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the CTH (Compact Tube Hybrid) Rev A thread... - Page 7

post #91 of 577

My board is completed but not quite working.  Green / red LED works as expected and I started the trouble shooting, but it's late and I have to work tomorrow! :) Which tube pin is TB+?

 

  • Measure between OG and SG. This should be very close to 12V. If it's not there might be a problem with the TLE2426 or with one of the devices in the rail splitter.

12.11V

 

  • If the OG measurment is good, measure OL and OR. They should also be very close to the voltage at OG. If they are the buffers and splitter are working.

both 12.11V

  • Set the heater switch for the heater voltage of the tube you want to insert. (no switch, 12.6 volts for 12AU7 tube)
  • Insert the tube and turn on the amp again.
  • Look for smoke. If there isn't any then . .

no smoke :)

 

  • Measure TB+. It should be between 95V and 105V.

what is tb+? 

 

  • If TB+ is ok, measure pins 1 and 6 of the tube socket. These should be approximately 80V. If they are, and if the previous measurments are correct, then your amp is ready to go.

 78 volts at pins 1 and 6 measured against SG.

 

Any thoughts?  I'm 100% sure that diodes are oriented correctly.  I'm off to try a different tube.

 

Thanks

post #92 of 577
Thread Starter 

TB+ is the hole by C10P. Measure SG to TB+. Hope that helps...

post #93 of 577
Quote:
Originally Posted by civilmonkey View Post

My board is completed but not quite working.  Green / red LED works as expected and I started the trouble shooting

I didn't catch what is not working with your amp... Did you mean the e12 LED is not working/latching?

 

I'd not worry about TB+ as that's HV & your 78V readings are good.  And your 12.X readings look good too.  If everything looks good (all Vs including heater - pins #4 / #5) but it doesn't go green I'd try these:

1)  try amp w/load (test headphones).  If the amp is very close to latch sometimes this does it.

2)  try different tube, but I'd bet this doesn't help,

3)  try BoM box caps in C4 positions.  There has been occasional trouble w/big, fancy caps there.  We should say "start with BoM C4 caps first".  E.g. I'd a perfectly working CTH that when I switched in V-Cap TFTFs would not latch.

 


Edited by cfcubed - 4/4/11 at 6:46am
post #94 of 577



Quote:

Originally Posted by cfcubed View Post

I didn't catch what is not working with your amp... Did you mean the e12 LED is not working/latching?

Sorry, I was not clear at 11pm last night; there is just no sound and loud buzing.  The e12 LED turns green and stays green.  I put a different tube in and the LED alternates between green and red.

 

Quote:
Originally Posted by cfcubed View Post

 

3)  try BoM box caps in C4 positions.  There has been occasional trouble w/big, fancy caps there.  We should say "start with BoM C4 caps first".  E.g. I'd a perfectly working CTH that when I switched in V-Cap TFTFs would not latch.

 


 

I found TB+, not sure why I couldn't last night.  So TB+ to SG is 105 volts and all checks test out.  For C4, I have some obligatos on long leads there.  I'll put in the bom c4.  That is a good idea and hopefully the fix.
 

 

 

 

 


Edited by civilmonkey - 4/4/11 at 5:31am
post #95 of 577
Quote:
Originally Posted by civilmonkey View Post there is just no sound and loud buzing.  The e12 LED turns green and stays green.  I put a different tube in and the LED alternates between green and red.

Switching to BoM caps may fix the e12 latch cycling but not likely any audio problem(s) like buzzing.  Still not a bad idea to get to std BoM baseline C4s to eliminate that variable.

I've never had anything like a moderate/loud buzzing problem w/CTH.  Would re-check wiring esp WRT grounds & grounding.  And re-check for solder bridges, assume you've washed solder flux/resin off (I use 99% alcohol & tooth brush).

Also remember 24VAC "floats" having no ties to any grounds, but I bet you knew that:)

 

I've had low-level/soft buzzing when amps are loosely wired up on bench in PCB vise w/lots of 60hz source close by (lights, soldering iron, etc).

 

BTW I've edited/bolded a bit of my prior post.


Edited by cfcubed - 4/4/11 at 6:59am
post #96 of 577


Quote:


 Would re-check wiring esp WRT grounds & grounding.  And re-check for solder bridges, assume you've washed solder flux/resin off (I use 99% alcohol & tooth brush).

 

My pot was wired wrong; it is correct now.  No solder bridges, I checked pretty carefully the first time around.  Yes, board was scrubbed with 99% isopropyl and a toothbrush.

 

I ran through the initial checks again.  I still have 12.11 volts at OG,OL and OR. TB+ is 105 volts.  

 

What has changed is that I now have 105 volts at Tube pins 1 and 6 (previously was 78 volts at each), and at heater pin #4, I have 0 volts which should be 12.6.  I'm noting that these voltages are without a tube installed. 

 

At heater pin #5 I have 12.6 volts.  I'm pretty confident that I had correct heater voltages previously, so I wonder is someone messing up the grounds fried something.

 

Hopefully nothing major...? 


