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

Thanks for the complement, Alan. That first cap (C25) is part of the voltage doubler. It's insulated as the metal body is carrying around 200vDC, so if you put a cap underneath to replace it ensure it's insulated too. The positive of that cap connects to the cathode of diode CR1, the 2.2k ohm - 7w resistor, and the center taps of the output transformers. Negative goes to the positive of the other 200uF cap (C26A) and one side of the HV secondary from the power transformer. Nichicon makes a 220uF/350v that's a good replacement for both of those 200uF caps.

edit: modern e-caps tend to have insulated bodies, so insulating may be redundant but still might be a good thing to do.
 
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Yes sir, I've got plenty of those. Sorry, I didn't see your last response until I'd posted that link. The way you explained it is very understandable. THANK YOU! Now I think I've got it. You're a lifesaver.
 
Sorry, forgot that most new e-cap bodies are insulated and probably don't need outside insulation. I'd probably insulate it just the same and, yes, heat shrink will work.
 
Nice. I can't thank you enough. Not sure when I'll get to it, but I'll keep you posted, if you don't mind. Getting excited to nail this psu down so I can change out all the signal caps. This will be going into one of my systems for sure. My first Fisher.
 
image.jpeg Ok folks, it's taking a little longer than I'd hoped, but finally have some progress. Was it peer pressure? Guilt trip? I don't know, but after seeing the work many of you guys have done, I felt totally wrong about adding psu caps under the chassis. So, I've begun my first cap stuffing. Replaced the old 40-40-20 with a new one, got that 220 out and apart. Thanks for the assistance AND inspiration.

Alan
 
Yes sir. Well I've been building motorcycles and cars since I was a puppy, and in construction since 1987. Retired, do to breaking my neck, as a master carpenter. I had faith I could pull off the mechanical part. I'm glad there are so many technical geniuses on here to assist me in that department though.
I did finish two of three of the cans-waiting on an order for the third, and I literally just finished replacing all the signal caps today. Including that hidden one. Used IC's on the preamps, orange drops to the outputs.
So, hopefully this weekend, one more can to stuff, and I need to replace that 2.2K resistor as well as the 'death cap'. Then I hope to get this baby biased asap.
 
So. I started my x-101-c, which I acquired quite accidentally, by replacing a bad cap and resistor in the bias circuit. While I was planning the next courses of action, I cleaned it up a bit, cleaned all the pots and switches as well as tube pins and sockets. Ended up taking advice from you kind folk and stuffed two of the three can caps (the third was common and just swapped in a new one), as well as all the higher wattage psu resistors. My next step was to replace all the signal caps. Preamp tubes got IC caps, outputs got orange drops. I had almost all of the parts I needed in my bins, though I was short one 220uf cap which showed up this morning from Mouser. Stuffed and installed the last can today and set my bias at the specified 40 volts. It's been playing now, with an FM-200-B, for about three hours. Not only does it sound absolutely beautiful, the tubes and trannies are not hot at all. I'm extremely satisfied. I thank you all, not only for the help I specifically asked for, but also for all the other threads I've read through over and over familiarizing myself with The Fisher gear. It's been a goldmine to me and I truly appreciate it. I'm going to say that for now, this project is done. I'll leave it where it is while the caps burn in, and keep an eye out for problems but eventually this is going into my living room system. I'm normally a scratch build guy, I owe it to you folks-and the gentleman I bought it from- for opening my ears to Fisher gear. I really love the sound this thing produce, right now through a pair of 8" Tannoy pro audio/studio monitor speakers (I8).
A question; there is no external ground point for a turntable. Should I add one? Or am I just not seeing it?
Anyway, enjoy your weekend. Thanks for listening. I suppose I'll have to recap that tuner next eh? Sounds wonderful now.
 
