Did a bad patch cable fry my LA3A?

[riggler]

Well I found that ANOTHER XLR patch cable that I had bought from Markertek about 5 years ago has pins 1 and 2 swapped. It was used between my converter output and the input of my LA3A.

It's the first time this cable has been used with this compressor. I knew it, I should have checked every one of them...

So, I hook it up today, and I start compressing a snare with it, and for a while everything is working fine. About after 2 minutes of messing around all of a sudden the snare track starts blaring through and there is no compression happening. INSTEAD, the VU meter lamp is sagging when compression should be happening!

I turned it off after determining I can no longer get it to compress. I find the offending patch cable, check the rest I have to be sure they are good, and I put a new one in its place. Still won't compress.

I just got the schematic from the Waltzing Bear site. I tried to post it to the Technical Documents page, but it says the uploads folder is full.

So here it is from Waltzing Bear:

Where should I start in looking for the problem? Something in the compression circuit must be causing the voltage to sag at the power transformer secondary.

Is it possible the cable caused this, or was it circumstance? It is an all-original unit and has not been re-capped.

 

[mulletchuck]

side-note, i had a question about the power transformer used on this.  What are the specs for it?  I can't find them anywhere. 

 

[riggler]

Chuck, here is a transformer:

http://www.ebay.com/itm/New-Replacement-Power-Transformer-all-UREI-UA-LA-3A-/320531179580?pt=LH_DefaultDomain_0&hash=item4aa125a83c

 

[ruckus328]

Chuck - what are you asking about the power transformer for?  Do you need one?  I have one here, unused, perfect working condition, hit me up on aim if you need it.

 

[ruckus328]

Damian, ironically enough I just happen to know alot about LA3A's and you just happen to be 45 minutes from me  Let me know if you need any help, I'll be home most of the week next week, if you can't figure it out and want to swing down let me know.

 

[RuudNL]

Is it possible the cable caused this

No. The output is balanced and floating (free from ground).
You can connect pin 2 or pin 3 to ground without any problem.
As long as you don't connect pin 2 to pin 3, it does not harm anything.
I think it was just coincidence...

 

[ruckus328]

Is it possible the cable caused this

No. The output is balanced and floating (free from ground).
You can connect pin 2 or pin 3 to ground without any problem.
As long as you don't connect pin 2 to pin 3, it does not harm anything.
I think it was just coincidence...

Yes, agree, unless somehow some high voltage fried the input or output transformers or something crazy, but don't see how this could be the case.  Should be easy enough to track down the problem, it's a pretty simple circuit, I have all the parts for them here if you need anything.

 

[mulletchuck]

Chuck - what are you asking about the power transformer for?  Do you need one?  I have one here, unused, perfect working condition, hit me up on aim if you need it.

i wanted to figure out what voltages were coming out of the power supply circuit.  wouldn't i need the power transformer ratio to be able to do that?