most transformer "hum" comes from loose windings. not DC. that is also why people tend to get "hum" from big current transformers. big current=thick copper. thick copper=hard to get tight windings.
I usually tape the bottom of the transformer and mix up some laminating epoxy and fill the center up to the top. When it kicks off, I take a forstner bit and make a level pad in the top, then drill through with a 5/16" drill.
I can mount using only a bolt, nut, washer and one rubber pad on the bottom.
You could buy one of those transformer covers I've seen on eBay and fill the whole thing with epoxy and see if the windings can get loose from all that epoxy!
I like epoxy.
Rush
I'm thinking of filling the transformer up with silicon rubber. Silicon rubber has some interesting properties that might come in handy eliminating transformer hum.
- It can be poured into the transformer, it's easy to work with
- It stays elastic once it's dry, thus good at absorbing vibrations.
- It can handle very high (and low) temperatures.
- Very high chemical resistance, it does not react with most other components
A wise man told me a long time ago
Quote >
exactly
when I tell to my supplier - " Iwanna300VAdonutwithstaticshield2x18Vacindependent notcentretapped36VacanditwillworkinclassAampwith10 0VAconstantjuice" , he answer : "yeahcorewillbedoublebakednextsizeandwirewillbesom ewhatthickerbutI'llchargejust10%morethanforusuall3 00VAdonutmadeforhalogenbl/i/o/nding"
simple , isn't it ?
at least 'till first time he forget to pass that info to winder
btw. - all what proper xformer can and must emanate is feel of scare and respect , in area 5 times greater than his own dims .
buzz isn't included , just because clever xformers know that old farts are usually deaf , and they must be scared , too ........
so - just matter of efficiency - don't waste power on buzz , so you can scare them more
end quote
A the time I had 2 1000 VA 20/24 V split secondary transformers made to order
both buzing like hapy vasp going to a party
As I did ask suplier to do real nice ones one went back
I had new tighter layer of thick tape and was put on hot bath of warnish
No more buz other one I use for mules.
By hot bath of warnish I believe they put trafo in metal buket fill up with varnish and cook for a while in prety hot oven so to get rid of air trapped inside not one of the things I wuld do in her kitchen oven then let dry for a while
others manufacturers may mention vacum diped.
Wuld I buy more trafos from same Dudes? NO
Wuld I buy traffo from known manufacturer at 2 time the price? YES
Off topic
Wuld I use same trafo for stereo F5 Turbo?
NO
reason one) 24 Sec for Turbo is waste of time 30 V ac is bare minimum
reason 2) 1000VA over 48 V = near enoug 10 A
considering 24 V ac X 1.471 : 4 ohms speakers = current clipping
By the way I have the DC protection as in ESP pages (600V30A bridge + caps ) it may not be needed but one can never be sure so why not especilay as it can be used before your mains go to the FiFi collection of extention leads and stacable plugs
Quote >
exactly
when I tell to my supplier - " Iwanna300VAdonutwithstaticshield2x18Vacindependent notcentretapped36VacanditwillworkinclassAampwith10 0VAconstantjuice" , he answer : "yeahcorewillbedoublebakednextsizeandwirewillbesom ewhatthickerbutI'llchargejust10%morethanforusuall3 00VAdonutmadeforhalogenbl/i/o/nding"
simple , isn't it ?
at least 'till first time he forget to pass that info to winder
btw. - all what proper xformer can and must emanate is feel of scare and respect , in area 5 times greater than his own dims .
buzz isn't included , just because clever xformers know that old farts are usually deaf , and they must be scared , too ........
so - just matter of efficiency - don't waste power on buzz , so you can scare them more
end quote
A the time I had 2 1000 VA 20/24 V split secondary transformers made to order
both buzing like hapy vasp going to a party
As I did ask suplier to do real nice ones one went back
I had new tighter layer of thick tape and was put on hot bath of warnish
No more buz other one I use for mules.
By hot bath of warnish I believe they put trafo in metal buket fill up with varnish and cook for a while in prety hot oven so to get rid of air trapped inside not one of the things I wuld do in her kitchen oven then let dry for a while
others manufacturers may mention vacum diped.
Wuld I buy more trafos from same Dudes? NO
Wuld I buy traffo from known manufacturer at 2 time the price? YES
Off topic
Wuld I use same trafo for stereo F5 Turbo?
NO
reason one) 24 Sec for Turbo is waste of time 30 V ac is bare minimum
reason 2) 1000VA over 48 V = near enoug 10 A
considering 24 V ac X 1.471 : 4 ohms speakers = current clipping
By the way I have the DC protection as in ESP pages (600V30A bridge + caps ) it may not be needed but one can never be sure so why not especilay as it can be used before your mains go to the FiFi collection of extention leads and stacable plugs
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F5 not working
Hi,
about a year ago I built a Pass F5 amp, based on the Cviller PCBs and component kits from TechDIY.
I am one of the gamblers who just connected it to the mains directly when it were finished, and a little smoke and smell appeared.
I probably have turned the bias pots the wrong way. Afterwards the power supply worked correctly, but it seems that no current were drawn - nothing else got hot.
I have posted about that problem earlier, and a nice member suggested that R11/R12 probably has burned. Indeed those resistors dont look good. It has been sitting on the shelf since then, but now I have ordered some new 0.47 ohms 3w resistors, and today I thought I would solder the old ones out.
They measured ok on my multimeter, and to be sure I connected them to my lab power supply, to see that there were working. And they were, so that was not the problem.
There were only 2 suggestions last time I posted, the other one were that I should only test 1 channel at a time, to avoid messing both channels up.
