VDC
2- 0
3- 57   VDC
4- 3.15   VAC
5- 3.15   VAC
6- 260   VDC
7- 0
8- 57   VDC
9- 3.15   VAC

V4
1- 55.2   mVDC
2- 3.15   VAC
3- 424   VDC
4- 422   VDC
5-   -33   VDC
6- 422   VDC
7- 3.15   VAC
8- 55.2   mVDC

V5
1- 54.7   mVDC
2- 3.15   VAC
3- 423   VDC
4- 425   VDC
5-   -33   VDC
6- 423   VDC
7- 3.15   VAC
8- 54.7   mVDC


After speed-reading the OTS topics, i tried swapping the Output transformes Primary wires on V4 and 5, Pins 3, and it got lot more quiet!!!     

I mean silent, with sporadic noise..... the noise is very close to the interference that the probe does while touching some of the tube's pins.... i haven't tried plugin my guitar, but i'lll eat something first.....

Is there anything to worry on these readings, wyatt?

... comparing with the voltage chart, it seems all High Tension Pins are colder in my build....


On V4 and V5, the negative voltage is also lower, but 1 and 8 are almost double!

I have sound ;D also noise :(   

Should i start to diagnose with an audio probe? where should i start?


I made a short audio with the noise... can you tell by what it sounds what it might be? Is it safe to keep running longer time?

Sounds like a bad connection. Maybe a cold solder joint somewhere.

You may have quick luck turning the amp on and tapping on joints with a basic disposable bamboo chopstick (so chosen because it's the ideal size and non-conductive).

You may note the noise goes away when you press on a joint, you may notice it gets works, but for most normal joints it shouldn't result in much more than a simple pop with you tap on it.

Does the noise turn down with the channel Volume?

The volume or any other pot doesn't interact with the noise. It's always there

 Checked most solder joints, reflowed some just to make sure... no difference.

The Bias pot all the way down reads more than 50mV on V5 and more than 40mV on V4 !!  I always keep it on for less than 3 minutes


I'm going to try chop suey test, and if no result i'll resolder V4 and V5

Thanks again waytt!
 
If any thing comes to mind, let me know

Check all the connections for the OT and the speaker out jacks.

If it isn't affected by the volumes it may be any connection to ground (filter caps...CT's...etc.) or between the OT and speaker.

Do you sand/file/grind the chassis (to remove any non-conductive finish or anti-rust coating) and use the star-style lock washers at all points were grounds connect to chassis?

In fact i didn't grind any ground connection to the chassis.... how noob is that? The chassis has no paint finish, showed continuity, so i didn't bother.

Instead of taking out screws and grind, i filed the chassis right beside the screw and solder a jumper to it. Did all the ground connections, plus the bias pot cover and Od Trim (this pot has lug 3 connected to ground, but i assume it's no problem).

The result was a very silent powerup :) but in less than 1 minute, the noise started to volume up; had a multimeter connected to bias probe V5. during this minute value raised from 20mV to 40mv....

Should i ground V4 and 5 Sockets to ground too?

Thanks again

Running out of ideas myself.

The crackling probably starts up after the tubes warm for one of two reasons...1) cold-solder joints separate when components heat up ad expand, stressing the joints...2) the tubes are warming up and finally start to amplify the signal and the noise. The former seems unlikely, it usually takes more than a minute for much of the amp to warm up and start causing problems with things like cold solder joints. Things like plate resistors, screen resistors, etc. that connect to the tubes could be a possibility.

My thoughts are, if the crackle isn't unbearably loud, it's probably not in the preamp signal path. If it were it would be amplified and  to high volume levels by the poweramp. That leaves things like the ground connections, and connects to power tubes.

I think i have the problem solved  8)

I would like to thank you wyatt, for patience, help and support! Without your feedback, i would have take it to a tech long ago...

.... Inspected, reviewed and rechecked most solder joints and ground connections. Everything was ok... The last thing before i take to a tech, was replacing power tubes.

Amp came out alive and well :) no noise, wonderful sound, everything 100%. Biased the used 6l6's (32mV-V4 39mv-V5), tuned PI trimmer to 6VDC difference and FET board trimmer as well, everything ok. Played for an hour or so. Stable voltage readings everywhere, no noise.

Then replaced the tubes with the new ones again. Noise again. So, i think i have solved the problem.

Now, one thing puzzles me : Tried the new 6l6's in my Cornford Roadhouse 30 (from where the used ones came). No noise, even in high volume.... Only blue light and extra heat was noticeable.
The new tubes look good and new from the outside.... How can i test/make sure that these tubes are faulty? A tube tester is the only way to go?

As for the OTS, i'll try to describe it in another post maybe.... I've played several amp models of brands like Fender, Marshall, Vox, Mesa, Soldano, Cornford, Orange, Bogner, Egnater... The OTS doesn't have all the best or signature sounds from the previous, but it's far superior IMO !!! Versatile, flexible, dinamic, transparent, powerful, detailed. And topping that, it has all the features for Gig and Studio work!

Thanks Wyatt for all the help

Mr. Nick too, for a huge contribution to the guitar world!!!

I recently heard a similar case where a pair of Tung Sol 6V6GT's were just super noisy in a 5E3 clone for no explainable reason.

First things first, were the power tubes properly biased?

Otherwise, shots in the dark...tube socket issue? Tube pins incompatible with socket? Several years ago JJ tubes shipped several tubes with pins that were too small in diameter in it caused random issues.

I couldnt even set a stable voltage for power tubes. They kept rising from 20mv to 50mv, and more, in less than 2 minutes...  Even though on Conford they were very silent, they got very hot in less than 5min.

These were identical to those i have on Cornford, they fitted the same way... Tube sockets don't seem to be the problem

I Have a Fender Super Sonic, gonna try those 6l6's there.

If they won't hold bias, then you can pretty much write at least one of them off as a defective tube. I wouldn't spend too much time trying to salvage it.

What make and model tube?

Both of them went to see the doctor today http://www.orangeamps.com/products/accessories/amplifier-management/vt1000/

And they are both working, but 3 of 4 grades apart. Not paired at all.

Bought 2 new tubes at the store. JJ 6l6GC, same thing. I'm doing a shootout with them

I have made a short clip with 4 paired 6L6's, in this order:

New JJ

4 year old Groove Tubes

3 year old JJ

Bad new(s) JJ

Used clean and distorted channels, with almost every knob at noon

I know the JJ 6L6GC's have been getting a reputation lately for having a lot of mechanical rattles. These are sounds you can hear form the tube, but aren't amplified as part of the circuit. Some people are getting fed up with it.