Not so obvious problem RESOLVED

[ditdah]

Eileen sent me some replacement caps...and FAST!  What great customer service!
Got the old caps out, installed new caps...and triple checked I had the correct ones at the correct locations  

Initial observation:  
The 2nd small pcb to get installed...LED's do not light up.  All other LED's light up.

Voltages
Terminal     Expected     Reading
1               75              90 and dropping
2               170            191.2
5               75              188 and dropping
7               100            120.1
9               100            184.8
13             170            188
15             185            201 (yay...not melted this time around)
19             0               87
20             206            0
A1             75              183
B1             75              82
B2             170            185
B3             100            116
B4             75              182
B6             170            184
B7             100            180

Anyone have any ideas?  The Crack w/o speedball works perfectly...readings are all textbook.  I've reheated all solder joints...don't think I could have installed anything else incorrectly.  I've double checked all wired are connected to the appropriate areas.  

[ditdah]

So, I'm checking the boards...this time, I'm checking components.  Diodes, resistors etc.  Since you all know I wasn't paying attention to the metal can caps...and assumed they were the same...give ya 3 guesses what I just found wrong.

...this time, I'm hoping it's the LAST problem and I get the speedball working! 

[ditdah]

ok...2 incorrectly located/placed components removed and put in the correct location.  This time, all diodes light up nicely.

All voltages are not textbook...but close and within 10%.  ...minus 2.  I get the following results at 2 terminals which confuses me since all other checks are close:

Terminal   Expected   Reading
19            0             87.6
20            206          0

...those readings remain consistent from the last check before I found out I had 2 additional components in the wrong place.  Finally, measurements at the TRS jack show a very slow climb, then a sudden spike to about 21VDC...then a quick drop again to 0.  The manual says 9VDC max...  Strange...any suggestions?

I'd like some input before I plug this in and turn on some music.

[ditdah]

ok...little digging and I came up with:
-terminal 19 voltage check is irrelevant
-terminal 20 voltage check should be zero
-terminal 21 voltage check should be 206...
...seems this correction is noted on the board...again, me assuming...I thought the manual was correct as the correction was posted in 2010.  
so, everything checks out...except the TRS jack voltage...which jumps to 21 for a very short time ...I'd say <1 sec...and drops to zero.  Can't figure that yet.

I found another post:  http://www.bottlehead.com/smf/index.php/topic,2946.0.html

It states:  "...the two unused solder terminals.  Connect both of those to ground (the terminal row closest to the chassis plate).  The 1/4" jack supplied has a switching function built in, so when no headphones are plugged in, the output is shorted to ground, and thus the coupling caps at the output will charge without restriction."

When you plug your cans in, that connection is lifted and your music will flow through."

I haven't done that modification...should I?  and why?
Question is...if everything is checking good, and no headphones are plugged in...how relevant is a quick spike to 21VDC on the jack going to be?  it goes to zero pretty quick.  What am I missing?

[ditdah]

Well, Just couldn't let it sit there ...I plugged in.  

I got a little popping and static when rotating the pot initially...and again after I tapped the knob on the pot.  I haven't been able to reproduce that...but haven't powered down yet.  Maybe it just needed more warming up.

I was worried about the momentary 21VDC on the jack...so left the headphones unplugged for about a min or so...then just plugged in hoping for the best.  I may try to do that mod previously mentioned about the TRS jack grounding...on the 2 unused lugs.  I'm out of time for this build for now...so I'll save that for next time I'm home.

What a day!  I'm quite pleased with myself for sorting it out on my own (well, with the help of the forums previous posts)...and extremely pleased I didn't fry anything with the 2 mistakes I had made in component location.

The last problem I had found...the larger board called for 2ea 31.6 ohm resistors ...but I accidentally put one of the 237 ohm resisters there.  Not sure how I had done that...other than they look identical to someone who hasn't bothered to check the resistance measurement or color code bands.  Lesson learnt...check everything before installing next time and save myself a TON of time!  Never take anything for granted.

Comments:  I don't really notice the speedball upgrade being more quiet...my base install was already dead quiet.  What I do notice, is more bass...more punchy I think.  Very good clarity and separation overall.

Conclusion:  I'm very happy with what I accomplished and the end results.  I don't even mind the road getting there...I learned (relearned) some valuable things that I won't be soon forgetting...and that I'll apply to my next build.  This is an excellent amp and I'm chomping at the bit to get my next one underway.

Thank you to those who gave me some great tips and advise.  Much appreciated.

Doc and Queen...thank you for your support and for the outstanding kit!

