Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › EHHA Rev A - Interest Thread
New Posts  All Forums:Forum Nav:

EHHA Rev A - Interest Thread - Page 102

post #1516 of 1657

Hi,

 

Strange indeed. It should not matter how you connected the two wires...you should have more than 10V

at the input. Could it be that one of your toroids is a 6V unit?    :rolleyes:

 

OK.. stupid reply since you have a toroid with two secondaries. Have you rechecked your readings and

have you tried with reversed connection?


Edited by stixx - 9/9/13 at 11:14am
post #1517 of 1657

First - a small preview what it's gonna look like :-)

 

 

Now - the two secondary windings are both 10.3V without load,

 

 

I did reflow all the solder joints and it works correctly now ...

post #1518 of 1657

No easy win here...

 

Attached the rest of the wires and found that the DC-offset on the right channel

does not drop - I'm reading 24V across G and OUT.

 

:mad:

 

The other channel is working fine.

 

 

Since I'll be going on holidays tomorrow I won't be able to do any more testing,

but nonetheless I'd be very happy about some hints where to start looking for the error.

 

:(

post #1519 of 1657

I purchased a semi-completed Rev A that had offset issues. It turned out that there was a cold solder joint on one of the resistors.

I believe it was R12 iirc.

post #1520 of 1657
Quote:
Originally Posted by Sathimas View Post

No easy win here...

Attached the rest of the wires and found that the DC-offset on the right channel
does not drop - I'm reading 24V across G and OUT.

mad.gif

The other channel is working fine.


Since I'll be going on holidays tomorrow I won't be able to do any more testing,
but nonetheless I'd be very happy about some hints where to start looking for the error.

frown.gif

How about some pics? Top and bottom, as much light and focus as you can muster. wink.gif
post #1521 of 1657

I won't be able to post some pics before the 23.09.2013, since I'm on holiday right now

(And getting married this saturday :-)  )

 

But I can't wait to get this amp to work, since I'm working on it for about 2 (!!!!) years.

post #1522 of 1657
Quote:
 First - a small preview what it's gonna look like :-)

very nice wrap job... looks like a can of worms.. or human internals.

You must be a surgeon then :D.

 

 

 

And CONGRATULATIONS to your wedding!

post #1523 of 1657

 

 

 

Here are the requested pictures, hope the are sufficiant.

 

I did also reflow all the solder joint, but still the offset is at 25V !

post #1524 of 1657
No expert in troubleshooting solid state stuff... your soldering quality looks really good, and as far
I could see parts orientation and such is all good also.
Did you check your DMM...? They can be faulty, and 25V offset is very high. Maybe also check that all
your semiconductors are in the good place on the pcb.

Good luck!
post #1525 of 1657

DMM is definitely o.k. - I did the initial check of all other boards with that one.

 
I'll try to check the transistors too - always possible to have them in the wrong place...
 
It's a pity runeight himself isn't present here anymore...
 
But i don't know where to ask anywhere else...

 

post #1526 of 1657

Here's how I would have go about troubleshooting.

 

1) Look for any shorts

 

2) Double check all components.

 

3) Check the BJTs using the BJT sanity tutorial an amb forums :

http://www.amb.org/forum/howto-bjt-sanity-check-t59.html

If there is some confusion , compare the results with the other working board.

 

4) Check & compare the resistances of output mosfets

 

Replace the faulty devices and see if you can get it working.

post #1527 of 1657

http://www.elexp.com/t_test.htm

 

 

Diode test your transistors, something is probably blown.  I would start with the VAS stage and servo booster, Q6, Q7, Q8, Q9, Q12, Q13, Q14 and Q15.  Another thing you can try, just to get bearings, is to pull the servo on both channels and measure voltages at different points, especially on the current mirrors.  Make sure the trimpot is set at the half way mark first.  Do note that some of the transistors in the current mirrors are set up to be a diode drop.  They will look like the attached.  When you diode test, that part will appear as a short, and should test exactly like a diode (such as 1N4001).

 

 

 

I haven't checked your pictures since stixx said it looks good.

post #1528 of 1657

I'll be back with results as soon as I can, but do not have the time today or tomorrow,

so don't check for results before friday here.

 

Thanks for the advice so far.

post #1529 of 1657

No worries.  Just make sure you are looking at the schematic as you are doing this.  Results can vary depending on how transistors are wired.  That said, you can brute force it and change a bunch of transistors for the heck of it, but that can be a big PITA unless you have a desoldering station.

post #1530 of 1657

I'm about to embark on my EHHA Rev A journey. Been waiting for a while -- built "The Wire" and a really nice ES9023 based DAC first. I'm planning on using the E12 and have used it in the past with the CTH. With the CTH I had to lessen the threshold for when it triggers. I still even find with certain headphones, the AKG K240 Sextetts for example, that it's pretty easy to get the E12 to trip. I'm thinking this might have more to do with the implementation in the CTH vs. other amps. Some tubes are worse than others. Other headphones don't have the issue as much. For example, orthos don't cause the CTH E12 to trip that easily or at all. What are everyone's experiences with the E12 in the EHHA Rev A? Did you guys find that upping the tripping threshold was required? Also, has anyone tried the EHHA Rev A with the Sextetts? If so, are they a good match? I figure I'll wait til January or February before I buy my kit from Glassjar. Just want to have my research all in order first. I'm thinking at this point socketing all the OL and CL gain resistors and going with an initial gain of 5 or so.

New Posts  All Forums:Forum Nav:
  Return Home
Head-Fi.org › Forums › Misc.-Category Forums › DIY (Do-It-Yourself) Discussions › EHHA Rev A - Interest Thread