Need help troubleshooting SLO 50 clone

[guile]

Musicfriends
I finished my SLO50 clone the other day. Took me quite some time, but loved putting it together. Unfortunately it's not working. I checked everything a 100 times but can't find any errors.

Problem 1:
First I checked the bias (http://www.c3amps.com/Photos/aSLOHead/T ... 0Bias.html).
Both read -50 VDC but the bias pot is not responsive..

Problem 2:
I put in all the tubes. The powertubes light up, no light in the preamp tubes. No sound..


I'm not an expert on this. I built a lot of pedals, and a small tube amp, but this is a lot more complex.
I hope someone can walk me through and troubleshoot. Please let me know.

Thanks.

(Tried to post bigger pictures, but not allowed abov 256k)

[clipless bumper]

Only thing I have to contribute is to upload your pics to an online site like photobucket or imgur - then link them here - you can have much bigger pics that way.

Attachments ARE limited.

[ajaxlepinski]

No hum, hiss... no sound at all?

[guile]

Yes I have hum/hiss.

Good call, I uploaded pics here: https://www.flickr.com/photos/115176149@N03/?

[ajaxlepinski]

Did you check each component for continuity (and value) before soldering them in?

[guile]

No, did not..
Jacks look to be good

[ajaxlepinski]

I see several 1/4" female phone jacks with switches.... are they all making proper contact?

[guile]

Please take a look:

https://www.flickr.com/photos/115176149@N03/?

[guile]

I spent the last days making the amp to work.
It works now but it's a very shrill, harsh and unforgiving amp
I checked all the parts and their values and all voltages but can't find an error. Swapped tubes and biased them correctly.
I have a second SLO clone (100watts) to compare with and it sounds radically different: very transparant, sparkly with tons of bass without being shrill. It sound great with all the pots at noon. I can't dial in an acceptable sound with the newly build SLO..

I can only think of the difference in transformers. The good SLO100 has a pcb from Tubetown and Hammond chocke and OT and PT (ring) from tube town (http://www.tube-town.net/ttstore/Transf ... :1120.html)

The bad sounding SLO50 has a transformer set of inMADout: http://www.inmadout.com/T-set.asp

Would love to hear suggestions
Thanks

[clipless bumper]

did you double check the leads you used on the OT?
could it be your are running the tubes at the wrong impedance?

[guile]

Thanks
I don thinks that's the problem.
I made some hi-res pictures: https://www.flickr.com/photos/115176149@N03/

Could you take a lookl?

[silverfox]

Don't take this personally. It's only in the last year that my builds look, to a reasonable degree, organized and clean. With all the parallel paths of wires and the fact the, choke?, is inside the chassis with all those wires nearby- This is an opportunity for oscillations, as one source of problems. You should seriously consider rewiring the amp and following traditional routing techniques.

Having said that, I've seen various radio chassis and Fender amplifiers that don't look much different and at times become sceptical over the degree wiring layout effects performance.

Do you have a schematic and test equipment like a volt meter and scope?

silverfox.

[guile]

Hi, thanks for your reply.

I laid the wires out as much a possible for the pictures.
I have a layout (C3amps), but pdf is not allowed on this forum (how practical)
I do have a multimeter, but no scope.

Amp is working, but lacks the typical bottom end.

[silverfox]

Try comparing the values of the bypass capacitors in the preamp stages with the real deal Soldano. Also take a look at the values associated with the tone stack. These parts are where most of the tone is created and filtered. Keep in mind the totality of the tone comes from the whole design. Here are a couple things to look at:

I don't know if your build has the tone stack in the power amp section but I've always liked that approach, personally.

There are several more images, like a PCB layout and a section on notes at the site above. The links don't work so well but if you go to the FTP section you can find lots of stuff. The notes txt file is very informative. http://www.blueguitar.org/new/schem/soldano

Here is another great site with information on how the Soldano circuit achieves the fantastic tone: https://www.ampbooks.com/mobile/classic ... -preamp-1/

I've found that building an amp is really just the starting point. After you get it up and running the real brain work begins in voicing it to get the tone your looking for. You might spend more time changing parts out and researching, after completing the build, then you did in putting the parts together.

silverfox.

[guile]

thank you very much!

[mortatone]

With any fresh build you have a 50/50 shot at getting the OT primary leads reversed. Take the two leads that go from the OT to the power tubes and swap them. This will always be the case for any amp build forever and ever amen.

Also, is there a center tap for the heater loop?

[mortatone]

And I'm assuming that since you are now getting sound at all that your preamp tubes all light up now?

[guile]

Hi I finally found the problem. The pcb trace between Treb3 and C15 is broken.. Don't know why and don't care!
The bass pot was never fully engaged in the tonestack.
Sounds great now, very silent too. Relieved!

[clipless bumper]

Congrats!!
Glad you figured it out.
How did you find it?

[ajaxlepinski]

Yeah man! Glad everything worked out!!!

[guile]

Thank you!
I had help from a friend (and his oscilloscope). I checked the whole amp many times so it had to be in the tonestack. We figured out that the basspot lug1 attached to lug1 of trebelpot did not function.

I'm little experienced in building amps but I was relieved to learn that I did not make a mistake.

[Zozobra]

Awesome to check this thread and see you've got it sorted. Bad pots can be a serious pain in a new build. The last OrMat I built had a bad bass pot and I wired the bax stack to the pots as it's a nightmare to wire cleanly to turrets so I was pretty pissed off about that.