I have an amplifier ICA2400 ( Industrial Contractor Amplifier) made by Peavey.
The problem is that the LFC (LOAD FAULT CORRECTION) LED is lighting up only on channel A, and the protect light comes on. i don't have any input or speakers connected to the amp.
The manual description of the LFC is
LFC is an innovative circuit that will instantaneously reduce channel gain to allow the amplifier tooperate at a safe level into an abnormal load. LFC activation is indicated by illumination of the LFCLED. Moderate activation of LFC is inaudible in normal use. In addition, if extreme low impedance ora short circuit is encountered during high signal level conditions, the amplifier’s output relay will open.
Can anyone advise me on what could be the problem and what to test. I have a little knowledge in electronics but willing to learn a bit more.
The problem is that the LFC (LOAD FAULT CORRECTION) LED is lighting up only on channel A, and the protect light comes on. i don't have any input or speakers connected to the amp.
The manual description of the LFC is
LFC is an innovative circuit that will instantaneously reduce channel gain to allow the amplifier tooperate at a safe level into an abnormal load. LFC activation is indicated by illumination of the LFCLED. Moderate activation of LFC is inaudible in normal use. In addition, if extreme low impedance ora short circuit is encountered during high signal level conditions, the amplifier’s output relay will open.
Can anyone advise me on what could be the problem and what to test. I have a little knowledge in electronics but willing to learn a bit more.
Some versions of the gain reduction circuit use an electrolytic capacitor to control the gain in a smooth fashion. After 20 years or more these can go leaky. The previous model I have uses a 2.2 uf cap into the gate of the jfet.
Check the peavey website, the service section, for a schematic diagram. If not there, phone them and they will usually e-mail you a copy. They also sell parts: obsolete parts like the J174 they are the best source because they buy 1000 every so often, whereas distributors don't stock them anymore.
For instant gratification, you can look at the DDF circuitry on the PV1.3k schematic on eserviceinfo.com The J174 crams down the input signal to the power supply rail, based on what the connected current amp is detecting of the high frequency content. LFC would move on to detect excessive current out the output, and provide additional input to the signal cramming jfet or equivalent.
Check the peavey website, the service section, for a schematic diagram. If not there, phone them and they will usually e-mail you a copy. They also sell parts: obsolete parts like the J174 they are the best source because they buy 1000 every so often, whereas distributors don't stock them anymore.
For instant gratification, you can look at the DDF circuitry on the PV1.3k schematic on eserviceinfo.com The J174 crams down the input signal to the power supply rail, based on what the connected current amp is detecting of the high frequency content. LFC would move on to detect excessive current out the output, and provide additional input to the signal cramming jfet or equivalent.
Is there DC voltage coming out of the speaker outputs? more than 0.15 V? Sign of bad output stage or bad idle bias control or bad centering. DC on speaker terminal will make the load fault light come on, usually. Also other things of course, you have to look at the design to see all the inputs to the fault detect circuit. The CS800x schem is useful, the fault detect was done in op amps before the next gen they put it all in a microprocessor softwhere where you couldn't see the calculations being made in hardware.
Did you get the schematic e-mailed to you from Peavey? They had an operation in Greece at one time. Usually they don't mind if you post it on-line.
With 2.2 uf caps costing $.06 each, and freight from farnell at $9 for each box, if I order one part for an amp, and it is over 15 years old, I order ALL the e-caps. I may not change them all as I work through the problems, but I change them ALL before I put the cover back on. Heck, the 10000 or 15000 uf main caps are down from $15 three years ago, to $5 now for the 3000 hour service life grade.
See the old amp repair thread here: http://www.diyaudio.com/forums/solid-state/136261-vintage-amplifier-repair-upgrade-manual.html
Don't post to that thread, but what Sakis (salis?) posts is mostly true. You could work through a trade school textbook to learn to spot shorted/open transistors and diodes, and how to use a DVM , which he doesn't cover very much. Shorted caps are pretty easy to spot, too, no Dc across them in the right places for DC to occur.
Did you get the schematic e-mailed to you from Peavey? They had an operation in Greece at one time. Usually they don't mind if you post it on-line.
With 2.2 uf caps costing $.06 each, and freight from farnell at $9 for each box, if I order one part for an amp, and it is over 15 years old, I order ALL the e-caps. I may not change them all as I work through the problems, but I change them ALL before I put the cover back on. Heck, the 10000 or 15000 uf main caps are down from $15 three years ago, to $5 now for the 3000 hour service life grade.
See the old amp repair thread here: http://www.diyaudio.com/forums/solid-state/136261-vintage-amplifier-repair-upgrade-manual.html
Don't post to that thread, but what Sakis (salis?) posts is mostly true. You could work through a trade school textbook to learn to spot shorted/open transistors and diodes, and how to use a DVM , which he doesn't cover very much. Shorted caps are pretty easy to spot, too, no Dc across them in the right places for DC to occur.
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