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

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!!

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!

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?

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???

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.

Hmmm...that is interesting. The output mosfets have all been replaced and I recall from your earlier post that the bias was going to have to be adjusted with the scope. However, would the bias being out of adjustment be the cause of the primary switching transistors to heat up and eventually blow the fuse (after 4-5 minutes) at idle with the gain set at zero? I thought that setting the bias correctly was a way to trim/adjust the gain to prevent clipping and/or speaker damage? I would not have guessed it would have such a dramatic impact on the primary side of the power supply and/or causing fuses to blow. Using an O-scope to diagnose issues with electronics is a black box for me and at this point is quite a bit beyond my expertise. I do know that having the knowledge to scope is an extremely powerful tool to have in the toolbox in the electronics repair world. I know just enough to be dangerous when it comes to electronics and I have dabbled in and out of it as one of my hobbies over the years; each time learning more and more. Now that I unexpectedly (and honestly unwillingly) have time on my hands, I was planning to use this amp repair project to further delve into this hobby a little more. For this project I already invested in a new Hakko FR-301 de-soldering gun (which is great BTW---makes the de-soldering process so much easier). However, I do not have a scope, but I was thinking about grabbing a LIUMY Professional LED Handheld Oscilloscope Multimeter from Amazon hxxps://www.amazon.com/Oscilloscope-Multimeter-LIUMY-Professional-Scopemeter/dp/B071F1H3PG/ref=sr_1_10?dchild=1&keywords=Oscilloscope&qid=1584052295&s=industrial&sr=1-10 and try learning how to use a scope to diagnose problems by looking through some YouTube tutorials. However, despite the likelihood that I will learn something valuable, part of me is worried that I have reached the point of diminished returns on this project already and I wonder if its time to ship the board off to the pros...especially if the feedback on that scope from Amazon is that it is not very good for this project. I guess if I had a service guide or schematic I'd feel much more confident. I don't want to throw in the towel, but scoping to me sounds really intimidating! As an option, would it be more cost effective to just send it to someone (like you?) and have the troubleshooting done with a scope?

Hah! Good to know that you are also OUNVME as well!😃 Here is an update: I reinstalled the safety capacitor and connected the mains and the ribbon cable. I checked the voltage between the Vregs and it was 27.2V. The voltage between R71 and R78 was 5.17 when the gain was turned all the way down and no input connected. The voltage between pin #5 and pin #11 on the BASH board was 12.62...The voltage between pin #5 and ground was like 68V. Based on those numbers, everything seems to check out! However, the amp was not working and the heatsink for the IRF740 mosfets was getting pretty warm so I shut everything down after about 2.5 minutes checking voltages. I turned off the amp, unplugged it, let everything stay unplugged and in the on position for about 25 minutes to drain caps and let everything cool down. I next wanted to check the temperature of the heatsink connected to the IRF740 mosfets for 10 minutes after turning the amp on. Below is a chart showing the heatsink temperature measured by a laser temperature gauge where I checked the temperature every minute: MOSFET heatsink temperature chart: As shown, the peak temperature of about 150 F was reached after being turned on for 5 minutes. However, I noticed that the temp started slowly dropping for the next few minutes.😲 Unfortunately, I then noticed that the power light was turned off and that the fuse (2A) was blown. 😞 I am out of 2A fuses so I am ordering new 2AL fuses from Amazon to replace the 2A fuse. I don't think the 2A fuse blew after 5 minutes because it wasn't a long-delay fuse and I fear that something else is going on. Any other suggestions??? Thanks!!!

Thank you for chiming in! I am just now seeing this after midnite; therefore, I won't be able to check out your queries in detail until later today. I rebuilt the PDC and replaced ALL components exactly as you specify despite me noticing it was different resistor values from the original PDC in my unit. The diac I purchased was a NTE6412 as suggested by this thread: I did every step (steps 1-9) in the above post BEFORE replacing Q5 which was originally a SOT23 transistor. I reassembled everything and connected the plate amp to the speaker. The fuse did not blow, but the amp didn't work. II noticed the heatsinks connected to the IRF740s (mosfets) got pretty hot in less than 3 minutes it was connected. After things did not work, I realized I did not swap out Q5. I removed the Bash board and used my heat station to remove Q5---I did not test it beforehand, nor did I realize I should have cut it off! It came off pretty cleanly and I added a bit of solder to each pad. Unfortunately, I had real hell trying to line up the legs of the 2N4401 in place so that I could solder the transistor in place. In my attempt to do so, the pad for the collector was pulled off the board by the leg of the 2N4401 that I soldered down to that pad. I removed the 2N4401and instead decided to solder flexible wire to each pad, and solder 2N4401 to the wires instead. Because the collector pad was messed up, I traced the connection back to the cathode side of diode D7 and soldered a wire for the 2N4401 collector to that connection. I hot glued the 2N4401 in place and reinstalled the Bash board. The picture below is the new Q5 installed before reattaching the Bash board: Q5 with 2N4401 connected by wires: Unfortunately, after installing the updated Q5, the results were the exact same: Amp not working, IRF740s heating up rapidly. You have given me some test points to look at. I have removed the safety capacitor at C21 to get the value so that I could order replacements if necessary. I will reinstall it later today and I will check voltages across the heat sinks between U4 and U5 (vREGS) and between R78 and R71 as you outline above in steps 1 and 2, respectively. I am assuming DC voltages...correct? Also, am I correct to assume that pin 5 of the BASH board is counting from the side that is closest to Q5? Thanks for the input bro!

Hello ngen33r, I am posting here in your thread to hopefully get some help. I have a RPW-10 that worked great for years and then no longer was working...I unfortunately left the switch in the "auto on" position. I don't use the surround sound system on this TV often, so i do not know how long ago it stopped working...it may have been several months ago! I found the fuse was blown, replaced it and it blew immediately. I removed the plate amp, but I did not see anything obvious in regards to blown components in the power supply. A Google search brought me to this thread and I was on my way! I followed every suggestion in this thread: 1) rebuilt PDC, 2) replaced mosfets, 3) full recap, 4) replaced TH3, and eventually upgrading Q5 to 2N4401 from SOT 23. Rebuilding the PDC was done based on your schematic in the first post of this thread. However, the values of my original resistors were totally different from those in your schematic---although the board number was exactly the same (660038RA). See pictures below: Original board: Rebuilt PDC: I also replaced the two IRF730 Mosfets with two IRF740 Mosfet transistors. I also replaced TH3 (DSP104) even though there was no damage to it and then I replaced all CAPs with Nichon and Kemet (470uf) 105 C caps except I did not change the two 35V 4.7 non-polar caps at C48 and C53 (I ordered regular polar caps by mistake). In addition to all of the suggestions you made in this thread, I also (6) replaced the two voltage regulators at U4 and U5, (7) replaced the transistor at Q8, and for good measure (9) I changed out all 5 of the output transistors (IRFZ14). The picture below summarizes all of the changes: Summary of All changes (before changing out Q5): Now, I am no longer blowing fuses but the amp is still not working. After a short period of being on, the Mosfets really start to heat up...I am not noticing any other components getting warm and there is absolutely no speaker noise. I am now stuck and I am almost tempted to replace the safety capacitors (yellow thingys) and the bridge rectifier. However, I wanted to reach out to you first for some guidance. I have no schematic and I haven't got the slightest clue how to trouble shoot without knowing voltage "test points". Can you please give some advice? I am tempted to throw in the towel and but a new plate amp replacement, but I feel like I am too far into this to quit now...do you have any advice for a hobbyist? Thanks in advance!