gar2520 build thread

[TillM]

Hi all, I built a couple of the gar2520 s. At least one is shorting out. Everything looks good but in the build three of the millmax pins wouldn't fit into their sockets on the circuit board. I filed the short ends of the pins down so they would fit I'm wondering if that's an issue. Other than that there's just what I thought were okay Bridges from the pins to other points. Any thoughts would be appreciated.  Thanks Patrick

It’s always good to post some Pics.
I saw a Post from you in the preamplifier thead. I would say that you have a false diode direction.
But without any pics from booth sides, it’s sometimes hard to tell.
The most issue I had with 2520 was false directions of diodes and output transistors or you have a solder bridge.

 

[Homestudio]

For me it was the late night and low light. Sure enough q7 & q8 were in the wrong spots. I'm anal about building. Double check before soldering then check the solder job. No more late night builds! Thanks

 

[gar381]

Hi all, I built a couple of the gar2520 s. At least one is shorting out. Everything looks good but in the build three of the millmax pins wouldn't fit into their sockets on the circuit board. I filed the short ends of the pins down so they would fit I'm wondering if that's an issue. Other than that there's just what I thought were okay Bridges from the pins to other points. Any thoughts would be appreciated.  Thanks Patrick

Hi Patrick

On rare occasions the PCB hole is just a little tight.  When I run into this I use a long nose pliers
and squeeze them in place.  Sometimes they even snap in place when you do this.

Best

GARY

 

[Homestudio]

All's good Gary. They're sounding great. Thanks for the great support!

 

[radtunez]

Hey,
I've got a problem with one of my Gar2520s in a VP28. The thing started giving off a wicked smell the first time I put it in my lunchbox, and it seemed to be coming from the op-amp. I tested that same op amp in my other VP28 that has been working perfectly, and same thing happened. This time around, however, I noticed the R9 and R13  56R resistors had been totally fried black :/ And may have singed the neighboring caps.  I double checked all of my resistor placement, transistor placement, solder bridges, and I'm not coming up with any reason.

Any ideas? Thanks in advance!

 

[radtunez]

Hey,
I've got a problem with one of my Gar2520s in a VP28. The thing started giving off a wicked smell the first time I put it in my lunchbox, and it seemed to be coming from the op-amp. I tested that same op amp in my other VP28 that has been working perfectly, and same thing happened. This time around, however, I noticed the R9 and R13  56R resistors had been totally fried black :/ And may have singed the neighboring caps.  I double checked all of my resistor placement, transistor placement, solder bridges, and I'm not coming up with any reason.

Any ideas? Thanks in advance!

Bump on this post. Anyone have any ideas?

 

[jsteiger]

Bump on this post. Anyone have any ideas?

The most common errors on these are accidentally swapping and/or turning the larger BD transistors. The 2nd most common is wrong facing diodes. Next would be misplacing the smaller BC5x0 transistors.

 

[murphster_matt]

I can confirm such a typical error, much to my haste I managed to overlook the correct positioning on one of my gar2520s where I swapped the BD-139 & BD-140 transistors (essentially swapping the NPN & PNP) and resultantly frying my RP1 & RP3 resistors on the VP28 board  :-[

Wont do that again  :

 

[nei02]

Good Morning,
I am new to this forum! I have some Kits in the CAPI basket and will order as soon as possible ;-)
But I have a question. Since I am fairly new to this project I am a little bit afraid to destroy my BAE 11 Rack PSU if something goes wrong.  (Although I have quite good soldering skills and electronic understanding) -> But who knows!

I am planning to buy the extension kit as well. Do you think the BAE PSU will go in protect mode if something starts to suck a lot of current? I don't want to kill my PSU ;-)

Viele Grüße
Ralf

 

[nei02]

bump

 

[jsteiger]

Good Morning,
I am new to this forum! I have some Kits in the CAPI basket and will order as soon as possible ;-)
But I have a question. Since I am fairly new to this project I am a little bit afraid to destroy my BAE 11 Rack PSU if something goes wrong.  (Although I have quite good soldering skills and electronic understanding) -> But who knows!

I am planning to buy the extension kit as well. Do you think the BAE PSU will go in protect mode if something starts to suck a lot of current? I don't want to kill my PSU ;-)

Viele Grüße
Ralf

Not sure what the project is but all but my single stage preamp kits have 10R PSU damping resistors that will go up in smoke before a direct short would damage your PSU.

 

[gar381]

Ralf

I  2nd Jeff's post..

