Sub-10 / Sub-12 / RPW-10 Repair Blog

[ngen33r]

If you don't put the time in and sacrifice a few amps, you wont learn anything. Why quit at 90%? eBay is full of defective amps should you kill this one.

 

The amp still operates in class A/B just the power supply has rail tracking so it runs as a class H. If the bias is not correct the outputs will draw excessive current. Thinking more on it. It sounds like the PDC board is still an issue. I would measure the resistors that you had if you still have them and then double check that board and make sure all the connections are correct. Check the gate drive resistors.

[ngen33r]

SUB-12 PLATE JIDG050400766

 

This one was rather interesting. It came to me with all of the power wires cut. I had to do the repairs and rewire the plate. I am not a fan of these all in one style boards. They are a pain to work on. The wires going form the speaker terminals to the plate were also cut. It was almost like someone wanted the copper and trashed the amp. This plate had the glue monster do some damage which is 99% typical for these. PDC rebuild, full recap, new fets and Q5 upgrade.

[wderbi]

On 3/13/2020 at 11:16 AM, ngen33r said:

If you don't put the time in and sacrifice a few amps, you wont learn anything. Why quit at 90%? eBay is full of defective amps should you kill this one.

 

The amp still operates in class A/B just the power supply has rail tracking so it runs as a class H. If the bias is not correct the outputs will draw excessive current. Thinking more on it. It sounds like the PDC board is still an issue. I would measure the resistors that you had if you still have them and then double check that board and make sure all the connections are correct. Check the gate drive resistors.

I won't give up yet.  I ordered the oscillator/multmeter in the link in my earlier post and I will try to learn how to use it.  I am expecting it to arrive on Sunday. I do have the original components including the resistors I removed from the PDC...I will check them out as you suggested.  In the meantime, I also ordered the bridge rectifier diodes, safety and ceramic capacitors to basically rebuild the entire primary side of the power supply (except the coils) just in case.  I will update as I proceed.

[wderbi]

OK, it's been several days and I have been ordering parts and playing around with this amp project. Where I last left off, the Mosfets overheated to ~ 150F with no volume and no input, and the amp blew a fuse after about 5 minutes.  I ordered the oscilloscope/multi-meter combo as I mentioned above started to troubleshoot.  First thing I noticed was that replacing the fuse with a 2AL (2 amp slow-blow) fuse, and it blew the fuse immediately!  In fact, the room lights briefly dimmed when I turned the amp on.  I didn't notice any obviously blown components or anything that fried upon initial inspection.  However, I removed the IRF740 mosfets and I saw that Q4 tested bad (shorted) and Q3 was still OK (tested by multi-meter). I replaced BOTH Q3 and Q4 with brand new IRF740s on the heat sink, but I did not install them into the power supply board just yet. Instead, I decided to do a complete rebuild of the primary power supply side of the board by replacing the bridge rectifier, all accessible diodes, all of the safety capacitors (both film and ceramic), the ceramic disc capacitors (470 pf), and I finally got around to changing out the two 35V 4.7uf bi-polar electrolytic capacitors (C48 and C53).  I tested all of the components once they were removed from the board...However, only the bipolar capacitors tested bad giving values of 9.7 and 11.3uf for C48 and C53, respectively.  I could not test ESR of any of the Caps, but it was not important because all were to be replaced with NEW components.

 

Before installing the new IRF740 mosfets and the heat-sink, I pulled the recently rebuilt PDC from the board and checked every circuit to make sure there were no shorts and that resistance values were as expected.  There were no short circuits, and the resistance going across the two 750ohm resistors at Gate 2 (R5,R6) was ~375 as expected, while the two 750ohm resisters feeding Gate 1 (R2,R3) was also close to 375 ohms as well.  The caps across SPLY1 and SPLY2 were both reading 3300pf as expected while capacitance between GND1 and D13 was about 4.6nF (4600pF).  Resistance across PRI+ and GND was really close to 201K as expected, and all diodes read a forward biased voltage (~.457) as expected.  I could not test D11, nor could I effectively test the Q11 transistor without taking it out the circuit.  I removed Q11, it tested fine, but I replaced it with a brand new one since it was out.  In the end, I really could not find ANY issues with my rebuilt PDC board.  I reinstalled it and soldered in the new IRF740s and heat-sink. 

