Power supply seems to work fine until it has a load on it. Puts out 13.8 volts, but will only handle about 2 amp load before the overload protection kicks in. My 2 amp load test is an 1157 light bulb and sometimes I can get it to light two of them. Tried replacing both transistors (2N3055) on back, but didn't help. Visually everything looks fine inside. Any help, thanks.

2 tens are not handling the power load from your amp. The protect light means that the speakers have an overload safety device so you won't fry(literally) the speaker voice coils. I suggest adding more speakers(making sure the ohms are still correct) or more heavy duty higher power handling speakers. If you are unfamiliar with this process, best to utilize the services of a professional.

The Parallax 7155 converter should not require battery support for any 12 volt load amperage that is less than the maximum amperage capacity of the converter. A standard RV incandescent 12 volt lamp draws about 1.5 amperes for each bulb. With the battery disconnected and other 12 volt loads off, turn on lamps (not fixtures) and calculate the number of bulbs which can be turned on. If you run out of lamps, turn on vent fans etc. The idea here is to try to get to 55 amperes of DC load if possible without going over 55 amperes. At a sustained DC load of about 25-30 amperes or higher, the fans should cycle on continuously after about 5 -10 minutes. Lamp brightness should be normal and the measured voltage from the converter should be above 13 volts if under 55 amps of DC load. If the voltage drops with only a few lamps on, a converter issue would be likely.

Diagnostic tests an RV technician should make would be to:
1. Disconnect the battery system.
2. With the converter system powered on, measure the DC amperage with a DC ammeter capable of reading at least 60 amperes DC from the blue lead at the DC fuse panel terminal VCC.
3. Measure the DC voltage at terminal VCC and DC ground.
4. Record both readings.
At any DC load amperage less than 55 amps, the voltage should be above 13.0-13.2 volts DC. This method should take out all guesswork and confirm a DC converter section issue or not.

What is the speaker load in Ohms that you are running? Or what exactly is hooked up to it? are you bridging it? The protection light will come on if the load is too much for the amp to handel. If the load (in Ohms) is less than the rated load that it can run, it will stop the output to keep the amp from self destructing. The amp will sense that the demand for power will be too high for the amps circuitry which will either make the amp get so hot that it will burn up the copper on the board or more likely burn up the power mosfetts that power the speakers. If the Ohms are within range then it will allow power to flow through the circuit until the rails that the mosfetts are bound to until they get so hot that it will go into thermal protection. So if your amp has both thermal and overload protection lights and the overload is light then the load is probably too much for the amp. if it's bridged in mono the you can only have 1 speaker setup hooked up it if it's a 2 channel amp. a 4 channel amp bridged in mono for both front and rear channels will be able to have 2 speakers rated a 4 ohms each hooked up to the amp 1 set per bridged output or channel.
Try it running in stereo with only 1 speaker per channel and see if it will produce sound. If not then you have an amp that has internal problems and will need to be serviced. Check your warranty to see if you are covered.

You are overloading your amp. IMO 640A cannot handle heavy loads.

Better change the speaker combo and connect something that puts right load on the 640A. Else, get a meaty amp from CA.

hows the amp wired from the load of your subs? 2 ohm 4 ohm ect. if the load is too low the amp will shut down and cool off then com eback on, thermal overload protection. if your amps bridged at a 2 ohm load, it more than likely cant handle it so run it stereo mode,

The most common cause is an unsafe load/speaker impedance. If you have the speakers wired correctly, you may have a short in the wiring. If the wiring is OK, the amp is likely defective

Let me know if you have any other questions.

you need to get the voltage regulator circuit checked in your ps-21k

Hi.
It very unlikely the voltage went down. I think you should re measure what the voltage should be yes it 13 volt is after the bridge you wil get this with dual 6.5 volt ac from the transformer, they don't change voltage unless you have a short at the output, and if you did you will blow the transformer, is your reading from 2 wires or is it three wires, output, the center to the end should be 6.5 and end to end maybe 13.8.
I would need to see the schematic to know what voltage you should be getting.
I wouldn't look on a bat transformer but ether, bad bridge or wireing.

I hope this help's

What About Bob

The amplifier may be overloaded, check to see if it can handle 4 OHM loads and 2 OHM loads. if it turns off at high volume the amp may be overloaded. if so try a 8 OHM load. if it still turns off it may be an internal problem.

In most recivers or amps yes if there is a short in one channel all the amps go into shutdown or into the protect mode. Now if you know how an amp works then you should be able with a schematic to find out what amp is causing the over load simply by see in the schematic where the speaker output is on the curcuit and then measure for a DC B+ . Thats the amp you would disconnect to conferm that all the others were ok as an output on an amp curcuit shouldnt have more then .3 to .8 volts dc unless its unbalanced.. Seek a pro to assit you if you dont have the equipment to test the amp and for sure get a service manual or schematic diagram. Good Luck