A tale of two Fishies - X-101-C integrated amp restorations

audiodon

Addicted Member
For your restoration pleasure:
I've got two Fisher X-101-C cathode biased 7591 based integrated amps to restore. One's for an audio friend and it's clean and powered up fine on the variac. I'll call it the pretty one.

This will be a Dickensian tale much unlike the Tale of Two Cities, because it will be about the cleanup and restoration of a child of pampered privilege and the cleanup and restoration of a child of neglect and squalor. There's nothing about guillotines, knitting, or substitution of one for the other. Who ever wrote better of the nature of squalor than Charles Dickens? That's not the arena in which I shall choose to do battle. But it seemed like a good title.

The pretty one works fine, just needs some love. Someone's replaced the coupling caps with cheap caps (you know, the kind you used to get for a quarter). When this one is done, it will sound as good as it looks. It will truly be a showcase piece and it will sound like being in a showcase would be a waste of a great sonic performer.

The other one is what I call the ratrig. I'm not sure what I'm going to do with it yet. The front panel is Ok to good, but everything else isn't. I must admit that I bought it off an AK'er but I don't recall who. Therefore I won't say a lot of disparaging things about the workmanship, but it does look like a garage amp. it's got a mixture of two different styles of knobs and there are no knob brights on the four knobs under the cover.
I've brushed off the last of the mouse droppings, but the rust will have to be wire-brushed and painted and it's none too pretty.
It's been recapped, but mistakes were made.
So, in a sense, I will have to undo what has been done and redo it to my satisfaction or to a level of respectability. I haven't decided which. Because the front panel is Ok and will clean up fine, this one will actually look great as long as it's put in a case so you can't see the chassis.
The ratrig in some ways will be the more interesting restoration, but the pretty one is the one that will command the big bucks.

The pictures in this post are of the pretty one.

I'm going to try an experiment and not clean this one up until I've finished the work on it.
I'll have to order some jewels. I'll probably order X-1000 jewels off ebay because at least you get five. Both of these, the pretty one and the ratrig, do not have the green jewel that belongs on the on light.
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The grid resistors are stock, 330k grid bias resistors and a 1k resistor to the tube's pin 6 audio input.

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These pictures are of the ratrig.

Here we have the front panel :scratch2: . . . looks just like the pretty one . . . except that the exterior knobs must have been scavenged from a late tube or early transistor Fisher.
I believe that the scratch near the middle left is not bad and will come off with a cleaning.
There are no knob brights on any other knobs. Probably raided for a more worthy project. That's Ok, the knobs aren't chipped.
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Observe the carnage that can happen to a rusted old hulk full of mouse droppings, that's spent its waning years in a wet and humid unheated environment. A quick and cheap recap and it's ready to go, right?
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No tubes, no bottom panel, only two tube shields.
This unit has deep rust that's worked its way through the coating and deeply into the steel.
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We look under the chassis and there are some flying caps.
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Had a case though, but that case is going to have to wait until the Spring to see an update.
 

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Does anybody have any knowledge about these blue coupling caps used to the output tubes? NRP caps?

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Needless to say, this unit wasn't too expensive. I got it a couple of years ago, threw some test tubes in, brought it up on a variac, wiggled the phase inverter tubes and heard static. I then pronounced it good and put it away for another day. In the meantime, I raided a bottom panel from a tuner, but it doesn't really fit properly so I'll have to find something or fabricate one.