 

Rebuilt primary power supply

 

Replaced bridge rectifier and safety capacitors

 

After everything was assembled, I turned on the amp and tested it with input to see if it worked...It DID NOT! 😔  Not a sound by the speaker.  I next lowered all volume, removed input and I tested: the voltage between Vregs (27.8V), between the large resistors R71 and R78 (5.15V), and between pin 5 and 11 of the BASH control board (12.62V).  I again noticed the heat-sink for the IRF740 mosfets getting pretty warm. so I shut everything down after about 3 minutes.  I let everything cool down and I grabbed the scope.  After about 20 minutes, I turned on the amp and tested the voltage points listed above with the graphical display on.  At each point, the DC voltage gave a nice straight line with little to no noise.  I tested the speaker output to see if there was any DC voltage output.  I noticed about 0.3V DC consistent at the speaker output, but no AC output. neither adjusting the gain or adjusting the bias seemed to have any effect on the scope reading.  I am unsure how to effectively use the scope much more than that without knowing where to test other than the DC test points you already suggested that I described above; however, I saw nothing out of place thus far.  I did notice that the IRF740 Fets heating up, so I shut the amp down after about 3-4 minutes.  

 

With this latest dead end, I decided to try something else.  As I mentioned above, my original PDC board had very different values for resistors 2,3 and 5,6 than was listed in your schematic.  The values in your schematic show 750 ohm resistors in those spots, but my board originally had 1100 ohm resistors in those spots.  The values for the resistors in parallel is 375 ohm in your schematic, but the resistance in parallel for my original configuration PDC was 550 ohm.  Also, my original board had 4700 pF 100V  capacitors in positions C1 and C2 and not the 3300pF capacitors shown in your schematic.    Because I felt I hit a dead end, I figured I might as well rebuild the PDF to the specs of my original board and give it a shot.  Also, I tested all of the older parts that were removed from the original PDC and they all tested fine!  Surprisingly, R1 and R4 had heated up so much the point that the covering had broken off and you could not see the bands; however, they still tested fine and had a resistance of 392 ohms!  Maybe it changed once they heat up, but they read fine at room temp.  I replaced the components at R2, R3, R5, R6, C1, and C2 with brand new components matching the values of my original PDC as it was installed from the manufacturer.   I did not have 1100 ohm resistors on hand, so I used a combo of 1000 ohm/ 1200 ohm pairs (545 ohm in parallel).  I also replaced the newly installed IRF740 mosfet transistors with 2 band new IRF730 mosfets to also reflect what was originally installed on my power supply board.

 

Modified rebuilt PDC to reflect my original board

 

After everything was installed and my amp power supply board was now more reflective of my original configuration (except with newer parts!) I was ready to power up.   As soon as i turned on the power, I noticed a high pitch squeal coming from the board!😬 I immediately turned off the amp and the squeal kind of petered out rather than abruptly stopping...it was sort of like air was being released from a tire.  I felt around the board to see if something was really heating up, but nothing was!  I turned the amp back on and the squeal immediately came back...this time i left it on for about 30-40 seconds before turning it off.  Again, nothing was heating up---everything was really cool to touch.  I powered the amp on again, and I tried to locate exactly where the squealing was coming from...I noticed that the squeal was emanating from the primary transformer area ( I think), on the side next to C130 and D31. I left the amp on for about 3-4 minutes, and nothing got hot!  I tested the voltage at the various test points: the voltage between Vregs (10.9V), between the large resistors R71 and R78 (3.1V), and between pin 5 and 11 of the BASH control board (15.3V)...all of the voltage appeared to be wrong.  I turned off the power, provided some input, and hooked up the speaker.  No sound (other than transformer squeal!) and no music...another failure! 😖  On the plus side, the IRF730 mosfets stayed very cool to the touch.