 

[Laudanum]

With Speedball the voltage at start-up seems to run higher.   It's millivolts, not volts by the way.   Manual states 9mV-DC with stock version.  There is nothing in the Speedball manual that suggests the voltage is higher.   I brought the question up after I installed Speedball.   I measured 9mV DC after building stock and 22mV DC after Speedball upgrade and film caps.   Another member measured 14mV.   You should be fine if all your other measurements are in line.   I have not yet connected the switched contacts to ground.  I turn the amp on for 30 seconds or so before plugging in headphones.  BUT,  with headphones connected, that small voltage at startup would be even lower and probably non consequential.   I just use extra caution and plug phones in after the 30 seconds.   Grounding those switch contacts should remove that small voltage.  But keep in mind that some folks use different headphone jack (like the Neutrik locking jack)  that doesnt have the switched contacts.  So, it isnt mandatory to ground those contacts.  Crack was out for a while before the guys posted about grounding those contacts.  Long way of saying that your 21mV at switch on should be fine and seems normal ... as long as it falls back to zero.  Also, after it falls to zero, you may or may not have noticed digits on the meter rapidly jumping all over the place, too fast to keep track of unless maybe you have a peak hold function.  This is also normal and, as Paul J. explained it, it is "leakage" from the electrolytic caps.   Also normal and inconsequential. 

I didnt notice Crack any quieter either after speedball.  Mine was dead quiet in stock form.  But I think some of that extra detail and/or clarity may be due in part to a quieter/cleaner background with Speedball installed.  Eventhough the background seemed "black" in the stock build.

Anyway, sounds like all is good now.  Happy to hear that you got her up and running.  The problems you had just makes for a good learning experience for the future.  Congrats and enjoy.  Really sweet amp, Im still loving mine.  Next up for you ... maybe film caps and tube rolling?     It can be hard to leave alone.   I stopped at the film caps internally.  BUT, I do have a pretty good stock of tubes to roll.  I think that mods get more subtle once Speedball is in, and maybe film caps in place of the electrolytics for the output coupling caps.  That's what seems to be reported by many.   If you do have plans for future mods, enjoy it as it is for a while before doing so.   But it sounds fantastic, even in bone stock form.  

[ditdah]

Laudanum, appreciate the comments confirming my voltages.  Also appreciate the correction 

I just may do the cap upgrade...it'll have to wait till I get home end of Oct...but till then I'll figure out which ones need replacing and with which ones.

[Laudanum]

ramicio ...  I checked the voltage with 300 ohm phones plugged in on turn on.   I dont have a meter with peak hold feature.   All I got was scrambling numbers that appeared very, very low in terms of millivolts DC.  But I cant confirm an actual voltage.  I just know that it appears to be much lower as it's been stated by the experts that it would be with phones plugged in.   I know that there were/are forum members that did/do keep them plugged in.   I dont keep them plugged, not only to be extra cautious but also because I have several cans in rotation and never know which I will be listening to.  My rack isnt right next to the amp either and my evil cat would eat the cord if it were hanging down over the stand 

ditah ... I was referring to the two, 100uf electrolytic output coupling caps as logical candidates for replacement with large 100uf film caps.   But others have replaced caps in the power supply.  PS resistor with a choke and so on.   Check some of the builds in the Gallery forum, you'll see what I mean.   

[Laudanum]

Sorry, yes NOT plugged in.  My mistake.   Thanks. 

But I still dont have a definitive answer, just relaying what I measured, or tried to measure.    I know that several members do/did keep them plugged in.  I asked a related question after my build and got responses that said it was fine to keep them plugged in (before the switch mod was discovered).  But I think the "cover your a**" answer would probably be to unplug them.   Personally, I'd be more worried about the output tube going south on start-up than the very small dc voltage.  But then again, the tube could go south any time. 

I know, I know ... what a great help I have been     

[Grainger49]

In stock configuration the 2490 ohm resistor after the output cap is there to send the startup DC to ground.  It should dissipate with a time constant of 1/2*Pi*R*C, or 0.6392 seconds.  After a few time constants the DC will all be gone. 

The magnitude of the voltage is dependent on the output cap's characteristics.  Dan measured with the stock electrolytic.  If you have upgraded to a film the resulting DC bleed through will be different.  I don't know if it will be higher or lower but it will be different.

Two other factors here are the resistance/impedance of your headphones and their susceptibility to the leakage.  Some headphones will weather the bleed through with no ill effects, others might burn out.  That is why Bottlehead has erred on the safe side saying not to plug in the headsets till the amp has been on for 10 seconds or so.

[Paul Birkeland]

There is also the factor that the cathode voltage of the 6080 is 0 at startup, then slowly climbs as the tube warms up.  With headphones plugged in (even 600 ohm ones), the parallel resistance of the 2.49K resistor and the headphone voice coil become very low, singificantly reducing the presence of this startup voltage.  FWIW, Doc and I have both left our HD-800's plugged into stock and Speedballed Cracks during startup plenty of times without giving it a second thought.