 


Edited by civilmonkey - 4/4/11 at 6:05pm
post #97 of 577

Make measurements w/tube in.  Heater voltage is between pins 4 & 5 and 12.6v is fine for 12.6 heater switch position.  Tube pins 1 & 6 can only read properly (about 75v->85v) with tube in.

 

So if you repeat the voltage measurements you did before with tube in & they are fine is there still something wrong w/the audio?

post #98 of 577

We are close.  With a tube in, pins 1 and 6 are 78 as before, voltage drop between 4 and 5 is 12.6 volts.  The amp wouldn't latch, so I replaced my Obbligatos with bom c4, the amp latches but alternates between on and off.  

 

Something I probably should have mentioned is that because of  the sloppy socket I received, I have another on air wired (on as short as leads as possible).  Partsconnexion has mailed me a new one, so a new socket is on the way and hopefully that solves everything.  When the amp was latched, music was playing for sure.

 

You guys must shake you head at folks like me.  'Oh, I forgot to mention, I air wired a tube socket'  Hah.  Hopefully the new PCB mounted one fixes any remaining issues.

 

Thanks for the help, I'll report back once I have the new socket in.

post #99 of 577

Tonight I had to air-wire a tube socket for the 1st time & my CTH was fine with it:

 

.clear_CTH_2.jpg

 

First time I tried using clear casting resin too... Should have been my 2nd time using it as I learned what sticks to what:)  And that it shrinks as it cures, pressing into any sockets not very well sealed in advance.

Always learning.,  The air-wired tube is temporary of course, a socket-saver will give its life & be epoxied into the recessed tube cavity.  Other than that its working well.

post #100 of 577
Thread Starter 

cfcubed -- what happens when you need to crack that thing open for some god forsaken reason? Looks cool though.

post #101 of 577
Quote:
Originally Posted by Mullet View Post

cfcubed -- what happens when you need to crack that thing open for some god forsaken reason? Looks cool though.

There will be no fixing it of course:)  But there's no reason to expect it to fail esp w/newer BoM revisions.  Would make an interesting paperweight if it was to stop working:)

Was going to just encase an unpopulated PCB but then two things happened; someone wanted my spare PCB & it seemed we were needing a 2nd fast build-out to proof the new rev.

 

BTW if I was to do it again I'd get it right:)   There were only 3 key mistakes; incorrect mold material (used release but resin fused to it), not using proper sealant (e.g. epoxy?) on parts that could be invaded, doing a 1"+ layer instead of building up thin layers (e.g. 1/4").  Maybe if I ever build a cable DAC I'd give this another try.  BUT it's not a recommended case design:)

post #102 of 577

That's a neat case.  I was thinking of an acrylic or plexi glass top on mine.  Nice to hear the air wired tube is working.  I'm going to try my air wired tube with thicker gauge and shorter wire to see if that get's mine to latch.  I still plan on PCB mounting a socket once it arrives in the mail, but it would be interesting to see if I can get the air wired tube to work properly.

post #103 of 577

Quote:
Originally Posted by cfcubed View Post

>  Chris, you built one of these with an RK27, right? Is the case in your Mouser BOM still a tight fit with the RK27?

 

I've only done RK27 w/the BoM "long/longer" case, like many CTHers did, see my pics about a page back in this thread.  But someone recently was able to squeeze an RK27 in the "small" BoM case through some effort (see his post in the build Pics thread a month or so ago? - I posted there commenting on it).  I did RK097 in the "small" BoM case, as many CTHers did, like rds' pics a page or 2 back.

 

I did the small case with a RK27. It will only fit if you mount the components on the front right side on the bottom side of the pcb. Caps need to be mounted flat on the pcb, the opamp dead bug style, transistors reversed, etc. It is doable, but only if you have a bit of experience.

 

My CTH has been working well and I have not been able to notice any ill effects from bottom side mounting the components.

 

CTH_RK27.jpg

post #104 of 577

So,

 

My socket is no longer air wired, all voltage checks, check out (12.1 volts at og, ol, or, 78 volts at pin 1 and 6, 105 volts at tb+, 12.6 volts between pine 4 and 5).  I have bom c4 caps.

 

Two differences from stock:

1.  Right now R18 have SIP sockets, each also with long leads, the intention being to allow bypassing them once I hook them up to a switch.  R18 is current 121 ohms.

2.  I have a 50k ebay knock off DACT right now

 

The amp will latch briefly, then unlatch, and back and forth.  This happens with and without headphones plugged in.

 

I will check the values soldered on the board carefully to make sure there are no errors, but in the meantime, anything I should be looking for?


I tried with 2 seperate 12au7 tubes.

 

EDIT:  I just realized I do not have a lead from IG to the PCB - I'll try this as well and report back.

 

Thanks


Edited by civilmonkey - 4/6/11 at 3:14pm
post #105 of 577

Not sure about long leads on R18s.  You may check the actual buffer offset that's causing the relay trips by measure OG vs the channel input pins on the relay.  I'd tack little wires there for the test.

Maybe IG -> PCB will help.  Also consider searching orig "A Very Compact.." thread for cycle,   cycling,   latch  for other idea.s

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