Ceriatone Forum

I have received a lot of help from this forum.  After much pain and heartache (as well as some stupid mistakes), my OTS is up and running on the clean channel.  However the overdrive squeals in a really bad way and when the OD trim gets turned up it gets worse...  

Another forum member thought it would be appropriate to start a new thread and post pictures of the guts so that responses could be easily found for the next guy who runs into this problem.

This is my first amp build, as you will see in the pictures.

Thanks in advance for all your help!!!  

So much crazy wiring - wouldn't know where to begin. You've got power wires running next to signal wires all over the place. Take a look at the commercial builds and HAD's builds and see how the wiring is on those - you really need it to be cleanly laid out as far as the wiring goes or you're going to get noise, hum and squealing. I'm not an amp tech, just someone who built one that works, so I don't know if this is fixable without a complete rewire.

I agree. It may be tough, but a complete re wire may be in order. also check all your solder joints as well


Gregg

My clean signal sounds great with less hum than my fender or Marshall... Don't know if that helps.  But i am open to your suggestions.  So what would you rewire first?  What areas should I focus on?  Where are my biggest problem areas?

I don't know if this helps, but the signal is fine when I switch to od when the od trim or levels are very low. As I turn up Overdrive level it starts to squeal very high pitch.  Independently If I turn up the trim it is loud hum, ala motor boat.  Is there a voltage to check? Clean is very nice, and I can get great crunch with manipulating the channel.

Hey Jeff
From what I can see in the pics there appears to be some cold solder joints, particularily on the preamp board where you have landed the coax. I would def reflow those. Heat up those eyelets until the solder pools up like the ones Niks crew soldered.
Also as the other guys have mentioned some of the wiring is left a little longer than should be. When I build my amps I always aim to keep about a 1/4'' of separation between all the wiring when possible.
The wire that runs from the PS board to the preamp board and ties to the PI pot should be rerouted under the board if possible.
Also if possible maybe post some closeup pics of the wiring at the preamp tubes especially V2.


Todd

http://www.youtube.com/watch?v=dboDWnEwxmE&sns=em
I recorded my amp to show you guys what is happening.

Also I rewired half the amp, routed every coaxial and most wires on the side of the pots.

The good: clean is awesome, and loud, master volume works, deep switch gets me a cool crunch that is responsive to the volume control.

The bad: no tone controls working, overdrive channel sounds terrible or buzzes/squeals.

I am starting to wonder if I have a bad relay or a damaged component, like my switch?

I'll post v2 pics in a minute....

Does your footswitch work and do the lights on it light when engaged?
If you have PAB engaged the tone controls do nothing!

Todd

Todd, the footswitch works, lights and everything. I understand the PAB ( I had the relay in their backwards) finally.
I am pretty confident that my main problem is some place isolated in the Overdrive Channel, but i have been staring at it so long, i probably missed something.

Here are the pictures of my attempt to clean up the wiring (thanks gregg/sduck) - especially the coax and spacing on v1, v2 and the pots on front.  I tried to re-solder a lot of stuff.

I tried just jumping the OD trim and it didn't do anything to alter the crazy noise.  I rewired and dressed the coax from the relay pcb....  Should i jump something else to try an isolate where my problem is?  How do you guys debug these things?

Running out of options, but I am obviously learning a lot.  I am going to gig this thing outdoors this weekend sitting on top of my blues deville combo.  Burn her in.   I will only use the clean channel (like I do with my fender).  If it fails, I will just plug the deville in.  I would sure like to get this overdrive channel figured out.  Maybe I should have started with an easier maiden voyage in amp building - I almost went Dizzy30 instead of this...

Pins 7 and 8 of V2 look awfully close in the pic but it may just be the angle.
Other than that nothing obvious is jumping out at me.
Are all of your voltages matching the voltage chart?
Did notice some stray solder globs on chassis that you will want to get out of there.
Have you tried chopsticking with guitar plugged in to see if moving any of the wires around increases or decreased the hum/squeal?
You said the relay was in backwards, do your tone knobs work now?

Todd

OK, all my tone knobs work now. I scraped the chassis where the pots are, I tapped and moved wires with a chop stick (ears are ringing still) to no avail.  Pin 7 and are not touching. 

Here are my preamp voltages - where is says Jeff, thats me.
I put NIK in here for reference (his is first)

My OD voltage is wacky????

Tube   Type           Pin1      Pin3                  Pin6   Pin7   Pin8
                           
V1   NIK        191      1.7         200      1.6
   Jeff           140      1.5         141      1.4
V2   NIK        200      1.7         201      1.7
   Jeff           175      1.8         191      1.7
   Jeff OD   188      1.9         300   -8.3   56

V3   NIK       298      56         289      56
            Jeff       282      28         267      56

I guess my next step is to try and see if anything is touching on the backsides of the boards???? 

