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Picked up a Rough KX-100 Tube Amp - Will need some guidance

Discussion in 'Fisher' started by Tim D, Apr 5, 2017.

  1. Tim D

    Tim D AK Subscriber Subscriber

    Messages:
    568
    Location:
    Melbourne, FL
    I scored some rough Fisher tube equipment a week ago and will begin the journey of restoring them. What I scored was a Fisher 500B receiver, a KM-60 Tuner, and a KX-100 Amp. None of them have cabinets and only the 500B has tubes. For this thread, first up is the KX-100 amp.

    The unit looks generally complete excepting for the missing tubes. It is very dirty and the chassis seems to have some pitting/oxidation, the trannies have some rust, and at least one cap (C1?) from the power supply has broken off due to corrosion. I'm going to restore it, but will need some guidance as to what "must" be replaced vs. what simply needs to be checked and cleaned.

    I've found an assembly manual for the KX-100 and two versions of the Service Manual for the almost identical X-100-B. The Service Manuals have good diagrams for the X-100-B which I understand have a different (adjustable) bias circuit. I've got a multimeter (RLC and V) and a USB oscilloscope. I intend on getting a variac before powering it up but that's down the road a bit. I'll be using deoxit on the controls as part of the cleaning. I haven't worked on tube equipment since the 1970's, so I've forgotten most of what I knew - still I have a healthy respect for the voltages involved and I understand electronics from a hobbyist perspective and electrical theory from a professional perspective. I am not an expert and I'm humbly asking for guidance.

    I have done no verification of anything on the unit excepting for a brief visual inspection. So where do I start? Should I undertake the cleaning of the Fisher Tube chassis based on the sticky in this Fisher area first? Would anyone recommend which parts I should replace right off such as the electrolytic caps? There seems to be C1, C2, C3 and C4 that are the only electrolytics some of which are combo caps. Not too many to deal with if that is the recommendation. I see there are mylar coupling caps on the diagram. If these are not damaged is there any reason to replace them out of hand? There is a KX-100 restoration thread I've read through that is very good, but it included a lot of mods mentioned and only some of it was diagrammed.Further down the road, I'd be interested to hear if those mods are strongly recommended or just an optional upgrade.

    Here are some pics to get started. I'll post some better closeups soon.

    IMG_2602.JPG IMG_2603.JPG
     
    Last edited: May 4, 2017
  2. Tim D

    Tim D AK Subscriber Subscriber

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    Location:
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    Here are the other pics. I opened it up and started looking underneath. In looking more closely it needs more help. It has some of the knob brights, but they are so dirty you can't tell. The speaker switch is completely broken. The tape monitor switch is chipped badly. The faceplate is loose and only seems to be sitting behind the knobs and not bolted on. The splotchiness is oxidation/corrosion on the chassis. You can see in the second picture where the capacitor leads corroded for the one that fell off (C1). I don't think it was the original C1.

    So I need:
    - A full set of tubes
    - speaker switch
    - tape selector switch
    - Knob brights
    - new C1 cap

    Will want to clean and paint the trannies.

    Will want to do a thorough cleaning of the whole unit.

    Will do a thorough cleaning of the controls with deoxit.



    IMG_2639.JPG IMG_2640.JPG IMG_2641.JPG IMG_2642.JPG IMG_2643.JPG IMG_2644.JPG IMG_2645.JPG IMG_2646.JPG IMG_2650.JPG IMG_2651.JPG
     
  3. Tim D

    Tim D AK Subscriber Subscriber

    Messages:
    568
    Location:
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    Here are some pics of the inside. Not nearly as dire as the outside and switches. Interesting that the C4 100uF electrolytic bias cap has a paper case. I haven't seen that in other threads on these units.

    The one that fell off seems to be 450mF which doesn't appear to be original at all.
     

    Attached Files:

  4. Tim D

    Tim D AK Subscriber Subscriber

    Messages:
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    Location:
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    Figured out why the faceplate was loose. The nuts behind two of the knobs that hold it on were loose.

