21-08

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Vas

Well-known member
Joined
Feb 9, 2008
Messages
199
Location
Greece
hi everyone!!!
i recently purchased 2x2108 faceplate with all switches and main pcb attached from ebay!!!

i was wondering as those are long out of production we could create a project out of this...

i already have a 2108 and its really great preamp so i was thinking if i could make some research and haunt the parts that would be a great project for everyone!!!!

this design uses cinemag 2610-IT input trafos and trafos simillar to the rev d/a project that are avaailable from mike at hairball!!!

other parts are some electroswitch switches and a couple of pots others are resistors,transistors and caps,i'm working on the values/types right now so maybe we can make a pcb and make this available...

let me know what you think....

best

bill
 
hi bill,
this sounds like a great project! 
i know this has come up before, but i don't think anyone had an actual unit in hand to research.

along with components and part numbers can you trace out a schematic?

i'm not sure about the input transformer.  if it is the same as the 610 mic pre input, it could be a CMMI-10C (1:10) - but i'm not sure.

I'm sure the ed anderson EA-5002 will work on output as it is a replica of the UA-5002 for the 1108 line amp.

there is a fet preamp section before the 1108 line amplifier in the 2108 that has eluded people.  this would be very interesting.  can you take pics or scan the PCB.

go for it bill!!
kind regards,
grant
 
hi grant!!!!

actually i dont have any experience on doing that but i have compete some projects and i am a quick learner ;)

anyway

i dont have a schematic thought it would be helpful...i do have a 1108 schematic but 2108 seems a bit different!!!!

regarding transformers,input trafos are made by cinemag and they are labeled 2610-IT no info on their site thought....outputs are ua 5002 copies just like edan adersons!!!!

i will have to do some work and find out values/types of the components,thought there three additional pcbs  on the unit  a relay pcb connected at the output a pcb for the power on/off and final one that should be an additional circuit that i cannot really tell without the schematic!!!

anyway those pres sound really amazing and should be a great project!!!!

thought i will definitely need anyones help...i could send the pcbs to any of the labs members that could help on that!!!!

best

bill
 
hi bill,
doubt we'll find a schematic for this so we're on our own.   thank you for taking the time to take those pictures.  i suppose it is alright to look into cloning this as it is a out of production unit, but ua still owns the rights to it so....we'll call it research and not make an exact clone.

the 1108 schematic will be helpful for the line amp section only of the 2108.  ua supposedly designed a new FET front end (pre-line amp section) for more gain on the input section to be used as a mic pre.  maybe look at mnats 1176 Rev.A for similarities to the front end section since that was supposedly the inspiration for the new frontend.  i think John H. (W.O'Boogie) stated that the newer 610 pres had the Cinemag CMMI-10C as input and they may have used the same transformer for the 2108.

if the front end is in fact very similar to the Rev.A then we have a pretty good idea of what's going on.  is the input transformer going straight into the gain switch?  is the first stage of the front end a fet (2N5457)?

you can trace the circuit.  i believe in you. ;)  and besides, you do need to know more about this circuit to complete the empty PCB which will help you troubleshoot any problems when you work on this build.

don't get distracted by the utility parts (metering, pad, phantom and polarity networks).  the relay PCB on the output XLR is probably for pad (if it has 3 resistors, protection diode and a cap) or a polarity (just the relay with protection diode and cap).  V+ is needed on that relay PCB to power the relay switching.  look to see if the V+ is coming from one of the switches on the front panel for the utilities and that will tell you which one it is controlling.
i believe that the front end also has a DI circuit and related switching as well.

i could not really see the third PCB you were talking about (the thin one.  it looks to just have resistors on it though it's difficult to tell from the pics as to what the IDC connectors are  

i'd be happy to help trace it with the spare PCB you have, but it would probably be easier for someone who lives near to you as i'm in the US (California).
can you get really good high rez pics of both sides of the PCB (stuffed PCB and empty PCB)?
cheers,
grant
 
Please scan the PCB front and back and send it to the Gmail account, I'm sure we can come up with schematics. also include the transformer models and lots of pictures of hte stuffed PCB.

