Purusha

Building Purple MC76 - troubles and solutions
« on: November 30, 2006, 08:11:51 PM »
1. I can't figure out how to solder the round input transformer and if I need to connect any wires to the 6,8 place next to it.





2. Is this the right way to jump the connectors to get 230V?





3. I can't find the place for the 22nF cap anywhere on the board. It's marked as C27 on the paper ... anyone.
Regards as always, Purusha


sintech

Building Purple MC76 - troubles and solutions
« Reply #1 on: December 01, 2006, 05:06:43 AM »
C27 is point to point, fixed to the back of the Attack Pot in parallel with a 470R

sintech

Building Purple MC76 - troubles and solutions
« Reply #2 on: December 01, 2006, 05:32:20 AM »
Regarding the Input transformer, looks to me like the board will accept both PCB pin type, and also a trafo with coloured leads. It would be interesting to see the back of the board at that point.. and the relationship between points 1, 5 7 & 8 any chance of a pic? ;)

Purusha

Building Purple MC76 - troubles and solutions
« Reply #3 on: December 01, 2006, 06:29:59 AM »
Thanks for the help sintech  :razz:

OK, here is the photo


Regards as always, Purusha

sintech

Building Purple MC76 - troubles and solutions
« Reply #4 on: December 01, 2006, 06:52:37 AM »
Cool, looks like you just solder in straight in, the traces on the back act as the wires from the T-attenuator +/- (point 1-5) in and out of the trafo to point 6 and 8

Also..Is the orientation of the trafo marked in any way?

Purusha

Building Purple MC76 - troubles and solutions
« Reply #5 on: December 01, 2006, 07:11:26 AM »
.
Just the wire from one pin to the shell

Regards as always, Purusha

sintech

Building Purple MC76 - troubles and solutions
« Reply #6 on: December 01, 2006, 07:23:28 AM »
Mmmm.. That might be Trafo Pin 7 that goes to the Mu Metal Can..

The Black dot near the 'Altran logo' should indicate Pin 1, how does that figure?

sintech

Building Purple MC76 - troubles and solutions
« Reply #7 on: December 01, 2006, 07:34:07 AM »
From another thread:

Q: I'm building a pair of mc77s with Altran c-3837-1 input transformers provided in the kit from Purple Audio. I have two questions:

1. I installed the transformer so the black dot on the label is above pin 1 on the pcb. Is this correct orientation?

A: yes the black dot indicates pin 1.

sorted! :-)

Purusha

Building Purple MC76 - troubles and solutions
« Reply #8 on: December 01, 2006, 07:41:14 AM »
Oh, yes! Great. Thanks for the help.  :thumb:
Regards as always, Purusha

Purusha

Building Purple MC76 - troubles and solutions
« Reply #9 on: December 01, 2006, 07:44:32 AM »
OK, now I need to solve only the second dilemma

Regards as always, Purusha


hitchhiker

Building Purple MC76 - troubles and solutions
« Reply #10 on: December 01, 2006, 12:11:57 PM »
hey Ed!  

   I read here that the original input transformer UTC 0-12 was wired 500:200 stepdown.
http://www.groupdiy.com/FORUM/viewtopic.php?t=5581&highlight=mc76&sid=fe7cd14e1855d956b9e22f866a458d62

When I measured my Altran c-3837 for resistances I found it to be marked pin one with the dot, a step up transformer copy of the UTC 0-12. If we put the Altran in with pin one matching pin one with the MC77 board numbering, matching #1 to #1, then wouldn't it then be a step up input (200:500) rather than a step down input?

SSLtech

Building Purple MC76 - troubles and solutions
« Reply #11 on: December 01, 2006, 12:19:53 PM »
Quote from: "Purusha"
OK, now I need to solve only the second dilemma


Take a look at the traces on the back. In one position (115V) they should make the primary wiondings parallel. In the other (230V) they should make them series.

Your red-line assumptions are probably correct, but it's a simple matter for you to confirm them yourself by following the traces on the other side of the board.

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Purusha

Building Purple MC76 - troubles and solutions
« Reply #12 on: December 01, 2006, 03:03:24 PM »
Hi Keith,

(blue lines) this is how the connections in the back go ...

Regards as always, Purusha

sintech

Building Purple MC76 - troubles and solutions
« Reply #13 on: December 01, 2006, 03:28:44 PM »
Could that be 115v setting!!?? and the top blue link makes the series connection for 230v??? (Red lines the opposite way)

SSLtech

Building Purple MC76 - troubles and solutions
« Reply #14 on: December 01, 2006, 04:51:58 PM »
Quote
Could that be 115v setting!!??

It would appear so... -unless there's been some confusion when inverting the board to have a look!

Hmmm..

Well you know what I did?

I just wired mine in parallel (115V) and never took the AC to the PCB.

I suggest you just wire yours in series and don't take it to the PCB. -I mean there's no benefit to it anyway, since you plainly don't intend to wire up the 115/230 switch, -right?

Keith
"A waist is a terrible thing to mind"
Quote from: PRR
Ah, but that was 1999; we don't party like that any more.

Purusha

Building Purple MC76 - troubles and solutions
« Reply #15 on: December 01, 2006, 05:00:37 PM »
Uh, it looks like I am too dumb for this. Can you draw a simple picture what do I wire with what?
Regards as always, Purusha

sintech

Building Purple MC76 - troubles and solutions
« Reply #16 on: December 01, 2006, 06:40:07 PM »
The suggested part number is:  Digikey CKC3001  maybe look at the data sheet, but my vibe is: make the Red links from center to top for 230v operation.

Maybe also make a pic of the back section of the Board at this point, just to double check.

I'm planning to skip this switch also :) so eager for conformation.

Purusha

Building Purple MC76 - troubles and solutions
« Reply #17 on: December 01, 2006, 06:45:30 PM »
The blue lines on the photo are the back side tracing

Regards as always, Purusha

sintech

Building Purple MC76 - troubles and solutions
« Reply #18 on: December 01, 2006, 06:49:18 PM »
Follow the schematic with reference to your pic, looks as if your photo is wired 115v.

hitchhiker

Building Purple MC76 - troubles and solutions
« Reply #19 on: December 01, 2006, 09:07:05 PM »
Purusha!  I did the same as Keith, and didn't take the ac to the pcb.  

For 220v primary I figure the split primary is wired in series. I think the primary hook up would be the orange and yellow wires tied and the white and black to the 220v ac . Hook the transformer up that way and measure the secondary voltage.  Mock up a switch affair to confirm the pcb makes the same result . If all checks out you are good to go!


 

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