Dayton APA150 AMP issues, only turns on when I physically heat it up w/ a dryer!
Alright so the stereo amp I have been using to power a pair of bookshelf speakers connected to my PC have recently starting shutting down on me. I can get it kicked into ON mode if I heat it up with a dryer, however, if the room gets too cold, I again have to take out the dryer.
I made a very lengthy post over at the EEVblog asking for help and even replaced what we thought might be bad diode to no avail, same problem persists. I will leave a link so you may view my post and pictures. OPA150 Stereo AMP issues, only turns on when I physically heat it up w/ a dryer! - Page 1
I guess what I'm now trying to do is pretty much Frankenstein this thing and that's where I could use some help. Unless someone can review the above post and knows a way around to keeping the amp on constantly, that'd be awesome.
I have been looking at Amp boards to replace the current boards that are in the Dayton amp, basically just use the case (which is nice), connections (RCA, Speaker etc).
I've heard great good deal about some Class D amps based on TPA3255 such as Amplifier Board - AIYIMA B2D2205 - TPA3255 | 4 Channel 315W Power Ampl It's two more channels than I need but I suppose has expandability in future?
That board requires a DC24-48V, I thought about getting this Amplifier Board - AIYIMA B2D1877 | Schottky Rectifier Filter Power Boa and just using the 28.4V toroidal transformer that's already in the Dayton and that takes care of my power supply.
But this is bit going over what I really want to spend on a Frankenstein build. Then I came to thinking that the rectifier 28vAC to 28vDC part of the Dayton amp works, why can't I just wack off the rest of the amp and keep just the rectifier part that gives out 28V DC and hook up a 2 channel board to it.
Do any of the electrical folks know where I would tap this DC power? The rectifier setup is not that complicated, Its AC-0-AC into a Rectron RS 802 single phase bridge rectifier rated at 100V, 8Amps and then into a pair of 5000uf caps for smoothing I guess usually from there it would go into a voltage regulator but that's where I got lost. Do these boards like the one I linked have their own voltage regulators? I'm pretty sure I can just tap the power somewhere after the caps.
given I have the power supply issue taken care of, is there any other 2-Channel boards you guys recommend?
Or should I just get Amplifier - AIYIMA A07 - TPA3255 | 2.0 Channel | 300Wx2 | HiFi and call it a day? Are these good?
I'm sorry my post is all over the place but I'm just tired of keep using the hair dryer to keep my amp running and I don't feel like spending $180 for another one. I've look at AudioSource amps as well but I dont like their form factor, I have no space on my desk for it.
Thanks for reading my nonsensical post, let me know if you guys have questions or ideas.
What about TPA3255 2x260W 2Ch Class D Audio Amplifier|Amplifier| - AliExpress paired with https://www.aliexpress.com/item/32880495843.html?spm=a2g0s.9042311.0.0.129c4c4d4HAXzH which I can connect to the transformer already in the amp. Would this work?
Any idea on how I can control volume on the TPA3255 Amp? I'm using a TOPPING D10 DAC and would like a physical knob and not rely on my computer for volume.
Alright so the stereo amp I have been using to power a pair of bookshelf speakers connected to my PC have recently starting shutting down on me. I can get it kicked into ON mode if I heat it up with a dryer, however, if the room gets too cold, I again have to take out the dryer.
I made a very lengthy post over at the EEVblog asking for help and even replaced what we thought might be bad diode to no avail, same problem persists. I will leave a link so you may view my post and pictures. OPA150 Stereo AMP issues, only turns on when I physically heat it up w/ a dryer! - Page 1
I guess what I'm now trying to do is pretty much Frankenstein this thing and that's where I could use some help. Unless someone can review the above post and knows a way around to keeping the amp on constantly, that'd be awesome.
I have been looking at Amp boards to replace the current boards that are in the Dayton amp, basically just use the case (which is nice), connections (RCA, Speaker etc).
I've heard great good deal about some Class D amps based on TPA3255 such as Amplifier Board - AIYIMA B2D2205 - TPA3255 | 4 Channel 315W Power Ampl It's two more channels than I need but I suppose has expandability in future?
