8 Channel, 3U NEVE 1073 completed

[North]

Weird problem. Anytime I try to get to anything on JLM Audio's website, I get this:

-"Forbidden You don't have permission to access /shop/index.php on this server."
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.:

Anyone else get this?

Delete your cookies for JLM's site...

      tzman...... You are THE man!!! thanks!

 

[bertt]

Martin,

recieved the 4 pcb's yesterday. looking great.
Perfect fit with the rotary switch.

bert

 

[digistu]

You have a bunch of wire loops on the output transformers and the wire leads for LO1166's RC network are rather long too. Make all these wires as short as is physically possible to avoid making antennas. In fact, make all wires as short as possible.

This has totally solved my interference problem.  Lesson learnt.  Thanks again for your help and for providing these great boards.

 

[madriaanse]

This has totally solved my interference problem.  Lesson learnt.  Thanks again for your help and for providing these great boards.

Fantastic! Congrats on a successful build!

M.

 

[Fuccimain]

sorry if this has been discussed befre..

but since the Xicon Film Capacitor STYRENE 50V 100P is no longer made, is it ok to go up to 150p or higher?

thx

s

 

[desol]

Lots of stuff is no longer made. Doesn't mean you can't find it...

 

[Fuccimain]

true,

i found the exact part after digging , but for simplicity in ordering, I'm still curious for an answer to my question.

thx

 

[sr1200]

justradios.com carries a great number of film capacitors that are suitable.  Dont arbitrarily change capacitor values ( voltages you can go above whats in the schematic if needed)

 

[Fuccimain]

thx sr1200,.

didn't think it was proper to just change cap values, but was curious what i could use instead as a last resort.

happy thanksgiving to those of you state-side

s

 

[madriaanse]

true,

i found the exact part after digging , but for simplicity in ordering, I'm still curious for an answer to my question.

thx

Can't really go wrong with WIMA: http://www.mouser.com/ProductDetail/WIMA/FKP2D001001D00JSSD/?qs=sGAEpiMZZMv1cc3ydrPrFwgzP98AO9idqD3jXfOTtd8%3d

M.

 

[critterkllr]

I was wondering if somebody could offer some help. I have 4 preamps that seem to be riddled with issues. I've spent around 20 hours attempting to troubleshoot and am feeling a bit overwhelmed. I took my time with every one of these and am frustrated that these issues are popping up.

All 0V points show .05V. is this normal? When testing at the PSU, 0V is 0V. All 0V points correctly show 10R resistance to the chassis.

Preamp 1: There is a random occurrence where the 12R 1 Watt resistor will fry along with the 10R (R6) resistor in the V- section of the AC/DC. I can't seem to figure out why it does this. It happened once in the middle of recording. I shut it off for a second and when I turned it back on, everything worked. So I ended up replacing both resistors later on. It happened again, but this time the 47R 1W (R7) resistor fried along with it. I haven't been using any mics that require phantom power so I left it and replaced the other two. I happened to be testing voltages when it happened again and the 0V signal went from .05V to -7.5V. I quickly turned the PSU off, unplugged the preamps, tested the voltages on the PSU and they tested good. Connected them back to the preamps and it was fine again.

Edit: Two of the regulators on the ACDC ended up touching eachother. I've permanently isolated them so it won't happen again. Seems as though the PSU must have been moved/jolted somehow.

Preamp 2: Everything appears to be working fine.

Preamp 3: All voltages in the BA183NV sections are very low. I ran voltage tests on everything I can think of. At the 270R resistor, it is 24V on one side, and 5.2V on the other. All other preamps show around 21V here. I swapped the 270R resistor with a known good resistor and get the same results. I've checked the orientation of all capacitors many times. Resoldered all solder joints. Verified all resistor values. Verified transistor orientation. Fine combed the circuit board with a magnifying glass for any bridges. I can't find anything out of the ordinary. Is there a way for me to find out if a specific transistor is malfunctioning? Anything else that I should be checking? The BA183AM section has correct voltages. I ran a signal generator through it and the sound is traveling through the circuit and biasing. I haven't listened to audio yet.

TR4 #1 (replaced, but no change)
C - 5.2V
B - .78V
E - .056V

TR5 #1
C - .78V
B - 1.3V
E - .8V

TR6 #1
C - 1.38V
B - .58V
E - .057V

TR4 #2
C - 5.2V
B - 2.3V
E - 1.7V

TR5 #2
C - 2.3V
B - 1.7V
E - 1.1V

TR6 #2
C - 1.76V
B - .87V
E - .32V

Preamp 4: When attempting to bias, when I get to 70db, the scope is showing an extreme amount of noise. I'm assuming this is the circuit oscillating? When I use a DMM to measure the voltage of the 2N3055 while its at 70dB, the noise on the oscope lowers tremendously, but still noisy. It will stay lower until I move it away from 70db and back. If I go to 75db, I still get more noise than I should, but it's not nearly as intense. Everything up to 65db looks fine. I've wired this unit identically to the other 3 preamps. When running the signal generator through it at 65db, the waveform looks normal when very low. When starting to raise it, there appear to be little notches or spikes coming out of the waveform. When loud enough to clip, the clipping is not flat like normal, instead the peaks start to get pointed. I can also hear a loud noise coming from the OT. This OT is the closest to the 4 pin power connector. I've moved the cable from the OT to the XLR around to make sure it's not too close to any 24V cables.

