Neve style 500 series mic pre 1290 1073

[jandoste]

Ok, I turn back here... I didn't get them work!
I get 0 V on the IN/Out tranx pins no voltage there...  it must on 2N3055 but I replaced them but the issue still there. when I turn on PSU I hear tranx noise after then relay takes more time for clicking...

any advice?

Thanks

 

[onlymeeee]

Ok, I turn back here... I didn't get them work!
I get 0 V on the IN/Out tranx pins no voltage there...  it must on 2N3055 but I replaced them but the issue still there. when I turn on PSU I hear tranx noise after then relay takes more time for clicking...

any advice?

Thanks

Hi, I didn't see these posts..  (if you don't get a response here in future, just send me an email and I'll get back to you much quicker)

Found out where the 24V gets lost. If it's not reaching the 2N3055 or output transformer then is is getting to the 12R resistor? 
Also if you post or email me some high res close up pictures, I'll be able to see if something jumps out. 


As a general troubleshoot walkthrough I'd recommend:
Before turn on:
1) Confirm that you have no shorts between power rails & ground. 
2) Confirm that you have continuity between the case of the 2N3055 & pin 1 of output transformer.
3)  Confirm that all molexes are screwed tightly.
4)  Confirm that the bias trimpot is turned completely anti-clockwise. At no point will this trimpot need to be turned all the way clockwise..  if when you're setting the bias, it isn't changing after 6 or 7 turns, then something is wrong..
5)  Confirm that all 3 grounds show continuity together.  Pins 1, 5 & 13.  They should be joined at the lunchbox powersupply or the PSU that you are using as your test jig.

After turn on:
(51X series) There will be a few seconds delay before the relay clicks and the pre is up to full power. 
(500 series) There will be a few seconds delay before the 1st relay clicks and the pre begins to turn on.  At this point there may be a little squeal as the DCDC converter gets to full power..  Another relay will then click once it's up to power.  And finally one last click which will unmute the ouput.
 
5) Confirm that you read 24V on pin 3 of output transformer.
6)  Confirm that you can bias the unit correctly by turning the trimpot clockwise until you read 22V on the case of the 2N3055.

At this point, we can be reasonably confident that the power is working correctly.  So we can now test the audio.

The easiest way to test a nonworking unit is with a simple DIY audio probe, or an oscilloscope.  With these we can trace along the circuit until we find the culprit causing the problem.

Firstly probe the input, to make sure that you can hear/see the signal correctly.  Once you have confirmed this, you can trace along the circuit.  At some point you will find that the signal disappears or distorts (depending on what the initial issue is).  Then you will have found the problem.  ie. a short, dry joint or bad part. 

 

[jandoste]

Thanks Peter,
Everything is looking Ok! now I have a distorted sound... I have 24V, 2N3055 is 23V.... 48V is there but I don't know why it is distorted.

any idea?

Thank you

 

[Deepdark]

Just out of curiosity, what are the 3 ground you're referencing? Their is the Chassis ground, taking all mounting holes and the big power transformer mounting pad and the analog ground taking all the signal ground. The third is for the 500 serie?

 

[onlymeeee]

Deepdark:  The power ground too..  It was more a general troubleshoot guide rather than just specifically for the NV73.  It's easy to forget to make sure the 3 ground pins are ties to ground in a test jig or something.. 
In the case of the NV73, this power ground is used for the first couple of power rail caps on the 16V rails.. 

Jandoste:  Certainly...
As stated in my last post, 2 ways really to troubleshoot ..    a visual inspection..  ie. checking that caps are in the correct way, no shorts, no missing parts, missing wires, unsoldered connections, wrong orientations... anything like that..    The high res photos would help in this regard.

Or signal tracing.. 
If you have a scope, (if not, then fashion a simple DIY audio probe) trace along the circuit.  Google for details on the audio probe.

In this specific case, you're looking for where the sine wave gets distorted... so...
Once you have found the signal at the input, (this makes sure your probe/test set up is good)  then position P would be a good place to begin.  Here you can see if the problem is before or after the output trim.  ie. if the input amp or output amp is the issue.
(position P in the top centre of the PCB.. where the cable underneath connects to)

 

[fontazuma]

Hi, Need some support for this Build.

