SM5TTI Tord Posted June 24, 2025 Posted June 24, 2025 De nyligen inhandlade Fosi Audio V3 Mono-slutstegen var inte helt friska. Trodde jag... Jag noterade snart att det ena blev lite varmare än det andra, såväl i drift som i standby (AUTO-läge). Eftersom det är garantitid kvar på dem så kontaktade jag Fosi Audio Support. Jag ångrade lite grand att jag inte beställde helt nya hos någon handlare istället för att köpa i andra hand, men snålheten... Efterhand kom jag också på att jag ju faktiskt äger en hyfsad IR-termometer och kunde därmed mäta lite på riktigt, inte bara med handflatan. Maken till tålmodigt och engagerat kundbemötande har jag nog inte upplevt sedan vi började handla på "nätet"! Jag kan kan försäkra er att jag normalt sett inte brukar vara så här fruktansvärt ihärdig och stå på mig heller. Men jag vill nog mena att just det fina bemötandet uppmuntrade mig till att gå hela vägen till att jag till slut kände mig trygg med att det inte är något fel på de små luringarna. Här följer konversationen mellan mig och Fosi Audio Support. ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// To: support@fosiaudio.com From: T…@outlook.com 2025-06-16 kl 11:35 Hello! Some time ago I bought second hand, a pair of V3 Mono. According to the seller, he bought them new this year. They work fine, and I am very pleased with how they perform together with my system. But I am now confident that one of the amplifiers does not cool down completely after it has switched down to standby mode. To be sure there is not any trouble with signal from the receiver preamp out occasionally trigging the V3 Mono, I swapped them. The problem followed the amplifier. So there is something with that particular one. If I set the switch in OFF position, it cools down completely. How to handle this? Kind regard Tord Ekh ====================== FOSI 250617 05:23 Hello,Tord ， Thank you very much for your information. Don't worry, we will track your problem until it is completed. Your problem is: one V3 MONO can be completely cooled when switched to standby mode, but the other V3 MONO needs to be switched to "OFF" to completely cool down, right? If yes, here are some troubleshooting suggestions that I hope will help you. 1) Please remove the problematic V3 MONO separately and disconnect the input signal, switch to standby mode, and observe whether it can cool down automatically. 2) If you have replaced the Op-Amp chip, it is recommended to restore the original op-amp before testing. 3) Cut off the power for 10 minutes and test again. 4) Confirm whether the problematic V3 MONO can automatically enter standby mode: With no cables connected except for power, please turn the unit to 'auto' mode and check if it goes into auto mode. The power indicator light should dim after 20 seconds. If it does, please use high-quality shielded RCA cables. Please check the attached video for more details. https://drive.google.com/file/d/1dH9KqO4lwnO9FSuWBbA_nwkmFUBM2y99/view?usp=sharing If the unit is in auto mode and remains inactive for 10 minutes with the RCA cable plugg Looking forward to your update. ---------- Always happy to hear your suggestions or ideas! Kind regards, Fosi Audio Support Team WhatsApp: +8613716612254 Global Community: https://community.fosiaudio.com Official Site: https://www.fosiaudio.com Support Center: https://support.fosiaudio.com ========================== JAG 250617 06:49 Hello! Thank you for instant reply! I will do as you suggest this evening. Kind regards Tord Ekh ====================================== FOSI 250617 kl 08:11 Thanks, If there is any update, pls let us know, We are here to solve any questions for you. ---------- Always happy to hear your suggestions or ideas! Kind regards, Fosi Audio Support Team ========================================== JAG 250619 10:18 Hello again! First of all, the OP-Amps are all original. Never replaced. I have done som different tests. 4) Both act normally and enter standby mode after about 20 seconds. A) Both V3 Mono in AUTO and played music for 15 to 20 minutes so they both went warm. One is then significantly warmer than the other during operation though. Turned the preamp off, but all cables still connected. Checked that the LED´s dimmed after 10 minutes, and they did. Waited overnight. In the morning none of them as cool as when in OFF position, but one is significantly warm. I would say 35-40 ° C sensed with the palm of my hand. The cooler one maybe around 30° C. B) Same as in A), but disconnected the interconnects from the preamp when I stopped playing music and turned the preamp off. Same result as in A). C) Same as in B), but also disconnected the speaker cables. Same result as in A) and B). Kind regards Tord Ekh ============================================ FOSI 250619 10:35 Hi,Tord, Thank you for your letter. This is a relatively rare problem and it has been escalated to our engineering team for thorough analysis. We expect to have a resolution for you within 1-2 days. Your patience and cooperation throughout this process are greatly appreciated. I will personally reach out to you with any updates as soon as they become available. Sincerely, ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team =========================================== JAG 250620 07:18 Hi Linda! Thank you for your response! Here's an update. I have done some more tests. With no signal in, starting from OFF position. Both V3 Mono cold. By listening to the clicks from the relays inside the V3 Mono´s, I can identify two different relays in each. A more discrete click when I turn from OFF to AUTO or from AUTO (dimmed LED) to OFF, and a more distinctive click when turning to ON or after 20 seconds from ON to AUTO or directly to OFF. Around 40 % of the times I switched both V3 Mono from OFF or ON to AUTO, the suspected V3 Mono does not go to standby mode, even after nearly 60 seconds. No dimmed LED, nor any distinctive click sound, which I guess means it is still in full operation. I did this OFF/AUTO/ON/AUTO-testing for about 10 minutes. During that time, I noticed that the temperature of the suspected V3 Mono was increasing, while the other was still cold. Kind regards Tord Ekh ========================================== FOSI 250620 09:02 Hello, Tord, Thank you very much for your update. Are your two V3 MONOs using the same power adapter? Do you have other power adapters with applicable specifications? If so, please use a separate power adapter for each V3 MONO to test whether the problem exists. Looking forward to your update. ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team ========================================= JAG 250620 09:31 Good morning, Linda! I use the original provided separate Fosi Audio 48V/5A power supply units for each V3 Mono. Kind regards Tord Ekh ========================================== FOSI 250620 09:51 Hi Tord. Thank you very much for your confirmation. We are checking with our technical engineers whether the temperature issue you mentioned is caused by the standby problem. If it is, replacing the V3 MONO board can solve it. I will let you know the update tomorrow. ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team ========================================== FOSI 250620 10:57 Hello, after analysis by our technical engineers, the problem you reported is normal. The signal detection of the current version of V3MONO is very sensitive, and even a slight vibration or interference signal can make it enter the working mode from standby mode. In addition, we are already improving this situation. If you have other questions, please feel free to contact us. ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team ========================================== JAG 250620 15:45 (Här började jag faktiskt trots allt bli lite irriterad, men försökte ”hålla tand för tunga”…) Hello again! The problem is not so much if it enters standby or not. This far it has always entered standby mode when set in AUTO and under normal operation and absence of signal. What really worries me is the significant difference in temperature between the two V3 Mono’s, both in operation and after several hours in standby. That also was what I initially told you about. Quoting my initial message: “Hello! Some time ago I bought second hand, a pair of V3 Mono. According to the seller, he bought them new this year. They work fine, and I am very pleased with how they perform together with my system. But I am now confident that one of the amplifiers does not cool down completely after it has switched down to standby mode. To be sure there is not any trouble with signal from the receiver preamp out occasionally trigging the V3 Mono, I swapped them. The problem followed the amplifier. So there is something with that particular one. If I set the switch in OFF position, it cools down completely. How to handle this? Kind regard Tord Ekh “ Med vänlig hälsning Tord Ekh =========================================== FOSI 250621 05:39 Hi Tord, Thanks for your update. We have sent your feedback to our engineers for further analysis! We will let you know once there is an update. Thanks again! ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team =========================================== FOSI 250621 12:08 Hello, this is our update. Because the signal detection of your V3 MONO is more sensitive, even a slight vibration or interference signal can make it enter the working mode from standby mode, so its temperature will be higher, unless you turn it off. Please put the V3 MONO away from the interference source (refrigerator/washing machine/router) to check if there is any improvement. Looking forward to your update. ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team =========================================== JAG 250623 07:42 Good morning! Yesterday I tested as you suggested. My Home Theatre / Stereo setup is in the living room against the wall at the end of the house. That means there are no interfering electric/electronic devices on the other side of the wall. I made everything in the room except for the V3 Mono´s powerless for more than 6 hours, leaving them in AUTO position (checked that they both were in standby mode). At the end of the day, I turned them upside down one by one and quickly measured the temperature at the center of the bottom of the chassi, with a semiprofessional infrared thermometer. The ”suspected” V3 Mono measured 34.7° C and the other 32.0°. The top side measured 2° C lower for both. On the other hand after continuous operation, playing music for more than 6 hours the day before they both measured around 50° C with a difference of only about 0.2° C. The room temperature is 22° C and the V3 Mono´s are standing by themselves on top of the HT furniture, which means they should have sufficient ventilation. The result is that in standby mode after cooling down, they differ almost 3° C in temperature. That is what concerns me! Kind regards Tord Ekh ============================================ FOSI 250623 11:22 Hello, Tord, Thank you very much for your update. We consulted with our technical engineers and got feedback that this difference in temperature is normal. If you are concerned about the temperature, you can consider adding a cooling fan. In addition, we will also apply for a 15% discount with code：FOSI-15 for you to purchase this cooling fan. Hope it helps. ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team ============================================ JAG 250623 15:52 Hello again, Linda! First of all, thank you so much for your patience with me and my worries! I absolutely want to state that you have shown a very good example of a customer oriented treatment! During this process I have also consulted a very good friend of mine, that has a lot of experience from amplifiers in general. Especially power amplifiers, both class A, AB an D, through repair, modification and DIY build. He also calmed my worries a lot. Thank you for the 15 % discount! A humble question: Will you accept that the discount would be valid if I also at the same time order a LC30-Y? That is one accessory I have had in mind since I decided to buy the V3 Mono´s. Med vänlig hälsning Tord Ekh ============================================ FOSI 250624 05:46 Hi Tord, Thank you so much for your kind words! I'm glad to hear you feel reassured. As for the discount, yes! You can certainly use the discount code for your order of the LC30-Y along with any other items. Just apply the code during checkout, and you'll receive your 15% off. But we need to clarify that only one discount code can be used for one order, and this discount code can only be used once. If you have any more questions or need assistance, feel free to ask! Best regards, ---------- We're always glad to hear your ideas and feedback! Kind regards, Linda Chen | Fosi Audio Support Team ============================================ JAG 250624 11:10 Thank you again, Linda! I just ordered. Since I am very pleased with this whole conversation, I wonder if you would accept that I publish it, from the beginning to the end, in one Swedish audiophile forum, Euphonia Audioforum https://www.euphonia-audioforum.se ? Kind regards Tord Ekh ============================================ FOSI 250624 12:03 Hi Tord Ekh Thank you for reaching out. You're so kind! We don’t mind. If you have any other issues, feel free to contact FOSI anytime, and we will do our best to assist you. ---------- Kind regards, Jaimy | Fosi Audio Support Team ////////////////////////////////////////////////////////////////////////////////////// "Som man ropar får man svar!" Ett socialt kompetent resonemang i positiv och konstruktiv anda kan få goda följder! byZan, LasseJ, lindvall and 1 other 4 Quote
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