gar2520 build thread

Did you verify that all transistors are in their proper places and the larger BD's are facing the right direction? I can't really tell from the pic.

Aw crud. I just realized that Q7/Q8 are different. It's extremely possible I have them swapped. Thanks for asking that question. I'll be all over that later.

I can't tell for Shure from your pics but in the first picture
the Diodes look like they might be in upside down.  The black
band on the diode should be facing the circle in the silk screen.

Hope you get her working.

GARY

jsteiger said:

Did you verify that all transistors are in their proper places and the larger BD's are facing the right direction? I can't really tell from the pic.

Click to expand...

Confirmed that I have reversed Q7/Q8 - go figure. Something silly.

Going to unsolder and swap 'em in a bit to check. I was really racking my brain here!

And Gary, diodes are confirmed black band to the circle. Thankfully!

Thanks again, guys!

Donny

UPDATE: Rookie mistake on my part - Q7/Q8 were swapped. Lesson learned! We're up and running! Thanks, guys!

Note: Dec. 7 2013

MURATA IS DISCONTUNING THE RPC SERIES OF CAPS USED IN THE gar2520 and gar1731!!

The RPE series is being replaced with the RCE series.  I will be phasing these in as my RPE
Stock diminishes. I will be using either 50v or 100v based on availability.  For you guys buying
Raw PCBs and sourcing your on parts here are some part numbers:

10p 50v..    RCE5C1H100J0A2H03B
10p 100v. .  RCE5C2A100J0A2H03B

39p  50v..    RCE5C1H390J0A2H03B
39p 100v..  RCE5C2A390J0A2H03B

47p 50v..    RCE5C1H470J0A2H03B
47p 100v..  RCE5C2A470J0A2H03B

680p 50v..  RCE5C1H681J0A2H03B
680p 100v.. RCE5C2A681J0A2H03B

1000p 50v.. RCE5C1H102J0A2H03B
1000p 100v.. RCE5C2A102J0A2H03B

In a pinch the AVX COG SR15  series...
50-100v 5% with a lead spacing of 2.5mm (.1”)
Should work fine as I have tested these

Some problems with a build from the summer that I haven't been able to test properly until now for various reasons:

I built two VP312DI modules and two gar2520. I had problems with one and narrowed it down to the opamp by swapping them around. At first I got a very weak signal with no bottom end. After reseating the 2520 it worked, but after more examination I've noticed that there's some high frequency distortion. It seems to be there all the time, no matter what I set the input level to (still need to double check that and I'm not in the studio right now).

I've tried swapping opamps so I know it's not the modules, and the 2520 behaves the same in both modules. I checked the soldering on the card but it seems fine. I also went over all the solder points with the iron again to see if it would kickstart it but it's still behaving the same way.

My plan right now is to simply order a new kit together with my next order from CAPI and just build a new one. But I figured I might try and fix this one as a sort of experiment. I'm a novice and building stuff is a bit like paint-by-numbers for me, so unfortunately I don't have much skill with troubleshooting yet and I don't own an oscilloscope either (and never even used one), so I realize this may not just be an easy fix. But if anyone has any idea what could be the problem and what I could try, I'm all ears!

I might add that when building the modules, I did make the classic mistake of swapping Q7 and Q8 AND I managed to run one opamp on 24V briefly. The problem is that I don't know which is which anymore...

Any ideas, anyone?

Hi, I recently put together two of these kits with the hope to use them as a gain stage in a pultec eq design. I am having problems testing these to see if they are working before i implement them in to the design. I Have a regulated PSU supplying +/- 15v to the power. aswell as ground from the PSU to ground. i am taking my output from the output pin with cold and ground going to the ground on the op amp. Input i have tried putting a balanced signal straight from my audio interface, hot to + and cold to - ground to ground. i have also tried hot to + and cold/ground to -. I get a very distorted signal.

