I intend on applying a sheet of alubutyl between the transformer and case to see if something changes. I am preparing myself not to be dissapointed if it changes nothing.
There are rubber washers between case and xformer, that is why i think that anti vibration devices will do nothing.
Also placed some rubber pieces between screw and xformer case, but that also did nothing.
I am thinking about doing a dc blocker, to try to eliminate the case not treat the symptoms - have to read up on the elliott sound article.
@zenmod - making a ne FE sounds good except I am extremely behind on my projects, but if pcb's are easy to source (and not outrageously expensive) in Europe i would order a couple to have on hand.
There are rubber washers between case and xformer, that is why i think that anti vibration devices will do nothing.
Also placed some rubber pieces between screw and xformer case, but that also did nothing.
I am thinking about doing a dc blocker, to try to eliminate the case not treat the symptoms - have to read up on the elliott sound article.
@zenmod - making a ne FE sounds good except I am extremely behind on my projects, but if pcb's are easy to source (and not outrageously expensive) in Europe i would order a couple to have on hand.
just ask in that thread for post with gerbers, Guyz will inform you
easy to order from JLCPCB and maybe some Guyz are having few leftovers
there are gerbers for Papa's and also for my iteration
easy to order from JLCPCB and maybe some Guyz are having few leftovers
there are gerbers for Papa's and also for my iteration
Please check physical earth connectivity from transformer housing till the mains cord, if it has three wires.
Otherwise also, see if doing so reduces the noise.
You can also remove the centre bolt, apply silicon to the top and bottom flanges, and fix it back, the silicon may act as a damper.
I think hot glue will also work...
Otherwise also, see if doing so reduces the noise.
You can also remove the centre bolt, apply silicon to the top and bottom flanges, and fix it back, the silicon may act as a damper.
I think hot glue will also work...
The case of the transformer is non conductive. If I want to ground it, i would have to get the paint off at one of the screw holes.
Got myself a dc blocker and also placed two layers of sound absorbing mats, and the buzzing while seems lower in intensity, it is still present. I also want to test de dc blocker hooked to the bucking transformer and see if it improves, but I have accepted the idea that I have to start looking for a replacement transformer.
Tested volte of one secondary and it is 38v, so I will be rounding up to 40. What I do not totaly understant yet is why the primaries have 6 wires - I am assuming two primaries with 110-0-100. Hooking a 0-230 instead should easy enough. Can anybody comment on the VA rating needed, is 500va overkill? Read somewhere about 400w, bI guess a bit of reserve can not be so bad
Here are a few fotos. Wondering if the big MKPs are original or some form of tuning?
Got myself a dc blocker and also placed two layers of sound absorbing mats, and the buzzing while seems lower in intensity, it is still present. I also want to test de dc blocker hooked to the bucking transformer and see if it improves, but I have accepted the idea that I have to start looking for a replacement transformer.
Tested volte of one secondary and it is 38v, so I will be rounding up to 40. What I do not totaly understant yet is why the primaries have 6 wires - I am assuming two primaries with 110-0-100. Hooking a 0-230 instead should easy enough. Can anybody comment on the VA rating needed, is 500va overkill? Read somewhere about 400w, bI guess a bit of reserve can not be so bad
Here are a few fotos. Wondering if the big MKPs are original or some form of tuning?
Small update from me, I ordered a 2x38v trafo from Toroidy which came a few days ago. I managed to swap it today.
A few things that might be noteworthy:
Also the new trafo has a smaller diameter, so there is more space to the nearest pcb.
A few things that might be noteworthy:
- bias was waaay up on both channels (even after turning it down a bit), but managed to set both to aprox 180mv
- what happens now and did not before, is a small thump on power on and off. Also the power light fades much more slowly on turn off than before
- rail voltage is 52v on both channel, so 3v up from the schematic
Also the new trafo has a smaller diameter, so there is more space to the nearest pcb.
Replaced big blue cans with higher rated ones. Also replaced the 2 elcos and tantals iirc and bridge rectifier.
I went with replacements from cheapest to most expensive (also applies to dificulty) to try to eliminate trafu buzz.
I am now certain the trafo was defective due to the observations posted above.
I am now assesing the sound quality to see if there are improvements - will post after a few more records.
edit: to answer your question, yes, new trafo was the only fix for me. I recommend doing it all at once. I did them separate, and undoing all the screws takes time and might cause wear.
I went with replacements from cheapest to most expensive (also applies to dificulty) to try to eliminate trafu buzz.
I am now certain the trafo was defective due to the observations posted above.
I am now assesing the sound quality to see if there are improvements - will post after a few more records.
edit: to answer your question, yes, new trafo was the only fix for me. I recommend doing it all at once. I did them separate, and undoing all the screws takes time and might cause wear.
Last edited:
Dunk the old one in varnish, keep in reserve for another project.
Another cause of hum in transformers seems to be from the new higher mains voltages, 240V instead of 220V earlier, which can drive the core into saturation.
The fix is an auto transformer, or a drop resistor...
Congratulations, enjoy the sound.
Another cause of hum in transformers seems to be from the new higher mains voltages, 240V instead of 220V earlier, which can drive the core into saturation.
The fix is an auto transformer, or a drop resistor...
Congratulations, enjoy the sound.
Here is a link to the schematic I use:
https://www.diyaudio.com/community/attachments/schematics-threshold-s150-s1000-amp-jpg.135878/
Tried the biasing procedure that you posted more than once. With the bias at 160 the heatsink reached about 40C (aproximated). Will measure over the weekend as i need to borrow a ir thermometer from work
That channel was not quite right ever since i got the amp, but was hooing it will get better after i change the caps, but it obviously did not.
https://www.diyaudio.com/community/attachments/schematics-threshold-s150-s1000-amp-jpg.135878/
Tried the biasing procedure that you posted more than once. With the bias at 160 the heatsink reached about 40C (aproximated). Will measure over the weekend as i need to borrow a ir thermometer from work
That channel was not quite right ever since i got the amp, but was hooing it will get better after i change the caps, but it obviously did not.
Man that did the trick. Had to improvise a bit as i had no 120k on hand so i did 3x33k.
The bias is set to 180mv with the trimmer set in the middle.
I can not thank ypu enough for your help, wo if you ever find yourself in frankfurt, alcoholic beverages are on me
The bias is set to 180mv with the trimmer set in the middle.
I can not thank ypu enough for your help, wo if you ever find yourself in frankfurt, alcoholic beverages are on me
observe Iq; if it is stable, both channels in temp equilibrium, you're good
if that channel drifts, few transistors need to be changed
if that channel drifts, few transistors need to be changed