Fisher X101B Questions

[Bengal777]

Joe Z.,
Thanks again. OK, I'll check the plate. The amp is on now and when I go to work and turn it off, I'll check that and see if I can find anything.

If the amp is having 'issues', would there be a degridation of the sound at all or is it an 'all or nothing' deal with tube amps? I guess I always thought that tube amps could degredate slowly so the listener might not know how much the amp has drifted from 'norm' over time. SS just fail, one day they work, the next they don't.

I guess my question is this, is there anything that I should be listening for that would make itself aware through audio output?

[josephazannieri]

Yo Bengal777:

You are right, tube amps do degrade slowly over time. In general, the degradation is shown when the amp develops a "softness" to the sound, in the sense that peaks become compressed and "squashed" sounding. You can view this sort of compression and clipping on an oscilloscope. Also, tube amps will develop hum and noise in output. Stick your ear right up to speaker with amp turned up. Try tapping the tubes with a pencil eraser with amp turned up and see if you get noises in output when you tap. If a tube makes ringing or rasping noises when tapped, called "microphonics" it has loose elements and should be replaced. This is most common in gain tubes like 12AX7's or phase inverter tubes where there is some increase in signal level within the tube. It's less likely in power amp tubes. You can often get back the original performance by replacing the output tubes and sometimes the phase inverter. You should replace noisy or microphonic tubes. When you replace output tubes you should check bias according to instructions in service manual. Also, output tubes should be replaced in matched pairs. Don't just replace one output tube.

The red glowing plate symptom appears when amp is operating, not when it is shut off.

In general, I believe that you are better off not running amp all the time. Heat is the enemy of tube amps. You should also be sure that there is lots of space around the tube amp for free flow of air. Many guys take off the wooden or metal case and let air circulate around output tubes. And good luck from that cool and well ventilated, but noisy old guy,

Joe Z.

[Bengal777]

Joe,
OK, I get what you are saying. Somewhat. I guess I view these as built to be used and damn if I don't love the sound so much. I do have it in the wood box and whatnot. I have a fan on it and I really don't think the heat output is much more than the Marantz 2230 I had. Maybe my memory is off though. I guess I could look for another receiver on CL. There might be a Sansui locally here.

Here's another question. These tubes are original, no doubt about it. They say The Fisher on them, powertubes and rec tubes I'm talking. I'm sure the 12AX7's are original too. Should I replace all of them and keep these original tubes for 'originality'? Are tubes viewed like cartridges? Should I find some decent replacement tubes and wrap these up and put them away?

[josephazannieri]

Yo Bengal777:

Putting a fan on amp changes everything. It will get your temperature way down and make amp and tubes last way longer. As for use of amp, I am certainly not suggesting you shouldn't use it. After all, good amps are designed to have long term reliability, and Fisher made a good product. I am suggesting diagnostics to determine if you have suffered degradation, and to fix the problems if there are any, but I certainly would not give the X-101 up unless it is seriously debilitated and not repairable. You can get out a voltmeter and measure the voltages in unit to be sure that it is running to spec, and that will tell you a lot.

Lots of guys love those original tubes, and you might find they are perfectly OK. Just pull them out, one by one, and stick them in a tube checker. Be sure to wear cloth gloves when you pull tubes, so you do not wipe the original paint off the outside, and do not get greasy thumprints on them. Those "Fisher" insignia make the tubes more valuable. If you find a bad tube, just replace it. And check your output tubes. If you want, you can completely retube it, but if you do that check all voltages and be sure to adjust bias if there is a bias adjustment, and then wait a couple of weeks and readjust bias after tubes have stabilized.

And good luck from that well stabilized old guy,

Joe Z.

[Bengal777]

Joe,
Thanks again for the time. I see you are in Ohio, Browns or Bengals or Who Cares? You can see from my handle where I'm at.

I do think that taking it to an amp guy is the thing to do at this point. I do use it almost everyday and it's on anywhere from an hour to 4ish hours. I don't run it more than that. Not that I don't want to, its just a thought of letting it cool down after working for a few hours.