 

For the final test, I left the modified PDC in place, but I replaced the the two IRF730 mosfets with two brand new, unused IRF740 mosfets. After soldering in the mosfets and heat-sink, I powered up the amp and the squeal was now gone...at least for the first minute or so before it returned at a lower volume.  I left the power on and tested the voltages at the test points: the voltage between Vregs (28.2V), between the large resistors R71 and R78 (5.23V), and between pin 5 and 11 of the BASH control board (12.56V).  After being on for about 3 or 4 minutes, the squealing completely stopped but the IRF740 mosfets were pretty warm at that point (126F).  The scope showed flat lines for the DC voltage points and about 0.3V at the speaker output that was not affected by either the bias adjustments or the gain knob.  There was also no AC output at the speaker (as measured by the scope), nor was their any sound or music when the input was connected and volumes turned up...Another Failure! 😭  I left the amp on for about 15 minutes to see if it would blow the fuse and to measure how hot the heat-sink would become---it reached a max temperature of about 139F and stayed there for the remainder of the test.  The fuse did NOT blow and the squeal did not return; however, I am at a dead end here as far as my expertise goes.  I am thinking maybe the primary transformer is bad (squealing?) or the problem is in the BASH control board.  Any suggestions???

Edited March 25, 2020 by wderbi

[ngen33r]

99% of the parts you replaced are never bad. PDC, Q5 Bash Board, caps, NTC and FETS are all I ever replace on these. With so many parts replaced the problem creates new problems, broken traces lifted pads. At this point it is almost better to trash that amp and start fresh with a new broken one, unless you go over the entire amp from a schematic. A SUB-10 power supply is identical to the RPW and is a direct fit on the plate. 

[wderbi]

8 hours ago, ngen33r said:

99% of the parts you replaced are never bad.

LOL!  Tell me about it!  After testing all of the parts that came off the board, I can say for sure that only the Fets (twice!) and the two Non-polar caps (c48 and c53) tested bad and/or out of specs using my multi-meter.  As I mentioned above, R1 and R4 had heated up so much the point that the covering had broken off and you could not see the bands; however, they still tested fine and had a resistance of 392 ohms.  All of the caps (electrolytic and otherwise) removed from the board tested fine in regards to capacitance (other than the aforementioned c48 and c53) and looked in good physical state; however, I could not asses ESR---which is important in audio circuitry.  Also, other than passing the continuity test between GD and S which all transistors other than the blown fets did, I could not conclusively implicate any of the transistors in this issue I am having.  I invested in a multi-function transistor tester that can also measure the ESR in electrolytic capacitors: hxxps://www.banggood.com/DANIU-3_5inch-Colorful-Display-Multi-functional-TFT-Backlight-Transistor-Tester-p-1083042.html?utm_source=Youtube&utm_medium=cussku&utm_campaign=16107093_1083042&utm_content=1087&cur_warehouse=USA.  I will retest the used components just for shyts and giggles and also for the learning process.

 

Yes, I have replaced a lot of components on the main board and PDC.  I am no expert and I do not do this for a living; however, I am pretty decent with soldering joints.  In the beginning, I did have a couple of raised pads on the PDC and a couple of raised pads below two of the smaller electrolytic caps on the secondary side due to the fact that I had a mediocre Metronics brand de-soldering gun that just did not have enough suction to remove solder from dual-sided solder joints without having to hold the de-soldering gun in place for quite a while.  However, I no longer had any problems after I upgraded to the 2X expensive Hakko FR301. That said, I was pretty sure to double check that newly installed components in the problem areas had continuity to their respective trace on both side of the board.  I can triple check these potential weak points just to be absolutely sure.

 

At this point, I am really leaning towards the BASH controller board as the problem.  I carefully looked at the board when I had it removed, but none of the SMD components looked blown.  It may be the processor that is under the glue.  BTW, what exactly does the BASH controller board do?  Also, have you ever seen problems with any of the SMD components on the BASH board?  What about the SMD components on the main board?  Do you have any insight into the high-pitched squealing noise that I heard coming from the transformer area after swapping the IRF740s with IRF730s?

