Here is one of my 652's sorry about the poor picture quality, I really need a new camera
I circled where they are here
An externally hosted image should be here but it was not working when we last tested it.
I circled where they are here
An externally hosted image should be here but it was not working when we last tested it.
TIP 35 and TIP 36 are the outputs for this amp. You can probably get away with using TIP36's in the power supply also IMO. < for durability reasons only>
The Grey Emitter resistors look like they have seen excessive heat, you might want to verify they are still in spec, and replace if need be.
Your insulator material looks pretty beat up. I would clean it and refresh the silicone paste on both sides also. Hope this helps...
The Grey Emitter resistors look like they have seen excessive heat, you might want to verify they are still in spec, and replace if need be.
Your insulator material looks pretty beat up. I would clean it and refresh the silicone paste on both sides also. Hope this helps...
Well, The bias will be read in milli-volts drop across the emitter resistors. I have no original spec for this amp. So I would check the good channel first just to see what you have already, as a possible guideline. < Hence the need to check the big gray resistors to make sure there values are to spec, their resistance affect the accuracy of the bias reading.
Your amp has been worked on by a lessor tech before now, so both channels might just be in left field. I would need to scope the amp to set the bias, and then I would need to let it run a day or two to gather more info on a proper set point. Amps like this "usually have bias set points in the 2 to 6 millivolt range in order to not have excess heat related issues.
hope this helps.....
Your amp has been worked on by a lessor tech before now, so both channels might just be in left field. I would need to scope the amp to set the bias, and then I would need to let it run a day or two to gather more info on a proper set point. Amps like this "usually have bias set points in the 2 to 6 millivolt range in order to not have excess heat related issues.
hope this helps.....
I tested the emmiter resistors got .4ohms in circuit. Do I need to take one leg out to get a good reading? The only writing in the resistors is3WR15J3. Also when I do test the bias voltage do I put the pos lead closet to the trans & the neg lead on the ground wire. Also would I be correct in starting with the lowest voltage & gradually turn it up over time?
It's probably a 3 watt 0.15 ohm resistor.
Most handheld meters won't read below ~1/2 ohm reliably. Touch your meter leads together and hold them together for 5 seconds. Subtract that reading from the resistance you read across the resistor to determine the resistor's value.
When adjusting the bias current, you set the bias pot to the lowest setting (generally, but not always fully counter-clockwise). Power up the amp and let it idle for a few minutes. Connect your meter across one of the emitter resistors for the channel you're working on and slowly increase the bias current until you see the current start to increase (current increase will cause voltage drop across the resistor). Set the bias so that you get ~1mv DC across the resistor. 1mv is a starting point. If there is no distortion, leave it there. If there is distortion at low output levels, you can increase the bias current slightly.
When adjusting the biasing, you want to use just enough bias current to prevent crossover/notch distortion. Too much bias current will make the amp draw excessive current and run hot. For some amps with high rail voltage and lots of outputs, 1mv may be too much but for this amp it should be OK.
Most handheld meters won't read below ~1/2 ohm reliably. Touch your meter leads together and hold them together for 5 seconds. Subtract that reading from the resistance you read across the resistor to determine the resistor's value.
When adjusting the bias current, you set the bias pot to the lowest setting (generally, but not always fully counter-clockwise). Power up the amp and let it idle for a few minutes. Connect your meter across one of the emitter resistors for the channel you're working on and slowly increase the bias current until you see the current start to increase (current increase will cause voltage drop across the resistor). Set the bias so that you get ~1mv DC across the resistor. 1mv is a starting point. If there is no distortion, leave it there. If there is distortion at low output levels, you can increase the bias current slightly.
When adjusting the biasing, you want to use just enough bias current to prevent crossover/notch distortion. Too much bias current will make the amp draw excessive current and run hot. For some amps with high rail voltage and lots of outputs, 1mv may be too much but for this amp it should be OK.
Well I installed the power supply & output transistors today. Also replaced the 2 turn on cars. No luck on power up. I have the transistors for the remote turn on, but have not replaced them yet. It looks like they have been replaced before. What I am wondering is if they might have been installed backwards. Is there a way to tell which way they go. I would hate to put the new ones in and cause something else to go wrong.
If it does not say on the board under it, look up the datasheet on them because they can be in any configuration. Once in a while they put letters under them telling you.
Counterclockwise- I fire it up with limited power and I put my fingers close to the outputs to see if they get any heat. They will get hot fast if the bias is up, and check the bias voltage right away.
Counterclockwise- I fire it up with limited power and I put my fingers close to the outputs to see if they get any heat. They will get hot fast if the bias is up, and check the bias voltage right away.
Just put the number in a search engine and you can usually find the sheets on them for free in 5 min. The small transistors are not all the same so hard to say what pin is what. Mosfets often have the #1 as the gate, but not the little ones so if you think they are not in right you have to get sheet on them. Try datasheetarchive.com
If it does not come on, put your meter on either one of the rails or the base of the power supply transistors (usually #1 that goes to resistor and then to driver). See if you get any jump in current at all when you touch the trigger. Ensure you have 12v at the power supply transistors often center leg, but most have 12v to them all the time if amp is hooked up to power. I have one protecting, it comes on but shuts right back down in half a second. (not a LP amp, do not know what if any protection circuits they have)
If it does not come on, put your meter on either one of the rails or the base of the power supply transistors (usually #1 that goes to resistor and then to driver). See if you get any jump in current at all when you touch the trigger. Ensure you have 12v at the power supply transistors often center leg, but most have 12v to them all the time if amp is hooked up to power. I have one protecting, it comes on but shuts right back down in half a second. (not a LP amp, do not know what if any protection circuits they have)
I have an old Linear Power 952 that needs the power supply repaired, however the parts are burnt so badly i cant tell what they once were.
Have looked at the pictures posted here but are not clear enough (laptop), the part is the smaller transistor (to220) looks like 2n6488 ???? , the larger ones are tip35 or 36's any help , schematics would be greatly appreciated. Also i have seen Perry had a picture of a 2502iq , it seems it has same problems, however someone had removed Q5 and the cap beside it , as well (from pic looks like 220uf,16v ?) .
Have looked at the pictures posted here but are not clear enough (laptop), the part is the smaller transistor (to220) looks like 2n6488 ???? , the larger ones are tip35 or 36's any help , schematics would be greatly appreciated. Also i have seen Perry had a picture of a 2502iq , it seems it has same problems, however someone had removed Q5 and the cap beside it , as well (from pic looks like 220uf,16v ?) .
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