gar2520 build thread

[tgs]

Managed to screw up double: I mixed up Q7 and Q8 AND I ran 24V into the DOA.  :

I just removed Q7 and Q8 and I'll try to replace them with new ones to see if the rest of the stuff is still working, but I made a mistake when I bought new ones: I got a BD139-10 instead of a BD139-16, and a BD140-16 instead of a BD140-10.

So before anything else: can I still use these or do I have to get new ones? BD139-16 is no problem to get here, but of the other one I can only get BD140-16 and BD140G locally.

 

[gar381]

Hi tgs

The -10 is a lower hfe part but will work fine in this circuit.

Best of luck..Get her working 

GARY

 

[tgs]

Great, thanks for the reply, Gary! Let's call it the "tgs mod" then. 

 

[steveau]

Gary,

I noticed on a recent 1731 build that the doc page 11 had specific "short checks",
I liked that, and caught a potential problem,
are any of these checks applicable to the 2520 build?

-Steveau

 

[Trench Recordings]

Well after some testing it looks like Q7 is faulty on both 2520 that I fryed. Everything else seems ok i think. Should I replace Q8 too ?

 

[gar381]

Gary,

I noticed on a recent 1731 build that the doc page 11 had specific "short checks",
I liked that, and caught a potential problem,
are any of these checks applicable to the 2520 build?

-Steveau

You can check that the -in millmax pin and the + in millmax pin have no shorts to any of the pads
around them if you like. 

Well after some testing it looks like Q7 is faulty on both 2520 that I fryed. Everything else seems ok i think. Should I replace Q8 too ?

You can replace Q8 if you like but you should be OK if they check OK.

GARY

 

[Terryb]

I just built a gar2520 and it's not working.  I do have a working one to compare it to.  Looking over everything, nothing stands out, no leads are touching on top and no bridges seem to have happened.
I reflowed solder to most of the joints and still can't get it to work.

My question is, have any of you used a hakko 808 desoldering gun on anything this small?  Will it work?
I've screwed this one up and a couple of gar1731s.  I'd rather reclaim than give in.

 

[gar381]

The Hakko 808 is the perfect desoldering tool for DOA work.

Hope you can get them working Terry.

GARY

 

[ajsteel]

How do I test the GAR2520 to confirm it's operating correctly aside from inserting it in to the pre amp circuit?

 

[kante1603]

How do I test the GAR2520 to confirm it's operating correctly aside from inserting it in to the pre amp circuit?

Hello and welcome to the forum,

I always test them in a circuit that I have access too.
But you're right,some kind of a simple testboard on perfboard would be fine.
I used my hakanai 8 channel input/summing boards so far,the input circuit is simple.
You can give it a search here,should be easily doable (go to the mixer/monitor section).
Or just copy anpther simple stage from any of the most circuits around here,just use a small perfboard,milmax sockets and some parts,aplly +/-16vdc,done.

Or Gary has a better solution?

Hope to have helped,

Udo.

 

[gar381]

Hi ajsteel

Like Udo says.. Welcome to the form.

Here is something from the gar1731 build thread:

Quote from: Terryb on August 04, 2013, 11:44:13 PM
Is there a way to test a build without plugging it in to a preamp?

You can build a jig and use an external PSU,signal gen and scope.
(If you are building lots of DOAs this might be worth doing.)
or you can just stick it in a preamp and see if it works.

five fish has a nice jig if you want to go that route but looks
like there is a waiting list..

http://www.fivefishstudios.com/diy-kits/op-amp-test-jig

GARY

« Last Edit: August 05, 2013, 05:10:35 PM by gar381 »

 

[BudCarroll]

Hey guys, so far have built 2 vp26s and two gar2520s.  My first 2520 that I smoked r11&12 works great/sounds awesome.  My second, seemingly well built one has a slight distortion to the tone.  I tried swapping cables and swapping amps out of the two vp26s, and the distortion follows the second 2520.  Anyone experienced this?

 

[ajsteel]

Anyone have built and tested GAR2520's they'd like to sell?  I'm looking to buy two.  Postage will need to be to Melbourne Australia.

Thanks
A.J.

 

[jakmusic]

Hi Gary,

I've built 4 - 2520s, and the first two I built are working fine. 

On the second two R9 and R13 are burning up when inserted in my known working VP28.  Any notes on where I should start looking?

I did not solder from top and bottom of my Millimax pins, so I will do that before I test again, but I thought I'd ask if there were any other troubleshooting points to check out before I tested the DOAs with fresh R9 and R13s.

Please see pictures below

https://www.dropbox.com/s/8v971ghyw65o9f6/IMG_1224.JPG

https://www.dropbox.com/s/w5waybi3ug2b07y/IMG_1225.JPG

https://www.dropbox.com/s/ukwi7ec0g17c0qu/IMG_1226.JPG

https://www.dropbox.com/s/st30g5lzpbuxcra/IMG_1227.jpg

thank you,

James

 

[gar381]

Hi James

Sorry to hear about your 2 problem guys.

Thanks for the pics but its hard to tell from them.
Whatever your mistake is its probably the same error
on both the bad ones.  I would A-B a bad one with a
known working guy.  USE A MAGNIFYING LAMP!! Closely make Shure the bad one
matches the good one as far as parts placement, solder bridges,
component leads touching etc.  Are the transistors and diodes in the right
holes-places?  Do the diodes have their cathodes facing the right way? 
Are Q5 and Q9 still healthy after the R9-R13 "melt down"?


Best of luck James

GARY

BTW.. after building 100s of these guys myself I now do the Millmax pins last
and only Solder from the bottom pre tinning the pins. 
I find this to be an easier and faster way to build these guys.

 

[jakmusic]

Gary,

I took your advise and worked through again checking everything on my not working 2520s to the ones that work and voila, I had put R6 where R16 should be. 


Everything's working. 

Thank you

 

[Triscuit]

Hi everyone,
I've completed a CAPI VP26 kit last evening with the gar2520 kit as well. I'm attempting to troubleshoot as there is no sound coming out when the unit is racked. I have a few replies in the official VP26 thread, but want to get a jump start on inspecting the gar2520 if the opamp construction is the root cause.

I constructed the opamp by soldering from the bottom (except for the pins) - I will take any and all feedback on how I could improve the execution on this. I do not have a preassembled opamp to test in the VP26, and really would like to nail the construction on the kit as it brings me a lot of joy to do it (and I REALLY hate failing).  This is my first time attempting solder points on a board this size, so I may not be seeing the problem as some of you would.

 

[Triscuit]

Better pictures:

 

[Triscuit]

And bottom (I tried to clean it up a bit; not feeling too confident though):

 

[Triscuit]

Top at angle - I'm noticing that the joint for the + IN pin looks rough on the top of the board. Should this be a concern?

I appreciate it everyone! I'm racking my brain here!