Re: troubleshooting definitive technology prosub 60
Hello Finster
I did hit a roadblock. My driver is bad. The first thing I did was perform the resistance check per DT and checked that the driver movement was free without noise/scratching. After swapping out the components and confirming there wasn't a short anymore I could indeed turn on the sub w/o the fuse blowing or a resistor blowing. I decided to hook it up to the stereo and I wasn't getting a very clear response from the sub. It was low and noisy. I checked the driver again and it scratches now...
khajr
Member
Last Activity: 11-13-2020, 06:20 PM
Joined: 09-18-2020
Location: Lexington, KY
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Last edited by khajr; 11-13-2020, 06:20 PM. -
Re: troubleshooting definitive technology prosub 60
Hey momaka...Sorry I was referring to the pins for that mosfet. 1 is gate, 2 is drain, and 3 is source.
It only appears that Q4 is warm. I will test as I don't have any spares. I tested R12 and it was fine. I will have to figure out where R5 is. Most of the resistors are soldered right next to the board and I can read the screen printing underneath them but I can figure it out.
I will also check C21 and C27 and C5 and C6. Thanks so much for your help....Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Ya. I have been concerned as well and have been checking trace connections above and below the board....Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Attached is an thermal image without the mosfets installed. The second pic has the labels. Not sure if this tells us anything. Took the picture with the sub hooked up with the dimbulb test with a 100 watt bulb in it. The bulb dimly lights up for moment and turns off....Last edited by khajr; 10-01-2020, 07:47 PM.Leave a comment:
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Re: troubleshooting definitive technology prosub 60
I did measure voltage going getting to each of the mosfet pins and everything was zero.Leave a comment:
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Re: troubleshooting definitive technology prosub 60
I tested to voltage at the connections for the mosfets and found the following:
Q1
P1 and P2 = +169V
P2 and P3 = -169V
P1 and P3 = -300mV
Q7
P1 and P2 = +163V
P2 and P3 = -169V
P1 and P3 = -6V
I will try and figure what they should be....Leave a comment:
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Re: troubleshooting definitive technology prosub 60
The new mosfets Q1 and Q7 ought to be here tomorrow or Friday. What is concerning is that I already swapped those out along with C2, C4, R19, D1, and U3. And the it still blew the fuse and R19. Maybe I got a bad component. My soldering sucks (its really pretty good). I know now to test the new mosfets before I install them.Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Attached is a pic of the board where C1/C2 and C3/C4 are. It looks like you either have C1 and C3 or C2 and C4. Since this is the large case I have C2 and C4.
I am using a 100 watt bulb in the dim bulb tester. With Q1 and Q7 removed the lit dimly for a moment and went out. Across C2 I get 168v. Across C4 I get 168 v. Across C2 and C4 I get 360v. Across the + and - of the bridge rectifier I get 336v....Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Thanks for the help momaka. I am waiting on new Q1 and Q7 mosfets to come in. Then I will check those voltages. Yeah...I am trying to be very careful. I took Q1 out and pins 2 (drain) and 3 (source) were closed. 1 (gate) and 2 (drain) were open. and 1 (gate) and 3 (source) were open. I am going to take Q7 out and check too....Last edited by khajr; 09-29-2020, 08:28 PM.Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Where should I be measuring the bridge rectifier?Leave a comment:
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Re: troubleshooting definitive technology prosub 60
The + and - voltages on the bridge rectifier were off by an order of magnitude and the there was current through the speaker wire....Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Yes. It’s Q7. Don’t know why I had Q4 in my head. All three pins on Q1 are shorted together. I will check speaker line voltage and the bridge rectifier. But I am going to guess the speaker line voltage is not going to be zero as it makes a hum.
My original replacement were the two mosfets, R19, the bridge rectifier, C2 C4. and the op amp. Would we still be concerned about the zener diodes at all?...Last edited by khajr; 09-27-2020, 10:46 PM.Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Attached is the IR image of the board. Nothing blew. R7 is hot. The camera was set to auto scale temp range based on field of view. so it was 169 degrees F but it got as high as 200 degrees F when looking at it for a few more seconds before I turned the power off. Is it supposed to be that hot? I will have to order one but I am not sure what to order to replace it. The markings are SCK 202 and on the schematic it says 20 NTC SL20002 US Sensor. But I can't seem to find anything on mouser that matches that. D1 shows hot but it is...Last edited by khajr; 09-27-2020, 09:09 PM.Leave a comment:
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Re: troubleshooting definitive technology prosub 60
I don't have a variac so I am going to use the lamp....I had all the parts in my garage to build one. I hope it stays on long enough to get a good thermal image of the board so I can pin point a problem.Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Let me rephrase this...I understand that the bulb is drawing the current but if use a 100 watt bulb will it still be safe enough to leave on long enough to get a good thermal image w/o compromising any parts?...Leave a comment:
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Re: troubleshooting definitive technology prosub 60
I had to look that up. That is a great idea. I have access to a flir camera can I use this in conjunction with the flir and identify hotspots...or am I supposed to unplug the sub when I notice the light doesn't go out?...Leave a comment:
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Re: troubleshooting definitive technology prosub 60
Thanks BadCaps. The new Q1 and Q7 are shorted source to gate. All pins were shorted on the ones I took out. I did replace U3d and more zener diodes are on order. I will check Q3, Q4, and Q5....Leave a comment:
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troubleshooting definitive technology prosub 60
Hello,
My prosub 60 is blowing fuses. I bought replacement 1.25 amp 125v/250v slo blo fuses. When I replace the fuse it blows immediately along with a loud buzzing/hum from the sub. Attached are the schematics from definitive technology. There was one bad resistor, R19, and I have replaced this with the correct 1/2watt 1ohm resistor. When I plugged the unit it that resistor pops and the fuse blows. I have also replaced the following: caps C2 and C4, the bridge rectifier D1, op amp U1D, and the power mosfets Q1 and Q7. I have also checked R18, R20, and R21 and they checkout fine (removed...Last edited by khajr; 09-26-2020, 03:40 PM. -
Re: New Members - please post your introductions here
Hello all. I am not new to electronics as I have spent years tinkering with raspberry pi's and arduinos as a hobby and have made some nifty little gadgets over the years. With the current state of everything going on in the world and local repair businesses shutting down I found the need to start repairing my own electronics. My first project is my def tech prosub 60 just stopped working. So the journey begins.Leave a comment:
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