Yesterday, awaiting the proper time to arrive fashionably late to drink some New Year's bubbly, I retubed it and brought it up again. Not much action to speak of. One channel kind of worked.
So, this afternoon, after New Year's recovery time, I took off the cover and started to look around. Here's what I saw:
Someone had misinterpreted restoration instructions and replaced the resistor that is in series with the output coupling cap that should be 1000 ohms with a 220k resistor that should be used for grid bias. This was repeated on all four output tubes.
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So, I repurposed those resistors for grid bias and put in some grid resistors as shown:
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Then, I found the current draw wrong on one tube and narrowed it down by testing both sides of the 10 ohm resistors that had been put in to check bias. One 10 ohm resistor was bad and that pin on the tube was 10 volts higher than the (should be) 42 volts you'd expect to see on a cathode bias setup such as this Fisher circuit. So, I replaced the two worst 10 ohm resistors and sparked it up.
It still worked on one channel so I poked around a bit and found that one coupling capacitor lead was shorted to a resistor lead in the tone amp section. I lifted the lead and, Voila! We Have sound on both channels.
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Actually, it's been running for about four hours now without a hiccup. The bias voltages are fairly close to correct and there's no redplating and no excessive heat. A fine New Year's late afternoon's work.

Oh, and while I was at it, I put two CL-80 thermisters on both sides of the primary, I glued down and tie-wrapped both the blue pair of flying capacitors and the stretched capacitor and just straightened out a couple of things.
Now, as long as I don't move it it's fine. The slightest movement and a cap lead shorts against the chassis. That won't do.

So, I haven't decided whether to completely tidy up the ratrig or not. This one I will clean up before the restoration and then decide.

Or perhaps I'll take a poll . . . though I may not follow the results. We'll see.
Well, thanks for reading as I begin my journey. This won't go too fast. The reality of the workplace and life will slow me down.
 

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If the ratrig were mine I would consider removing and repainting the trannies for a home brew piece. Keep the chassis around....if you don't like the results of your home brew, you can pick up where you left off.

Happy New Year!
 
Nice work, Don. It might be kind of cool to get the ratrig playing beautifully but leave the cosmetics as is. It would be the Susan Boyle of tube amps. :yikes:
 
If I pulled the iron, Hatrack71 would be after my front panel as fast as a fly finds doodoo.
 
FWIW, I vote for a complete restoration of the ratrig, (assuming it's doable, of course). There doesn't seem to be too many X-101-C's left and, IMHO, I think it's one of the coolest units ever made by Fisher.
 
Hey Don,
I felt a little funny when you said the ratrig was from an ak'er, but then I saw that was'nt my work! Phew!! I dont think my old one had ever been under the knife.
 
kymers,
Yours is my go-to integrated that taught me what these are capable of. It's my reference piece.
 
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Back to the pretty one.
It had a bad switch. I'd bought one that came up for sale on BT a while ago and I'm glad I did. I put the switch in, removed the on switch jumper I'd installed and the unit purred along happily. It sounded quite good actually. Better than it had a right to considering the quality of the aftermarket coupling caps that had been put in.

I set the bias properly and was rewarded with pretty good sound. Power is limited, but everything essentially works. I don't know that I've ever had a unit with tighter tube sockets than this one.

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I spent a good part of the weekend working on the pretty one.

First I put two CL-80 thermisters on each side of the primary winding of the power transformer. Then I changed the diodes to Jim McShane's favorite thousand volters and I replaced the .01uf death cap.
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I've replaced all the resistors from the volume pot through the output tubes with Takman RFT carbon films, hand-matched to within 1%. The only ones that aren't Takmans are a few of values I don't have in Takman, also matched and also carbon film and the 1000 ohm grid resistors. I use Kiwame green carbon comp resistors in those positions. Plus I think it's good to mix it up a bit. Who knows, there could be a Takman RFT sound.
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I've also put in the 100 ohm screen stability resistors, 10 ohm biasing resistors, and all the coupling caps. I tested every coupling cap and matched values in microfarads and put the shield side towards the input.

I'd considered using some RFT Multicaps I have, but they're too large in the .1uf configuration used with 220k grid resistors and won't fit. So, I used K40Y paper in oil caps. I did shrink wrap them. Why? Because it's tight in an integrated amp and these are around resistors and I don't want resistor leads shorting on the cap bodies. You don't have to shrink wrap them in receivers where there's plenty of room.

