Good day, I am happy to be making my first post on this site. I have been viewing the content for many years and applaud the community for all it's contributions made to all those who benefit from its existence.
I am in need of help with repairing a Directed 1100d5 amplifier. There is a problem in the class D sub section that causes the amp to draw high current. I have tried to repair it using the Search function but was not able to succeed. I may just need new outputs for the Class D section but I would like to confirm this before purchasing and replacing said parts, just in case they are still good and my problem lies elsewhere.
HISTORY
This amp was purchased a couple years ago with the two rear channels distorted but front and sub channels operating normally. I used it as-is until last year when I opened her up and changed all the four channel section outputs (TIP 35 + 36). Amplifier tested well on all five channels after that but was not yet reinstalled into a vehicle. When it was finally put back into a vehicle it was initially only connected as a subwoofer amp using the Class D section with the A/B section unused. There was very little bass so I tried it on bridged channels of the A/B section and there was very little bass also. After playing it for a while, I realised that the protection light was on so I disconnected the amp. Came to find out that the sub box had massive air leaks which caused the wimpy bass response but only after damaging two other amps subsequently.
On the bench, I removed the rear channel outputs (TIP 35 + 36) and the sub section outputs (IRF640 + 9640) and the protection light went out, green light stayed on and front channels played fine. Ended up replacing the TIP 35 + 36 Transistors again which got the four channel section playing again without distortion and the green light stays on as long as the Class D section is disabled in some way. If the outputs, or rectifiers are out of the circuit, she will power up, relay will click on and the green light stays lit while the A/B section operates normally. If the Class D section circuits are complete, the amp will power up normally but as soon as the relay clicks on the current limiting bulb will start to brighten and the green light goes out but the red(protection) light will not light up bright. Both lights however go dim as if the whole amp is shorting out. I currently have the IRF640 and IRF9640 outputs removed and amp is normal except for no bass channel.
TEST VOLTAGES:
Using a car battery for testing, battery voltage is currently 12.3v.
Input voltage at power terminals is 10.2v at idle with 640s + 9640s removed.
With 640s + 9640s installed the input voltage drops down to 6.9v as the current draw increases.
With all outputs installed, the A/B rail voltage goes up to 50-53v before dropping down to 35v as the current draw rises.
With all outputs installed, the Class D rail voltage goes up to 82-83v before dropping down to 56v as the current draw rises.
With the IRF640s removed the pads read -36v, 0.7v, -39.6v and amp idles without problem and relay clicks on with no problem.
With the IRF9640s removed the pads read 37.3v, 0.7v, 41.2v and amp idles without problem and relay clicks on with no problem.
TRANSISTORS BAD?
The outputs were tested according to the Transistor Test Page instructions but I am unsure of the procedure and/or results. With 1-3 shorted, the three IRF640s read 504,505,506 with DMM in diode-test mode while the three IRF9640s read 725, 823, 800, 773, 802. There did not seem to be a drastic effect caused by turning on/off the transistors other than maybe a drop in the number by about 4. (e.g. The 9640 that read 823 before, read 819 after the test.) These are almost the exact readings shown by just probing between 2-3 without first turning on the Transistor. I am not sure how to interpret this reading/result.
It would appear that both power supplies are functioning properly since the amp powers up without protection and produces rail voltages once the Class D outputs are not in the circuit. Can someone please provide some assistance and tell me what to check next. If everything seems ok and should work properly with just purchasing and replacing the outputs, please let me know. I don't want to damage anything else and I also don't want to purchase parts not needed since I have other things that money will be better spent on. Sorry for the long post but I tried to be as thorough and concise as possible. Thanks in advance...
I am in need of help with repairing a Directed 1100d5 amplifier. There is a problem in the class D sub section that causes the amp to draw high current. I have tried to repair it using the Search function but was not able to succeed. I may just need new outputs for the Class D section but I would like to confirm this before purchasing and replacing said parts, just in case they are still good and my problem lies elsewhere.
HISTORY
This amp was purchased a couple years ago with the two rear channels distorted but front and sub channels operating normally. I used it as-is until last year when I opened her up and changed all the four channel section outputs (TIP 35 + 36). Amplifier tested well on all five channels after that but was not yet reinstalled into a vehicle. When it was finally put back into a vehicle it was initially only connected as a subwoofer amp using the Class D section with the A/B section unused. There was very little bass so I tried it on bridged channels of the A/B section and there was very little bass also. After playing it for a while, I realised that the protection light was on so I disconnected the amp. Came to find out that the sub box had massive air leaks which caused the wimpy bass response but only after damaging two other amps subsequently.
On the bench, I removed the rear channel outputs (TIP 35 + 36) and the sub section outputs (IRF640 + 9640) and the protection light went out, green light stayed on and front channels played fine. Ended up replacing the TIP 35 + 36 Transistors again which got the four channel section playing again without distortion and the green light stays on as long as the Class D section is disabled in some way. If the outputs, or rectifiers are out of the circuit, she will power up, relay will click on and the green light stays lit while the A/B section operates normally. If the Class D section circuits are complete, the amp will power up normally but as soon as the relay clicks on the current limiting bulb will start to brighten and the green light goes out but the red(protection) light will not light up bright. Both lights however go dim as if the whole amp is shorting out. I currently have the IRF640 and IRF9640 outputs removed and amp is normal except for no bass channel.