I Have also tried in line with my eq setup. Without the 2520 i get a good signal through the EQ and it works great (albeit very low output signal compared to input signal as expected) i replace the input with the hot going to + and the ground output going to the -. same massively distorted signal. Have i made a mistake in building these or am i wiring it up wrong?I cant see any bridged solder joints and i was fairly precise when i was putting them together.

Sorry please ignore that, I was having on of those mornings!  :-\

I just finished my second one of these tonight and I'm having issues. When I insert it into a preamp and power it up, I don't actually get any power to the rack. I know its not the pre because I tried it with the first doa I built and it worked fine. I think I might have a bridge somewhere so I'm going to double check that but wanted to know if theres anything else I should check?
Thanks!

Hi Houstnwehavuhoh

gar381 said:

Check post:  http://www.groupdiy.com/index.php?topic=33970.msg425092#msg425092
This may help a bit.

As John (Stagefright13) says use a magnifying light for both assembly
and checking your work.  My old eyes are so blind I couldn't build
a gar without one. :-[

Most problems are solder bridges on the bottom side
or componet leads touching each other on the componet side.

Click to expand...

While checking side by side (good guy and  the bad guy)
make Shure that all the parts are in the same place.
Check for solder bridges around the input pins.

Hope you get it working !!

GARY

Thanks for the info Gary,
It seems I had a bridge at C1 and C2 to the millmax pins, which is unfortunate because thats the first thing I did basically D: but I corrected that and checked that everything else was in the right place and there were no more bridges. However, I did notice that I put the diode in D3 with the band facing the correct way (toward the circle on the silk screen), but with the actual body of the diode not over the circle, if that makes sense

Now Im getting power to the rack but the opamp is getting really hot ?

Are the transistors in the right places and facing the correct direction??

Okay, I am having trouble with the Op Amp.  I bought the kit from Jeff at CAPI.  First I had the Q7 and Q8 swapped.  It would blow fuses in the 51x power supply.  It didn't seem to follow a pattern, one +16V, then one -16V, then both +/- 16V.  Checked for the most obvious problem, and there it was, they were backwards.  Fixed that.  Just in case anyone was wondering, the Hakko 808 is one of the coolest tools ever.  So I put it into the A1 position on the VP28, and it got hot real fast.  R12 got a bit of a tan, but still reads 5.6.  Both Q7 and Q8 were hot, and at least one of the nearby pins was hot as well.  So back to the obvious.  All the diodes are positioned in the proper directions.  All of the other transistors are facing the correct direction.  And finally Q6 and Q9 are BC560C's.  I am out of easy things to check, and am hoping someone has something smart that I have missed.  The pictures I took are not very easy to see anything so I am going to skip posting them for now.
Patrick

You might want to try swapping the transistors that were inserted backwards and any components that look damaged. Other than that, maybe a solder bridge on the topside of the Opamp?

gar381 said:

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. 



GARY

Click to expand...

This did it for me!

hello, anyone has gar2520 full kit support docs? because jeff forgot to send them. I need to finish the assembly!

Thank you very much


Nicolás

GT electrónica

You can have a look here:
http://groupdiy.com/index.php?topic=41741.0

Best // M

FWIW, I very rarely miss sending a support doc email out. They very often end up in spam/junk folders so please check there.

Finished building my first VP28 the other day and had a pair of gar2520's that I also assembled that I put into it.  After putting it into my rack and powering on, i saw a hint of smoke coming from one of the op amps. turned the unit off immediately and noted that the smoke was coming from D1A-D1B soldered pair of Diodes.  After inspecting the op amp components to try and find what was wrong, I realized that Q8's silk screen wasnt facing the correct way so I had it in there backwards.  Everything else looks good though and in the proper place, no solder bridges etc...

I've since turned Q8 around to its proper configuration but am hesitant to put it back into a VP28 before asking here... should I replace the pair of diodes that were smoking?  A visual inspection leads me to think that they're probably fine as the casings and such do not appear to be damaged... but that's not to say that the insides werent fried.  I'm assuming I should replace them just to be safe but figured I'd ask here first.  Much thanks!