 

[critterkllr]

Preamp 3: All voltages in the BA183NV sections are very low. I ran voltage tests on everything I can think of. At the 270R resistor, it is 24V on one side, and 5.2V on the other. All other preamps show around 21V here. I swapped the 270R resistor with a known good resistor and get the same results. I've checked the orientation of all capacitors many times. Resoldered all solder joints. Verified all resistor values. Verified transistor orientation. Fine combed the circuit board with a magnifying glass for any bridges. I can't find anything out of the ordinary. Is there a way for me to find out if a specific transistor is malfunctioning? Anything else that I should be checking? The BA183AM section has correct voltages. I ran a signal generator through it and the sound is traveling through the circuit and biasing. I haven't listened to audio yet.

TR4 #1 (replaced, but no change)
C - 5.2V
B - .78V
E - .056V

TR5 #1
C - .78V
B - 1.3V
E - .8V

TR6 #1
C - 1.38V
B - .58V
E - .057V

TR4 #2
C - 5.2V
B - 2.3V
E - 1.7V

TR5 #2
C - 2.3V
B - 1.7V
E - 1.1V

TR6 #2
C - 1.76V
B - .87V
E - .32V

Perhaps I posted a bit too much at once. I'll work with JLM on the Preamp 1 issue and deal with Preamp 4 later.

Can somebody tell me what to look for and why the voltages in this one specific section might be so low? The 270R resistor tested good. 0V measures .05V all the way across on every preamp. Should I be looking for a leaky/defective transistor? Perhaps the 470/25V cap isn't doing it's job? R11 (33K) and R13 (5K1) resistors were verified to be the correct color code, but weren't swapped for known working.

I don't have a way to post the schematic as a jpeg right now, but the schematics are located on the last two pages of this pdf: http://s3.amazonaws.com/EZ1290/assembly4.pdf

 

[madriaanse]

If you disconnect R51, what are the voltages on BA183AM? Likewise, you can disconnect R56 and check BA183NV voltages to start narrowing the problem to a specific section. You can remove R11, R13, TR6 to start narrowing it down to a specific NV section.

Can you share a closeup pic of the PCB?

M.

 

[critterkllr]

If you disconnect R51, what are the voltages on BA183AM? Likewise, you can disconnect R56 and check BA183NV voltages to start narrowing the problem to a specific section. You can remove R11, R13, TR6 to start narrowing it down to a specific NV section.

Can you share a closeup pic of the PCB?

M.

Thank you for your suggestion! I was able to use this to find that C16 was bad. Replaced it with a silver mica I had handy and it's working good! Preamp 1 is good to go as well. Now I'll just need to figure out this oscillation issue and everything is all set. I've found plenty enough advice on tracking down oscillation to keep me busy for a while.

Thanks again Martin!

 

[sr1200]

I was testing some things out the otherday (namely sweeping sine waves and pink noise thru my preamps)  And I noticed out of the 6 channels I've build from Martin, ONE sounds particularly better than the rest.  After sweeping it, i noticed that the very FIRST channel i built, has a freq. response somewhat like a DJ smile (bump in the subs and above 8k).  All the rest of the channels sweep out almost identical (VERY flat, with a slight bump in the bottom end, talking 10th of a db bump... REAL slight)  What could I have done wrong (or right...) on that first channel?

 

[madriaanse]

Thank you for your suggestion! I was able to use this to find that C16 was bad. Replaced it with a silver mica I had handy and it's working good! Preamp 1 is good to go as well. Now I'll just need to figure out this oscillation issue and everything is all set. I've found plenty enough advice on tracking down oscillation to keep me busy for a while.

Thanks again Martin!

Nice work! Keep me updated on your oscillation findings.

Best,

M.

 

[madriaanse]

I was testing some things out the otherday (namely sweeping sine waves and pink noise thru my preamps)  And I noticed out of the 6 channels I've build from Martin, ONE sounds particularly better than the rest.  After sweeping it, i noticed that the very FIRST channel i built, has a freq. response somewhat like a DJ smile (bump in the subs and above 8k).  All the rest of the channels sweep out almost identical (VERY flat, with a slight bump in the bottom end, talking 10th of a db bump... REAL slight)  What could I have done wrong (or right...) on that first channel?

Different sound between identical modules always intrigues me. It's usually related to component tolerances (especially transformers). Did you use any different components between your builds? The pre should be flat out to 40-50K, but if it sounds right it IS right.

M.

 

[Fuccimain]

Hey all,

I lined up a purchase of BC184C transistors to build some of these pres, but the min order is 200, they are $1.30 a piece, and I don't want to drop $260. all at once etc, SO.........

Any one interested in some?  let me know and I'll put a list together,  it's getting harder and harder to find these...

ok peace

sean

 

[desol]

1.30 each? Insanity.

 

[Fuccimain]

Yeah we'll. NOS. No longer made. Once they gone they gone I guess.  I'd rather pay 1.30 a pop then have to sort out compatible substitutes that are also in limited supply.