I have mostly build tube amps, and I am not that good at FET circuits - where do I start looking for errors, and what is a good fault finding proces ?
Thanks in advance
Arthur.
Hi,
about a year ago I built a Pass F5 amp, based on the Cviller PCBs and component kits from TechDIY.
I am one of the gamblers who just connected it to the mains directly when it were finished, and a little smoke and smell appeared.
I probably have turned the bias pots the wrong way. Afterwards the power supply worked correctly, but it seems that no current were drawn - nothing else got hot.
I have posted about that problem earlier, and a nice member suggested that R11/R12 probably has burned. Indeed those resistors dont look good. It has been sitting on the shelf since then, but now I have ordered some new 0.47 ohms 3w resistors, and today I thought I would solder the old ones out.
They measured ok on my multimeter, and to be sure I connected them to my lab power supply, to see that there were working. And they were, so that was not the problem.
There were only 2 suggestions last time I posted, the other one were that I should only test 1 channel at a time, to avoid messing both channels up.
I have mostly build tube amps, and I am not that good at FET circuits - where do I start looking for errors, and what is a good fault finding proces ?
Thanks in advance
Arthur.
----------------------------------------
Thanks for the reply - isn´t there an easier way
... It is so nicely assembled, and it is not easy to disassemble.
I have read Pass´s documents on FET matching.
In a tube circuit I would have measured the voltages on all the tube pins, and probably from that been able to diagnose what is wrong. But I can not do that in a FET circuit.
I did search for a schematic with voltages, but didnt find one.
Best regards
Arthur.
You can use a light bulb in series, set pots correctly (fully shorted gate to source, putting output in cutoff - easy to measure). At this time F5 pulls practically no current, not even as much as a Class D amplifier.
Use a variac to bring up the voltage and if the bulb lights, the output is smoked.
Note that as per Mr. Pass the Drain resistors are somewhat optional. If you do not want to smoke your new set and do not want to buy new equipment, I suppose you could try gambling again, but I'm not sure a public forum should discuss such things.
Another easy way to test is with a low-voltage, current-limited power supply to see if the outputs are indeed toast. I think 12V, 1A regulated and current limited supplies should be easily available, or you could simply hook up two computer PSUs, cheap ones, in series - ensure they have working current limiters, set bias to zero and see if the supplies trip at startup. I would think even a single supply should do it is all you're testing is output failure. Just don't put a big honking transformer on it.
I would suggest fuses in the DC line, but I don't know if they will offer protection from fire and smoke.
Use a variac to bring up the voltage and if the bulb lights, the output is smoked.
Note that as per Mr. Pass the Drain resistors are somewhat optional. If you do not want to smoke your new set and do not want to buy new equipment, I suppose you could try gambling again, but I'm not sure a public forum should discuss such things.
Another easy way to test is with a low-voltage, current-limited power supply to see if the outputs are indeed toast. I think 12V, 1A regulated and current limited supplies should be easily available, or you could simply hook up two computer PSUs, cheap ones, in series - ensure they have working current limiters, set bias to zero and see if the supplies trip at startup. I would think even a single supply should do it is all you're testing is output failure. Just don't put a big honking transformer on it.
I would suggest fuses in the DC line, but I don't know if they will offer protection from fire and smoke.
Cviller and Sangram,
thank you for your replies. I will check the voltages.
I have no access to a variac, but the other suggestion with the low voltage testing is a very good idea - I have 2 small variable power supplies with current limiting on the way home. 2 because I wanted to be able to make an easy +/- supply.
About the gambling you could be right, but on the other hand I guess most of us are here to learn from other peoples successes and failures, and I am not the first, and I am sure also not the last, who will turn the bias pots the wrong way.
I did read the entire thread once, but never saw a schematic with voltages, which I think is kind of strange.
Best regards
Arthur.
thank you for your replies. I will check the voltages.
I have no access to a variac, but the other suggestion with the low voltage testing is a very good idea - I have 2 small variable power supplies with current limiting on the way home. 2 because I wanted to be able to make an easy +/- supply.
About the gambling you could be right, but on the other hand I guess most of us are here to learn from other peoples successes and failures, and I am not the first, and I am sure also not the last, who will turn the bias pots the wrong way.
I did read the entire thread once, but never saw a schematic with voltages, which I think is kind of strange.
Best regards
Arthur.
I don't think the variac is needed when using a lightbulb
but do not adjust to full classA with lightbulb
if considered ok and working, remove lightbulb, and adjust
if I remember correctly you should also measure DC when adjusting bias
slowly adjust both bias pots, bit by bit, and keep DC in grip
(hope this is correct)
but do not adjust to full classA with lightbulb
if considered ok and working, remove lightbulb, and adjust
if I remember correctly you should also measure DC when adjusting bias
slowly adjust both bias pots, bit by bit, and keep DC in grip
(hope this is correct)
Arthur, the voltages of interest are all available on the original schematic. The build guide has some typos (it omitted one decimal point in the schematic), look at the original schematic from the website - the owner and service manual for the F5.
All voltages indicated start at zero for the starting setting, and ramp up as you begin to supply gate bias. The three voltages of interest, as has already been stated, are the voltage across R11, R12 and the output. The former two have to be close to 0.6V, and the last to be as close to zero as possible.
Good Luck with your troubles and the gambling
All voltages indicated start at zero for the starting setting, and ramp up as you begin to supply gate bias. The three voltages of interest, as has already been stated, are the voltage across R11, R12 and the output. The former two have to be close to 0.6V, and the last to be as close to zero as possible.
Good Luck with your troubles and the gambling
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