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Hi- I'm hoping someone can check my work here. I'm trying to install IBBA in my KX-100 after having installed the Zener modification earlier. Attached is my revision to the KX-100 schematic to reflect the changes I've made. Thanks.

KX-100 output tube schematic revised with modifications.

Thanks for clearing that up for me. A couple more questions as I prepare to install this. In Dave's original schematic for the IBBA mod, the electrolytic caps are installed with + to ground. I assume this is because the machine he was working on used negative filament supply voltage. This is...

As I consider the IBBA, are the values shown on Dave G's schematic OK for the KX-100 which uses 7868 tubes?

Thanks to you both. Given current tube prices I'm inclined to go with IBAM/IBBA so now I must choose between those two mods.

Thanks so much. I had a feeling this was a problem. If I install IBAM/IBBA, what's a good target for output tube current?

Hello to all and a belated thanks for the help with my KX-100. I finally got around to doing the Zener modificaiton. I was hoping someone here could take a look at my numbers and see if they're reasonable: C1 466v (440 spec) C2B 400v (365 spec) C3A 389v (350 spec) C3B 377v (340 spec)...

Thank you, Tim D. You just introduced me to a section of AK I didn't know existed! http://www.akdatabase.org/AKview/albums/userpics/10007/Fisher%20KX-100%20Schematic.pdf

Let me add my congratulations to Dave, with many thanks for his direct help and his sharing of his encyclopedic knowledge.

Thanks to both for the info. Here is the schematic I originally uploaded but now with changes marked. And the same section from the original Fisher x-100-b schematic.

I don’t know whether I should revive this thread or start a new one, but I am hoping to modify my KX-100 with Dave Gillespie’s Zener diode string, as well as a couple of other things picked up on this forum. Before I lift a finger, I want to make sure I have these things correct. Attached is a...

Tim D - The white noise is present regardless of input source selected. It migrated from left to right when I swapped the output tube pairs from left to right.

In case anyone is still following this thread, or maybe just for a sense of completion and to add to the knowledge base, it appears that when this amp came to me the right channel output transformer leads to pin 9 of tubes 9 and 10 were connected contrary to the schematic and the assembly...

Thanks, I do plan on covering up those caps.

Thank you all for the questions and comments. I have been occupied with work and other matters the last few days. The amp was working for a couple of years and then the pops appeared and about a year ago seemed to begin to happen more often. This summer it reached a point where I concluded...

Unfortunately, I have no test equipment beyond a multimeter plus a healthy fear of a slipup while attempting measurements. I'll keep looking for mistakes, as I have been for some time.

No, I get no music through the left channel when the balance is all the way to the left. The squeal comes from the right, and as I turn the balance to the left I do hear just a bit of scratchiness. But other than that nothing from the left side. The right is all squeal.

Nice to know I'm not alone, anyway. After further investigation I found that the speaker on/off switch was intermittent on at least one side. I've replaced that, and done some further clean-up inside. The squeal is coming from the right channel only. I can't say whether the left channel is...

Thanks for the comments. So far, no luck. I checked, rechecked and even re-soldered some of the connections in the output tube section and still, the squeal. A side note: I've seen a number of pictures of other KX-100s and X-100-Bs that show the wire connected to the X channel of the center...

Thank you for asking. Before changing the sockets I had been hearing occasional pops. The tubes fit very loosely -- at one point I had tried EH tubes, not knowing of the pin size difference. I tried fiddling with the sleeves with dental tools and this seemed to help but after hours or even...

Hi- The short version: after replacing output tube sockets, wiring the new ones, and cleaning up my earlier sloppy job of replacing the old power supply caps, I get nothing but an earbleeding squeal from the amp, independent of volume or any other controls. I was going to ask, what caused...

Thanks to Dave for this modification -- it looks like something I'd like to try on my KX-100. I ran across the thread while searching for info that might help me solve an oscillation problem. This Zener string will be on my list after sorting out the current problem. Has anyone successfully...

A belated thank-you to all for the guidance. A year later -- after having to put this aside due to life annoyances -- I went back to it. Pointing me to the discriminator led me to R58 (Sam's #) which seemed to be out of spec. I replaced that and the FM seems to be working well now. (The caps...

Thank you both. I've done the tube socket cleaning and I have non-residue QD on the way. A bit concerned about access to the fins - the gang is tucked away neatly in a box on the 90R. Will definitely look at C48 -- I think that corresponds to C3 on Sam's. A previous owner had all of the...

Thanks to all. I tried Deoxit on the tube sockets with no luck. Have some QD on the way. 88.3 is HD but so are many others. I've also posted this on the Fisher forum, as fred soop advises.