• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Fisher X-101-C

Just quickly, I'll post a scan as soon as I can...from the service manual:

Bias Adjustment:

1. Set volume control to minimum.
2. Connect DC VTVM to Pin 5 of any output tube. (V7, V8, V9, or V10.)
3. Adjust Bias control for 40.0 volts.
 
I can't get mine to go up to 40V for the bias. Thanks for the quick reply fisherdude.
It's at 38.4. Oh well. It'll need some service.
Been critically listening to it for a day and a half. It is the most microdetailed 7591 Fisher amp I've heard. I agree that it's not as punchy as others, but then again it has stock brown body .047uf couplers in it. It's going to get a smattering of .1 uf K40Y PIOs in the pre stage and .1 Jensen Copper foil in oil for the outputs. Not till later though.

Sadly the power transformer on both this X-101-C and the X-101-D hum. I'll try the usual suspects, but I suspect a parts unit will be required. I'll need to make sure I get one before I invest real money in it.
Fisherdude,
How's yours doing?
 
It's doing fine. However, if I start to push it a bit harder with not-very-sensitive speakers, I start to hear some just audible distortion from one channel. Not strong at all, but it shouldn't be there. Since my unit is untouched underneath, I'm going to bench it until I have time to get inside. Not a good idea to take any unnecessary risks.

In the meantime, I've put my big number 800C in the downstairs spot. Wow!
 
audiodon657 said:
Sadly the power transformer on both this X-101-C and the X-101-D hum. I'll try the usual suspects, but I suspect a parts unit will be required. I'll need to make sure I get one before I invest real money in it.
Fisherdude,
How's yours doing?
Click to expand...

I don't want to hijack this thread but I'm curious to know what's the consensus about PS humming. Am I correct to assume that it's just an annoyance, not a real problem?

I ask because I have some that hums (Scott LK-72A, Fleetwood little console amp, Electrohome console amp, Clairtone console amp) and some that don't (Fisher X-100A, Heathkit's AA-32 and AA-100, Nordmende Menuett, another Electrohome console)... Apart the fact that it could disturb music appreciation at low volume, could it cause severe problems (or be the symptom of an imminent failure)?

Thanks.

Patrice
 
gugusse said:
I don't want to hijack this thread but I'm curious to know what's the consensus about PS humming. Am I correct to assume that it's just an annoyance, not a real problem?

I ask because I have some that hums (Scott LK-72A, Fleetwood little console amp, Electrohome console amp, Clairtone console amp) and some that don't (Fisher X-100A, Heathkit's AA-32 and AA-100, Nordmende Menuett, another Electrohome console)... Apart the fact that it could disturb music appreciation at low volume, could it cause severe problems (or be the symptom of an imminent failure)?

Thanks.

Patrice
Click to expand...

Don't confuse power supply humming with power transformer humming.

Power supply humming is heard through the speakers, and is bad. Always. Unless it's barely, barely, audible, you shouldn't really use the amp until the power supply filter capacitors have been replaced. If you continue to use it, there is a chance that a capacitor can fail completely while the amp is on, and if this happens it will cause serious damage to other components.

Power transformer humming can be heard when you put your ear near the transformer. It can be simply due to the bolts holding the end bells to the laminations being loose, or it can be serious internal problems in the transformer.
 
Last edited:
Fisherdude said:
Don't confuse power supply humming with power transformer humming.

Power supply humming is heard through the speakers, and is bad. Always. Unless it's barely, barely, audible, you shouldn't really use the amp until the power supply filter capacitors have been replaced. If you continue to use it, there is a chance that a capacitor can fail completely while the amp is on, and if this happens it will cause serious damage to other components.

Power transformer humming can be heard when you put your ear near the transformer. It can be simply due to the bolts holding the end bells to the laminations being loose, or it can be serious internal problems in the transformer.
Click to expand...

My bad, in my case it is power transformer humming as the amps I own are all rebuilt (well, almost as the Electrohome Conway is stock and I plan to redo the power supply of the little Fleetwood during the Holidays).

In the event it is serious internal problem, my Scott LK-72A should be right dead now as the PT hums since I got it in february and it is running at least 2-3 hours each day, isn't it? I assume it is just something loose inside as I can vary the hum intensity just applying some pressure with my hand on the endbell...

Thanks.

Patrice
 
In my case, I simply find the transformer hum annoying as I can hear it. Seems to me that it's a sound an amp shouldn't emit.
 
audiodon657 said:
In my case, I simply find the transformer hum annoying as I can hear it. Seems to me that it's a sound an amp shouldn't emit.
Click to expand...

At the deafening levels I listen (my girlfriend think I'm deaf, half-true as I lost some hearing in the highs... :D ), it's not a problem. Only if I put my ear right beside the amp at low volume...
 
Last edited:
gugusse said:
...I assume it is just something loose inside as I can vary the hum intensity just applying some pressure with my hand on the endbell...

Thanks.

Patrice
Click to expand...

Break out a screwdriver and tighten the nuts and bolts holding the endbells. You might be surprised! Got my fingers crossed for ya!:yes:
 
Tightened up the end bells on my X-101-C and had no change. I will try the isolation stuff before deciding it must be replaced though. That's the next project in queue when the recapping of my Spendor BC1 speakers is finished.
Don
 
Haven't had any time to work on anything. Clyde, I'm not going to bring the 101-C, I'm bringing something far more rare.
 
That thing just looks so right, and I know the Fisher sound is phenomenal.

Got yourself a real piece, definitely a lifetime keeper.

Cheers
 
Bringing back this thread so I can hopefully add something helpful. I was getting a low level hum on my X-101-C in the right channel, and tried all of the above suggestions without improvement. Finally, started jiggling the tubes. Well, get to the last 12AX7 tube on the right(as I look at the front of the amp), jiggle it, hear a bit of static, jiggle some more, reseat it, and voila, hum gone.

I mention this because while I'm sure most of you already know this, sometimes it's the easiest, most common sense fixes that we don't try that ultimately do the trick. I know that it's very helpful for me to read this kind of stuff so I'm hoping it might help somebody else.

Love my X-101-C

101c1_zps7a062cc9.jpg
[/URL][/IMG]
 
You must log in or register to reply here.
Back
Top Bottom