I cannot seem to properly bias the output transistor 2N3055. It doesn't go below 23.8VDC when the bias trip pot is fully clock wise. I followed the trouble shooting guide but still cant bias the output transistor.

Before turn on all checks OK, no shorts. After power on, the delay and relays operation are fine.  The transistors for BA284NV and BA283NV are biased OK.  I compared my values with the schematic are they are spot on. Just cant bias the output. I swapped out the 2N3055 with a spare, and have the same results.

Here are my measurements on BA283AM.

BA283AM    C            B              E
T1B                2.08        0.97      0.39
T2B              23.9        2.07      1.53
T3B              23.9        1.53      1.12

Thanks,

Leo

As a general troubleshoot walkthrough I'd recommend:
Before turn on:
1) Confirm that you have no shorts between power rails & ground. 
2) Confirm that you have continuity between the case of the 2N3055 & pin 1 of output transformer.
3)  Confirm that all molexes are screwed tightly.
4)  Confirm that the bias trimpot is turned completely anti-clockwise. At no point will this trimpot need to be turned all the way clockwise..  if when you're setting the bias, it isn't changing after 6 or 7 turns, then something is wrong..
5)  Confirm that all 3 grounds show continuity together.  Pins 1, 5 & 13.  They should be joined at the lunchbox powersupply or the PSU that you are using as your test jig.

After turn on:
(51X series) There will be a few seconds delay before the relay clicks and the pre is up to full power. 
(500 series) There will be a few seconds delay before the 1st relay clicks and the pre begins to turn on.  At this point there may be a little squeal as the DCDC converter gets to full power..  Another relay will then click once it's up to power.  And finally one last click which will unmute the ouput.
 
5) Confirm that you read 24V on pin 3 of output transformer.
6)  Confirm that you can bias the unit correctly by turning the trimpot clockwise until you read 22V on the case of the 2N3055.

 

[004le]

I assembled two 51x version NV73s and they sound very nice.  However, the gain switching seems incorrect because after step 8 (45db), the gain decreases until it begins climbing again at 11 through 12 (60 - 65db). Hopefully, the attached picture of a recording of successive gain steps from 1-12  (0 - 65 db) makes the issue clear. 

I am still new to electronics and believe the problem lies in the joining of the amplifier sections of the circuit marked "Parts ending in C" and "Parts ending in A" but am looking for further direction.

Could someone be so kind as to suggest a fix for this?  Thanks in advance for any help!

 

[onlymeeee]

From 55dB onwards, the amplifier with parts ending "C" comes in to the equation...

As there is still gain boost 55 - 65dB.. then the gain switch should be ok.. 

So as you say, the problem will be in the amp section with parts ending C. 

I would start with a good visual inspection..  shorts/cold joints/wrong values/orientation/missing parts etc etc..    If nothing jumps out, compare to the "almost" identical amp section next to it..  use the silkscreen on my site as a guide.. 
http://www.thedonclassics.com/nv73diymanual.html (bottom of the page)

Reflow any suspect joints.. 

I'd then change out the transistors as they're socketed and easy to do..

If this doesn't turn anything up, then I'd use an oscilloscope if you have one, or a simple DIY signal probe..  (or a multimeter, depending on which you have) and chase along the circuit until you find the point where all the signal gets lost.   

 

[004le]

Thanks very much for quick, helpful response.  After looking many times at the my board, the schematic, and other's pictures, I finally realized I switched the 120 and 120k resistors... on both boards!  Not the brightest move.  After switching the resistors, the gain works properly.

Looking forward to working with them later this week.

Thanks again!

 

[JukkaJukka]

Hi! I hope I still can reach someone here altough the thread has been dead for quite a while now. I can't get my hands on the KSD1273QTU, and start getting a bit desparate here. My knowledge in electronics is not great enough to just source a part that I could replace the KSD1273QTU with. Could anyone please help me out finding a part which I could replace it with or source me that part since I've pretty much tried everywhere? Thanks!

 

[Whoops]

Hi! I hope I still can reach someone here altough the thread has been dead for quite a while now. I can't get my hands on the KSD1273QTU, and start getting a bit desparate here. My knowledge in electronics is not great enough to just source a part that I could replace the KSD1273QTU with. Could anyone please help me out finding a part which I could replace it with or source me that part since I've pretty much tried everywhere? Thanks!