Sorry about the ears!
Your voltages are low all around
What are you reading for HT and also at the OT CT?
Also are the voltages at V4 and V5 off as well?
At every ground did you sand or grind the white paint off to bare metal?

Todd

Your wiring is the possible problem of the oscillations, they are on various points crossing other wires or sitting on them where they shouldn't. Not just 1 wire; all over.

The voltages; I couldn't see the colours of your dropping string correct; maybe post a better pic of that. However the last dropping string resistor; you have a 22k instead of a 2k2!

I Am sorry for my ignorance, but what are the string resistors?  Tried to research that, and can't find anything I can relate to my build.

Follow the B+ from the rectifier and you will see a number of resistors in series which create the correct plate voltages for each tube. Each dropping string resistor creates a node, usually labeled B+1, B+2 etc. The big caps simply smooth out the AC ripple and for the purposes of testing can be ignored. Its easier to see how this is arranged if you look at a schematic rather than a layout. If you get one of these wrong then you will be dropping the voltage too much or too little and the tube will not function as designed. If you get one wrong early on it has an effect on all the nodes down the string.

Ok when I think of the dropping string I am thinking of the resistors on the Ps bd where in previous post it was pointed out that there wAs an incorrect resistor. That will screw everything up. I am colorblind so it is impossible for me to confirm. Please tell me this has been corrected.

Todd

http://www.ceriatone.com/images/completeAmpsPic/CTOvertone/board/left1B.jpg
http://www.ceriatone.com/images/completeAmpsPic/CTOvertone/board/Leftend2B.jpg

I have been still going through the preamp.  My clean is awesome, od sucks bad...

Gratefully from the feedback here I see a problem.  In the pictures (links above) i see a 20k (black resistor) on v1 pin 2 and an unknown resistor where the 2k2 goes next to cap on the end. 

On the layout, it calls for 22k on v1 pin 2 NOT 20k!!!

I  didn't get a 2k2 2w from nik.  I got both 20k (black resistor) and a 22k (light blue).

I initially i put the 20k on v1pin 2 , and the 22k where the 2k2 should be ( since that was my last part). Could this be my od problem?  I now have the 22k on pin 2... My 20k is where the 2k2 is but is wrong I think.

At RadioShack they have only 1/2 watt resistors in stock, no 2 watt... Mouser????

This is where you need to check your values. See resistors highlighted in pink. There is a B+5 which I've not labeled as for these purposes its not relevant, it is the FET supply.

Pins 1 and 6 are the anode (plate) which are connected to the B+ nodes so check the values of your resistors against the layout for your amp.

Pins 2 and 7 are the grids, ignore them for now, you need to get your plate volts right before you go any further.

Hywelg - thanks a lot!  I did not think to check niks resistors for whatever reason.  Anyway, i did not receive a 2k2 2watt resistor for B+4. I just ordered and will post results when I get them.

Ok guys, I got the B+4 correct by ordering a part off the internet and have the following voltages

Tube   Type   Pin1      Pin3      Pin6     Pin8
                           
V1   NIK       191      1.7         200      1.6
   Jeff           177.     1.7          245.    1.1
V2   NIK        200      1.7         201      1.7
   Jeff           180.      1.9.      265     1.1

V3   NIK       298      56         289      56
       Jeff       288.     56          276   56

What can I do next?  Overdrive sorta starting to work but sounds like a bass synth pedal phaser...

Something is still amiss with your voltages. V1b and V2b (both pin 6's) are both now 20%+ on the high side.

What is the voltage at the OT Centre tap?.

Next step is to download all the pics from the website and start redressing your leads to look identical, that is routing, and length. Very important this, you might need to unsolder some and shorten some others. Google 'Dumble Lead Dress ' and you'll find loads. It seems to me that what you have is oscillation in the od circuit. So give special attention to V2.

Hey guys, I just wanted to follow up.  I took the amp to a local tube amp guru (Utah), and he went through the entire amp and checked my work.  It turns out my main problem was I left the ground off the bar and had a few cold solder joints.

The repair was very reasonably priced and my amp now rips!!!!  I am so excited.  I could not be happier.  I have not gigged the amp yet but had rehearsal last week and it really cut.

Thank you to the many people that helped me from this forum.  The tech said don't be afraid to use a really hot iron.  I personally turned my iron down because I overheated my deville pcb board when I recapped it. 

Thanks again !!!!!! U rock!