I didn't end up taking a whole lot of pictures this go-round. A few just so I didn't 'lose my spot' so to speak. I did take one yesterday, after I replaced the signal caps, before I finished the last of the PSU. I'll post it here, but please, before you get overly critical of my placement and/or soldering know this; I have a ridiculously destroyed neck, and I can't feel the thumb, index and middle fingers on BOTH of my hands. So this type of work is an exercise in patience and concentration. Maybe not the prettiest but sure sounds good!
Oh another question I wanted to ask! The 10 ohm 'safety/bias read' resistors; safe to add to an x-101-c? Necessary?
Thanks! image.jpeg
 
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Two last notes, for now. As it sits on my dining room table burning in, I have a couple cosmetics to work out. All of the knob fronts, or brights, have fallen off. I have three, I've seen them on that auction site. Also, that tiny strip of tolex on the hidey-hole door has come completely unglued. I'll be addressing those
 
Alan,

Enjoyed reading your journey on getting your X-100-C running! I'm a long way from doing the work you did but with more reading and learning I hope to tackle my X-100-3. I remember when I put the bottom plate back on thinking that the rear center screw might be an acceptable ground for a tt. It looks like yours has a similar center screw. Hopefully others will be along to answer that and your other questions. Great work. Every thread I read and view gets me a little closer to having the confidence to tackle my own restoration.

Thanks
Mark
 
If you want to monitor individual tube draw in ma, then yes install the "cathode" resistors. Dave would know exactly if they are as necessary in a cathode biased unit vs. a fixed bias unit.

Use a flexible set adhesive like shoe goo or similar to glue on the brights. Gorilla glue will work you just have to watch how much it expands, so don't use a whole lot on them. I prefer Shoe goo. It set's up and is pliant once it sets up finally. So that if you twist the cap wrong (grab the front and the bright) it won't shear the bright off in a few years.

Looks good, considering your medical problems. I had C5-C6-C7 fused a few years ago and still occasionally get numbness in the hands and fingers. guess thats what i get for banging my head all the time on the low overheads and pipes on submarines when I was active duty back in the 70's.
 
Mark, keep reading! And ask questions, there are extremely knowledgeable and helpful kind people here. I learned that quick. Good luck!

Notdigital, terminal marked four, as in the four ohm speaker tap??

Larry, thanks! I was hoping Dave would read this eventually as well!
I was going to use some 3m contact adhesive for the tolex. It worked for me for many years holding laminates and veneers, gorilla glue on the brights; I'll give that a try. Thank you.
I'm fused from 3 all the way down to 7, and they went back in through the from AND the back to try to repair it. Three times under the knife, three times made it worse. I've got more metal and plastic in there now than bone! Yikes
 
Yes the 4 ohm speaker tap. The way they wired the transformers the ground wire is above chassis ground and the 4 ohm tap is at chassis potential. Don't use a chassis screw like on most receivers/amps to ground Turntables or tape decks, CD players, etc. You'll end up making what little hum you have now worse.
 
Right Larry, that's why I was asking. I remember reading in a few threads that these are 'above ground' Thanks for the quick response. I'll have to write that one down.

Take a note of that Mark!
 
RU -- The 10 Ohm current sensing resistors are certainly nice to have on a 101C, as they allow you to check that all four tubes are handling an even share of the overall output stage current flow. As you are aware, the current through these tubes is used to light the heaters in the phono preamp and line/tone stage small signal tubes. If the quad of output tubes are not well matched, then usually one poor tube ends up carrying the brunt of the current flow, causing it to show color in the plate to some degree or level. By installing the resistors, you can check to make sure that the current draw through all four tubes is nearly equal so that they all share equally in the load.

If you install the current sensing resistors, just remember to install them between pin 5, and all the other wiring originally connected to that pin at each output tube socket. These resistors DO NOT connect to ground like they do in the receivers or other integrated amplifiers. When you check the current flow for a given tube, your meter must connect directly across the resistor for that tube, rather than connecting the meter common lead to the chassis, which you should NOT do in this case.

The current sensing resistors do add a degree of safety in the X-101C, but are hardly needed to produce stable output stage operation. In this case, their primary purpose would be to install the output tubes in the most balanced fashion possible.

I hope this helps!

Dave
 
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