I found a Sansui AU 5500 locally that I'm going to check out tonight. If it fits the bill, I'll put that one in and take the 101 to the local amp guy. I'm sure he'll have it for about 6 months but when it comes back it will be as perfect as it can get.

Another question, should I pull the tubes and take it to him tubeless? Save the tubes for pictures and giggles? I guess I wouldn't see any harm in that. I would want it retubed and biased anyway.

[josephazannieri]

Yo Bengal777:

I am not a football fan, and not much of a sports fan. So, the varous sports teams are not on my radar. I do listen to baseball games in the summer time, and I have a number of friends and associates who are Indians fans.

If you want, you can pack up the tubes and ship them to me, and I will identify any that are bad for you, since I have 2 tube checkers. Just put them in a shoebox wrapped in bubble wrap and fill up the space left over with packing peanuts. Identify the output pairs separately. I will check them for you, mark the bad ones and send them back. You pay the shipping, but no charge for scoping the tubes. My wish for success to another HIFI nut. PM me and I will give address to send to.

You also have the option of giving the amp to your service guy, with or without tubes, but with tubes is better, becasue you will need the tubes in the chassis to measure the voltages. Chances are your service guy will have a tube checker too, and be able to identify bad tubes. I would give the amp to your service guy and have him or her check the filter caps and the rectifiers and be sure that they have not leaked and lost capacitance. I just recapped my Dyna ST-120, which had a bunch of filter caps that had opened up and lost all capacitance over the years. New filters, stock values, improved performance noticeably, particularly in loud passages. You should also check coupling capacitors to be sure that you are not leaking DC onto grids of output tubes.

Anyway, good luck with your X-101. I think you will be pleased with the result, and it will certainly ready you for another 30 years of goood service.

And good luck from that slightly leaky, but well filtered old guy,

Joe Z.

[Bengal777]

HA! Chalk one up to the older gear. I went last night and bought a Sansui AU 5500 and pluged it in this morning and on the right channel the high end is clipping. Not sure if it's a connection problem, the RCA imputs cut in and out with minimal torque or if it's a bad connection.

So the replacement for the tube amp is going to the amp guy BEFORE the old tube amp is. Classic.

Thanks for the offer for the tubes. I might just take you up on that.

[josephazannieri]

Yo Bengal777:

Check to be sure that your speaker wires are not shorted into or contacting each other. In the past, when I was attaching to screw terminals on older gear, particularly tube gear, this happened to me more than once. The short will reduce output considerably and increase distortion noticeably. All you need is one strand of speaker wire making contact, either at speaker end or at amp end. For screw terminals, I now use spade lugs. Lots neater than using bare wire, and far less likely to short out.

So, scope it out. AU-5500 is a nice little amp. Did you get to hook it up before you bought it? If you can, you should try amp before you buy and make sure that it is OK. Bad RCA plugs usually won't cause clipping, which you can hear as severe distortion. Bad RCA plugs will simply make the sound cut in and out, but sound will be good when it is present. A short such as I have described will induce clipping, and the louder you turn it up, the worse it will be.

ANd good luck from that well-clipped old guy who is now cutting out,

Joe Z.

[Bengal777]

Joe,
I love all your signatures. You personalize them to the topic. Very cool.

The Sansui was on when I bought it but he only had a tuner hooked up and he told me about the cutting out issue. It might just be that the rca imputs need cleaning. The clipping issue is another issue. The highs are clipping so I think this one will go first to the amp guy and I'll baby the Fisher until the Sansui gets back then I'll take the Fisher in.

I bought a Soundcraftsmen PE2217 last night with the intentions of using is as a preamp for the Sansui and bypass that preamp incase the clipping is coming from the preamp stage. But to check it out first I hooked it up to the Fisher using the tape loop. Damn if these EQ's are not as quiet as can be. Now I have too many knobs to mess with and endless combos. Makes time pass.

Thanks again for all your help.

[up.north]

Some speakers to check out are the Tektons. Great speakers with great reviews and surprisingly affordable. I have a pair of the Lores I use with my Fisher 500B and Dynaco ST-70. Very efficient at 98dB 1W@1m.

http://www.tektondesign.com