Neve 2254 build with ba185, ba191, ba192, ba283

[Spencerleehorton]

Ok dude, thanks for that , I’m going to use a digital adjustable Psu first of all and power up slowly and carefully!!!

 

[Spencerleehorton]

I will take it that the U feeding the 10R resistor is 24v.
Don’t know why this wasn’t called B+!?
24v connections are
S and F on ba185.
N and M on ba192.
F and N on ba191.
N and M on ba283.

 

[Rob Flinn]

I will take it that the U feeding the 10R resistor is 24v.
Don’t know why this wasn’t called B+!?

Because it's pin U on the connector at the back of the 2254.

 

[Spencerleehorton]

Ah I get ya now, external or separate Psu connector

 

[Rob Flinn]

Ah I get ya now, external or separate Psu connector

Not really.  All the i/o & power are done on the same connectors as are on the back of a 1073 etc

Remember these compressors were not really designed as stand alone units.  They were designed to be plugged into slots on a desk, & as such have the same female 18pin edge connector that all the modules of this era have.

 

[Spencerleehorton]

I get ya, putting together and working out ba192 was harder than I thought!!
Have worked it out now and getting components.
So far only one channel nearly done, put some power on but computer with scope software is having problems so need to use another laptop and reinstall OS!!!
Should have some signal going through soon and hopefully some compression !!!

 

[Spencerleehorton]

Ba185 is looking a weird with signal through it!!!

Anyone have any transistor voltages or further voltages for any of the 185, 191 or 192 pcbs please?

 

[Spencerleehorton]

Looking at the EZ2254 colour book schematic I can see a couple of wiring mistakes, bit easier to read.

 

[Spencerleehorton]

well we have some descrepencies on the BA185 schematic, the original has 5uf/64v caps before the matched pair of transistors before the output to the 10468, but the DB54 says to use 22uf here and the audio maintence uses 10uf/50v?
And i dont really understand why the voltage rating would have to be so high?

Im not getting output on R, so this part of the circuit needs looking at.

Will change both transistors as I didn’t match these first of all.
Will record voltages and see if something pops out!!

 

[Spencerleehorton]

Just testing the ba185 Pcb and can’t get signal past the two 10uf caps before the base of the match transistors to outputs R and T?
I can see a little signal at N?

Am I missing something here?
Do I need to connected something else to get the signal up?

I also see signal at H, A, C, D, and F, lots of noise in all the signals?

Need a bit of help here!!!

 

[Spencerleehorton]

Getting output now, needed to put in other txf as they block dc

 

[Spencerleehorton]

Here is a pic of the noise, so far 5k output pot works fine and adjusts the output signal along with the other 5k pot to set gain.
Will work on other pcbs and connect, is the noise due to it not being in a metal case?

 

[Spencerleehorton]

Transistor replacements to try instead of bc214b is bc559 and bc560.
Looking at others for replacements.

Bcy70

2n5320

 

[Spencerleehorton]

I just thought, I dont have a chassis ground as im making this circuit out of chassis on bench, could this be where there all the noise is coming from?

is there a work around for not having a chassis ground, Im using a digital adjustable PSU for the 24v, its has +/- and middle as ground which is then connected to - by a plate.

 

[Spencerleehorton]

All the noise appears after the first transformer?
Have built the 191 and 192 now connecting up with switched pots, will see how it looks when everything is connected!!!

 

[Spencerleehorton]

Some signs of compression but need to get rid of this noise/dc on the audio signal in ba185?!

Is there meant to be 12v on R and T on output of ba185?

 

[Spencerleehorton]

I think my noise issue might be this Psu as it looks like it’s compressing now, going to build a Psu or try batteries and see if I can get rid of the noise.

 

[Spencerleehorton]

Noise problem was Psu, getting no noise on waveform now.
to move onto getting the waveform from F on 283 better.
Top is chopped off and seems to appear on the other side of the output transformer!!???

I will trace the signal to see exactly where it’s going wrong, seems to be 2n3055?

 

[Rob Flinn]

Noise problem was Psu, getting no noise on waveform now.
to move onto getting the waveform from F on 283 better.
Top is chopped off and seems to appear on the other side of the output transformer!!???

I will trace the signal to see exactly where it’s going wrong, seems to be 2n3055?

Have you set the trimmer on the BA283 ? If it not set correctly it will clip on one side more quickly than the other.

 

[Spencerleehorton]

I probably didn’t describe what was happening correctly, the output txf has two connections off it on the secondary, one side I get 3/4 of the waveform and the other side I get what looks like the other bit of the waveform!?
Usually I would get the same shape waveform in both connections.
The bias 5k pot I had adjusted to 22.66v but I can now see it says to adjust to 23v, so will twiddle a bit more in and see if it changes!