That's great! And it would definitely cause the problems you are having with the mis-connections made the way they were.
Congrats on getting it going!
Dave
Congrats on getting it going!
Dave
Finally acquired a X-202, but it has an issue
- Thread starter RS Steve
- Start date
I am still perplexed why those two phase inverter tubes do not have their capacitors and resistors as per the schematic. The area looks original and unmolested, do you think I should put it back as the schematic shows, or do you think this way will perform as good?
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A final parting shot of the X-202, it played for hours last night without any issue and sounded amazing hooked to my Klipsch Chorus speakers. The ultimate test was hooking the X-202 to my Miracord turntable and running my Klipsch Heresy's as a combo. Any doubts that I may have had that the X-202 is the best sounding Fisher were laid to rest, amazing is the correct word to describe this amp. Thanks to all that helped me get it sorted out!
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Congrat's Steve! 
Most all of us can intuit the troubleshooting
and just need a nudge (in my case, with the sharp end of a bayonet) to find the problem. You keep T.S.ing and we'll keep
nudgeing you along. 
Most all of us can intuit the troubleshooting and just need a nudge (in my case, with the sharp end of a bayonet) to find the problem. You keep T.S.ing and we'll keep nudgeing you along.
It's a great feeling to bring these gems back, now I have to fall back to my unfinished receivers that have tuner issues.Congrat's Steve!
Steve -- Great job! Check that with volume control at minimum, rotation of the balance control is quiet without producing any static in either channel.
Let me know.
Dave
Let me know.
Dave
Production change maybe? Usually I leave things as-found unless I have a good reason not to. I figure that it probably worked that way when it left the factory, so it will work that way again. Often when you run into that, there is some less obvious change elsewhere that has to be done in order for everything to work properly.
I did not notice any static, this thing is dead quiet without any hiss, crackle or hum while moving any of its controls. Probably the nicest outcome of any that I have restored.
My next step was to trace things back from the balance control and refer to the schematic in order to make sure all connections were in the proper place. Well, guess what I found, pin 7 of V4 had the end of C58 soldered to it instead of pin 6. So here was another problem the former owner created, that is two connections soldered to the wrong connection point, no wonder he wanted to pass it on.
This amp is now working perfectly!
As frustrating as this has been, it has been a very good learning experience. I get to really understand the circuits along with using the schematic to verify. Special thanks to you Dave, I don't know how you put up with my non electronic brain, but you do.DAVE
I guess I was lucky with the one I had- it needed LOTS of parts, but nobody had been in it before I reworked it.
I've had to re-fix "DUH" mistaken connections in other amps before, though. They can definitely cause no end of distress, until you finally just SEE the damn thing that's in the wrong place- then it's like "oh good grief"...
In this case with this X202- at least neither wrong connection actually blew anything up!
Regards,
Gordon.
Yeah, I did a KX-200 restoration a while back that had one wire soldered in the wrong place when built, chased my tail for a few weeks before finding it. My process is to unsolder one end at a time, and solder the new component there before removing the other end. It works well if everything is correct to begin with.
But it makes you feel a bit stupid if you solder the new one in the same wrong fashion. If I ever go back inside this X-202, I plan on removing some of the very ugly solder joints the previous person did, not that they are going to fail, but there is just too much solder and not pretty. Once I understand the EFB mod I will most likely install that at some point.I'd like to do a little Fisher shootout between the X-202, X-202B, KX-200, and KX-100, I'm curious to see how close they are in sound quality. But I can honestly say I am sick of hooking speakers up to the X-202, it can be a real PITA.
I picked up this beautiful wood cabinet for the X-202, not sure what it is made for, but it is very close to being a perfect fit. It's about 1/4" too tall, but is the correct width inside. I might be able to create a filler piece or just cut it down.
Steve -- Understand that within the run of the X-202, other than the phase inverter circuit, Fisher service manuals show only a very few rather minor changes in the design of the X-202 over the course of its run -- very few as in only adding an extra filter cap in the phono stage (although every unit I've seen within all the official versions have it), and making the red center channel jewel glow dimly in later versions to act as a pilot lamp. But the phase inverter stage is an entirely different story, with (by my count) at least a half dozen variations on the original design. It would seem that the version of the phase inverter stage built in your unit was seeking to serve a number of purposes over previous efforts:
1. Cost reduction through reduced parts count, which saves not only on parts cost, but with less parts to install, labor time for production is reduced as well. It further saves labor production time because that area of the chassis -- which is normally quite parts dense -- becomes easier to work in as the build progresses.
