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Old 18th July 2013, 04:06 PM   #1
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Join Date: Jul 2013
Location: Perth
Default Need help with PSB Subsonic 5i

I have a PSB Subsonic 5i subwoofer which has been working fine for two years until yesterday. It suddenly started blowing fuses. There had been a few treads in this forum with the PSB Subsonic 5i having similar problems. It would be most appreciated if someone with experience in fixing this porblem can provide some help and guide to fix this sub. Also can someone send me a copy of the service manual as well.

Thanks.
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Old 19th July 2013, 03:07 AM   #2
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Location: Melbourne
Hi Tony
Check your email, I have sent you the info you need.
Cheers.
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Old 4th September 2013, 03:01 PM   #3
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can i also get the service manual

Thanks
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Old 14th September 2013, 01:15 AM   #4
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Hi Gatekeeper01,

Ill send you the manual if you leave your email address here.

BTW, I've fixed my sub! Over the past few weeks, I've learned a lot about the problems of this sub from postings, provided by very knowledgeable people at various forums. This eventually helped me to pin point the culprit and fix the problem.Thank you very much everyone!

I'll share my experience and findings later.
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Old 16th September 2013, 03:35 PM   #5
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Further to my previous tread, PSB Subsonic 5i Sub keeps blowing fuse, Jim Filaktakis has kindly sent me a copy of the service manual. Thank you, Jim.

After studying the manual for a while, I removed the amp from the cabinet. Apart from some corrosion on most of the boards, visual check didnít reveal any obvious sings of burnt parts or tracks. After cleaning out the corrosion, I started to desolder components for out of board testing with a digital multimeter. The two power MosFets, Q401 & Q402, IRF730 x 2 (mine were IRF740) were found shorted. These were replaced. As there was no other obvious failing parts, I reconnected all the boards and give it a try. The fuse went again with a big spark!
Then I read an article about repairing a Subsonic 6. The author replaced all four power transistors and fixed the problem of fuse blowing. So this time I replaced the 2 IRF740ís together with Q200, IRF540 & D200, MUR420. Meanwhile, I would like to determine whether the SMPS itself or the Amp Board was causing the problem. So this time the SMPS was tested by itself. The retrial ended with another big spark!

Then another article caught my eye. This article pointed out the that the glue used on the BASS amp boards could became conductive after time and causing short circuit to parts. I cleaned up most of the glue and there was one big lump on the C438 sticking to the PDC1010 board. After cleaning up this lump of glue, there was a little bit of burnt residue of the glue, about 2mm in size, on the corner of the PDC, on the opposite side of the Diac. So I carefully desoldered the PDC out of the Main Board and cleaned up the area and had another good visual. No other burnt marks or parts could be seen. I then removed the Daic DB6 from the PDC and tested it with a DMM. Both sides measured >20m ohms and it was cleared of any fault. What a relief! I was so worried that it was a faulty Diac and it couldnít be sourced anywhere after numerous search on the internet unless you buy 1000 pieces from the manufacturer.

Then I used an 8x magnifying glass to look closely at the components as there were so small. Then I noticed a hair line crack on the side of R4 (392 ohm). Out of board measurement was 200K ohm.
R5 & R6 tested alright. To be on the safe side, I replaced all 3, R4, 5 & 6. Resoldered everything back and reassemble the amp and tested it. Hurray!!! No more blowing fuse and it worked again!

After leaving the sub on low volume for about10 hours, I thought I might reset the Bias current. Following the instructions in the service manual step by step, I disconnect the control board cable from J6 and the driver wires from J102 and J101.Adjusted R714 & R 734 on the Linear PCB fully counter-clockwise. Connected a DC voltmeter to the bias header J103. Power on the amp. Checked initial meter reading which should be less than 1.3mV. Mine was reading 1.7mV. Then adjust R714 until the meter reads the initial value +0.3mV. Adjust R734 until the meter reads the initial value +0.6mV. Here is the problem. As I turned R714 or R734 clockwise, the reading started to go above 1.7mV instead of coming down. Any help from anyone regarding how to fix this problem would be greatly appreciated. The sub seemed to work alright with R714 & R734 set at fully counter clockwise position. Would this cause any damage to the amp?

Thank you guys.
Attached Images
File Type: jpg Glue 1.jpg (615.4 KB, 180 views)
File Type: jpg Glue 2.jpg (673.9 KB, 166 views)
File Type: jpg R4.jpg (784.6 KB, 162 views)
File Type: jpg PDC1010 board.jpg (173.3 KB, 162 views)
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Old 2nd October 2013, 04:14 PM   #6
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Default Please help me with the part values.

Hi,

Thank god that i was able to find the same PDC board on this forum. i too have the same but its being used for PolkAudio Psw 125. and the component around R4 are burnt badly. so if you could give me the values of all the component around R4..it will be of great help for me in repairing this sub of mine...

waiting..

thanks,
Hemant.
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Old 16th November 2013, 09:02 AM   #7
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Quote:
Originally Posted by Hemz View Post
Hi,

Thank god that i was able to find the same PDC board on this forum. i too have the same but its being used for PolkAudio Psw 125. and the component around R4 are burnt badly. so if you could give me the values of all the component around R4..it will be of great help for me in repairing this sub of mine...

waiting..

thanks,
Hemant.
Hi Hemant,

Sorry I didn't realise Polkaudio PSW 125 uses the same PDC board.

Please let me have your email address and I'll send you the service manual.
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Old 18th November 2013, 01:18 AM   #8
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Join Date: Jul 2013
Location: Perth
Quote:
Originally Posted by Hemz View Post
Hi,

Thank god that i was able to find the same PDC board on this forum. i too have the same but its being used for PolkAudio Psw 125. and the component around R4 are burnt badly. so if you could give me the values of all the component around R4..it will be of great help for me in repairing this sub of mine...

waiting..

thanks,
Hemant.
Hi Hemant,

After looking through the service manual, there is no mention of the PDC board anywhere in the manual except in the block daigram section which is no help. Luckily, I did make a note of the value of the components. Some labelings are original and some I just make them up my self becasue they are obscured by the components. I double check the resitors with a digital multimeter and all the others are the actual markings on the individual parts.

Hope this helps.

TonyH378
Attached Images
File Type: jpg Sister board 2z.jpg (457.4 KB, 119 views)
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Old 22nd November 2013, 03:56 AM   #9
kbjj is offline kbjj  New Zealand
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Join Date: Nov 2013
Hi TonyH378
Can I have a copy of the psb subsonic 5i service manual please. My amp dosn't have the pdc board that you talk of, so the manual sounds like exactly what I'm after
Cheers, Jeremy
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Old 25th November 2013, 07:28 AM   #10
Ronee is offline Ronee  Singapore
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Quote:
Originally Posted by TonyH378 View Post
Hi Hemant,

Sorry I didn't realise Polkaudio PSW 125 uses the same PDC board.

Please let me have your email address and I'll send you the service manual.
Hi TonyH378
Can I have a copy of the PSB subsonic 5i service manual please?

I brought this woofer back twice to have this problem re-solved but this 3rd time, i will try repairing it my self.

Thank you,
Ronee
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