Kaz...

http://www.waltzingbear.com/Schematics/Urei.html

I'm sure looking at the 1108 would be a start....
 
dissonantstring said:
hi bill,
doubt we'll find a schematic for this so we're on our own.
hey grant!!!i have a friend working at the distributors shop so we may find a service manual that i am sure it contains the schematic ;),not sure thought,but i will give it a try!!!!

dissonantstring said:
the 1108 schematic will be helpful for the line amp section only of the 2108.  ua supposedly designed a new FET front end (pre-line amp section) for more gain on the input section to be used as a mic pre.  maybe look at mnats 1176 Rev.A for similarities to the front end section since that was supposedly the inspiration for the new frontend.  i think John H. (W.O'Boogie) stated that the newer 610 pres had the Cinemag CMMI-10C as input and they may have used the same transformer for the 2108.
i'm sure about what those are labeled but maybe its a unique and not a product line code from cinemag?
what I'm saying is that maybe they used a trfo from cinemags line but rename it?
maybe contacting cinemag?

dissonantstring said:
if the front end is in fact very similar to the Rev.A then we have a pretty good idea of what's going on.  is the input transformer going straight into the gain switch?  is the first stage of the front end a fet (2N5457)?

there are 7 wire coming out of the transformer,2 of them black,white goes to the ground,3 of those grey,red and orange are connected to the mic input not direct but through the pcb and the last couple yellow and green it is connected on the pcb but paralleled direct to the switch too!!!

components that are used and can help you figure out some things are
2n3053,lm-317,lm-337,lm-1085,tl783c,lm3915n-1,2n3906,2n3904-308,2n3391a,2n3707,k170 bl4c,k246 bl31,k389 ,no 2n5457 hope this helps!!

dissonantstring said:
don't get distracted by the utility parts (metering, pad, phantom and polarity networks).  the relay PCB on the output XLR is probably for pad (if it has 3 resistors, protection diode and a cap) or a polarity (just the relay with protection diode and cap).  V+ is needed on that relay PCB to power the relay switching.  look to see if the V+ is coming from one of the switches on the front panel for the utilities and that will tell you which one it is controlling.
i believe that the front end also has a DI circuit and related switching as well.
the relay pcbs consists of 47uf/50v electrolytic,a 0.47uf,0.22uf wimas,a resistor a diode an ne555n k53340 labeled ic and nec ec2-12nj relay this is connected to the power switch pcb and the outputs....

as for the third pcb it consists of 6 resistors and 3 caps i will get the values and i will let you know!!!

i was thinking scanning and hires photo everything and when I'm finished comparing stuffed and unstuffed  pcb send it to someone that can help with Gerber's and construction!!!
best

bill

 
hi bill,
it would be great if your friend did indeed have the service manual.  things would be a lot easier to trace.

i would do as kazper and i suggest and scan the blank PCB (top and bottom) and if you can do an overlay image of both sides with some software.

the input transformer probably isn't essential to get the exact model as long as the ratio is correct.  all cinemag transformers spec very well as far as frequency response in many conditions.  it may be that it is just an "off-the-shelf" 1:10 or 1:7 mic input transformer which was renamed.  W'OB may have actually have helped specify the requirements for this transformer with his work in design for the ua610 which i think became a part of cinemag's product line (CMMI-10C).  so yes, it may just be an "off-the-shelf" transformer.

lm-317,lm-337,lm-1085,tl783c,lm3915n-1 transistors - pretty sure they are all for V+/-, phantom and metering. 

2n3906,2n3904-308,2n3391a,2n3707,k170 bl4c,k246 bl31,k389 transistors - amp sections?  pretty standard transistors, but
k170 = Toshiba JFET(?) 
k389 = 2SK389(?) what does the transistor look like (how many legs)?
k246 = another toshiba part?

for the bl4c and bl31 = BL4C and BL31? or B14C and B131? either way not familiar.

good work so far bill!
keep it coming!
-grant





 
dissonantstring said:
i would do as kazper and i suggest and scan the blank PCB (top and bottom) and if you can do an overlay image of both sides with some software.

