The Fisher KX-200 - I'm looking forward to this project. Your insights?

I

IanMcI

Active Member
After any number of vintage audio pieces going through my hands, I've built up a small collection of what both interests me and serves their purpose. While I always hoped that tube stereo would find itself in the mix, it did seem mostly a dream, given my circumstances.

But now, with the acquisition of this Fisher KX-200, I'm looking forward to having at last met something of a goal. Here's to my "getting it right".

https://imgur.com/gallery/8KyUc

This was an estate sale find. It looks to be in very good condition. But I do plan on taking heed of advice I've seen on AK forums before: replace the electrolytic capacitors, at least.

So, here's my plan, as near as I can put together with what little knowledge and experience I have:

• Replace all electrolytic capacitors.

Well, that was easy.

Actually, while that would be my first step, I wonder if it would make sense to dive into other suggested mods while I'm at it, i.e., diode replacement, switching ability for separate access to amp and pre-amp, and whatever else may be suggested by those of you who have there before me.

I did ask a local pro what it might cost to do this, but I'm in no position to pay those prices, so DIY is my plan.

• I do have the service manual from FiFi Engine, but will need to identify those capacitors I need to replace. The last photo shows what I'm looking at with the amp opened up.

I do have the controls cover.
I'm missing three "brights".
There is no cover, but that is not an issue.

As of this moment, I'm not sure what else I may need to get this beauty singing. Your thoughts?

Ian
SF Bay Area
 
Ian,

Nice KX200! I bet if you brought it up on a variac it would work based on how even the getter loss in the power tubes is. It's helpful to be able to start service work from a baseline of knowing it fundamentally works. If you don't have the tools needed to bring it up I'd be happy to help. I'm in Oakland and have variac, tube tester etc.

Once you now it works you can replace a few things, verify it still works, then replace a few more. What you do really depends on what you want to get out of it beyond making it safe.

I'm sure Larry will be linking to a rebuild thread pretty soon that has as much or more than you would ever want to do. I don't know how Larry remembers all these threads...
 
I don't. I get lucky on Search. But I've yet to remember a KX-200 thread(after thinking about it all afternoon....Ok, the last two Hours.) Maybe Dave did one on a X 202 (which is similar to the KX-200 IIRC,.......I've got so many G.D. numbers running around in my head, I feel like a Philadelphia Bookie!), of which there are a few threads in the STICKIES. Try there 1st.
 
Between a 500c and a stock circuit dynaco pas3x/st70, the kx200 sounded best to me.
You have yourself a real sleeper that sounds great. Congratulations!
 
Thank you for these initial replies! Yes, this is certainly a keeper, in that I'm lucky to have found one worth refurbishing.

Though, I must confess, rufleruf's suggestion that I may be able to power this up (using a variac, of course) is very tempting and his reasons for doing so are sound. I do have a single tube to source before attempting that. And thank you, rufleruf for the kind offer of help in getting that done! I'm in San Mateo, but will be in touch if I'm planning a trip to the East Bay.

Thanks to others with links to appropriate threads! I do have a lot to learn.

Ian
SF Bay Area
 
So, I began "baking" my amp, as has been suggested in any number of threads, in order to help drive out any moisture that may have built up while the amp was in storage.

The suggested temperature is anywhere from 125 to 175, with 140 being most commonly accepted as optimal.

I have a "warm" setting on my oven, which is as low as it will go, and I believe it may be as warm as 150 degrees or more. Googling suggests that most ovens will have 150 degrees as a minimum temp, while others are calibrated to cycle at 175.

After about ten minutes at "warm" (150?), I decided to turn off the oven and just let the amp sit. I'll give it an hour, as I do not like where the smell suggests things are going with this.

This looks to be a very clean amp. No signs of anything like goop leaking from caps, etc. No corrosion that I can see.

After this step, I'll get into powering things up using a variac (following a combination of suggestions on how to best do that).

Ian
SF Bay Area
 
You did turn it upside down, Right? The smell is normal. It's no worse than sitting on the side of the road and watching a road crew lay asphalt. But if you are using the house oven, Hopefully you asked SWMBO (She who must be obeyed) 1st and got the OK?

Most transformers run at between 120 and 150 (depending on the load they carry) and some as high as 180 when running. 190 and higher is a death sentence for a lot of them so is not to be exceeded.
 