That board requires a DC24-48V, I thought about getting this Amplifier Board - AIYIMA B2D1877 | Schottky Rectifier Filter Power Boa and just using the 28.4V toroidal transformer that's already in the Dayton and that takes care of my power supply.
But this is bit going over what I really want to spend on a Frankenstein build. Then I came to thinking that the rectifier 28vAC to 28vDC part of the Dayton amp works, why can't I just wack off the rest of the amp and keep just the rectifier part that gives out 28V DC and hook up a 2 channel board to it.
Do any of the electrical folks know where I would tap this DC power? The rectifier setup is not that complicated, Its AC-0-AC into a Rectron RS 802 single phase bridge rectifier rated at 100V, 8Amps and then into a pair of 5000uf caps for smoothing I guess usually from there it would go into a voltage regulator but that's where I got lost. Do these boards like the one I linked have their own voltage regulators? I'm pretty sure I can just tap the power somewhere after the caps.
given I have the power supply issue taken care of, is there any other 2-Channel boards you guys recommend?
Or should I just get Amplifier - AIYIMA A07 - TPA3255 | 2.0 Channel | 300Wx2 | HiFi and call it a day? Are these good?
I'm sorry my post is all over the place but I'm just tired of keep using the hair dryer to keep my amp running and I don't feel like spending $180 for another one. I've look at AudioSource amps as well but I dont like their form factor, I have no space on my desk for it.
Thanks for reading my nonsensical post, let me know if you guys have questions or ideas.
What about TPA3255 2x260W 2Ch Class D Audio Amplifier|Amplifier| - AliExpress paired with https://www.aliexpress.com/item/32880495843.html?spm=a2g0s.9042311.0.0.129c4c4d4HAXzH which I can connect to the transformer already in the amp. Would this work?
Any idea on how I can control volume on the TPA3255 Amp? I'm using a TOPPING D10 DAC and would like a physical knob and not rely on my computer for volume.
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I think the amp is an APA150 not OPA150 - you might want to change the title to get more interest.
I have this amp. Very good amp and reliable too. Parts Express has a very good customer service policy and warranty. Have you contacted their service department? Manufacture date on trafo is Dec 2019. You are still under a year old. Why not let them fix it for free?
The TPA3255 is a Class D amp with single rail supply. The APA150 has a dual rail supply and voltage is too high if you made the dual rail a single rail in series. Max voltage on TPA3255 is +51v.
You should look for a simple 75w compact Class AB amp board to replace it. But it won’t be so simple as the heatsink is centrally mounted and fan cooled when hot.
Something like one of the Apex amps or Carlos’ DX amp would be more suitable. Even a 3886 chip amp would be more suited and perfect voltage range.
A few other reasons why TPA3255 won’t work besides voltage. It’s got a BTL output. Meaning you can’t connect the black (negative phase) to ground or use the relays in the APA150.
My guess why it won’t work based on the requirement to heat it with hair dryer: there is a bad thermal cutoff switch inside that is used as last resort to prevent the amp from melting in case the fan fails.
There is a temperature sensor on the heatsink. Either it is bad, or the circuit it has a connected to is bad. You may have a mechanical thermal switch like used on coffee maker. Round aluminum covered button with two spade connectors. It might be bad. Those are replaceable.
I have this amp. Very good amp and reliable too. Parts Express has a very good customer service policy and warranty. Have you contacted their service department? Manufacture date on trafo is Dec 2019. You are still under a year old. Why not let them fix it for free?
The TPA3255 is a Class D amp with single rail supply. The APA150 has a dual rail supply and voltage is too high if you made the dual rail a single rail in series. Max voltage on TPA3255 is +51v.
You should look for a simple 75w compact Class AB amp board to replace it. But it won’t be so simple as the heatsink is centrally mounted and fan cooled when hot.
Something like one of the Apex amps or Carlos’ DX amp would be more suitable. Even a 3886 chip amp would be more suited and perfect voltage range.
A few other reasons why TPA3255 won’t work besides voltage. It’s got a BTL output. Meaning you can’t connect the black (negative phase) to ground or use the relays in the APA150.