Replacement and equivalent transistor for KSD1273

You can replace KSD1273 with 2SC1985, 2SC1986, 2SC2075, 2SC2315, 2SC2316, 2SC3310, 2SC3795, 2SC3795A, 2SC3852, 2SC3852A, 2SC3866, 2SC4242, 2SC5241, 2SC5353, 2SD1273, 2SD1273A, 2SD772, 2SD772A, 2SD772B, 2SD792, 2SD792A, 2SD792B, 2SD823, BD241B, BD241C, BD243B, BD243C, BD537, BD539B, BD539C, BD539D, BD543B, BD543C, BD545B, BD545C, BD799, BD801, BD809, BD951, BD953, BD955, BDT83, BDT83F, BDT85, BDT85F, BDT87, BDT87F, BDX53D, BDX53E, BDX53F, BDX77, MJE15028, MJE15028G, MJE15030, MJE15030G, MJE15032, MJE15032G, MJE15034, MJE15034G, MJE8502, MJE8503, MJF15030, MJF15030G, TIP150, TIP151, TIP152, TIP160, TIP161, TIP162

Just watch out for different packagings and Pinouts

 

[Whoops]

Onlymeeee does't login for more than 1 year now.

The Don classic website is down also.

I guess this project is over.

Strange thing is that the White market thread is still active

 

[onlymeeee]

thedonclassics.com and all projects are still alive and kicking.. 
The replacement for that part is the TIP120 as per the Mouser BOM..  (I will update the general BOM now)
If you're ever in a rush for an answer just give me an email, as I don't get on the forum as often as I would like to these days..

Onlymeeee does't login for more than 1 year now.

The Don classic website is down also.

I guess this project is over.

Strange thing is that the White market thread is still active

 

[Whoops]

Hi Onlymeee,
sorry I tried the website some days ago and it was done, maybe I was following the wrong link or and old link.
Sorry for that

I'm happy that all is running, very nice kits, thanks

regards

 

[jandoste]

Hey Onlymee,
I'll add 1073 EQ addon for the NV73 micpres... I'm afraid that mouser doesn't have  this Header on mouser in their stock...
https://www.mouser.fr/Search/ProductDetail.aspx?R=D3448-89120virtualkey51750000virtualkey517-D3448-89120
and I'm not sure which Header I can add instead of  this one Mouser Part No: 517-D3448-89120

Please let me know if you have used another header....

Thank you
Jandoste

 

[onlymeeee]

Replied to your email.. but just in case anyone else needs the info..  I've updated the general BOM to include alternatives to that part.  Basically any IDC header with strain relief is suitable..  for example 710-61202023021 has the strain relief included.

 

[bugfight]

for those who have the error where bias adjustment never drops from 24v, i am going to risk exposing my ineptitude, in case it might help someone. in my case (51x only build) i had installed the dlyRLY relay on the wrong side of the board, which of course prevents it from being activated.  probably most people are having some problem (maybe the same one) with this relay as it interrupts the ground connection to R7B.  this is not on the schematic and is pretty hard to see on a stuffed board.  with only the full 5k of the trimmer as a path to ground, TR3B never turns on, and thus with no collector current, the voltage can never drop below the 24v supply.

 

[kante1603]

Thank you very much for sharing your experience,posts like yours really help (good explaination btw.).


Best regards,


Udo.

 

[bugfight]

thanks, i'll be thrilled if it helps somebody.  i've learned tons here, even if it took 8 years to finally build this one...

 

[evanbradford]

Hi there everyone, looking for a little guidance on a couple of NV73s that were given to me already built. I've built some kits (including the 250EQ, which is fantastic), but have never had to do any troubleshooting.

I made an audio probe per the recommendation earlier in this thread and figured out that C15A wasn't getting to point P because a trace had been burned off the top of the board. Seems to be working great now.

The second one  seems to be having a somewhat peculiar problem that I'm hoping someone can shed some light on. When I test the output of the card, pin 2 or 4, I get a normal signal, so the signal is making it through the circuit. However, when I go to use an XLR, the signal is very low, almost nonexistent, UNLESS I just barely plug it in and find a "sweet spot" where the signal sounds normal. I'm guessing that this sweet spot is where only one of the pins of the XLR is actually making a connection. Any ideas why positive and negative output together seem to be canceling out?

Thanks in advance!