com clone 2

[s buckley-jones]

Afternoon

 

Has any body built the com clone belt backs ? . I find my self grounded in the house just now 2 weeks into heart atack recovery program , to fill in time I have started a couple of units as fill in project , going well so far have buss to main out put stages working .the issue I have relates to the mic stage . your input advise / if there is a miss print cant spot it as yet

 

 

yours stephen

[Brian]

Yes, I built some many years ago. What's your problem?

[dirkenstein]

.the issue I have relates to the mic stage .

Built 4 of them about 3 years ago. Did you use the premade PCBs? What's your problem with the mic stage? What kind of microphone are you using? Hint: the 'default' commclone preamp config assumes dynamic microphones and _doesnt_ work with biased condenser capsules...

 

Dirk

[s buckley-jones]

.the issue I have relates to the mic stage .

Built 4 of them about 3 years ago. Did you use the premade PCBs? What's your problem with the mic stage? What kind of microphone are you using? Hint: the 'default' commclone preamp config assumes dynamic microphones and _doesnt_ work with biased condenser capsules...

 

Dirk

 

PCB as per track lay out component as per list, audio source dym mic / audio sig generator . r 30 not used .pin 3 ... u1 10<> V .. PIN 6 <> V/2 SUPPLY LEVEL

 

mute not fitted no audio input

[Brian]

pin 3 ... u1 10<> V .. PIN 6 <> V/2 SUPPLY LEVEL

Not quite sure what you mean but I would expect...

 

Pin 2, -ve input = 1/2 VCC

Pin 3, +ve input = 1/2 VCC

Pin 6, output = 1/2 VCC

[dirkenstein]

pin 3 ... u1 10<> V .. PIN 6 <> V/2 SUPPLY LEVEL

 

As Brian saya, I'd expect v/2 on pins 2, 3 and 6, to within a few mV, without any signal. On Pin2 even without r30 unless I'm confused.

Also check that the input track to the missing r30 has v/2 on it.

If you've left the mute open, maybe you have a short in R10/R11/c8 somewhere. The track separation isn't good on some of the boards I obtained, amd easy to bridge.

 

Have you built only one at this stage, and you're looking for sidetone?

 

I assume you're driving these off a 24v supply? Or a tecpro station?

 

How are you testing for audio output?

[s buckley-jones]

I assume you're driving these off a 24v supply? Or a tecpro station?

 

up date ! noted that I was getting feed back off the test rig now and again . started again today , while checking supply level ran the supply down to 0 volt . at 15 volt mark board " works" output to bus and speaker/headphone . side tone does not function at this stage no change when pot adjusted . going to try using powersupply to replace ua2 supply " off board ." mic circuite works as birdnest rig of board .

 

It is not my intent to use this a blog page as such if mod feel I am over setting it

 

yours stephen

[fpn]

Hello,

 

I also have an issue with the mic input.

I am building 6 units for a 100 seats studio/theater. I am testing with a ClearCom RM400A station.

After some investigations I found it seemed to work at first but later the sound faded out with kind of saturation/scraches then muted (with no sound on both the station/the party line & the beltpack sidetone).

 

The issue arised 5-10 minutes after the first time I plugged in power. If plug it off then wait then on again the issue comes more quickly untill nothing works at all.

 

I need some help. Is your issue similar to this ? I could not find out in your posts - english is not my mother language -

What should I test ? I have an oscilloscope, a volt meter and a R-L-C meter. I know electricity, soldering and RLC circuits learned at college, long time ago. I am not familiar with op-amps.

I am sticked on this problem. I've solved other early issues - cut in tracks on 2 boards in 6 of the premade PCBs and soldering shorts of my own -

 

Thanks in advance for your reading this.

 

Regards,

Fpn

 

 

 

2 headsets with dynamic mics : MB Quart K800 (very good) and Koss SB40 (cheap but good).

 

I found ComClone2 is "version 2" dedicated to condenser mics, (it is the early version 1 for dynamic). It seems you just need to remove R30 for dyn mics. This is confirmed by ClearCom MR102A circuit diagram. I found comclone2 is a clone of MR102 : diagram, values & op-amps are the same. MR102 is for usual headsets with dyn mics, I suppose. So it should works.

 

Tried with PC-board class condenser mic with R30 soldered and it worked at first on several circuits but not one week later.

I suspected R12, C23 then NE5534 op-amps and changed them all and it worked...10 minutes.

