i will do so.
I assume i will be checking for the signal at the stk2240 packs? if so, could you help me make heads and tails of this diagram? no one has the pinout for them, and the data sheet doesnt list it...
also what voltage should i be looking for at the pack? datasheet says recommended operation of +-33.5v
I wouldn't check on the IC. One slip of a probe could destroy it.
Connect an input signal and a speaker.
For half of the IC,
Pin 1: input drive
Pin 2: positive rail voltage
Pin 3: output, likely directly connected to pin 4
Pin 4: pin 4/5 possibly used as part of the protection circuit
Pin 5:
Pin 6: negative rail voltage
Pin 7: input drive
Connect an input signal and a speaker.
For half of the IC,
Pin 1: input drive
Pin 2: positive rail voltage
Pin 3: output, likely directly connected to pin 4
Pin 4: pin 4/5 possibly used as part of the protection circuit
Pin 5:
Pin 6: negative rail voltage
Pin 7: input drive
So, got audio hooked up to it. I only checked one of the two packs as theres a bunch of wires covering the other pack's solder points. I can check it if necessary, but seeing as neither work, I will stick to just this one.
Voltage at the pack is +-25.8v. I checked for the audio into the packs at the capacitors pointed at in the pic as they are connected to the supposed input pins. All thats there is 2.41v DC on one set of inputs, and -2.41v DC on the other. Turning off the audio source made no difference.
Seeing as theres no audio present at the packs, I take it the issue is further upstream? Do I need to start checking the outputs of each of the op amps?
welp. hopefully this makes sense. The 1-5 match the drawing layout I made earlier.
VCC 13.55v
1: LF353N; (V-) 1.51v, V+ 14.61v
2: LF347N; (V-) 1.51v, V+ 14.61v
3: LM13600N; (V-) 1.51v, V+ 14.69v
4: NE5532N; GND 1.51v, V+ 14.61v
5: LM3900N; GND 0v, V+ 14.98v
something tells me the V- needs to match V+?
Yes. The 7915 is the negative regulator. The voltage on its pins should be something like:
ground
negative rail voltage
negative 15v
ground
negative rail voltage
negative 15v
Just checked.
Ground: 0v
Input: -25.7v
Output: 1.5v
Replace the regulator and see what happens?
It could be bad or it could have a load that's pulling it down (up). Generally, I'd suggest inserting a 1 ohm resistor in series with the output of the regulator and measure the voltage across that resistor to determine to current flow but I don't know if that's possible here. You can simply replace it if that's the best option for you.
Are any of the op-amps heating up?
Are any of the op-amps heating up?
the board has to come out anyway to remove the regulator. though im not sure if i have any 1-ohm resistors kicking around.
if i can get the regulator locally ill toss one in to see what it does. if it still doesnt work ill lift the output leg and tie in the resistor.
as for them heating up, i havent explicitly checked, though I'd imagine it wouldnt heat up much with the entirety of the amp drawing less than 1 amp. ive got a cheapo laser thermometer i can check with.
You would be able to feel the heating.
Just a fraction of a watt of dissipation can make something like an op-amp too hot to touch. It doesn't take much.
The regulator is likely defective. The resistor simply gives another troubleshooting technique. If you have to buy one, buy one rated for 1-5 watts so it doesn't burn.
Just a fraction of a watt of dissipation can make something like an op-amp too hot to touch. It doesn't take much.
The regulator is likely defective. The resistor simply gives another troubleshooting technique. If you have to buy one, buy one rated for 1-5 watts so it doesn't burn.
Local parts store doesnt have a -15v regulator in a to220 package. All they have is an NTE1919, which is a to3.
Any other parts you think I should order just in case from digikey?
The rest of the various op-amps and other DIP ICs on the board are so inexpensive, you may as well order at least one of each. It would be cheaper than shipping if you had to place a second order.
I am working on this same amp right now ('87 Continental). Mine runs for about 20 minutes with low voltage sounding saturation then dies. After it cools it will run for another 20 minutes.
First question: I am having trouble trying to figure out how to set it up for bench testing. I don't dare power it when the board is removed from the heat sink. Are you doing all of your probing from the top of the board only without being able to see the bottom, ie, with the board bolted to the heat sink?
Second question: What does the large red wire do? The yellow/black is 12V in. I measure about 9V on the red wire when the unit is powered on and 0v when powered off. I am assuming the red wire provides some type of power back to the head unit, but I notice the head unit will power on when the amplifier is unplugged.
First question: I am having trouble trying to figure out how to set it up for bench testing. I don't dare power it when the board is removed from the heat sink. Are you doing all of your probing from the top of the board only without being able to see the bottom, ie, with the board bolted to the heat sink?
Second question: What does the large red wire do? The yellow/black is 12V in. I measure about 9V on the red wire when the unit is powered on and 0v when powered off. I am assuming the red wire provides some type of power back to the head unit, but I notice the head unit will power on when the amplifier is unplugged.
So, there's a good chance you have the same variant amp as mine. Though, it would very much appreciated if you made your own thread on this as I'm still in the middle of fixing mine, and my issue is completely different than yours.
This is my trash-tastic bench setup. Basic 13.8v supply, multimeter being used as an amp gauge, second multimeter for voltage check, oscope and a spare phone to feed audio into it. You really need a scope to fully diagnose an audio amp.
Yes, I'm only checking the top of the board. While it is multilayer, there's not really much on the underside.
Kinda sounds kind you're having a thermal breakdown of a silicon component. You'll prolly need to get some canned air to try and diagnose what part is going bad. From what I've heard the Sanyo packs are notorious for failing.
You'll need to post a picture of your connectors and wires. The large Red(?) (Mines a red-orange) is ground. Yellow 12v, small orange under big orange is enable.
Bob321:
Please don't post in a repair thread that was started by someone else unless you are trying to help them.
Start a new thread if you need help with a repair of your own.
If you think this thread is relevant, include a link to it in the original post of your new thread.
Please don't post in a repair thread that was started by someone else unless you are trying to help them.
Start a new thread if you need help with a repair of your own.
If you think this thread is relevant, include a link to it in the original post of your new thread.
Got most of the parts. digikey doesnt have the buz71 nor do they have a thru hole lm13600. meh, should be okay.
Replaced the 7915 today and she works great! Had to clean the pots on the radio, but aside from that, shes fully working! Thanks @Perry Babin !
