[BUILD] 1176 Rev A - Back to the beginning...

[ChrioN]

Checking voltages on my rev 1.2 board and having a 0vdc reading at TP11. There should be 10vdc or so at this point. At least on the rev 1.25 board. Every other point of interest measured ok. Where should one look for sources of the issue I'm having? Everything seems correct as far as I can see. Correct values, components etc..the basics

http://mnats.net/files/1176REVA_125_VOLTAGES.pdf

 

[hrby]

So I finally finished up the wiring for the rev a and I was moving on to the calibration.  when i plugged it in and hit the gr button the meter light turned on and the meter moved up.  butmy victory was short lived...i powered it down and then hit the gr button once again and nothing happened this time...ahhhh  there is no burning smells...the fuse looks ok...
where do i begin?
thanks
Dennis

 

[Harpo]

...the fuse looks ok...
where do i begin?

don't look at, measure the fuse for continuity. If the fuse measures infinity ohms (=fuse blown), you just might have fitted a wrong value fuse. Min.value fuse rating and fusing characteristic is dependant on your kept a secret type and VA-rating of your mains transformer and your kept a secret local mains voltage. Good luck.

 

[hrby]

I am in need to some help.  I have finished up my rev a original  build and I am on to the calibration.  The first thing that I notice is that my output knob is working backwards.  When I turn it up I see and hear less output from the unit and when I turn it down I get more.  There has to be something simple that I am missing?  I hope it's simple..where do I start

thanks

Dennis

 

[Echo North]

I am in need to some help.  I have finished up my rev a original  build and I am on to the calibration.  The first thing that I notice is that my output knob is working backwards.  When I turn it up I see and hear less output from the unit and when I turn it down I get more.  There has to be something simple that I am missing?  I hope it's simple..where do I start

thanks

Dennis

You've just got it wired backwards.

You've got the wiring to the two outer terminals on the pot reversed or 15 and GND reversed at the output pot terminal block.

 

[hrby]

i am on to the calibration phase of the old rev a build.  i have noticed that the output knob is reversed.  so when i turn it up the output level decreases.  i think that i need to resolve this before i can get thru the calibration.  any ideas where i begin? 

 

[Echo North]

i am on to the calibration phase of the old rev a build.  i have noticed that the output knob is reversed.  so when i turn it up the output level decreases.  i think that i need to resolve this before i can get thru the calibration.  any ideas where i begin?

Hi,

I answered this in the post above last week.

You've got it wired backwards.

Mike

 

[hrby]

I reversed the wirering of the output knob.  here is what i have.  pad 15 from the ratio and 15 from the main pcb going to the right lug on the output ground from the ratio and main pcb 16 going to the left lug and main pcb 17 going to the center lug. its getting a bit sloppy because i have taken them off and on so many times.  i am stuck.  i am no longer getting the tone coming thru the output transformer.  i can't hear it like before. 

i am sooo close...at least i think

 

[mattmartin831]

I noticed on mnats site the etch files for the V1.0 main board are downloadable as a pdf, but it does not include etch files for the switch boards. Does anyone know where I can find etch files for the ratio switch board and vu controls switch board?

 

[Echo North]

I reversed the wirering of the output knob.  here is what i have.  pad 15 from the ratio and 15 from the main pcb going to the right lug on the output ground from the ratio and main pcb 16 going to the left lug and main pcb 17 going to the center lug. its getting a bit sloppy because i have taken them off and on so many times.  i am stuck.  i am no longer getting the tone coming thru the output transformer.  i can't hear it like before. 

i am sooo close...at least i think

You just need to go through that wiring again, replace if needed, and confirm all connections are making contact.  Make your wat through the wiring guide again.

Mike

 

[hrby]

there was a wire that came loose on the input transformer. ...thanks for that...
the other issue that i have blown 4 fuses that came from you guys the 250ma 250v ones.  i was reading that you have increased them to 350mA-400mA SLO BLOW fuse

is this my issue?

 

[Echo North]

there was a wire that came loose on the input transformer. ...thanks for that...
the other issue that i have blown 4 fuses that came from you guys the 250ma 250v ones.  i was reading that you have increased them to 350mA-400mA SLO BLOW fuse

is this my issue?

400mA is correct for 120 mains.  We adjusted that a year ago.

You output is still backwards? That should be a real easy fix. Your output must be wired backwards.

Mike

 

[nickcion]

hello. i have a fresh built Rev A on the bench. not getting any signal after the input transformer. soldering is good. i have it scoped up with a 1k sine wave going in.

other weird thing i found while poking around is that the input gain pot shows no change in amplitude upon the input signal any any pad. just the same constant signal on my xlr.

how can i check the transistors in circuit? i assume I'm looking for a short to ground in my signal path?

any direction is helpful

 

[Echo North]

hello. i have a fresh built Rev A on the bench. not getting any signal after the input transformer. soldering is good. i have it scoped up with a 1k sine wave going in.

other weird thing i found while poking around is that the input gain pot shows no change in amplitude upon the input signal any any pad. just the same constant signal on my xlr.

how can i check the transistors in circuit? i assume I'm looking for a short to ground in my signal path?

any direction is helpful

The signal will be very very small after the input transformer. Less than 100mV.

Set your unit to:
Input: 12 O’Clock
Output: 12 O’Clock
Attack: GR OFF
Release: Full CW
Ratio: 20:1
Meter: GR
Signal: Sine 1kHz @ 0dBu

With your DMM measure your AC at the following test points using the chassis as you reference (black probe).

-Input XLR +
-TP1
-TP15
-TP17
-Output Transformer BRN
-Output XLR +

 

[nickcion]

-Input XLR +  = .775v
-TP1  = 2.0 mV
-TP15 = 100mV
-TP17= 15mV
-Output Transformer BRN = nothing?
-Output XLR +  =239mV

 

[Echo North]

-Input XLR +  = .775v
-TP1  = 2.0 mV
-TP15 = 100mV
-TP17= 15mV
-Output Transformer BRN = nothing?
-Output XLR +  =239mV

You are losing signal after your input.  A bad input would be VERY rare so I would not expect that straight out.  Do you have the older version with input on its own PCB?

If so double check your wiring.

Using the test above, what is your AC at:

TPAD PCB in+
TPAD PCB out+
Input transformer  PCB in+
Input transformer  PCB out+

Mike
(I'll be offline the rest of the day)

 

[nickcion]

This is  a brand new pcb. I assume newest revision. just got it in the mail.

will wait to hear from you. thanks so much.

 

[Echo North]

You are losing signal after your input.  A bad input would be VERY rare so I would not expect that straight out.  Do you have the older version with input on its own PCB?

If so double check your wiring.

Using the test above, what is your AC at:

TPAD PCB in+
TPAD PCB out+
Input transformer  PCB in+
Input transformer  PCB out+

Mike
(I'll be offline the rest of the day)

I'm going to move this so the proper thread...
https://groupdiy.com/index.php?topic=63600.0

 

[eriksunding]

I'm helping a friend out with a build he's doing. He's done 2 of the Rev A's and got one of them to work perfectly but not the second one.
Signal is passing thru but there is no compression. Also when switching to GR mode the needle isn't moving to 0.

From what I could find, so far, when comparing them both to each other the volt value of Q5 and Q6 are different. The one that isn't working are showing these values:
Q5
Base: 1,3v
Collector: 27v
Emitter: 0.7v

Q6
Base: 0.7v
Collector: 30v
Emitter: 0.1v

Any idea what might be the cause? Transistor broken or maybe something else affecting these? Anything I could look for?

Thanks

 

[eriksunding]

I also have 0 VDC on TP18 and on either side of r83 and r60.