 

After taking on this project and spending just shy of $600 USD on this plate amp (including purchasing the Hakko and the Oscilloscope/meter), I have come to a similar conclusion that after so much time and money thrown at this board, it may be time to move on to a different board.  I managed to find and purchase a used RPW-10 off EBay that is supposed to be in working order.  That said, I still want to test the theory that the BASH board is the problem.  If the used sub I purchased this afternoon actually does work, I am really tempted to remove the BASH board and temporarily install it into this project just to check.  Do you recommend against doing that?  If not, do you know of where I could purchase just the BASH board so that I could install it to test my theory regarding this plate amp?

[ngen33r]

The equipment is an investment and can always be used for different projects. So you didn't waste your money, especially on a Hakko. The BASH boards are usually good, Maybe 1 in 50 I have to replace the IC. That board is a BUCK regulator controller. It takes the output of the transformer and varies the voltage based on the demand of the amp. These amps are Class H which is Class AB with a tracking power supply to gain efficiency. If you have ~5V on the 2 resistors that feed the mosfets the BASH board is good. The squealing is most likely from the main transformer or from the other inductor. The switching frequency is what causes that noise and I have no idea what would cause that without looking at the board. I still think that the PDC has some issues. I have an RPW in my to be fixed box, if I have time this weekend I will pull out the supply and measure the values of the resistors on the PDC.

[ngen33r]

So I did a little research and there are 2 different component values for these boards. If the board has C1 C2 472 capacitors the resistor values are 1.1K 1% BROWN BROWN BLACK BROWN BROWN for R2 R3 R5 R6. If the C1 C2 capacitors are 332 the resistor values are  750R PURPLE GREEN BLACK BLACK BROWN for R2 R3 R5 R6.

 

The RPW-10 that I have on the shelf uses the 1.1K resistors on the PDC. All of the SUB-10 PDC boards that I have use the 1.1K resistors and all of the SUB-12 PDC boards use the 750R. My testing board is made from the guts of a SUB-12 and it powers on no problems with either board, that doesn't mean that it is supposed to be that way.

[wderbi]

So, my PDC is not an anomaly having the 1.1K resistors...thanks for the confirmation in seeing it elsewhere.  I wonder if the PDC configuration has any impact on whether the switching mosfets were IRF730 versus IRF740?  The spec sheets show that those two mosfets are substantially  different although there is a suggestion that IRF740 can still replace the outdated IRF730, but not the other way around. I am fortunate that I do have both available to install because I ordered both.  My board originally had IRF730s and I do know that the combination of the IRF730 mosfets and having 1.1K resistors in the PDC had resulted in me having significantly lower voltages at all of the test-points you told me to check (see my earlier post above). While you do have access to your RPW10 with the 1.1K resistors installed, could you determine if you have IRF730s installed and if so, could you please check if the voltage between Vregs is ~10.9V, between the large resistors R71 and R78 is ~3.1V, and between pin 5 and 11 of the BASH control board ~15.3V?

 

I am still waiting on my Ebay order of a used RPW-10 plate amp that is supposed to be a working board.  I still really want to get to the bottom of my mystery...having a second board that works might be helpful in troubleshooting more effectively.  Hopefully it will be here by Thursday and that it actually works!   

Edited March 31, 2020 by wderbi

[wderbi]

OK, here is the follow-up so far:

My transistor tester came in and I got to testing all of the components that were removed from the plate amp of the RPW-10 that has been giving me trouble.  The tester works really well and is pretty much a must have for someone who does this kind of work all the time.  What I found is that all of the smaller electrolytic capacitors (100uf and less) tested had an ESR that was too high!  Even though capacitance was in specs, the ESR showed that the capacitors had needed to be replaced.  Strangely enough, the larger 470ufv100V capacitor that was removed from the amp and replaced a few weeks ago tested totally in spec. I could not locate the larger 470uf 200V cap---I must have tossed that one when it was removed. I also noticed that the smaller yellow film safety capacitors (104K, 250V) had too high of a ESR value; however, the larger 0.22 uF yellow film safety capacitor tested just fine.  All of the other components tested fine and will be saved for recycling in another project.