SWMBO was out of the house, and I had sense enough not to let her know of my plans. Actually the smell dissipated quickly enough to not be an issue (whew!)

Yes, upside down.

Ian
SF Bay Area
 
UPDATE INITIAL POWER-UP: Yesterday, I used a Variac to bring up the Fisher per instructions in this blog posting: https://www.circuitspecialists.com/blog/using-a-variac-to-power-up-an-old-radio-or-amplifier/ I kept the power tubes out for this.

Today, I've installed the power tubes and will use the Variac again to bring the amp up. But before I do, I thought I'd post this update for any relevant feedback.

I did install one new Tung Sol 12AX7 tube that was missing. I did not notice any issues - no smoke or hum. Though, I did not have speakers attached (I will have speakers attached when bringing this up with the power tubes). All tubes (all 12AX7) showed a small glint of glow. I noticed nothing unusual (but I've never done this before, so I may have missed something).

I picked up a pair of The Fisher XP5A speakers today at an estate sale and will press them into service for this next round. I don't plan on hooking up an audio source at this time, just going for capacitor reforming, etc.

Edit to ask: any preferred control settings for a startup like this? I'm thinking Stereo; Center Speaker off; Loudness Contour off; High Filter off; Volume at minimum; Bass, Treble, Balance "normal".

Ian
SF Bay Area
 
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UPDATE POWER-UP WITH OUTPUT TUBES: I've installed the power tubes, set the controls as noted and powered up in the sequence as before. I'm not sure what I'm looking for, but the unit is pretty much silent (no audio source, volume at minimum). Preamp tubes are only slightly glowing: pin-pricks of orange light in each (all working?). The power tubes are glowing more. There was a slight blue glow for a few minutes, but that seems to have gone away.

I'm at 110 volts and it took this voltage, or close to, to get the tubes at what I guess to be full warm-up. They seem to be holding steady after about 10/15 minutes at 110v.

I'll hold this for a few minutes more, then power down. Tomorrow I'll install the preamp tube shields and try an audio source to see just what I have to work with here.

Ian
SF Bay Area
 
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UPDATE BIAS AND BALANCE ADJUSTMENT: I adjusted the bias and balance on the unit. I was, I'll have to admit, happy to see that the meter is working and that it responded to the adjustment.

On power-up today, there was a slight hum. When adjusting the balance, the service manual suggested that I turn the balance adjustment control throughout its range to ensure proper adjustment; in doing so, an obvious hum was heard at the adjustment extremes (one extreme, I think, though I don't recall which). It was gratifying to hear the hum disappear when the needle approached the target mark.

I hope these updates aren't disruptive to the narrative; I'm hoping to best track the process so that I can refer to them later, if necessary.

Ian
SF Bay Area
 
UPDATE AUDIO SOURCE: Following the instruction manual, I hooked up a Sony TC 651 (these two units were from the same estate sale and it may be that this is the first time they've been paired and played in decades).

Equalization: Tape; Center Speaker Level: Off; High Filter: Off; Tape Monitor: Off; Stereo Dimension: Stereo; Loudness Contour: Off; Input Selector: Tuner; Mode Selector: Stereo; Bass, Treble, Balance: Normal; Volume (about 2/3).

Speaker (new to me Fisher XP-5As) sound pretty nice. Tweeter is working, which, apparently, is saying something for these. I just picked these up yesterday from a local estate sale and this is their first audition.

Source is a tape of Simon and Garfunkel Parsley, Sage, Rosemary and Thyme (recorded from the album onto, I'm pretty sure, this very Sony 651, as I say, decades ago). Tape speed is 7 1/2.

I'm very pleased that this is up and working! I'm sure a recap (McShane Kit?) would help.

I do have this in a small listening space, and I don't have the speakers placed as I would normally, as this is a test and I haven't brought the system into rotation; and I may not, if I instead set it up in our living room.

My goal would be jazz vinyl on a decent TT (something I don't have at the moment).

Any thoughts would be appreciated. Thanks!

Ian
SF Bay Area
 
(NOTE: I typed this up between the times posts13 & 14 were being done, then forgot to post it. So for future reference.....................)

When you are powering up, you need to check voltages on the plates and screens (Pins 3 & 4) of the output tubes and the heaters of the small signal tubes (Pins 4-5)(12ax7's). Measure across Pins 4 and 5 on the heaters in DC Volts (all measurements above are DC Volts). You should have btwn 12.0 and 12/6 on the heaters. The Screens and plates should be within 10% of the nominal voltage on the schematic @ 117vac input voltage.