TEST VOLTAGES:
Using a car battery for testing, battery voltage is currently 12.3v.
Input voltage at power terminals is 10.2v at idle with 640s + 9640s removed.
With 640s + 9640s installed the input voltage drops down to 6.9v as the current draw increases.
With all outputs installed, the A/B rail voltage goes up to 50-53v before dropping down to 35v as the current draw rises.
With all outputs installed, the Class D rail voltage goes up to 82-83v before dropping down to 56v as the current draw rises.
With the IRF640s removed the pads read -36v, 0.7v, -39.6v and amp idles without problem and relay clicks on with no problem.
With the IRF9640s removed the pads read 37.3v, 0.7v, 41.2v and amp idles without problem and relay clicks on with no problem.
TRANSISTORS BAD?
The outputs were tested according to the Transistor Test Page instructions but I am unsure of the procedure and/or results. With 1-3 shorted, the three IRF640s read 504,505,506 with DMM in diode-test mode while the three IRF9640s read 725, 823, 800, 773, 802. There did not seem to be a drastic effect caused by turning on/off the transistors other than maybe a drop in the number by about 4. (e.g. The 9640 that read 823 before, read 819 after the test.) These are almost the exact readings shown by just probing between 2-3 without first turning on the Transistor. I am not sure how to interpret this reading/result.
It would appear that both power supplies are functioning properly since the amp powers up without protection and produces rail voltages once the Class D outputs are not in the circuit. Can someone please provide some assistance and tell me what to check next. If everything seems ok and should work properly with just purchasing and replacing the outputs, please let me know. I don't want to damage anything else and I also don't want to purchase parts not needed since I have other things that money will be better spent on. Sorry for the long post but I tried to be as thorough and concise as possible. Thanks in advance...
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If you test the output with leads 1 and 3 shorted and read anything other than an open circuit in one direction (2-3), the FET is defective.
Do you have a scope?
Do you have a scope?
Thanks for the reply. The FETs all read open circuit in one direction and give a reading in the other. 504-506 for the 640s and 725-823 for the 9640s between 2and 3 and show no shorts. Shorting 1 and 3 seems to make no difference other than returning a reading between 2 and 3 that is lower by about 4 (e.g. A 640 that reads 506 before the test will read 502 after. I don't know what this is telling me, whether the FET is defective or not, or operating properly or not.
I did notice though that the current limiting bulb that I am using does have a very faint glow with the amp idling. Most of the other amps I have benched will usually dim straight out after turn-on. Could this current draw be part of the problem? The faint glow was there even with all the outputs removed.
I do have a scope but it is a USB scope, Sainsmart DD120 I believe. It was a gift and I am not yet versed in how to use it, or any oscilloscope for that matter but if given detailed directions I am sure I can follow them and achieve successful results. The only thing I have successfully done with it is read the square wave output on the signal generator tab.
What do you want me to do next?
I did notice though that the current limiting bulb that I am using does have a very faint glow with the amp idling. Most of the other amps I have benched will usually dim straight out after turn-on. Could this current draw be part of the problem? The faint glow was there even with all the outputs removed.
I do have a scope but it is a USB scope, Sainsmart DD120 I believe. It was a gift and I am not yet versed in how to use it, or any oscilloscope for that matter but if given detailed directions I am sure I can follow them and achieve successful results. The only thing I have successfully done with it is read the square wave output on the signal generator tab.
What do you want me to do next?
On the board behind the board with the TL494, you need to find the 8-pin op-amp that's the equivalent to U151 on the following diagram. The component values may vary slightly and the circuit board designations won't match but you should be able to find the IC.
http://www.bcae1.com/temp/jbl - bp150.1.pdf
http://www.bcae1.com/temp/jbl - bp150.1.pdf
OK, would like to update the post for future reference so that others may possibly help their own similar situations. I did test the opamps located on the vertical driver boards and everything read correctly regarding the + and - inputs etc. I then suspected that my problem concerned the output FETs since everything else checked out. I played around with the number and order of the five p channel FETs and was able to get the amp playing continuously using four of them but installing the fifth one would always cause the amp to go into protect and the current limiting bulbs to illuminate full brightness until power was disconnected. So I went down to my local electronics store and requested 5 irf9640s from the same batch with similar specs. It took a while as I tested the FETs with my multimeter until I got 5 identical transistors much to the growing annoyance of the sales staff. I ended up with readings of 750, 752, 753, 754, 754 which means they are much closer than the previous ones. I put the new ones in and bench tested the amp. It now makes bass with minimal illumination of the current limiting bulbs and they no longer stick at full brightness and amp no longer goes into protection. Amp has been put back into the vehicle and no problems at present. The lesson that I have learned and would like to share is the importance of components with similar specifications, especially in class D amplifiers since it was working at low load but gave trouble when the load increased. Thanks for the assistance DIY...
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