 

That said, I think I may have stumbled on a major breakthrough that may solve my problem: I apparently installed the WRONG output transistors in my RPW-10...which was part of the first wave of repairs to my RPW-10.  While I was preparing the output transistors for testing on the transistor tester, I took the opportunity clean the old output transistors and I got a good look at the printed labels.   What I saw basically made my mouth drop to the floor:  All of the output transistors were NOT the same!!!  😲  When I originally I looked at them early last month, I thought they were all IRFZ14 N-channel Mosfet output transistors, so I ordered a set of 10 and replaced all of the output transistors with IRFZ14s.  When I got a good look at them last night, I saw that there were only 2 IRFZ14s.  The other transistors were 2 IRF9Z14s and 1 IRF530 to make the total of 5 output transistors.   I tested all 5 of the old output transistors and none tested bad!  However, the mV value, the Vt, gate capacitance, and RDS were very different between the 3 transistor types.  This tells me that the transistor typess are NOT interchangeable and the fact that I installed IRFZ14s in all slots (Q7, Q19, Q13, Q20, and Q14) likely explains why my amp is not working and why the switching Mosfets in the power supply are heating up with no input or volume.  I feel like a complete idiot for making that mistake! 😖 However, in my defense, it is really easy to mistake the IRF9Z14s for IRFZ14s because these things are very difficult to read!!!

 

What I need to know now is which slot takes which output power transistor...can anyone check the output transistors in the RPW-10 and let me know the values for Q7, Q19, Q13, Q20, and Q14?  I ordered some new replacements as it makes no sense to re-install the old ones at this point!

 

Thanks!!

Edited April 1, 2020 by wderbi

[alhim]

On 1/14/2020 at 6:52 AM, ngen33r said:

SYNERGY SUB-12 PLATE SERIAL 06230184

 

This amp was blowing fuses. The PDC control board failed and took out the mosfets. I had to clean and rebuild the PDC, replace the fets, replace Q5 and TH3. TH3 is almost always bad when fuses are blowing. After the board was working, a full recap was done on the amp.The active crossover was especially fun due to all the damn glue used.

 

[MechEngVic]

On 4/1/2020 at 2:08 AM, wderbi said:

OK, here is the follow-up so far:

My transistor tester came in and I got to testing all of the components that were removed from the plate amp of the RPW-10 that has been giving me trouble.  The tester works really well and is pretty much a must have for someone who does this kind of work all the time. 

Can you tell us which tester you bought? 

[wderbi]

I mentioned the tester 6 posts above this one.  The one component that it would not test properly is the DB6 diac---everything else was cake!

 

 hxxps://www.banggood.com/DANIU-3_5inch-Colorful-Display-Multi-functional-TFT-Backlight-Transistor-Tester-p-1083042.html?utm_source=Youtube&utm_medium=cussku&utm_campaign=16107093_1083042&utm_content=1087&cur_warehouse=USA

 

 

Edited April 7, 2020 by wderbi

[alhim]

Hi! ngen33r. I got you a problem with the plat Sub-12. And this board just burnt to ashes, damaging all the connecting tracks.With the help of your photos, I was able to restore this from the side of component installation, but I do not know how it was on the back of the board.I would really appreciate you taking photos here of this back side of the board?
I have experience in repairing radio equipment and have tools, but this sub - 12 is very rare for our litle city of Orenburg and two days of searches on the Internet did not bring me luck in obtaining a service manual or other useful information. And all the most useful links on the Internet lead to you! I really hope for help with photography and of course thank you anyway!