The tone amp section uses Kimber caps and upstream are the yellow polys that came in the amp. Even though I moved all these yellow polys into their present positions, removing brown turds to do so, I don't know if they'll stay there. It sounds a little dull upon initial release, but I'll be working at home tomorrow and will run it all day. It actually sounds duller now than when the brown turds were in there. I can probably swap them for Orange Drops pretty quickly.

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Pictures will have to follow because I can't access the computer that I upload my photos to at the moment.
 

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Don is back working on classic Fishers. All is right with the world again. Or at least a part of it...
 
Why do I replace all the resistors from the volume pot to the output you ask?
Fisher does use carbon film resistors for everything but the grid resistors, but they're specified to 10% or 5%.
I hand match each channel as closely as possible, barring changes from soldering. What that provides is a difficult to beat stereo image, with both channels summing everything beyond the pots in evenly matched output networks.
Doing this resistor mod is expensive and time consuming. But it's not a mystery, only science. Those resistors come out to close to a buck each when you factor in shipping. Well, the pink ones a bit less, but the carbon films for the output tube grids are close to two bucks each. Plus, it takes time to prepare the circuit and plan out what needs to be changed. When you're going after maximum performance, it's worth it. It takes a full day to pull and hand-match the resistor pairs and solder them in. Days at the bench are precious.

I'll adjust the phase inverters using tones and a scope to finish it off in the final reckoning.

In the last photo, you could see three of the original caps repurposed for the input and tone/voltage amp sections. What you don't see is a second tone/voltage coupling cap. It's hidden.
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Pull up the stuff around it and, Voila! Hidden brown turd cap.
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After running the amp for 12 hours, it sounds much better, but those preamp/tone amp caps may still go. The amp is punchier and has more extension because I suspect that the only unused caps, the K40Ys, have ripened some.
Upgrading the power supply will add power and punch, but I will reserve judgement on those little poly caps until after the power supply upgrade.

I'm waiting on some caps that Hayseed Hamfest had to make, so I'm done for now and will be moving back to the ratrig. I'm on a roll.
 

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Very nice work. I like the styling of the 101-C. I'd like to add one to my collection some day. It will be really interesting to see the progress on the poor old rat.
 
I'm working on the ratrig again.
Tom from Hayseed Hamfest states that the caps for both of these units will be manufactured soon.

I decided to do the resistor upgrade discussed in post#12 on the ratrig since the caps aren't here yet.
I did this with one difference from the pretty one - and that difference was in the selection of coupling caps.

Backstory:
Close to a year ago, I bought some, what I thought were, Psvane teflon caps from Parts Connexion.
That purchase spurred this thread:
http://www.audiokarma.org/forums/showthread.php?t=424943
And dovetailed into this thread:
http://forum.audiogon.com/cgi-bin/fr.pl?htech&1327073472

Well, by this time I had paid a premium that I thought was inexpensive compared to Vcaps and I didn't read any feedback that said they don't sound good from people with experience, so I decided to sit on them until the right project came along. I believe that Psvane stuff is up and coming and that the people in that company care. All the feedback was about misrepresenting the caps with the word Teflon and business ethics and China bashing, which is all foolishness. I read through both threads again today to see if there was something I missed, and most of it is internet claptrap.

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I'm not much for internet controversy and didn't play in any of those threads because I just would have been crapped on as a fool and how could I possibly not have demanded my money back and on and on . . . you know the drill.

