pucho812

another a-range channel strip puzzle
« on: October 04, 2020, 12:45:08 PM »
This is a puzzler sort of.  I was going over some channel strips at the studio and noticed one of them had the following problem, I got a huge drop in level with the EQis inserted while the boost and cut on all four bands are  at unity.  This is a good 6dB or so difference compared to a working channel, where with the same settings  I have less then half a dB when the eq is inserted.   I have confirmed measuring at the output of the EQ output amp that we have a  the difference as well as confirmed it on the VU meter, and other test equipment.  Since all 4 eq bands are working and are the filters,  would it be safe to assume the problem is in the output amp and although working the amp is not working correctly, either by having a failed component or  bad solder joint or bad trace?

 
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


abbey road d enfer

Re: another a-range channel strip puzzle
« Reply #1 on: October 05, 2020, 01:37:10 AM »
6dB loss is typical of losing a leg in a balanced connection. Without a schemo or a crystal ball it's tough to guess.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

pucho812

Re: another a-range channel strip puzzle
« Reply #2 on: October 05, 2020, 06:39:32 PM »
6dB loss is typical of losing a leg in a balanced connection. Without a schemo or a crystal ball it's tough to guess.
I understand, I can get a good copy shortly.  I am just pondering how a 3 transistor amp can work to any extent of one of the transistors?
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.

QUEEF BAG

Re: another a-range channel strip puzzle
« Reply #3 on: October 05, 2020, 07:45:19 PM »
most likely a transistor (output amp)
loss of ground will once in a while be an issue for a section of these modules...
and each section has it own ground trace.

i have been using these replacements:
413  -  2n2484
416 -   5087 (backwards due to pinout) sometimes a 3904
40361 - 2219A
40361 - 2905A
« Last Edit: October 05, 2020, 07:56:54 PM by QUEEF BAG »

pucho812

Re: another a-range channel strip puzzle
« Reply #4 on: October 05, 2020, 08:34:07 PM »
most likely a transistor (output amp)
loss of ground will once in a while be an issue for a section of these modules...
and each section has it own ground trace.

i have been using these replacements:
413  -  2n2484
416 -   5087 (backwards due to pinout) sometimes a 3904
40361 - 2219A
40361 - 2905A

nice thanks... We have parts bins galore so I should be o.k. I didn't dive into it further yet, got dragged away
into other things
You tell me whar a man gits his corn pone, en I'll tell you what his 'pinions is.


 

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