2. Addressing potentially excessive signal bleed at a minimum volume control setting. By eliminating R51/R103 and C31/C58, it eliminated some of the "antennas" at the input of the power amp section, so that the build was less susceptible to signal bleed possibilities.
3. The same four components identified in #2 above also make up the forth permanent LF filter that Fisher built into the design of the X-202. Their removal then helps to enhance LF performance, as well as minimizing signal bleed. Fisher may have deemed at that point in the production run, that the remaining three permanent filters were still plenty effective in controlling changer rumble, record warp, and wow&flutter concerns -- particularly in potential console settings.
4. In the bigger scope of Fisher products produced specifically in the latter half of the 50s (as the X-101 was), Fisher, as well as a whole host of other manufacturers were working like crazy to address new norms of HF stability performance being established at that time back in that day. It may be therefore that the effort to address other issues also became an opportunity to revisit stability performance as well -- although of all the versions I have come into contact with, none showed any particular concerns in this area.
5. Evolution of the phase inverter design also brought into play the earliest efforts to restrict the ultimate drive signal capability that can be supplied to the output stage -- a forerunner of the "noose" I described in my 400 thread that (among other things) accomplishes the same purpose.
The version of the phase inverter installed into Steve's unit certainly covers points 1, 2, 3, and 5 above, with point 4 being an unknown -- although it appears that the components addressing HF stability were altered in his unit as well.
To that point then, of what I can see, these are the collective circuit detail changes that apply to Steve's unit (based on the Sams schematic), that are different from any other unit I've seen:
A. C31/C58 are shorted out, eliminating them from the build.
B. R51/R103 are simply eliminated.
C. R53/R105 are changed to 4.7K. (this was done to maintain proper bias in the tube sections they serve, when the components in A and B above were eliminated)
D. A new 150 pF cap has been added from pin 6 of each 7247 to ground. This component addresses HF stability.
E. There is no evidence of C33/C60 being installed, or the 22K resistor associated with these caps in some versions. These components (when installed) also address HF stability, with their removal necessitating point D above.
F. R7/R8 are almost certainly 10K components in this version, since it appears that there is a new 12K resistor added between these pots and the other three components these pots normally connect to in this general version of the phase inverter circuit. This change makes for easier adjustment of the phase inverter control.
G. It appears that C37/C64 -- or some altered value of them -- do not appear in this version.
Steve -- when you get a chance, if you could verify all of these observations it would benefit the Fisher community at large, as your unit appears to be yet another separate version of the X-202 (meaning that it has enough changes to be considered its own version) that appears to be at this point completely undocumented by Fisher.
As to whether you convert your unit to the closest "published" version, I'm not sure you'd gain anything but some level of personal satisfaction in doing so. Under routine/normal use, the biggest effect of these changes is to remove a permanent LF filter -- something I accomplish slightly differently by increasing the value of C31/C58 to .027 uF which effectively accomplishes the same thing -- and reducing the tendency for any signal bleeding at minimum volume settings -- which I accomplished by relocating (in part) the components of point A to balance control area. Since these are both positives relative to previous versions, I'd leave it alone and enjoy. It will be very interesting to see if any other X-202 turns up with this version of the build as well!
Dave
1. Cost reduction through reduced parts count, which saves not only on parts cost, but with less parts to install, labor time for production is reduced as well. It further saves labor production time because that area of the chassis -- which is normally quite parts dense -- becomes easier to work in as the build progresses.
2. Addressing potentially excessive signal bleed at a minimum volume control setting. By eliminating R51/R103 and C31/C58, it eliminated some of the "antennas" at the input of the power amp section, so that the build was less susceptible to signal bleed possibilities.
3. The same four components identified in #2 above also make up the forth permanent LF filter that Fisher built into the design of the X-202. Their removal then helps to enhance LF performance, as well as minimizing signal bleed. Fisher may have deemed at that point in the production run, that the remaining three permanent filters were still plenty effective in controlling changer rumble, record warp, and wow&flutter concerns -- particularly in potential console settings.
4. In the bigger scope of Fisher products produced specifically in the latter half of the 50s (as the X-101 was), Fisher, as well as a whole host of other manufacturers were working like crazy to address new norms of HF stability performance being established at that time back in that day. It may be therefore that the effort to address other issues also became an opportunity to revisit stability performance as well -- although of all the versions I have come into contact with, none showed any particular concerns in this area.