But Psvane's response made sense to me. Working for a big company, I know mistakes can happen, especially when language translation is at issue and the process of addressing an issue like that is not set in stone for that company - yet.
Psvane said that these caps sound good and that the wires are teflon coated. My take was that the caps were mislabeled, and possibly overpriced, but wouldn't be available in this configuration again. In fact, Psvane's representation seems to have dropped because of this incident. But for any of you who have used the better Shugang tubes, those people are Psvane now and I continue to expect great things from them.
So, my take is that someone not intimately involved with the caps, and might not have had access to the designers. put teflon on the labels because the word teflon was in the specs. It could have been as simple, and yes I'm projecting here based on my own experience, as problems with a product ready to go and rushed to market.
Was I wrong and was the misrepresentation deliberate? I don't know, but as long as the caps sound good, regardless of their formulation, I won't feel taken and I actually don't care.
To paraphrase Randy Newman's song "Rednecks" and speak about myself in the third person for a moment, "He may be a fool, but he's our fool" - at least as far as these coupling caps go.

Well, what better project to try those Psvane caps, which I already own, out in than the ratrig? They are long caps, but the diameter is small, making them ideal for an amp designed to be small with very little chassis height.

My intent is to have a cool looking unit with all damage hidden in the cabinet that also has an amazing power plant under the hood. So, I had a couple more Kimbers and four Psvanes and I installed it all and brought it up this evening. I actually expect this ratrig to turn out even better than the HK Hot Rod did. http://www.audiokarma.org/forums/showthread.php?t=416045&highlight=Chorale


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This amp may look like it's been under a leaky soil pipe with lead stuffed in the joints in a damp cold cellar, but the sound first time I turned it on after this update was rich, open, airy, extended, punchy, and silent between passages . . . and that's after it's been running for only half an hour.

I biased it up again because after changing the diodes it was running very cold and B+ had changed in value.

It liked Pantera, classical SACDs and The Beatles Magical Mystery Tour 2009 CD mono remaster.

It's close to being done in some ways, because even though the caps look awful, the values are close enough to acceptable for me to run it until the new ones come.

Here are a couple of pictures of this amp on the bench. It just has sandlot pick-up preamp tubes, not a tested functional tube team, and the parts bin included a pair of Japanese made Raytheon 12AX7s, a pair of Tung Sol 12AX7s and a pair of RCA short gray plate 12AX7s labeled Hammond. Outputs are three coin based Sylvania 7591s and one other standard base Sylvania. I didn't even test the 12AX7s before putting them in. They're right from the parts bin.

Here are a couple of pictures of the amp on the bench.

Underside:
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Topside:
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I turned the ratrig on this morning and a few hours later I heard a loud snap from two rooms away and behind a closed door.

One of the caps is discharging. If I tap on the top of the unit, a cap discharges against the chassis. I'd never bothered to clean those leads up, other than to move them away from metal.

Oh well, it was on long enough for the transformers to get good and warm, and that's what I wanted. Any water vapor in those trannies is boiled off now.

The next step is to clean up the chassis and front panel.
 
God, I hope you strip that chassis and at least wirebrush and paint it. You could really get fancy and fill the pits with molten lead then file it all down. Better than Bondo. Surprised as hell it works. That says a lot for Fisher Engineering. But the "jury rigged" caps said to me, someone had a death wish. Tom should have the can's by the end of the month and shipped. I've got him building a set of can's for my 800C . Then it's rebuild the power supply 1st. Then I'm gonna re-do all the replacement caps and resistors that were put in earlier. It works but I'm not happy with how it was done.

Those PSVANE's in the X101C are like the long skinny Tootsie Rolls! Damn they are huge! I think I'll leave the K-40's in it and mix up the rest with OD's and Illinois.
 
Here's the before picture:

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When the transformers are unbolted, you can move them around somewhat. Power transformers often have wires on both sides and are sometimes more difficult to move, but you can still get masking paper underneath before spraying.

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I cleaned up the chassis and spray painted the rusty area with some silver gray rustoleum I had.

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I've also painted the transformers with black rustoleum last night.

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I was pretty rough with it, used a lot of ammonia/water mix and used a nylon wire brush as well as a steel wire brush on the toughest spots. It cleaned up fairly well though.
After its bath, I blew everything out with canned air and positioned it in front of the kickspace heater in the kitchen so that when the heat came on overnight, it blew hot air onto the chassis.
 

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