My guess why it won’t work based on the requirement to heat it with hair dryer: there is a bad thermal cutoff switch inside that is used as last resort to prevent the amp from melting in case the fan fails.
There is a temperature sensor on the heatsink. Either it is bad, or the circuit it has a connected to is bad. You may have a mechanical thermal switch like used on coffee maker. Round aluminum covered button with two spade connectors. It might be bad. Those are replaceable.
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I've gone over all three baords and re-flowed most every joint I could get to, same issue.
Unfortunately, the amp is now about 5.5 years old. It started to exhibit the issues right after warranty expired. I contacted Parts Express for possible resolution and they pretty much told me not much they can do, nor can they provide replacement parts, even for a price. My only option that they presented was that they still make this amp and I can buy a new one.
Odd that the 1-2 star reviews (Besides mine) also state the SAME exact issue of amp starting to click on/off after a few years. One reviewer said he uses a few of them and they all exhibit this behavior but he just buys new ones, not sure why haha. I don't know how long you have had yours but you must have lucked out.
Do you see a temp switch anywhere in the pics I posted? I couldn't see one physically but it could be packaged differently and I'm unfamiliar with it. But the thermal switch would be protecting from over heating and not being too cold right? how does that play into this situation?
My 2nd option (Easiest and Economical) is to just gut it and keep the 28V Transformer, plugs/wiring and get the following: TPA3255 2x260W 2Ch Class D Audio Amplifier|Amplifier| - AliExpress and AIYIMA 35A Rectifier filter Board 10000uf/50V AC to DC Audio Amplifier Supply Power Board Diy Kits For 3886 7293 Amplifier DIY|Amplifier| - AliExpress
The 28V AC Transformer should provide roughly 38-40V of DC using the rectifier linked above and I've read the 3E TPA3255 AMP is more than capable of handling that voltage. I can reuse all the connections including power switch. The volume knob is just a 6 pin pot that's prewired, I can stick that between the inputs before they go to the TPA3255 board right? otherwise I was going to get 1pc Japan ALPS RK27 Volume LOG Stereo Potentiometer 2 gang Dual 10K/20K/50K/100K/250K/500K Slotted Shaft + PCB|Switches| - AliExpress which really is no different than the pot that's in the APA150 now, maybe little better quality?
Do you see any problems going this route?
One more thing on existing problem. In the last picture you'll see I've drawn a red rectangle around few resistors and a diode. This area specifically when heated keeps the amp on (Relays switch on). I've replaced all these parts and to my surprise, same problem with needing heat in same area. So either there is a microfracture somewhere in that area on the board or the heat changes the resistor values enough that it kicks it on.
Thing to note is that the voltage across that ZD6 diode is dropping, when I warm it, it gets to 10.2V, but over time it drops and once it gets below 9.75V, the relays click off. I have to keep the heat trapped in the amp for it to stay on longer. The colder the room, the faster it'll shut off. I don't even know where to start to keep the thing on constantly.
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One more thing. In the last picture you'll see I've drawn a red rectangle aorund few resistors and a diode. This area specifically when heated keeps the amp on (Relays switch on). I've replaced all these parts and to my surprise, same problem with needing heat in same area. So either there is a microfracture somewhere in that area on the board or the heat changes the resistor values enough that it kicks it on.
Thing to note is that the voltage across that ZD6 diode drops over time, when I warm it up, voltage starts around 10.2 and amp works fine but over time it's dropping. The more heat can escape, the quicker it drops, once it hits 9.75V, the relays click off and that's it. I have to keep the heat trapped in the amp to keep that voltage from dropping too fast but ever couple hours gotta bust out the hair dryer and It's getting very annoying. But it works really well for those 2 hours haha.
Thing to note is that the voltage across that ZD6 diode drops over time, when I warm it up, voltage starts around 10.2 and amp works fine but over time it's dropping. The more heat can escape, the quicker it drops, once it hits 9.75V, the relays click off and that's it. I have to keep the heat trapped in the amp to keep that voltage from dropping too fast but ever couple hours gotta bust out the hair dryer and It's getting very annoying. But it works really well for those 2 hours haha.