5. Evolution of the phase inverter design also brought into play the earliest efforts to restrict the ultimate drive signal capability that can be supplied to the output stage -- a forerunner of the "noose" I described in my 400 thread that (among other things) accomplishes the same purpose.
The version of the phase inverter installed into Steve's unit certainly covers points 1, 2, 3, and 5 above, with point 4 being an unknown -- although it appears that the components addressing HF stability were altered in his unit as well.
To that point then, of what I can see, these are the collective circuit detail changes that apply to Steve's unit (based on the Sams schematic), that are different from any other unit I've seen:
A. C31/C58 are shorted out, eliminating them from the build.
B. R51/R103 are simply eliminated.
C. R53/R105 are changed to 4.7K. (this was done to maintain proper bias in the tube sections they serve, when the components in A and B above were eliminated)
D. A new 150 pF cap has been added from pin 6 of each 7247 to ground. This component addresses HF stability.
E. There is no evidence of C33/C60 being installed, or the 22K resistor associated with these caps in some versions. These components (when installed) also address HF stability, with their removal necessitating point D above.
F. R7/R8 are almost certainly 10K components in this version, since it appears that there is a new 12K resistor added between these pots and the other three components these pots normally connect to in this general version of the phase inverter circuit. This change makes for easier adjustment of the phase inverter control.
G. It appears that C37/C64 -- or some altered value of them -- do not appear in this version.
Steve -- when you get a chance, if you could verify all of these observations it would benefit the Fisher community at large, as your unit appears to be yet another separate version of the X-202 (meaning that it has enough changes to be considered its own version) that appears to be at this point completely undocumented by Fisher.
As to whether you convert your unit to the closest "published" version, I'm not sure you'd gain anything but some level of personal satisfaction in doing so. Under routine/normal use, the biggest effect of these changes is to remove a permanent LF filter -- something I accomplish slightly differently by increasing the value of C31/C58 to .027 uF which effectively accomplishes the same thing -- and reducing the tendency for any signal bleeding at minimum volume settings -- which I accomplished by relocating (in part) the components of point A to balance control area. Since these are both positives relative to previous versions, I'd leave it alone and enjoy. It will be very interesting to see if any other X-202 turns up with this version of the build as well!
Dave
Thanks again Dave for the explanation, I will try and address, and document all that when I get back to that amp. Currently working on my HK A500,
yep I have other brands lurking around here also. I'm considering opening up the Gordon restored X-202 to compare those areas, and possibly install the bias mod for convenience.
I did a comparison with the X-202B you worked on for me, the X-202 lacked some of the solid grunt, but had such a more dynamic, detailed sound. The X-202B would be my choice for pound it out rock and roll, but the X-202 is heaven on earth for jazz and instrumental tracks. My Heresy's have never sounded better than when paired with the X-202, I can't wait to hear them hooked to the Cornwalls!
I have the Gordon restored X-202 hooked to my Cornwall's finally, talk about a match made in audio heaven! I will honestly say, I doubt I have ever heard a better sounding tube system. I am in the process of documenting the X-202 that I restored since it is a slightly different version, and I'm working on fitting it with a wood cabinet.
Looks like this X202 I restored has some type of issue causing the left speaker to have its woofer pulse in and out like a low frequency rumble. I tried the amp with two different sets of speakers with the same result, loudness switch and rumble switch didn't have much if any effect. I then hooked up my 400 receiver with the same input, no woofer pulse was noted with it. Any ideas what could cause this?
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Steve -- Does it do it with the Balance Control turned to completely favor the left channel? If so, then the problem will be in the power amplifier section of right channel. If not, then with the Balance Control centered, is it volume control dependent? If so then the problem will be in the line amp stages. If not, then it will be in the tone control stage. If it is volume control dependent, then check if it is input dependent. If only in phono, then the phono preamp is suspect. No doubt you will pinpoint the location of the issue at some point with these checks.
Good luck with it!
Dave
Good luck with it!
Dave
I will have to do more investigation as per your questions, and I had posted it was the right channel when I meant to say the left in the original post. I had not checked any other input other than the AUX jacks, so I will check the other inputs also and check back with what I find.
It is volume dependent, does not occur when balance is turned to the right (left side is offending side), and it happens in tape, AUX, and tape monitor, I have not tried phono yet.
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