Almost - not quite. Help? [resolved]

ALL212 · 2405

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Offline ALL212

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on: July 05, 2016, 03:35:09 AM
I'm pulling this out of the other thread I have so that it can be troubleshooting only.  Maybe it will be a shortcut for someone else to figure out an issue rather than read through the entire other thread.

Paul was helping me on this earlier but I'll summarize.

I have 6 LED's out of 8 lit, the other two were on initially but then went out at some point.

All resistance checks good.  All heaters come on.
Initial voltage checks were good and I'm sure all LED's lit on initial startup.  But I didn't continue to watch them all.  I finished the tests but hadn't adjusted voltage.  Upon 2nd power up only 6 LED's came on.  The A side back two LED's do not come on.  The C side all come on, back side quickly, front side after some seconds.

I switched left and right tubes and replaced the 12au7 - same.  Paul asked for some voltage checks:
Bad side        Good side
0A - 220           220
1B - 220           220
0B - 220           145

OB does not change on bad side.  OB does change on good side.

R1's are good, board completely reflowed, no shorts at the board that I can see.

Just before putting it back I put the magnifier on the socket.


 I had a cutoff shorting 5 to 6 on the A side socket.



I have the same results at the board after this but what may have died by shorting pins 5 and 6 at the socket?

Would I be safe by reversing the outside boards?  Or could I blow something else up in the process?

« Last Edit: July 09, 2016, 08:41:43 AM by Caucasian Blackplate »

Aaron Luebke


Offline Doc B.

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Reply #1 on: July 05, 2016, 08:03:40 AM
Pin 6 is the cathode, pin 5 is the heater. If they were shorted, maybe the 2N2222A in the bias circuit on that side was blown.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline ALL212

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Reply #2 on: July 05, 2016, 09:20:06 AM
I'll order up a couple from Mouser or Digikey.  Anything else you might suspect that I should order up?

Would it be worth the test to switch the boards?
« Last Edit: July 05, 2016, 10:12:38 AM by ALL212 »

Aaron Luebke


Offline Paul Birkeland

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Reply #3 on: July 06, 2016, 06:19:06 AM
You should also try swapping 6C45's between channels, just to rule out any damage to the tube itself. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline ALL212

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Reply #4 on: July 06, 2016, 09:51:08 AM
I think sometimes I forget the "thank you's".

Thanks guys!  Without your help I'd be driving blind here.

Parts are ordered.  When they get in I'll replace the 2n2222a's and see what happens.  I do have a spare pair of 6C45's also.

Aaron Luebke


Offline ALL212

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Reply #5 on: July 08, 2016, 04:48:52 PM
I replaced both 2n2222a's so they were from the same manufacturer and I have full LED's now!  I even have SOUND!!!  8)

Are the LED's supposed to come up at different times?  Just curious...

I have two more issues - I know they are something I've done but I can't locate it.

I used my own wire - the cat5 is much easier and I've probably crossed something with mine as the colors aren't all different.  I have perfect sound on high impedance, I completely drop the left channel on low impedance.  My left/right channels are correct.

I also have a volume increase when I use the fine attenuation when going to -7.5db.  It's as if it's 0db.  All the steps work except for that one.  I just got done checking all the fine/course resistor placement and wiring.  I can't find anything wrong there with my eyes.

Have the HD650's on it and only have about 1/2 hour listening time but this is very....very....very nice stuff!  Dead quite (no repercussions because of the choke placement that I've noticed), soundstage is very good, bass is tight and the caps aren't broken in at all yet.

Aaron Luebke


Offline ALL212

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Reply #6 on: July 09, 2016, 04:36:02 AM
Sometimes just a good nights sleep and fresh eyes...and mind.

Dropping of the left channel when going to low impedance is fixed.  Wires reversed at 6 and 7 at the OT-3.

I'll post pictures next of the fine/course volume controls.  Still can't find that issue.

If the 12AU7 is switched does the 145v have to be readjusted?
« Last Edit: July 09, 2016, 10:54:17 AM by ALL212 »

Aaron Luebke



Offline Paul Birkeland

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Reply #8 on: July 09, 2016, 07:26:31 AM
Are the LED's supposed to come up at different times?  Just curious...
Yes.
I have two more issues - I know they are something I've done but I can't locate it.
I also have a volume increase when I use the fine attenuation when going to -7.5db.  It's as if it's 0db.  All the steps work except for that one.  I just got done checking all the fine/course resistor placement and wiring.  I can't find anything wrong there with my eyes.
Is this the same on both channels?

Do you get the -0dB step where expected, or is it missing? 
« Last Edit: July 09, 2016, 07:29:21 AM by Caucasian Blackplate »

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline ALL212

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Reply #9 on: July 09, 2016, 07:33:59 AM
Same on both channels. 

Now that I've really listened I'm not so sure there is any difference between 0 and -1.5.  It does sound like -7.5 is louder than 0.

Aaron Luebke


Offline Paul Birkeland

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Reply #10 on: July 09, 2016, 07:36:36 AM
Do you get the -0dB step where expected? I think you may just have the stop washers improperly set on the switch (see page 21 of the manual).  Can you set your switch on the front to -0dB on the fine switch, then take a photo of what it looks like on the inside?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline ALL212

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Reply #11 on: July 09, 2016, 08:03:34 AM
crap...I can tell by just comparing the course to the fine... I have five clicks - I'm just one click short of a full load that's all!

I suppose the only way to fix this is to disassemble...?  Lie to me - tell me I can just wave a magic wand!

Thanks for pointing me in the right direction - I'll heat the magic wand up and get the silver fairy dust that comes on a roll ready to go.

(http://i905.photobucket.com/albums/ac253/all212212/DSC_4616_zpsedrrdqve.jpg)


Aaron Luebke


Offline Paul Birkeland

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Reply #12 on: July 09, 2016, 08:37:19 AM
It's not as bad as it sounds.  Disconnect the 4 wires that go from the selector switch to the 5 lug switch by the fine attenuator, I would disconnect them at the attenuator. 

Just removing those wires may be enough for you to be able to just unscrew the three screws that hold the terminal strips down and the attenuator plate to the chassis, then lift the attenuator plate up to access the switch nuts.  With the switch nuts loose, the attenuator plate can be removed and the stops can be adjusted.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline ALL212

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Reply #13 on: July 09, 2016, 08:39:42 AM
PB - thank you!  Always love these kits and especially the assistance that goes with them.

I not going to even feel bad about saying this....  The fix will wait - I'm just having way too much fun listening to this!!

Aaron Luebke