I had one of my amps burned up in flames. Major failure with burned traces and shot output transistors. Clouds of smoke with flame coming through the top cover. Scary stuff... Oh well, so is life. This happened back in 2020. Messaged Tony at Parasound and placed the order for new Main and Driver boards. The parts are not obtainable through reputable stores and the cost buying from Parasound wouldn't make it worthwhile effort at the time. When I tried to install the mainboard I realized that the new board is not compatible with the chassis and there is interference with protection board. So I had to replace the bars transistors are mounted to with the old ones. I have used the thermal grease recommended by Tony which I bought at mouser. Fired the amp up, adjusted bias, let it sit for 1 hour monitored bias, all good.
Fired it amp played music for 2 hours and it burned again. This time I was able to pull the power plug pretty quick. Looks like all output transistors are gone (brought 4 probe ohm meter from work), all emitter resistors on SC3264 side are gone. One emitter resistor R72 on the SA1295 side is gone as well. Looks like protection board tried to stop this uncontrolled non-sense until Q2 and R6 were burned in flames and 50V C69 got swollen from excitement seeing the firework show. Some other low power resistors are gone (R24, R137) and it doesn't stop there as there is a problem with the driver board.
Family health issues kept me away for quite some time attention. Now I am back to audio hobby and would like to give this amp a third chance. Wrote to Parasound about a year ago but the ownership has changed. The new quote for both boards was substantially higher.
. Contacted Parasound recently (same email) but no reply. Filed the form online and got reply they don't sell parts. . A few days ago I noticed they have opened an online store with replamenet boards The cost of boards is almost 3x of what I have paid initially... (( Since I have nothing to loose I would like to try to repair this guy but buying a replacement board at that cost make no sense as I can obtain a used amp for that price (likely cheaper).
The biggest question who is selling the parts for JC1? How closely do they need to be matched?
a) output transistors 2SC3264 and 2SA1295
b) fets: 2SK1530 (Q38) and 2SJ201 (Q37)
c) (Q1) 2SK3421 and (Q30) 2SA3058. Haven't checked them yet...
d) Driver board Q32 IRF610 and Q31 IRF9610
e) Any recommendations for emitter resistors brand and nominal value (metal oxide)? In the schematic they are 0.1Ohm, but I have heard they have switched to 0.15Ohm later on. Strange color code. I forgot what mine measured at (those that are still alive).
Another interesting observation the complementary output pair 2SC3264 and 2SA1295 on the new board I bought in 2020 had the last letter covered with the paint on all transistors. On my working amp with the old board I have 2SA1295 95Y and 2SC3264 5NY. I removed the paint on the transistors on my "new" main board and saw 2SA1295 65O and 2SC3264 64O (and 65O). Not sure if I understand this correctly, but O vs Y is hfe rank per datasheet. Does it even matter? I think it does since they were covered with paint https://www.semicon.sanken-ele.co.jp/sk_content/2sa1295_ds_en.pdf
Please help or tell me to forget about it...
Fired it amp played music for 2 hours and it burned again. This time I was able to pull the power plug pretty quick. Looks like all output transistors are gone (brought 4 probe ohm meter from work), all emitter resistors on SC3264 side are gone. One emitter resistor R72 on the SA1295 side is gone as well. Looks like protection board tried to stop this uncontrolled non-sense until Q2 and R6 were burned in flames and 50V C69 got swollen from excitement seeing the firework show. Some other low power resistors are gone (R24, R137) and it doesn't stop there as there is a problem with the driver board.
Family health issues kept me away for quite some time attention. Now I am back to audio hobby and would like to give this amp a third chance. Wrote to Parasound about a year ago but the ownership has changed. The new quote for both boards was substantially higher.
. Contacted Parasound recently (same email) but no reply. Filed the form online and got reply they don't sell parts. . A few days ago I noticed they have opened an online store with replamenet boards The cost of boards is almost 3x of what I have paid initially... (( Since I have nothing to loose I would like to try to repair this guy but buying a replacement board at that cost make no sense as I can obtain a used amp for that price (likely cheaper).The biggest question who is selling the parts for JC1? How closely do they need to be matched?
a) output transistors 2SC3264 and 2SA1295
b) fets: 2SK1530 (Q38) and 2SJ201 (Q37)
c) (Q1) 2SK3421 and (Q30) 2SA3058. Haven't checked them yet...
d) Driver board Q32 IRF610 and Q31 IRF9610
e) Any recommendations for emitter resistors brand and nominal value (metal oxide)? In the schematic they are 0.1Ohm, but I have heard they have switched to 0.15Ohm later on. Strange color code. I forgot what mine measured at (those that are still alive).
Another interesting observation the complementary output pair 2SC3264 and 2SA1295 on the new board I bought in 2020 had the last letter covered with the paint on all transistors. On my working amp with the old board I have 2SA1295 95Y and 2SC3264 5NY. I removed the paint on the transistors on my "new" main board and saw 2SA1295 65O and 2SC3264 64O (and 65O). Not sure if I understand this correctly, but O vs Y is hfe rank per datasheet. Does it even matter? I think it does since they were covered with paint
https://www.semicon.sanken-ele.co.jp/sk_content/2sa1295_ds_en.pdfPlease help or tell me to forget about it...
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I wish I knew the root cause of the problem for both failures. I did look at the protection board, measured a few things and it looked good. I did a quick check on the driver board and compared it to the good board. The second failure appeared to damage the driver board, no issues with original driver board based on a quick check vs known good one.
Then my suspect would lead to high frequency oscillations. If this happened in 9-pairs power stage, there was not much chance to survive. It goes quickly. What was the speaker load, type of speaker cable and the length of the cable?
BTW, the original resistors were 0R1/5W, long ago. It would be best to measure what you have.
BTW, the original resistors were 0R1/5W, long ago. It would be best to measure what you have.
Roughly 8 Ohm speaker. You can see these DIY speakers based on Yamaha NS1000M here. The woofer is from Radio Shack 8 Ohm nominal impedance. Speaker wire was Monster Cable M20.2s. This is identical to M2.2/M2.4 cables I have, a car version without network terminators (parallel resistors) and unterminated ends. The length is 10 ft. The woofer burned. The sound had some distortions before voicecoil burned.
I had these amps since 2005. I have repaired them a few times. When I bought them initially I decided to check the bias and noticed that one of the transistors wasn't working. What was strange is that the base resistor (10 Ohm was opened). I replaced it and haven't had issue ever since with the output stage. I did have to rework the unit couple of times due to LED driver circuitry (there were 2 reworks for the same issue). Thankfully Tony was helpful with the instructions. It didn't affect the amp functionality other than flickering between red and blue LEDs.
I had these amps since 2005. I have repaired them a few times. When I bought them initially I decided to check the bias and noticed that one of the transistors wasn't working. What was strange is that the base resistor (10 Ohm was opened). I replaced it and haven't had issue ever since with the output stage. I did have to rework the unit couple of times due to LED driver circuitry (there were 2 reworks for the same issue). Thankfully Tony was helpful with the instructions. It didn't affect the amp functionality other than flickering between red and blue LEDs.
the base resistors on the schematic are 10 Ohm. On my older boards they are indeed 10 Ohm. Though the new replacement board has 4.7 Ohm resistors loaded. I am trying to identify if this is expected or not. Also checking with Parasound but with new ownership they no longer release schematics, they no longer sell spare parts.