I can do that fairly easy with some good quality scans.
 
kazper said:
dissonantstring said:
i would do as kazper and i suggest and scan the blank PCB (top and bottom) and if you can do an overlay image of both sides with some software.

I can do that fairly easy with some good quality scans.

great i will do that!!!!!
 
dissonantstring said:
hi bill,
it would be great if your friend did indeed have the service manual.  things would be a lot easier to trace.

i would do as kazper and i suggest and scan the blank PCB (top and bottom) and if you can do an overlay image of both sides with some software.

the input transformer probably isn't essential to get the exact model as long as the ratio is correct.  all cinemag transformers spec very well as far as frequency response in many conditions.  it may be that it is just an "off-the-shelf" 1:10 or 1:7 mic input transformer which was renamed.  W'OB may have actually have helped specify the requirements for this transformer with his work in design for the ua610 which i think became a part of cinemag's product line (CMMI-10C).  so yes, it may just be an "off-the-shelf" transformer.

lm-317,lm-337,lm-1085,tl783c,lm3915n-1 transistors - pretty sure they are all for V+/-, phantom and metering. 

2n3906,2n3904-308,2n3391a,2n3707,k170 bl4c,k246 bl31,k389 transistors - amp sections?   pretty standard transistors, but
k170 = Toshiba JFET(?) 
k389 = 2SK389(?) what does the transistor look like (how many legs)?
k246 = another toshiba part?

for the bl4c and bl31 = BL4C and BL31? or B14C and B131? either way not familiar.

good work so far bill!
keep it coming!
-grant
i will update u asap!!!!
 
thanks for your "research" on this bill.  very much appreciated!

kaz, can you do the a trace overlay of the top and bottom like the LA-3 (x-ray) scan/image floating around.  that would make tracing much easier i think.

cheers,
grant


 
I can post the pcb to kazper cause i cannot really scan it as it has switches and pot already soldered!!!!

will that work?

if it does pm me your address!!!

also i have been working on a bom and all the parts seems to be an easy trace,only gain switch seems hard to get but i think we can replace this easily?...though,i will have to draw a schematic for the 3 pcbs i don't have unstuffed,but i will do that next week as i am on vacation now!!!!

all the best

bill
 
hi bill,
can you desolder the pots, gain/rotary switch, jack and pushbuttons?  remove the front panel then you can desolder the pot, switches and jacks more easily.  just make notes as to which switch goes to which pads and also the orientation if need be (i have a bad memory so i always make notes for myself  ;D).

if you can't do the scan and kazper for some reason can't do it, i could do it for you i think.  what are the dimensions of the large PCB? 

i have a scanner, but no graphic software for a good overlay image.  :-[  i could send the scan file to kazper to pretty it up. 

bill, i just noticed something on the output transformer image.  it is a little difficult to tell, but it looks like the output transformer has 10 wires coming out of it connecting to the PCB.  are there 8 or 10 wires (the EA-5002 has 8) on your output tranformer?

cheers, grant

 
sorry for the delay!!!!!!

i was on vacation when when i got back we had to transfer the studio to a new location!!!

anyway!
got some free time and made some progress with this!!!

so i got an almost full bom(some diodes are missing but I'm working on that!)

and made some drawings of the secondary pcbs!!!

so we are almost there!

i will send the pcbs to kazper or grant so we can get some good scans!!!

all the best

bill
 
grant!

output trafos are identical to hair balls!!!

I'm working on a wiring diagram right now!!!
 
I had already figured that the output transformer is covered under the Cinimag or one of EA versions that are available via Mikes shop.

Send me a email and we can talk about the PCB scan's etc.. Just press my
email_sm.gif


BTW I almost won some Neve EQ PCB's of the bay a few weeks ago but I couldn't beat a bigger bank.

Kaz
 
hi bill,
were you able to make any progress on the scans of the PCB or tracing the circuit?

also, i am curious as to what the model number is on the cinemag input transformer (it's a little difficult to read from the pictures).
edit: sorry Bill i remembered that you mentioned the input transformer model number in the first post - 2610-IT :-[

on-ward!
kind regards,
grant
 
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