Rs1 Rs2 says on the schema 300 ohms but shows on mouser as 300mohms.
The trimpot shows as Vishay Beyschlag MELF 0204
Edit: Is it 2SK209GR or is it 2sk117GR?
The trimpot shows as Vishay Beyschlag MELF 0204
Edit: Is it 2SK209GR or is it 2sk117GR?
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> Rs1 Rs2 says on the schema 300 ohms but shows on mouser as 300mohms.
My mistake. Should be TWW5J30RE.
> The trimpot shows as Vishay Beyschlag MELF 0204
I always use fixed resistors to trim.
> Is it 2SK209GR or is it 2sk117GR?
PCB will take both.
Patrick
My mistake. Should be TWW5J30RE.
> The trimpot shows as Vishay Beyschlag MELF 0204
I always use fixed resistors to trim.
> Is it 2SK209GR or is it 2sk117GR?
PCB will take both.
Patrick
All buttoned up but I can’t get ride of an audible hum on my Antek 3218. It’s mounted vertically with rubber under the toroidal and all the other rubber discs and retaining ring in place. I’ve rotated it from about 10 o’clock to 2 o’clock with no change and varied the tightness of the mounting bolt. It’s also hotter than I expected, 58 C. The heat sinks are about 50 and the washers over the Mosfets are 66 C. Any thoughts? I’ve hooked up my B1K and speakers and it sounds sweet. But the hum is audible in the room even with the top on. The transformer is quiet at cold start but starts to hum after maybe 20-30 seconds and continues at about the same loudness.
Post pics of how you have the transformer mounted. You don't have it mounted in such a way that you have a shorted turn, do you?
Yes please post pics. I temp probed everything and I am using an antek 3-series as well and it gets as hot as yours but no hum. I use a 21V sec. The mosfets are cooler than yours though. Is your bias ~1.3A per amp?
After heroic search 🙂 , I found my post #3443 for how I mounted mine on G10 plate. I used the cover, but cover or no cover it does not hum.
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I have two Antek 3218 supplies, one for an F6 w/ xfmr mounted horiz. to the chassis bottom panel and one for an M2x w/ xfmr bolted vert. directly to the chassis rear panel. No hum directly from either transformer. Very, very faint hum from F6 loudspeakers. No hum from M2x loudspeakers.
Any possibility either one of the primaries or one of the secondaries is hooked up in reverse polarity from the other primary or secondary?
Any possibility either one of the primaries or one of the secondaries is hooked up in reverse polarity from the other primary or secondary?
to Marconi118 #4928
Hello Marconi118,
the only real change is Rs11/Rs12 (5.1kOhm resistors) in parallel to the caps
Cs1/Cs2.
Or Patrick can chime in. 😉
Greets
Dirk
Hello Marconi118,
the only real change is Rs11/Rs12 (5.1kOhm resistors) in parallel to the caps
Cs1/Cs2.
Or Patrick can chime in. 😉
Greets
Dirk
Here’s a photo. This is simply a piece of angle iron. I have put another layer of dense foam under the transformer and added a nylon washer to the mounting bolt. I made sure the mounting bolt has no contact with the inside of the toroid and the rubber washers are in place.
I don’t think I’ve miswired anything. Wouldn’t that show up as a wrong reading on the secondaries?
Attachments
The narrow iron bracket is not my preferred method. When you tight the central bolt you are not applying uniform pressure all around the core but only in two narrow strips areas. What if you take a small book and place the transformer horizontally on top of it and inside the case far from the steel base or anything iron. Does that still hum?
I manipulated it several ways while it was unmounted and it continued to hum. I do, however, have some different voltage readings on left and right boards. I will pop the top tomorrow and post some measurements. But as I recall I was getting about 660 mV across one of the power resistors compared to about 550mV on the other board.
Almost done my M2x main boards. I must admit, some of the nicest boards I've worked on in a while.
Regards,
Dan 🙂
Regards,
Dan 🙂
jfuguay:
Reverse polarity on one AC primary in parallel with the other (for 120V operation) theoretically would cause the windings to "buck" each other and cause the transformer to hum noticeably. So, BLK+BLK and RED+RED across the AC line would be correct for the AS-3218.
A reversed secondary would put only the ripple out of polarity. I just listened to my transformer with an automotive vibration stethoscope and then reversed one secondary at the bridge. There was a very slight change in hum tone with the out of polarity setup actually sounding a bit smoother and the in polarity a bit raspier. But I'm leaving it connected "in polarity" because it seems there would be a potential loss of transformer efficiency and you can only hear the hum listening very carefully with that stethoscope.
Reverse polarity on one AC primary in parallel with the other (for 120V operation) theoretically would cause the windings to "buck" each other and cause the transformer to hum noticeably. So, BLK+BLK and RED+RED across the AC line would be correct for the AS-3218.
A reversed secondary would put only the ripple out of polarity. I just listened to my transformer with an automotive vibration stethoscope and then reversed one secondary at the bridge. There was a very slight change in hum tone with the out of polarity setup actually sounding a bit smoother and the in polarity a bit raspier. But I'm leaving it connected "in polarity" because it seems there would be a potential loss of transformer efficiency and you can only hear the hum listening very carefully with that stethoscope.
I did the following for my own education. With the 3218 you really can't go wrong?
Regards,
Dan 🙂
Attachments
Thanks for the suggestions on my transformer hum. I haven’t found anything wrong with the transformer wiring, but I do have some odd readings on one amp board. The left board gives readings of right at 650 mV across R13 and R14. But the right board measures 510 mV across R13 and 790 mV across R14. I’ll try to get some good photos of the right board, but would appreciate any ideas in the meantime.
I solved my transformer hum issues but it was a long process.
I guess the hum starts after a while after power-on. M2x build up bias very slowly and hum starts when bias has built up?
You could start with DC-blocking at primary to ensure it is not caused by DC at the mains.
Problem is that you can create DC at secondary if current draw is asymmetrical at secondary (not even draw at both sinus halfwaves). This was my problem. The transformer hum could start suddenly and it could raise and then be silent again. Sometimes left amp and sometimes right amp (I have mono blocks). But now it is silent after I ensured symmetry at secondary. I also have very stable DC-offset < 5mV.
I guess the hum starts after a while after power-on. M2x build up bias very slowly and hum starts when bias has built up?
You could start with DC-blocking at primary to ensure it is not caused by DC at the mains.
Problem is that you can create DC at secondary if current draw is asymmetrical at secondary (not even draw at both sinus halfwaves). This was my problem. The transformer hum could start suddenly and it could raise and then be silent again. Sometimes left amp and sometimes right amp (I have mono blocks). But now it is silent after I ensured symmetry at secondary. I also have very stable DC-offset < 5mV.
I forgot to mention regarding my transformer hum: there is no hum until I connect the boards. It can run all day with just the PS plugging away and not make a sound. With one board connected there is slight hum. With both boards connected there is louder hum.