Roger Mayer RM57 build?

[Spencerleehorton]

Ive just done a new pcb which includes both boards more like the Italian studio pictured pcb, looks much better and has a smaller foot print, looking like i'll probably make quite a few of these!!!
Just missing some pots and we should be good to go ahead and start testing.

I've settled on either the 2N2222 or 2N3053 for the NPN transistors, 2N3906 for PNP and 2N3819 for the JFETs.

 

[Spencerleehorton]

before putting this together i just wanted to ask a couple of thing, as all the schematics are slightly different and some show points that are connected and others at the same place don't.

Q9 crossroads junction or does Q9 connect only to VR5?
Q8 Emitter junction connection only to R12 or to C6 and R10 as well?
Q7 to V+ or connection to C4 and Q6 emitter and R9?

I have gone with Q9 connects to VR5
Q8 emitter to R12
Q7 to V+

just wanted conformation on this incase of mistake?

 

[Spencerleehorton]

Done a couple of boards today and populating now but just seen part of the schematic which I haven’t included!!!
Will make up the extra part!!!

 

[Spencerleehorton]

My mistake I’m just missing the 18v regulator, I can do this another way.
Will try and build Psu tomorrow then finish populating , then I will test!!!

 

[mig27]

Just took a closer look at this and it seems that you got it just right.
Keep up the good work!

before putting this together i just wanted to ask a couple of thing, as all the schematics are slightly different and some show points that are connected and others at the same place don't.

Q9 crossroads junction or does Q9 connect only to VR5?
Q8 Emitter junction connection only to R12 or to C6 and R10 as well?
Q7 to V+ or connection to C4 and Q6 emitter and R9?

I have gone with Q9 connects to VR5
Q8 emitter to R12
Q7 to V+

just wanted conformation on this incase of mistake?

 

[Spencerleehorton]

Still getting parts together but getting there.
Edge of the pcb I will tidy up.

 

[Spencerleehorton]

Just missing some 0.47uf tantalum caps and gotta build Psu and case tomorrow.
Hopefully by the weekend should be putting some sound through it!!!

 

[Spencerleehorton]

Need to finish 18v Psu and missing a couple of pots.

 

[Spencerleehorton]

Just out of interest what’s the s/n like on these compressors?

 

[Spencerleehorton]

Have powered up , no smoke but signal doesn’t pass yet!!!
Will go through and see if I can find what the problem is.

 

[Spencerleehorton]

So far I can’t get signal past C19!!
Just goes horrible after Q11?

 

[Spencerleehorton]

Right first problem, I need p channel jfets!!

 

[Spencerleehorton]

would appreciate some help if anyone can.
here is my pcb with values, could you guys check this please?

 

[Spencerleehorton]

now looking at the drawing of the schematic, R16 and R17 are connected to Q9 base and it gives a voltage of 3.64v at that point
and it connects C6 +side to Q8, R12 and R10

 

[RuudNL]

The junction of R16 and R17 is going nowhere on your PCB...

 

[Spencerleehorton]

Yeah sorry I rubbed that bit off but on the pcb it’s there along with the other connections I’ve just said

 

[Spencerleehorton]

Sorry Ian, try this one, if you can find my mistakes i would be very grateful.

 

[Spencerleehorton]

this is the drawing schematic which i'm taking it off

 

[Spencerleehorton]

and heres the other.

i've used 2n2222 for the NPN general transistors and a 2n3906 for the PNP, the Jfets ive used J201 but not got any signal past Q11 yet?
Ive got some 2N5088 which could be used which are quite similar to the 2N3707 which you can see on the schematic.

From what i've seen the JFET used was a 2N5461 which is a P-channel which maybe different from the N-channel one i've used?

If anyone could explain why one would work and one wouldn't i would appreciate it.

Just need to clarify the circuit first and make sure i've done the connection correctly, then i can start messing around with slightly different transistors.

any help on this is much appreciated.

 

[Spencerleehorton]

My findings first are that the Jfet's are are not letting the audio pass as when i take the Jfet J201 out i do get audio to Q11.
I have tried J201, 2N5457, i have 2N5952 and K118, but im pretty sure they are all n-channel?

How have some people got this working with J201?