Cracking glass and problems with my first build

[halfbackstrat]

Greetings all, i have completed my first build and wondered if you would be able to help me with a few things

I built one of the Ceriatone 50W FM OTS. This was my first build and it seemed to go ok. I got it up and running first time. The clean channel sounded good however the OD section was quite harsh and I wondered if I had made a mistake wiring it up. Anyway I just left it and didn't use the OD section. A few days ago I switched the amp on and had absolutely no sound. When I opened it up I noticed my phase inverter tube was cracked!! Is there anything electronic that could have caused this?
I have a link to pictures which I will update this post with once I get home to my computer.
For reference I used JJ ECC83S tubes.
Any help that you guys could offer would be most appreciated!
I can't remember exact Plate voltages from when I built it but they were high 400s as expected.

The other problem is that the Drive Ratio and OD trim pots have no influence over the OD section when the Pedal activated the OD. They function as they should when the OD section is activated on the back.

Also, the OD section sounds very harsh to me, certainly not smooth and sustaining violin tones like Robben (although I appreciate i am not RF, this sounds like something is wrong!)

The pictures are here

http://www.flickr.com/photos/94683768@N03/


One adjustment has been made since these photos were taken, the blue and brown output transformer primaries have been switched around since then as this was a problem i had and then solved with Nik to get the amp to initially start up.

Any help would be hugely appreciated!

[wjdunham]

I have seen quite a few EH 12AX7's that would crack around the pin. Less common with other brands but still see it happen once in a while. I have not seen it with a JJ, but doesn't mean it can't happen. Unlikely it's anything you've done in the circuit and just a stress related failure in the tube.

Bill

www.sebagosound.com

[halfbackstrat]

JJ Tesla 12AX7. The crack is as you indicated across the base of the tube between the pins.

[NickC]

I'd guess a hairline manufacturing/materials defect triggered by normal expansion and contraction cycles from the tubes heating and cooling.

[halfbackstrat]

Any suggestions as to what i can do to avoid it happening again? I'll probably not buy JJ this time, i think i might go with TAD. I order from Watford Valves in the UK.

[Kassie]

Any suggestions as to what i can do to avoid it happening again? I'll probably not buy JJ this time, i think i might go with TAD. I order from Watford Valves in the UK.

Yeah I got a couple of High Grade TAD 12ax7's.. lovely tone, lovely identical to a JJ. They are just restamped and for that you pay twice the price.

Just seek out a good amptech in the area and order tested tubes from him/her.

[halfbackstrat]

Fair enough, I see that Watford offer a balanced version of the ECC83 which they say is for use in phase inverters. Assuming this balances each triode is this necessary for a phase inverter?

[halfbackstrat]

Here's the photo album, once correction to the amp has been made since these pictures were taken. The Blue and Brown wires to the primary of the output section have been swapped around to be correct. This was the only issue i had on start up.

The problems I have with the amp are that the OD section doesn't sound quite right, also the when i activate the OD section using the footpedal, the ratio level and od trim on the back become non functional.

That and anything that might have caused the glass to crack on the phase inverter tube!

http://www.flickr.com/photos/94683768@N03/


I shall update the OP and title with this information!

Thanks very much for all comments so far and any still to come.

[Kassie]

Fair enough, I see that Watford offer a balanced version of the ECC83 which they say is for use in phase inverters. Assuming this balances each triode is this necessary for a phase inverter?

Euh.. a sort of balanced tube works better to adjust the PI trim. Reading voltages, and just according to your ears taste. In v1/v2 it's not necessary because those are cascading gain stages (one after the other), while the PI is parallel out of phase, necessary to make the signal 'push pull' for the Output tubes.

there is a lot of myth regarding this balanced tube.. some people don't even like a balanced tube, they like a certain mismatch to the powertubes for a slightly different (more pleasing harmonic). If you want to have it perfectly balanced you also need to consider the caps and resistor tolerances...

I never put a balanced tube into my other amps.. and they are biased just fine within limits. But for my OTS build I am using one just to make my life easier with the trimmer.

I use tung sol myself.. especially in v1. That is my favourite tube.
For v2 you could try a JJ since it's a bit more mellow.. and v2 creates the OD in the overtone.

As for your other problems.. try locating cold solder joints in either the footswitch wiring jack/switches... or the relay boards.. you have the relays inserted right?

[halfbackstrat]

Thanks for the input Kassie!
Yeah I'll avoid the balanced tube then

The relays are in yes

Would the most efficient test for cold solder joints to be to test using the continuity setting on my multimeter?

[Kassie]

Thanks for the input Kassie!
Yeah I'll avoid the balanced tube then

The relays are in yes

Would the most efficient test for cold solder joints to be to test using the continuity setting on my multimeter?

I know they are in, but are they in the right way?

I am going through your pictures, focusing on the relay boards, pedal jack/switches.. but so far can't really see any faulty things...

Hmmm yeah cold solder joints... hard to tell with a dmm.. I usually do it on the point past the solder. So put it on a resistor lead and trace to another component.. with the solder joints inbetween, and then on the lowest resistance setting (200 ohms) to check the resistance of the joints.

You can try to reflow joints, or just clean them with a pump or litze... remember use a hot tip.. heat all the components for 2/3 seconds.. and let solder flow in.. the solder should flow really quick. Use the correct solder for that (for fine electronics/circuitboards).

I tell you this because I see blobs.. often indicating a solder-iron that's too cold, or solder itself that's crappy and doesn't flow, or reheated joints that caused the solder to stop flowing (solder on top of solder blobs).

[Kassie]

http://www.flickr.com/photos/94683768@N ... tostream/
That red wire going into the relay circuit board... doesn't look solidly soldered to me.

Further... you daisy chained the power from the voltage regulator.. using 1 wire to the circuit boards.. I don't know exactly if that's ok to do.. try using 2 wires to both relay boards as per layout.

[halfbackstrat]

I must admit the solder was just regular solder from the local department store which I had in the house for plugs or anything that needed it!
I'll run an iron over any blobs of solder I can see and double check the relay orientation but I'm sure these are correct as they do switch the PAB on and off.
As for the bridging the relays power source, surely in electronic terms this is exactly the same right?

[Kassie]

I must admit the solder was just regular solder from the local department store which I had in the house for plugs or anything that needed it!
I'll run an iron over any blobs of solder I can see and double check the relay orientation but I'm sure these are correct as they do switch the PAB on and off.
As for the bridging the relays power source, surely in electronic terms this is exactly the same right?

I guess so. I have not an electronics degree, Just an enthusiastic hobby builder so my knowledge is very limited compared to fellow bretheren here. I just go by what I see.

Hmmm yeah... try to find an online electronic wharehouse.. and buy a proper soldering station and solder... I buy my solder for 1.5 euro's... and a soldering station for 15E (makes sure big wattage so you can stoke it hot if needed, 50/60watt), way cheaper than in any DIY store in the area. And works like a charm (different tips included). I experimented with different solder and there is huge differences in flowing rate (try to find low melting temperature, and good flowing properties according to the description). Also buy a desolder-pump and desolder braid. Thank me later. Good luck!

[halfbackstrat]

Checked continuity on all connections on the relay boards and I they all seem fine.