That I cannot answer.
MC225 transformer heat
- Thread starter Alfmonster
- Start date
That I cannot answer.
Alfmonster
Active Member
That is super interesting - even though it seems obvious now, I never thought of the difference in voltage from when these amplifiers were made to now— the 110-120+/-..the video @MACKIE1975 posted was also helpful in explaining this.
what kind of Thermistor did you change to? I may have to order one of those power monitors today. Is there a device or some sort of a step down transformer that would get the voltage closer to the 110v?
Would this work:
https://www.bhphotovideo.com/c/prod...Ch08wgHpEAQYAiABEgIOkPD_BwE&lsft=BI:514&smp=y
Alfmonster
Active Member
Thanks @62caddy — I figured this might be something I need to ask Ryan. I might need to head over to AudioClassics to drop off the 4100 so maybe I can ask then.
do you use a step down transformer or power conditioner to get the voltage down to the 110-117v for yo vintage Mc gear?
If you do, tell him to get cracking on my MAC4100!
Never did - I doubt it would be necessary for such a small voltage difference.
Alfmonster
Active Member
Jesus - that’s horrible. The idea of seeing the tar drooling out of the transformer. But also very helpful to know. Btw that’s some amazing gear! Yeah the temperature on my 225 after 6 hours is not so hot that I cannot keep my hand on it, but hot enough that it gets uncomfortable after a short time.
It’s good to know that it seem the PT temp issue is not that much of an abnormality or that other owners also have similar experiences.
Bill Ferris
Lunatic Member
As to my selection of a thermistor value different than the original factory one installed, I`m sorry, that I don`t remember, as for 2 reasons : 1, it was a long time ago, & 2, I had purchased a complete range of thermistors, and empirically tried & selected the one that provided me with the results that dropped the AC voltage to a level to satisfy the tube filaments voltage range when the thermistor was operating under load and hot without messing with the amps dynamics.
Maybe someone else can provide you with a helpful thermistor part # !
There is, it`s called a "bucking transformer" , that can be easily built, or found & purchased on line.
That device you linked is not what you need !
Good luck, Alfmonster, Sir.
Ciao
Alfmonster
Active Member
If you do, tell him to get cracking on my MAC4100!
Never did - I doubt it would be necessary for such a small voltage difference.
Haha I will pass along the message!
Alfmonster
Active Member
clinic-audio
all on YAMAHA untill 1990
Hello
This is so interesting - how do you test for a defective selenium diode ? easy to do with one amp meter in serie . Any abnormal power consuption is the key
Also is this a normal procedure that is done when most of these units are being restored ? no many don't know and some replace selenium diode bridge just because they think this is a time bomb
do you know if this is a standard restoration process at AudioClassics ? I don't know but I have no doubt that RYAN is taking care of that
This is so interesting - how do you test for a defective selenium diode ? easy to do with one amp meter in serie . Any abnormal power consuption is the key
Also is this a normal procedure that is done when most of these units are being restored ? no many don't know and some replace selenium diode bridge just because they think this is a time bomb
do you know if this is a standard restoration process at AudioClassics ? I don't know but I have no doubt that RYAN is taking care of that
Measure your house voltage, if it's consistant and in the correct range you're off to a good start.
There is a possibility that any selenium rectifier will short, which can do collateral damage so any restoration or service at this time involves a diode rectifier with series resistor to create the same voltage drop as the selenium rectifier.
I buy my thermistors from McIntosh Parts, they haven't run out yet and they seem to work well.
There is a possibility that any selenium rectifier will short, which can do collateral damage so any restoration or service at this time involves a diode rectifier with series resistor to create the same voltage drop as the selenium rectifier.
I buy my thermistors from McIntosh Parts, they haven't run out yet and they seem to work well.
nj pheonix
Lunatic Member
I rebuilt a 225 a couple of years ago. ( total rebuild, new chassis, sockets, barrier strip. Really just xfmrs original. ( and one thing maybe power outlet?)
Anyway
Buyer called to ask me why one of the 3 transformers got hot and the other two didn't.
In fact the PT was cool enough to keep your hand on, just much hotter than the OPTS.
Patrice is likely right about selenium rectifier.
I'm merely pointing out that functioning normally it might be perceived as hotter than it should.