Did you try replacing the ZD6 diode? I assume that’s a 6v zener diode. If you detect a temperature varying voltage there maybe it’s a bad thermistor or NTC somewhere in the circuit. It would be good to see a schematic. Can Dayton provide you with that?
The 28v trafo, if dual secondaries can be paralleled for 39vdc out. If it is center tapped, you can only use 1/2 of the VA rating. That’s an ambitious project to retrofit this with a 3255. That amp needs a reset button and be careful with making sure both speaker outputs are isolated from ground.
The 28v trafo, if dual secondaries can be paralleled for 39vdc out. If it is center tapped, you can only use 1/2 of the VA rating. That’s an ambitious project to retrofit this with a 3255. That amp needs a reset button and be careful with making sure both speaker outputs are isolated from ground.
Yes, I've replaced the diode in question, no luck, same problem needing heat to turn on. It's a 12V (C12) Diode. And I think the transformer is center tapped. it's output is 28v-0-28v, can it be wired in parallel?
In the case of not, instead of guessing, I may just opt for a 36V switching supply and call it a day. If going this route, for that amp board, would you recommend staying with 36V or going with a 48V?
Thank you
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When you say "When the room gets too cold", how cold are we talking. Electrolytics will go down in capacitance when they get cold. I had a furnace (in the attic) that would fail if the night temps dropped below about 32. I took a hairdryer into the attic and heated the board and it would work. I ended up replacing all the caps and it worked again without the hairdryer. I was curious so I put a cap meter on the caps one by one and stuck them in the freezer. One of them dropped to less than 30% of its value after about a minute in the freezer.
low 70s high 60s F. I mean cold as in when AC is running. not freezing cold. It's enough to cool the amp down enough, I hear it start clicking and boom and then off it goes. The clicking comes from the relays which basically is what's controlling the output. Temp is what causes the relays to switch on / off. If the amp is in a warmish room 77-80F, it stays on once I kickstart the amp with a blow dryer.
Surges in power also make it turn on/off/on (Laser Printer, turning off/on AC etc). Im phrasing this incorrectly, The amp STAYS on, it's just the output cuts off/on because of the relays which keep flicking on/off. I've replaced the relays too and same problem.
I think I'm over this amp haha. It's taken up so much of my time that in hindsight, I should have just bought a new amp long ago. But I been stubborn about it.
hmm I'll try reflowing it but it's all through-hole components and backside where leads come out is soldered pretty well.
There's actually a few components where they are soldered well on the backside but the hole looks "empty" when viewed from top (component side). Not the greatest soldering as the solder should flow through even if only soldering on the backside. I'll reflow it thoroughly and see if it helps. Thanks, will keep you posted.
It look like double sided board, solder should flow through both side tho.
Double Sided PCB - The Engineering Projects
Double Sided PCB - The Engineering Projects
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Did you ever get this problem resolved? I'm having similar problems on (2) APA150s. Like you, I suspect it's one or both of the thermistors, or the circuit before the thermistors. I've spoken to Parts Express and Dayton audio, both say they've never heard of this. My units shut off from what I believe is heat. But the heat sink never gets hot. When you disassembled your amp, did you remove the large heatsink. It looks like there is a thermistor thermal pasted it to the heatsink on each channel card. Did you try to heat the thermistor itself?
Resolved: If you own an APA150 and it randomly shuts off, the problem is likely a loose connection. A strong indicator is if the fan doesn't come on before shut down. When I disassembled my 2nd failed APA150, I noticed that the speaker spade connected at the PCB was loose. This was causing a fault, the amp would shut down, and the fan turn on. After I checked and tightened all screws on in the amp, the problem was solved. I've seen this problem before on a Yamaha DSP3090 receiver. It would shut down randomly until chassis screws were tightened. For the APA150, the indicator is the cooling fan not coming on until shutdown. When resolved, the fan will come on in high load situations, but will cycle off when system is cooler. I hope this helps other with similar problems.
