Welcome, Guest. Please login or register.
January 23, 2018, 05:50:01 PM
Home Help Search Login Register
News: Ceriatone Forums are up and running!!!
 
Guests please register
Note: If you want to help you can donate to keep the forums alive.










Do you want to advertise on this forum ? Send me a private message.



 


Amplified Parts
+  Ceriatone Forum
|-+  Website, Store
| |-+  Support
| | |-+  Troubleshooting OTS 50w
« previous next »
Pages: 1 [2] Go Down Print
Author Topic: Troubleshooting OTS 50w  (Read 7337 times)
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #15 on: October 09, 2013, 04:27:10 PM »

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?


Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #16 on: October 09, 2013, 04:34:57 PM »

... 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!

Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #17 on: October 09, 2013, 06:10:48 PM »

I have sound Grin also noise Sad   

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?

* ots noise.zip (78.92 KB - downloaded 63 times.)
Logged
wyatt
Guest
« Reply #18 on: October 09, 2013, 08:57:08 PM »

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?
Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #19 on: October 10, 2013, 08:40:49 PM »

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
Logged
wyatt
Guest
« Reply #20 on: October 10, 2013, 09:29:23 PM »

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?
Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #21 on: October 12, 2013, 06:16:21 AM »

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 Smiley 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
Logged
wyatt
Guest
« Reply #22 on: October 13, 2013, 11:49:58 AM »

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.
« Last Edit: October 13, 2013, 12:20:54 PM by wyatt » Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #23 on: October 13, 2013, 12:46:32 PM »

I think i have the problem solved  Cool

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 Smiley 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!!!
Logged
wyatt
Guest
« Reply #24 on: October 13, 2013, 07:27:30 PM »

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.
Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #25 on: October 13, 2013, 09:19:41 PM »

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.
Logged
wyatt
Guest
« Reply #26 on: October 14, 2013, 09:48:02 AM »

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?
« Last Edit: October 14, 2013, 09:49:58 AM by wyatt » Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #27 on: October 14, 2013, 07:45:54 PM »

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


* 6l6.jpg (1262.31 KB, 2592x1944 - viewed 169 times.)
Logged
parrosa
Newbie
*
Offline Offline

Posts: 23


View Profile
« Reply #28 on: October 15, 2013, 06:39:05 PM »

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

* 6L6 shootout.zip (1999.16 KB - downloaded 81 times.)
Logged
wyatt
Guest
« Reply #29 on: October 15, 2013, 08:36:04 PM »

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.
Logged
Pages: 1 [2] Go Up Print 
« previous next »
Jump to:  


Login with username, password and session length

Powered by MySQL Powered by PHP Powered by SMF 1.1.12 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!

CeriaTone Forum is not afiliated with Ceriatone Amplifications. The CeriaTone and name, logo and related trademarks and service marks, owned by CeriaTone. , are registered and/or used in the U.S. and many foreign countries. All other trademarks, service marks, and trade names referenced in this site are the property of their respective owners.