Channel strip test procedure

[Sturoc]

Would like to know how to go about testing IC based channel strip.
Basically to see if the strip is working 100% as it should and to pinpoint any failing parts that need to be replaced
I have over 24 strips to check and cannot afford sending them out or having a good tech do the work,
Right now they are pulled but can be mounted back in the console's mainframe or tested individually on a bench with an external p/s

Am good with basic parts replacement stuff per soldering but would like to go deeper and learn more.
If anyone can offer a step by step how-to, this would be most appreciated, along with any Test gear suggestions i.e a scope ?

 

[Brian Roth]

A test signal generator is the very first item you need. A DAW can be used, but having both a sine AND a square wave signal isn't always easily produced with a DAW's basic "test tone" facilities. I prefer a stand-alone generator. I've observed some very competent ProTools or Logic users having to dig around in the menus to find the tone generator and then fiddle with the on-screen controls.

A scope is an essential tool if you want to go any further than "well, that channel seems to be passing some sort of signal..."

Bri

 

[Sturoc]

A test signal generator is the very first item you need. A DAW can be used, but having both a sine AND a square wave signal isn't always easily produced with a DAW's basic "test tone" facilities. I prefer a stand-alone generator. I've observed some very competent ProTools or Logic users having to dig around in the menus to find the tone generator and then fiddle with the on-screen controls.

A scope is an essential tool if you want to go any further than "well, that channel seems to be passing some sort of signal..."

Bri

Thanks Bri for the quik reply,

Will acquire a test sign gen and keep my eyes out for a good used Scope. About 2/3rds of the channel strips passed a mic signal before i pulled them for inspection and cleaning, the remaining did not or barely. So I will have to go further in testing.
Any tips on that level of testing would be greatly appreciated.

 

[gyraf]

Do you have schematics? If so, please post it..

 

[Sturoc]

Do you have schematics? If so, please post it..

Will post in the morning .

 

[Brian Roth]

Out of curiosity, what desk are you testing? Perhaps I can offer more specific testing.

Often, just removing modules, carefully cleaning the innards and reinserting them MIGHT clear some problems. Having the frame and a working power supply is a huge bonus for you. (sidebar....you know NOT to remove or insert modules with the power on.....)

I don't have a "new" suggestion for a generator but I used (still do) use one of these antiques:



I built the kit in the mid 1980's. Purists will SCREAM...."UGH! A function generator has horrible distortion levels on the sine wave out!" OK....maybe 0.5% THD. If you want ultra low distortion, then spend 4-figures for an Audio Precision. I like the specs of the wide frequency range, ULTRA flat frequency response, and ultra fast settling time when sweeping frequencies. Perfect for me when aligning tape machines. Plus, it's compact. And it can produce a square wave....more on that later.

I am sure my comments will ignite a flame war here...lol. "OMG You need a HP model 122342715!" "No, you need a BippityBoppityBoo model WTF47965!"

Sidebar....our own John Roberts designed a test set marketed by Loft. That was years ago and I forget the model number......TS-1? Cool unit if you can find one in good condition (but alas, no square wave out).

Again showing my age....for years I used a Tektronix 2215 scope. 60 MHz bandwidth dual trace. I recall when I bought it new in the 1980's it cost $2200 ($6600 today). Plenty of bandwidth for audio (but nowadays "lame" when probing around inside high sample rate/high bit width digital stuff). The 2215 was smallish for it's time.

I now have a much smaller Rigol (model????) with a fancy color screen, yada yada. Cost $500-ish. It does the job, but with only 8 bit sampling so waveforms are "jaggedy" (newer units are 12 bit) and a slow...think it's called refresh rate...it acts like a slug when rapidly changing levels or frequency. The other day I fired up my old 2215 to see if it still worked (yes) and I realized how painfully slow the Rigol "reacted".

Folks here will scream "well, you need faster digital scope." OK....so gift me some money for a new five-figure Tek digital scope! Christmas is coming up....lol!

Square wave signal generator along with a scope lets you quickly detect dying lytic caps in a console's signal path and also do a quick check of the action of EQ on each channel. I am really simplifying things here, but I can elaborate....and I bet others will chime in!

Bri

 

[ruffrecords]

I have two scopes. A digital one for making fancy measurements and grabbing pretty pics into my PC and a proper analogue one sitting underneath it for when I want to see what is actually going on.

Cheers

Ian

 

[Brian Roth]

I have two scopes. A digital one for making fancy measurements and grabbing pretty pics into my PC and a proper analogue one sitting underneath it for when I want to see what is actually going on.

Cheers

Ian

Your analog scope is how old? Do you expect the fancy looking digital scope to last that long? <G!> I will be surprised if the Rigol lives for 5 years......but it looks really fancy dancy with the color screen and menus!

Bri