Testing a LA-2A T4A module?

[jwhmca]

Hi,

I have a LA-2A that has stopped compressing. It passes audio just fine, but no compression.

I have replaced the 12AX7 and tested the 6AQ5

Is there a way to "test" the T4A module or anyway to test the rest of the system for compression issues?

 

[CJ]

pull the cover off and watch for the EL panel to glow with the Peak Reduction control all the way on,

 

[jwhmca]

pull the cover off and watch for the EL panel to glow with the Peak Reduction control all the way on,

Thanks CJ, I'm correct ing understand the EL panel wears out? and no longer glows after awhile?

 

[mulletchuck]

I put these in my LAZ LA3A-500 build.  they work great.  just remember that the white side is the one that lights up.  i didn't discover that for like 2 months cuz i didn't have working op amps in my build (the metal can transistors were shorting out against the pcb) 

http://www.ebay.com/itm/New-EL-panels-for-T4A-T4B-cell-LA-2A-LA-3A-/150764138701?pt=US_Pro_Audio_Parts_Accessories&hash=item231a3e30cd

 

[Brian Roth]

The EL panels can wear out, but other problems can cause the panels to remain dark.  You need to poke around with a scope to be sure the electronics is producing the AC voltage to properly drive the panel.

Bri

 

[SSLtech]

Take the cover off. Run audio through it in a darkened room. -Shine a flashlight on the T4 guts, and you should hear it turn down, and you should also see the GR meter take a dive (one opto turns down the audio, one opto makes the meter dive).

If that works correctly, your EL panel isn't lighting up. -It's scope time. -If you have signal at pin 3 of the T4 octal socket (with the T4 removed is easiest, and watch out, the voltage can be pretty high!) then the EL panel is bad.

 

[jwhmca]

Is it true you can resistance measurement across the EL panel to test for short? Mine measures 1200 ohms... is that bad?

 

[Brian Roth]

1200 Ohms across the EL terminals, with the T4 module removed??  That doesn't sound right, since the EL is essentially a capacitor, and should measure open circuit.

Bri