Edited April 10, 2020 by alhim

[ngen33r]

On 4/8/2020 at 1:38 AM, alhim said:

Hi! ngen33r. I got you a problem with the plat Sub-12. And this board just burnt to ashes, damaging all the connecting tracks.With the help of your photos, I was able to restore this from the side of component installation, but I do not know how it was on the back of the board.I would really appreciate you taking photos here of this back side of the board?
I have experience in repairing radio equipment and have tools, but this sub - 12 is very rare for our litle city of Orenburg and two days of searches on the Internet did not bring me luck in obtaining a service manual or other useful information. And all the most useful links on the Internet lead to you! I really hope for help with photography and of course thank you anyway!

 

 

That board is not worth fixing. I have several of those in my graveyard. Toss it and replace the amp.

 

You would have to do epoxy board repairs, add new copper planes, rebuild the bash board, recap the entire board, replace the outputs and pots at a minimum. Scrap it and get a "good condition" broken amp that hasn't almost caught on fire.

 

[dudaindc]

Hello ngen33r!
Thank you for the very good and very well documented information provided here so far - very helpful indeed,
I was wondering if you had any luck repairing RPW-10D amps with the typical "LCD does not work but blinks when the amp is turned off" issue.

Thanks in advance.

[ngen33r]

19 hours ago, dudaindc said:

Hello ngen33r!
Thank you for the very good and very well documented information provided here so far - very helpful indeed,
I was wondering if you had any luck repairing RPW-10D amps with the typical "LCD does not work but blinks when the amp is turned off" issue.

Thanks in advance.

 

I didn't know they made an RPW-10D. I know they made RW-10 and RW-12D subs. When I see that issue on them it typically requires a recap, replacing SMT diodes and the SMT VREG. About 60% of the time the digital volume IC is fried when the VREG goes. Those are not fun to solder in. If it is an RW series, please post in that blog. I want these threads to stay on topic.

[dudaindc]

On 4/14/2020 at 12:04 PM, ngen33r said:

 

I didn't know they made an RPW-10D. I know they made RW-10 and RW-12D subs. When I see that issue on them it typically requires a recap, replacing SMT diodes and the SMT VREG. About 60% of the time the digital volume IC is fried when the VREG goes. Those are not fun to solder in. If it is an RW series, please post in that blog. I want these threads to stay on topic.

My bad - I meant RW-10D.
I was not aware of an RW Series thread, but will look for it.

Thanks for the info!

Edited April 15, 2020 by dudaindc

[alhim]

I agree with you that this my undertaking is a big waste of time. But a mail package with a new board from you to my region of Russia - Orenburg - also not an easy way out...Therefore, I still wanted rebuild my bad board.And I just wanted to remove the entire burned-out piece of the board, replacing all the tracks connections with a solid surface mount. And the most interesting thing is that all the output mosfet transistors turned out to be working and in the power supply is also ok! (I don’t even know what made this shit so hot - apparently heating and bad tin soldering disturbances on two 160 oHm resistors) 
So if you help me with a photograph of the back of the board, then I would venture to revive this and Then I’ll write about the results here + a photo of all the work

[alhim]

On 4/13/2020 at 3:33 AM, ngen33r said:

 

That board is not worth fixing. I have several of those in my graveyard. Toss it and replace the amp.

 

You would have to do epoxy board repairs, add new copper planes, rebuild the bash board, recap the entire board, replace the outputs and pots at a minimum. Scrap it and get a "good condition" broken amp that hasn't almost caught on fire.

 

I agree with you that this my undertaking is a big waste of time. But a mail package with a new board from you to my region of Russia - Orenburg - also not an easy way out...Therefore, I still wanted rebuild my bad board.And I just wanted to remove the entire burned-out piece of the board, replacing all the tracks connections with a solid surface mount. And the most interesting thing is that all the output mosfet transistors turned out to be working and in the power supply is also ok! (I don’t even know what made this shit so hot - apparently heating and bad tin soldering disturbances on two 160 oHm resistors) 
So if you help me with a photograph of the back of the board, then I would venture to revive this and Then I’ll write about the results here + a photo of all the work

Edited April 20, 2020 by alhim