Anyway
Buyer called to ask me why one of the 3 transformers got hot and the other two didn't.
In fact the PT was cool enough to keep your hand on, just much hotter than the OPTS.
Patrice is likely right about selenium rectifier.
I'm merely pointing out that functioning normally it might be perceived as hotter than it should.
Alfmonster
Active Member
I wanted to write an update to this heat situation. After @Bill Ferris introduced me to the bucking transformer, I did some searching and settled on the AmpRX Brownbox which was originally designed for vintage guitar tube amps.
I have both the MC225 and MX110z plugged into the Brownbox (max wattage that it can handle is 550w — the MC225 using 200w at rated output and the MX110z using 75w? I think this is correct?) and its now going on 8 hours at around 117-118v (124-125v without the Brownbox) and the MC225’s PT is running a cooler than before to where I can keep my hand on the PT without it getting uncomfortable. The MX110z PT is also running a bit cooler but is still ‘uncomfortably warm to the touch’.
To be honest, I didn’t know if the sonic improvements would be noticeable but it was immediate. At least for me. And the music that started coming out was, for my lack of a better description, some of the sweetest sounds I have ever heard from these units.
I have both the MC225 and MX110z plugged into the Brownbox (max wattage that it can handle is 550w — the MC225 using 200w at rated output and the MX110z using 75w? I think this is correct?) and its now going on 8 hours at around 117-118v (124-125v without the Brownbox) and the MC225’s PT is running a cooler than before to where I can keep my hand on the PT without it getting uncomfortable. The MX110z PT is also running a bit cooler but is still ‘uncomfortably warm to the touch’.
To be honest, I didn’t know if the sonic improvements would be noticeable but it was immediate. At least for me. And the music that started coming out was, for my lack of a better description, some of the sweetest sounds I have ever heard from these units.
not being able to keep your hand on the trans after 6 hrs of use does sound hot. I have a couple of 225s, both remain very cool even during extended use.
may want to look at DC leakage through coupling caps (did the service work change them out or leave them in?; the dog bones in the 225 are usually pretty reliable, but would still check), Then would look at total idle current draw, and take some bias measurements to make sure a resistor has not drifted.
may want to look at DC leakage through coupling caps (did the service work change them out or leave them in?; the dog bones in the 225 are usually pretty reliable, but would still check), Then would look at total idle current draw, and take some bias measurements to make sure a resistor has not drifted.
jimimac
UTOPIAN UNIVERSE?
Very interesting technical stuff here.These Transformers you mention getting Hot or leaking tar were designed way before I started Potting. I believe it was 1998 that I left my warehouse position to take over the potting Job because the old guy was retiring. You have to respect the 450 degree compound because it will Hurt your Skin. I know when they run High voltage through the unit to test them they get Hot.It could be many technical things. Mine are Perfect. The Master Technician status I have Obtained over the years. Keep em Cool guys...
jimimac
UTOPIAN UNIVERSE?
You should keep the amps out of cabinets,away from direct sunlight mabe put some kind of fan to move some air. The Vintage stuff may get warm. The potting compound has A flash point of 550 degrees. Heat is not good.Could affect circuit boards. I wonder how type A power amps last baking from heat ???
Alfmonster
Active Member
I had a suspicion that the heat was not good for the amp — but thanks for the placement advice and for replying to this and confirming about the negative effects of heat on the circuit boards. It’s also good to know about the suggestion of a fan bc I did find using a fan on top of the mx110z cooled down the running temp of the PT.
I’ll have to get a thermometer gun to get the exact temp. Would you say that in your experience, that also a bad sign if the power transformer of a vintage unit gets warm? Should it run completely cool?
so far, from using the bucking transformer at 117v for last few days, it seems to have both improved the performance and brought down the temp of the PT on the 225.
@mcgjohn I’m not sure if the coupling caps have been replaced - I’ll have to ask Ryan at AudioClassics. I’m not sure how to do the other tests you mentioned - however perhaps I can ask Ryan about that as well.
Many many of these spent their lives inside of stereo consoles and cabinets, ... it was designed to handle it within reason and wasn’t built in the day when everyone had air-conditioning either.
damacman
Resident Psycho
jimi - you're back!!