You do have the manual, Right???? Once you get it to 117VAC on the Variac, check the internal voltages as above, and if everything is cool, then follow the instructions for setting bias and balance. Go SLOW and get as close as possible. There will be some variance, and the procedure is interactive between channels. Dave has an upgrade for the bias circuit that should be implemented. It's in the thread above in post 5.

Note on tube glow. What you are seeing is the heater filaments inside the assembly. Some tubes have more of the heater exposed than others. Cup your hand around the small tubes and look straight down into the tube (presuming that the getter is not on top) or as close to the top as you can. You can have an under voltage on the heaters and they will still glow. Undervoltage is not really good as it causes the tube to take forever (you may have great grandkids before they heat up totally) to get to full heat or conduction, and creates distortion. Overvoltage will cause a shorter life on the heaters, and also distortion. 12.6 + or - 5% are the usual limits although FISHER dropped the heater voltages 10-15% in some cathode biased units.

I attached the S.M. in case you don't have one.
 

Attachments

  • fisher kx-200 sm.PDF
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Thank you for the feedback and info! I will admit that I've yet to reach that level of knowledge and skill that I can easily appreciate what you're telling me here; I'll need to step it up in regards to electronics. I have neither the tools nor experience, as yet, to affect the level of testing you illustrate, but I am confident I'll get there (to some degree).

I did take the easy way out, here. I'm hoping that having got this far, I'll more easily be able to understand the more-involved process of restoration. You will no doubt be running into further questions in continued posts, as I get more into the next level of the hobby. I'm very happy to have those here on AK as a resource; very much enjoying vintage audio!

Ian
SF Bay Area
 
Sometimes it might be easier for you to drive from San Mateo to Oakland and get with Ruffleruff, where you can get hands on instruction, vs. you trying to figure out what we are trying to tell you. Matt's good people. What's the toll on the bay bridge now. It was $0.25 or $0.50 when I was on it last(late '75). Now with the new span on the East side it's probably $10.00 now.
 
larryderouin said:
(NOTE: I typed this up between the times posts13 & 14 were being done, then forgot to post it. So for future reference.....................)

When you are powering up, you need to check voltages on the plates and screens (Pins 3 & 4) of the output tubes and the heaters of the small signal tubes (Pins 4-5)(12ax7's). Measure across Pins 4 and 5 on the heaters in DC Volts (all measurements above are DC Volts). You should have btwn 12.0 and 12/6 on the heaters. The Screens and plates should be within 10% of the nominal voltage on the schematic @ 117vac input voltage.

You do have the manual, Right???? Once you get it to 117VAC on the Variac, check the internal voltages as above, and if everything is cool, then follow the instructions for setting bias and balance. Go SLOW and get as close as possible. There will be some variance, and the procedure is interactive between channels. Dave has an upgrade for the bias circuit that should be implemented. It's in the thread above in post 5.

Note on tube glow. What you are seeing is the heater filaments inside the assembly. Some tubes have more of the heater exposed than others. Cup your hand around the small tubes and look straight down into the tube (presuming that the getter is not on top) or as close to the top as you can. You can have an under voltage on the heaters and they will still glow. Undervoltage is not really good as it causes the tube to take forever (you may have great grandkids before they heat up totally) to get to full heat or conduction, and creates distortion. Overvoltage will cause a shorter life on the heaters, and also distortion. 12.6 + or - 5% are the usual limits although FISHER dropped the heater voltages 10-15% in some cathode biased units.

I attached the S.M. in case you don't have one.
Click to expand...
Hello Larry!
Thanks for all your help on my 800-C…that receiver is beast and sounds oh, so sweet! Almost done just need to install that IBAM that’s sitting on my bench. Question, with the KX-200, do you have any idea if the OPT’s are the same(electrically) as the 800-C just a different part number? I remember reading here on AK that the X-101-B OPT’s are the same electrically/physically as the 800-C just not the same part number. I’m looking down that KX-200 rabbit hole right now and thinking about repairing the problem it has according to seller.
Also, sorry about jumping on this 5yo post!

Gilbert
 
No idea. I would imagine they are similar to the 800c if it's running 7591's.
 
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