Neve 2254 build with ba185, ba191, ba192, ba283

[Spencerleehorton]

Ok, so the bias 5k pot does seem to rectify the problem, waveform now good on both connections, my next problem is there doesnt seem to be any gain!!
Comparing the input signal to output shows very little difference, I don’t know how much gain there should be but I am sure there is plenty to show a significant difference.
Compression is looking pretty messed up so will need to look at after, also Vu meter is working slightly but I have to adjust the signal generator to about 2v output rather than the 0.775v to get any signal to register, so will look at that last.

 

[Spencerleehorton]

Getting nice waveform now, changed 283 Pcb for another, loads of gain, meter showing GR but not showing input and output level yet.
Even though meter is showing compression and ratio, recovery and threshold all work but I’m not seeing compression on output?

 

[Spencerleehorton]

Getting and seeing compression on output now, meter is not working now!!!
One step forward, two back!!!

 

[Rob Flinn]

Have you calibrated the meter circuit ?

 

[Spencerleehorton]

Hi rob, just come off a night shift and to be honest haven’t had enough time to look at the 192 Pcb.
Pretty sure I’ve just wired it wrong but need to get some sleep then I’ll have another go tomorrow.
Nearly there now, happy I’m getting compression just want to get this meter working properly then I’m going to try and build a case for it so it sort of looks like the original.
Then I’ll need to build the other channel and case and also going to put another two 1290 mic pre’s together, then I have my 12 Neve mic preamps that I wanted, two of which are 1073.
Seems to be quite if bit of gain on this 2254 now, so will have to think about dialing that down a bit, but will wait until finished as it may change!!!

 

[Rob Flinn]

Seems to be quite if bit of gain on this 2254 now, so will have to think about dialing that down a bit, but will wait until finished as it may change!!!

That doesn't sound right.  I had one on the bench last summer & it didn't have unusually large amounts of gain available from memory.

 

[Spencerleehorton]

Don’t suppose you have any transistor voltages?
Might help a bit as I can see bc184c, bc550c, bc109, bc107 we’re used in different units.
I’ve used mainly bc184c but also trying out bc550c as have large stock of these at 550hfe and above.

 

[Rob Flinn]

Don’t suppose you have any transistor voltages?
Might help a bit as I can see bc184c, bc550c, bc109, bc107 we’re used in different units.
I’ve used mainly bc184c but also trying out bc550c as have large stock of these at 550hfe and above.

I don't have any voltages sorry.  I would doubt your transistor choice has anything to do with it.  The gain is averaged out by the components around it.  That is whyt you can put 2 different Hfe transistors in the same circuit & they pretty much do the same thing.

 

[Spencerleehorton]

I thought maybe that was the thing with the transistors.
I must have a wrong connection or left out a resistor somewhere.
At the moment I just want to get the circuit sort of working, which seems to be happening now.
Hopefully get a bit further in the morning.

 

[Spencerleehorton]

I’m getting GR on meter but can’t see any level on input or output on the Vu meter?
I’ve put the scope on the + of the meter and can see I’m getting level it just isn’t moving the needle???
Any ideas what to check here?
When I up the level of the frequency generator it then moves the needle but I’m pretty sure it should move at 0.775v of input?

 

[Rob Flinn]

I’m getting GR on meter but can’t see any level on input or output on the Vu meter?
I’ve put the scope on the + of the meter and can see I’m getting level it just isn’t moving the needle???
Any ideas what to check here?
When I up the level of the frequency generator it then moves the needle but I’m pretty sure it should move at 0.775v of input?

Looks like it comes from the BA192.    AT the end of the day you will have to go through it and find the mostake or faulty part.    In my personal experience it's more likely to be one of those scenarios than the other

 

[Spencerleehorton]

i'm shooting in the dark really here as i dont know what level I should be getting to see the input level or output level going into the meter?
its probable that i have wired it up wrong, i'll do a basic drawing of how ive wired up the meter switch to see if thats the problem.

One thing i havent tried as i havent built the full PSU yet is powering it with 24v and seeing the levels, i've been using some PP9 batteries as the digital PSU i was using was horrible and noisy.

Why i was confused was because i was seeing the GR level on the middle meter selection on switch, but no level when switched to input or output, but i could see i have level there when probing with scope? hopefully this will sort it's self out once i give it full power!!!

 

[Spencerleehorton]

Here’s my crude meter switch!!!

Is there a problem with this?

 

[r2d2]

..let me say a "folishness"…..  :
in some other diy … 54 project here
somebody have found mistakes on the comp section diodes orientation ,

also between original neve schematic and BA cards

working BA cards  different than scheme ,
( probably  a wrong rev of scheme ?  )
cheers

 

[Spencerleehorton]

Yes I’ve sorted the correct orientation of the diodes, the zener goes in a different place.
I now seem to have input and output level on meter but very low? But no compression!!
It’s almost like I’ve got a gnd issue bringing all the signal down?
If I put 2v into input from signal gen then it registers on the meter, any less and it does t appear to swing the needle?
I get about 1.3v dc scoping at meter when it registers.

 

[Spencerleehorton]

Any advice on how to fault find this would be handy!!!
I might just break it all down again and check each pcb

 

[Spencerleehorton]

Problems I’m having off the schematic the 283 Pcb on the schematic says F should connect to P? Is this Back to P on 283?
C5 and C3 I’ve put in 1000uf here could this be a problem?

I think I may have killed the compression by not putting in the dpdt sw6 switch and I have the 470R down to gnd, will disconnect and see what changes!!

 

[Rob Flinn]

In response to your PM (your inbox is full)

There is no definitive diagram for a 2254.  There are about 5 different models rev A to rev E. 

When I was repairing the one I had on the bench last summer I was just using the one that was correct for the rev I was working on.      You would probably do best to not try and combine more than one diagram.  Obviously the rev E is more complex because it has more functions than a rev A.    They aren't easy things to work on.  I remember it was a bit like having a disected chicken on my bench  trying to measure voltages without shorting parts out.

 

[Spencerleehorton]

Any ideas on the F to P connection?

 

[r2d2]

……..
In response to your PM (your inbox is full)….

+ 1 here about…

There is no definitive diagram for a 2254.  There are about 5 different models rev A to rev E. 
……. the rev E is more complex because it has more functions than a rev A.    They aren't easy things to work on. …..

reason why , most .. 54 diy projects are " limiterless "  ?  :-[
cheers