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Pyle Pro PTA1400

Shblack

Mar 13, 2023
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We have a small community center where locals get together and jam once a month, some are pretty darn good. The audio system includes a Pyle Pro PTA1400 power amp. Channel A has been problematic for a while, turn it on, no sound, turn the volume way up, there is a deafening bang, then it would work normally. It has now died on channel A, channel B continues to work fine. Did the usual cable swap, no joy, it’s the amp. Opened it up, wiggled connectors, tapped on things, flexed boards a bit, not a peep. We are in a rural area, services are a hour or two away so I took on the project of trying to get it fixed. First, does anyone have a schematic they could share? I contacted Pyle, so far no response. Any suggestions as to what to look for - problem seemed like something was breaking down with the volume up high?
 

kellys_eye

Jun 25, 2010
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Check the connections from the circuit board to the speaker output terminals. I suspect a loose connection at the circuit board - around the main output capacitor(s).
 

Shblack

Mar 13, 2023
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Check the connections from the circuit board to the speaker output terminals. I suspect a loose connection at the circuit board - around the main output capacitor(s).
the R/L PA boards connect through the power supply board to the speaker terminals. I first checked continuity between the P/A board and the output terminals, open circuit. But it was open in both sides, including the working side. Pulled the power supply board, found that the P/A outputs run through a relay to the speaker terminals, suspect this is part of the protection circuitry. Examined all solder connections under 5X mag, didn’t find anything. Measured continuity between the P/A output and the relay, relay to the speaker terminals. When powered up, channel A’s P/A output is sitting at 28mv, which also appears at the speaker terminals, channel B was at 78mV. Both cases are no load, no input. Smells like the P/A itself, wish I had a schematic.
 

kellys_eye

Jun 25, 2010
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We can only offer guesses here. Lacking a schematic makes it hard - lacking pictures doesn't help either.....
 

Shblack

Mar 13, 2023
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We can only offer guesses here. Lacking a schematic makes it hard - lacking pictures doesn't help either.....
Here are some photos, left is the power supply board, black cube is the overload relay. Second from left is the PA board with no output. Board does appeared to have been worked on in the past, there is a black smudge next to a power transistor that looks to have been replaced. Center is the rear board with the I/O connectors on it. Second from left is a downward view showing the toroidal power transformer and power supply board, left is the front panel. A schematic would be invaluable, still no word from Pyle.
 

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Shblack

Mar 13, 2023
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Given this, I'd tend to check the volume control and surrounding area.
The output from the two volume controls connects to the A (defective) and B (working) power amp inputs via a pair of 2-pin plugs. With the plugs disconnected each input to the amp measures 19.5K-Ohms to ground. Measuring from the 2-pin plug to ground each measures 0 to 10K-Ohms depending on the volume control setting. Measuring from the amplifier input to the 2-pin plug, each measures 29.5K (volume down) to 19.5k-Ohms (volume all the way up). Basically both sides measure the same, plus nothing seems intermittent when I run the volume up and down. Sure wish I had a schematic!
 

Delta Prime

Jul 29, 2020
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Could not find a single schematic.Apologies if you've already seen this...
Pyle PTA 1400 Power Amplifier Repair.
 

Shblack

Mar 13, 2023
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I finally heard back from Pyle’s customer support folks “Thank you for reaching out. I will be happy to help. We, Pyle, is not giving out schematics or circuit board diagram of any of our products. Can you please tell us more about the issue you are having with the unit? Please tell us when did you purchase the unit?”

Not very encouraging. This is after their on-line chat told me that the unit was discontinued and thus schematics were not available. You know this makes no sense, a PDF document is liable to hang around in the archives forever. So I responded, explained the problem, see what happens. Next step is a polite letter to the CEO, seeing if he is willing to step in. Behavior like this is why “right to repair” laws are gaining traction. The PA circuit board is single sided, not the end of the world to trace & draw a schematic but hate to spend the time.
 

kellys_eye

Jun 25, 2010
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The amplifier clearly has two identical channels (modules) so you could compare voltages on each side to see where there are specific differences.

The large 'bang' does, however, point to intermittency in the speaker outputs. Whether this is as a result of a dry joint on the board that holds the speaker connection sockets or a loose pin actually IN the socket also needs to be determined. A continuity test from the speaker lead to the back of the socket (on the pcb) whilst giving it a good jiggle might reveal something.

It's a 'bog standard' linear BJT audio amplifier (dual units but capable of being connected in a 'bridge' form to increase the output power) and 'basic' schematics are probably available on t'internet if you search for those that use the 2SA1941/2SC5198 pair in the output stages.

You should note that the 'identical' modules are not 'mirrored' in that the 2SA1941 is upper-most on one module and 'down-most' on the other. You do not specify which module is dud but you should remove them both to access the power transistors on the other side of the heatsinks to make checks on their functionality.
 

Shblack

Mar 13, 2023
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The amplifier clearly has two identical channels (modules) so you could compare voltages on each side to see where there are specific differences.

The large 'bang' does, however, point to intermittency in the speaker outputs. Whether this is as a result of a dry joint on the board that holds the speaker connection sockets or a loose pin actually IN the socket also needs to be determined. A continuity test from the speaker lead to the back of the socket (on the pcb) whilst giving it a good jiggle might reveal something.

It's a 'bog standard' linear BJT audio amplifier (dual units but capable of being connected in a 'bridge' form to increase the output power) and 'basic' schematics are probably available on t'internet if you search for those that use the 2SA1941/2SC5198 pair in the output stages.

You should note that the 'identical' modules are not 'mirrored' in that the 2SA1941 is upper-most on one module and 'down-most' on the other. You do not specify which module is dud but you should remove them both to access the power transistors on the other side of the heatsinks to make checks on their functionality.
Well, my ancient tektronics scope died, ended up getting a less ancient 2230 plus a CFG250 function generator. Got the amp hooked up, each channel loaded with an 8-ohm, 100W resistor, resistors connected to the binding posts on the rear of the amp. Both channels have been working flawlessly for the last 6 hours, each pumping 20Wrms into a load. Will shut down and see if it starts up cold in the AM. One difference is I am using the binding post outputs, wondering if I have inadvertently found the problem, we were using the speakon outputs at the community center.
 

Delta Prime

Jul 29, 2020
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Well, my ancient tektronics scope died, ended up getting a less ancient 2230 plus a CFG250 function generator. Got the amp hooked up, each channel loaded with an 8-ohm, 100W resistor, resistors connected to the binding posts on the rear of the amp. Both channels have been working flawlessly for the last 6 hours, each pumping 20Wrms into a load. Will shut down and see if it starts up cold in the AM. One difference is I am using the binding post outputs, wondering if I have inadvertently found the problem, we were using the speakon outputs at the community center.
Hehe! I wouldn't say inadvertently.
She is my wonderful, constant companion."Serendipity!!"
 
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