I bought this to replace the Allied and it seems to run as hot with more hum. Rated At 200ma vs. 175ma. Using 6550/5ar4/6201. I am still very new to this so don't make fun of me, but are power transformers supposed to hum? (Fairly loud) The amplifier works fine and sounds good so I think wiring is correct. I've had it running fine for quite a while with the Allied transformer. There is no hum whatsoever out of the speakers, just the transformer itself. Anyone out there using this transformer?
EDCOR - XPWR033-120
EDCOR - XPWR033-120
A new transformer should neither run hot nor hum. They do though, but it shouldn't hum at an annoying level in a sensible installation and it should be warm, but not hot.
The first thing, you have a lot of voltage there, even with a choke input PSU.
Perhaps it'd be best if you gave a description or other details of the circuit.
The first thing, you have a lot of voltage there, even with a choke input PSU.
Perhaps it'd be best if you gave a description or other details of the circuit.
Tubelab sse. Optional choke and cap. 560ohm cathode resistor. Running in ul with two 6550. One 5ar4. One 12at7.
without knowing your actual temperature, it is hard to make a judgement, as per specs, classB insulation, as long as you do not exceed that temperature you should be fine...
as to traffo humming, are you using steel chassis? if so, rubber pads underneath the traffo mounting can help....
Ok. Give me a little time. I'll get it good and hot, then check the temperature with my meter. Yes it is a steel chassis the previous one hummed, but not like this. Same chassis. Have the kids today so could be a while please keep checking on me. It won't blow up, will it?
you can do the 5 seconds test, hold it with both hands and count 5 seconds, if you can not stand the heat by then, then it is really hot....
how many minutes before the traffo turns hot?
how many minutes before the traffo turns hot?
Running hot and vibrating is an indication that something is wrong. Either the transformer is small for the application or there is a wiring issue. The second being seriously dangerous. Double check your wiring
Don't know about the heat, but I mount all my transformers on EAR Isodamp SD-40, available from Michael Percy.
Unlike other damping materials, there's no anecdotal or magical qualities to EAR products; they are thoroughly tested (the results are on their webpages).
EAR Specialty Composites -- Isodamp, Isoloss, VersaDamp, Tufcote, Confor
Unlike other damping materials, there's no anecdotal or magical qualities to EAR products; they are thoroughly tested (the results are on their webpages).
EAR Specialty Composites -- Isodamp, Isoloss, VersaDamp, Tufcote, Confor
Well this is intended to be used with minor hum/vibration cases that can occur either from working near the trafo's specs or when there is some DC in the power network.
Having a trafo that works hot and fairly loud is an indication of problems.
Having a trafo that works hot and fairly loud is an indication of problems.
I recently had a Ming Da amp do something similar: transformer uncomfortably hot, loud hum, vibration. The problem was a faulty bridge rectifier (tested it with a multimeter). Replaced that and it's working great, so far.
How hard are you running those 6550s? I'm using the XPWR035 in mine, which is rated somewhat similarly to yours except the HT is 370-0-370. It is dead quiet in most cases, except when I lean on it really hard. With KT-88s on the hottest cathode resistor setting, it develops a bit of a buzz and gets toasty after a few hours. I am essentially overloading it: the KT88s draw nearly 100mA each.
Do you have SS diodes installed?
Do you have a clamp-on meter? If you can measure the current going into the amp, we can see if you are exceeding the traffo's VA rating.
Do you have SS diodes installed?
Do you have a clamp-on meter? If you can measure the current going into the amp, we can see if you are exceeding the traffo's VA rating.
Could he pull one of the output tubes to check loading? If so try each output tube. Let it cool good between powering back up though. Is that the new board with IN4007 or UF4007 SS diodes added? Maybe as Russ mentioned a problem with those like polarity.
Randy
Randy
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Looks to be well within spec for the transformer, about ~130mA on a 200mA tranny, 5AR4 draws 1.9mA good there, 3.2mA on the KT88 heaters, good to go... how about the OP taking some voltage measurements at the PSU and on the output tubes and report back. Wiring problem or faulty part. Something is drawing too much current, the power tranny should be loafing along and be barely warm under normal conditions.
Cheers,
Bob
Cheers,
Bob
So I gutted the entire amp today. Checked and rechecked all wiring. Reassembled and even left out the triode ul switch. Just wired it straight ul with cfb. No extra switches. Just on off. Then got rid of the auxiliary capacitor for a new one. Shortened up some wires. Mounted the transformer on felt pads (grounded it to the case of course). And for now used 5u4 and some 6l6gc's. Same 6201. Less hum. Less heat. After several hours I can touch the thing for ten seconds and not get burned. This could be an improvement or could just be the tubes change felt pad thing. Can a bad c1 cause transformer to hum? I think it is fine but it is a little bit big. 56uF. I forgot I had it in there. I'll change it tomorrow and then try the 6550/5ar4 combo. If all that doesn't change the heat/hum issue, then I'll call it a bad transformer.
The is a tad on the big side for C1, but it will be more stressful for the 5AR4 than the transformer. The voltage across the cathode resistors when in operation with the 6550s will help us determine the load. However unless something is going on with one or both of those tubes, they should be more on the cold side with those resistors.
When running the 6L6's this time, it sound like the transformer is operating fairly efficiently. What is your line voltage? Is the transformer buzzing or humming? Do you have the SS rectifier option installed?
GREAT QUESTION. My line voltage has been running quite high. I'm on the east coast and I think George had the same problem. I measured almost 127 the other day. I have no idea what the power company is doing. Must be all these windmills! Supposed to be 115. I'll try to do a full checkout with the meter today if I can get to it.
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