TOS new build issues

[talsmag]

I fired up the TOS and something is not quite right.  I'm not getting very much overall volume and there is hardly any clean headroom on the clean channel.  There is a fizzy, buzzy kind of sound even at very low volumes.  If I turn the gain or the tone on the clean channel past about 3/4 I get a high pitched squeal.  The overdrive channel sounds pretty good, but again, not much volume.  My smaller amps are much louder.  I have posted the voltages under my username "talsmag".  Any help would be greatly appreciated.

Gary

[tubenit]

Gary,

It is a wonderful sounding amp when working right, so don't give up!  You'll get it working OK.

The voltages on the 6L6 screen don't look right compared to the plate. Too much of a difference between the screen and plate.  Should be just a few volts difference not a 100+ voltages difference.  Check the screen resistor values for sure.

474v on plates and 217v on the screens is waaaayyyy off.

Have you tried other tubes?  Could be a bad tube?

Other voltages look reasonable.  

While you're "not" suppose to hear sound with the OT hookup backwards, I have before.  I got a low volume distorted tone that would eventually oscillate & squeal as I turned up the volume. Either disconnect the negative feedback or try switching the OT wires to see if the issue is resolved.

When you are doing the trouble shooting, work with JUST the clean channel until it sounds right.  It is quite possible that the OD channel will sound fine also after the clean channel sounds OK.  

Be sure to safely "chopstick" all the soldering.

IF you are using a relay,  I'd try safely jumpering (bypassing the relay) from the clean to the LTPI.  

IF you used a passive effects loop, try bypassing that.  I've had the amp do what you describe once and found out it was a bad shorting jack.

Just some things to try.  PLEASE report back after trying things and let us know what you have found out.

With respect, Tubenit

[talsmag]

Well I first checked the screen resistors and they looked good, so I proceeded to check all the rest of Tubenit's suggestions to no avail.  Finally, I went back to the resistors and discovered what a dumb shit I was.  I had misread my meter and actually had 470K ones in there.  So, I replaced them and now the clean channel works as advertised. 

When I switched on the overdrive channel though, I got initial sound for about a second, and then nothing.  It was as though a fuse had blown.  I updated the voltages and noticed that pin 7 on V3 dropped from 43 volts to 4.9.  Bad tube in V3?  I didn't have a replacement to check it.  The overdrive channel had worked fine prior to this.  Any more ideas?

Gary

[tubenit]

OK, you got the TOS clean channel working!  Excellent.  That's progress.

Regarding the TOS OD channel.  Look at some of the same list of concerns:

- bad tube
- bad solder joint
- poor ground for cathode resistor/cap (which might explain the voltage problem)
- bad relay

Remember that you can bypass the relay and hook up the OD directly following the clean channel and then into the LTPI. Just jumper things safely.

PLEASE keep us informed of what you find.

With respect, Tubenit

[talsmag]

Good news.  It turned out to be a bad 5879 tube.  Wow is all I can say right now!  Still playing with the controls, but this amp really kicks it!  Thanks Tubenit, for the solid advice.  Can't wait to play with it some more, and figure out the best settings for the sound I'm looking for.  One question, is it better to run pedals through the effects loop, or just go guitar to pedal board to amp?  I've been reading about the Kleinulator and wondered if anybody has any thoughts on that.

thanks again,
Gary

[daveyajd]

Congratulation talsmag! I am building a TOS of my own and would love to see some pictures of how yours came together. Sound clips too if ya got 'em!

Aaron

[tubenit]

HOORAY !!!!!!!!!!!!!!!      

You got it up and running!   Congrats!

Delay or reverb thru passive effects loop.

Overdrive or distortion or compressor thru the input.

Yeah, soundclips would be good if you can share one.

With respect,  Tubenit

[Willabe]

WOW, glade you got her up and running great talsmag!

Our good forum friend Tubenit has come up with some great tube amp designs, no doubt!

Plus, he's _ALWAYS_ here to trouble shoot with _anyone_ who builds one.

Hat's off to Tubenit!        


                  Brad      
  

[tubenit]

Regarding the Kleinulator ...................

The original TOS did benefit from a D-lator type device plugged into the passive effects loop. It helped with the blooming feature.

Having said that, once I put a cathode follower in on the OD channel, ............ I found no significant difference for me using a delay in the passive effects loop.

A delay is the only effect I use in that loop, so others may have a different experience?

with respect, Tubenit