ALSO..If you double check the PCB for shorted solder bridges and make shure the
Output Transistors are in the right locations and facing the correct way
before powering these up, you should be fine. 

The very very worst case situation...  The DOA might release
a bit of "Magic Smoke"  if something is not right with your build.
Your PSU should be able to handle it.

All the best with your builds

Gary

 

[Mylithra]

Good Morning,
I am new to this forum! I have some Kits in the CAPI basket and will order as soon as possible ;-)
But I have a question. Since I am fairly new to this project I am a little bit afraid to destroy my BAE 11 Rack PSU if something goes wrong.  (Although I have quite good soldering skills and electronic understanding) -> But who knows!

I am planning to buy the extension kit as well. Do you think the BAE PSU will go in protect mode if something starts to suck a lot of current? I don't want to kill my PSU ;-)

Viele Grüße
Ralf

The best advice I can give to anyone building these, Take your time. Don't get in a hurry, don't work when you're tired.
Have good soldering equipment. Bad equipment makes this hard and frustrating. Good equipment makes it a lot easier.
Scrutinize every solder joint you make. Take the time to make every one perfect. Clean your work when you're done (Deflux is a must). Go over everything with magnification. (esp if you're building the DOAs too). Follow the guides and you should have no issues.

 

[mrmike186]

Just an observation but I've had working op amps suddenly not work, usually after uninstalling and reinstalling but  I've had some luck with re-heating the milmax pins and making sure the are seated all the way in. My guess is that handling them can invoke stress on the pin joints.

 

[dr_daw]

I can confirm such a typical error, much to my haste I managed to overlook the correct positioning on one of my gar2520s where I swapped the BD-139 & BD-140 transistors (essentially swapping the NPN & PNP) and resultantly frying my RP1 & RP3 resistors on the VP28 board  :-[

Wont do that again  :

D’oh!!! I did the same thing   Didn’t notice that they were different. Guess those are blown, hopefully I can source some in northern British Columbia.

 

[gar381]

dr_daw

You can try swapping the 139 and 140 back to where they should be ...
9 times out of 10 they survive this mistake.  

Best of luck !

GARY

 

[Gonzriel]

Hey,all. I just completed a VP26 Litz and gar2520. At first the gar2520 was silent.  Then tested with a pre made 2520 and it worked fine.
I went back and checked all the facings, retested the component values and re heated solder points.
RE tested and it passes signal however it is slightly distorted.
The pre built 2520 registers -79ish dB harmonic distortion the one I built registers -48db  harmonic distortion.

My question is has anyone run across this?
Everything looks and tests ok but obviously I’m missing something.
Any advice is welcome. Thanks.

 

[Potato Cakes]

Hi, Gary,

I'm wanting to use your gar2520's for a mod I'm doing for the buss EQ section in recently completed TAC Scorpion rebuild. The console runs on +/-17.5V rails and the prototyping phase for this project went very well and now I'm looking at doing a production run. However, I noticed that the 2520 starts generating a bit of heat when inside the console when it's been powered on for a while. Its not alarming like I've had when a DOA had an issue where they couldn't be touched, but it's still warm. I am using your garAM16 through the console and have not noticed them putting out any heat, but they are operating well under their maximum voltage. So with the slightly unnecessary preface complete here are my questions:

Are there any components that could be altered to allow for slightly higher voltage handling? (power resistors?)
Will running on 17.5V rails ultimately be fine?
Is heat being generated by the gar2520 inside a closed case (console) any reason for concern?

The EQ circuit being implemented is basically a 553 and the 2520 seemed to be the recommended op amp to use. I will need to order more 2520's to do all 16 busses, but I need to make sure that the ones I choose will not have issues with the slightly higher rails than what is spec for typical +/-16V style applications.

Thanks!

Paul

 

[gar381]

Hi Paul

I burn in my assembled gar2520 at +/-18v.  and yes they do run warm in fact they
are the warmest running of all my DOAs.  Not to worry,  they should be fine in your desk.
BTW.. To my ears (subjective), try my gar1731 in 553 type EQs.  These are my favorite DOAs for
any swinging LCR type EQs.

Best

GARY

 

[Potato Cakes]

That's great news.

I will have to try the 1731s. I want to make a decision one way or the other as I already have a pile of other EQ options and the desk it pretty versatile, so I don't want to add more ways to confuse myself with what to do with audio during mixing. I have to buy more DOA boards but I'll hold off till I do some proper listening.

Thanks!

Paul