It seems that both condenser & dyn mics behave the same way : works at start then fades the mutes, more and more quickly.

 

My power is a laptop-like 24V-1.5A. The station makes the power termination.

All other functions work OK : all from station (headsets mic&ear and call signal and others sources), call sig and ear at comclones, The overall sound is very good and once it is boxed, it is about to be the beltpack we are waiting for.

 

[paulears]

First thing to check is if it is only when certain units are connected, so I'd suggest connecting the clearcom master station to one pack, and testing, adding another if no fault appears. Hopefully this will allow you to confirm if an individual pack is causing the problem, or if it is current demand that shuts the power supply down in the master station when you exceed a limit. Probably worth adding an ammeter and voltmeter to allow you to monitor what is happening. I'd bet that it's a power supply problem but the exact cause could be so many things, but it just means substitution and careful reading of the data to track down if it's an errant cable or dodgy pack causing the problem.

[fpn]

Thank you for your help.

I tried several options you proposed.

Since I face the issue on several units, I decided to focus on one of them. All tests are with a single pack and the station.

I found the voltage input for the mic preamp is going lower as time goes by. R17 and R18 should set a middle point, and divide in halfes the 24V supply. But the Voltage goes down from about 26-12-0 to around 26-7-0.

I did not found the resistors getting warm...

Next measure will be current & power, overall and preamp, and may be I'll change R17/R18 for 1% or more powerful.

 

Thanks again,

fpn

[timsabre]

I found the voltage input for the mic preamp is going lower as time goes by. R17 and R18 should set a middle point, and divide in halfes the 24V supply. But the Voltage goes down from about 26-12-0 to around 26-7-0.

I did not found the resistors getting warm...

 

 

This sounds like a wiring error or PCB error - or the resistors of the divider are a much larger value than they should be.

[dbuckley]

Increasing the wattage of R17/18 will make no difference, as between them they are 440k , which with a 24v supply means they are dissipating about a milliwatt between them. Changing tolerances will also achieve nowt.

 

C9 would be my first port of call. It's vastly oversized, at 47uF, given the weedyness of what is supplying it, but irrespective of that, it's leakage could certainly be enough to significantly alter the mid rail. It should probably be a tantalum for that scale of value.

[Brian]

I'd look around U1, the 5534: they have a few odd characteristics...

 

1) The input resistance is quite low, around 100k, which will load down the R17/R18 divider.

 

2) If there is more than about a diodes drop of DC between the inputs then lots of current (>10mA) can flow into the inputs.

 

Check the DC values on that chip on pins 2, 3 and 6

[sauce]

Hi everybody,

 

First sorry for my very bad english I am french.

 

I have built 2 units of this comclone and I have some issues :(

First just with one unit connected to power supply : with a NE5534P the sound is very crappy, unusable. With a TL081CP the sound is quite good but the LED flashes when I speak. On the other side RV2 sidetone has no effect on my voice.

 

Second with two unit connected : the sound becomes crappy and unusable even with the TL081CP ! The call function is OK on both units.

 

Every voltages are ok VCC, VCC/2.

 

My power supply is this one : http://www.sonelec-m..._simple_003.gif with a 2x12V 2A 48VA transformer. It delivers 28.3V.

 

What could I check please ?

Why just replacing NE5534 by TL081CP make the sound good ? They are quite equivalent, aren't they ?

 

Thank you in advance.

 

Eric

[dirkenstein]

 

Why just replacing NE5534 by TL081CP make the sound good ? They are quite equivalent, aren't they ?

 

Although they're both op-amps, the NE5534 is by no means a close equivalent to a TL081.

 

The TL081 has JFET inputs which makes its input resistance to all intents and purposes infinite. At least with anything approaching a 'normal' voltage source (so not an unbuffered/unamplified condenser microphone element, for instance).

 

The NE5534 is a bit of a weird beast compared to most other op-amps, as Brian mentions. It's optimized for absolute minimum noise and distortion at audio frequencies. The 100k input resistance is rather low and the inputs are bipolar and draw an appreciable bias current under normal operation (and rather a high current outside of ideal operating conditions).

 

You shouldn't be getting bad sound with an NE5534 used. Worth rechecking voltages (V/2) at relevant input pins of the 5534. What kind of microphone capsule are you using? dynamic/condenser?

 

Your PSU output voltage seems a little high. 28V is rather close to the NE5534 absolute max rating of 30v. If there's an LM317 in there, can you regulate output down to 'real' 24V.