    Started stripping it down a bit. Took off the knobs using a spoon as a lever and a folded paper towel to make sure that it didn't scratch the faceplate. The volume knob was previously broken and came apart as I took it off. I might be able to re-glue it or maybe just get a replacement if I can find one.

    Took off the plate from behind the controls. It has a label on it about it being approved by Canadian Standards Association. Is that typical or do I have a Canadian sold model? See pics below.
     

    Attached Files:

  5. rufleruf

    rufleruf AK Subscriber Subscriber

    Messages:
    879
    These are nice amps - I have one and like it a lot. I'm curious to see what the others look like.

    If you want me to post pictures of the underside let me know.
     
  6. Tim D

    Tim D AK Subscriber Subscriber

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    568
    Location:
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    Hi rufleruf,

    Do you have a KX-100 or are you talking about the X-100-3 in your footer?
     
  7. rufleruf

    rufleruf AK Subscriber Subscriber

    Messages:
    879
    KX100 - just like yours.
     
  8. audiodon

    audiodon Addicted Member

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    Check out the stickies at the top of the forum for answers.
     
  9. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    The 450uf 350WV radial in your #54 pic is a replacement. The badging is HITACHI. Could be from Late 70's. The Orange Axial (the paper covered cap)100uf-150v is a somewhat common cap in early 60's FISHER amps, and radio chassis'. If I recall it's part of the bias circuit and should be right around the phono tubes. That one is original to the chassis.

    As the KX-100 was a kit, and sold in Canada also, the Canadian equivalent of the US UL Labs had to put their certification on it. So there you have it. A KX-100 that was designed for (and probably built) in Canada. The main difference between Canadian and US models is in how the power supply is built before the main transformer. Check the assy manual for it to see if there is a Canadian power supply section in it. Or build it to US Spec.
     
  10. Tim D

    Tim D AK Subscriber Subscriber

    Messages:
    568
    Location:
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    Thanks larryderouin,

    Interesting about the Canadian label. I'll check the assembly manual to see if it lists anything about Canadian differences with a special eye on the PS. The panel was inverted with the label facing inside which preserved it pretty well. The panel seems to be reversible. It feels funny that I might have something a bit unique - even if it is only the label. BTW, where do I look for the serial number on this unit?

    They took a big jump in capacitance with that 450uF replacement cap for C1. I'll check it on the multimeter, but I'm thinking to get something that looks more like it belongs on the chassis. I don't suppose anyone has an old C1 they don't want that I can re-stuff? (Maybe an old C2 or C3? I don't mind if it isn't the paper covered C1.)

    Should I be replacing the electrolytics because they typically have a lifespan to them? I.e. C1, C2, C3, and C4?
     
  11. rufleruf

    rufleruf AK Subscriber Subscriber

    Messages:
    879
    I probably have a paper covered can from a 400 you could make work.

    Are you missing the fuse cap, or is it just not shown?

    Are you set on originality, or are you considering updating the RCA jacks and speaker binding posts since yours are a bit rough?
     
  12. Tim D

    Tim D AK Subscriber Subscriber

    Messages:
    568
    Location:
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    Hi Matt,

    You are right I'm missing the fuse cap too.

    I'd like to salvage the originality, but if it gets too bad or too ugly, I'll step back and punt.
     
  13. Tim D

    Tim D AK Subscriber Subscriber

    Messages:
    568
    Location:
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    Tonight I started cleaning the knobs and the faceplate with dish soap and a soft toothbrush. I took the chassis out to the garage and blew it out with compressed air and brushed it with a soft paint brush. I think I got 90% of the loose dirt out. Most of the appearance problem is with rust/corrosion and oxidation.

    The knobs are cleaner, but the brights on them aren't getting brighter. Do you think some Brasso will brighten them up?

    The faceplate cleaned up but it appears that there is some stubborn blemishes on them. I'll try working on some of the areas away from the stenciling to see what works best. Some of this might be corrosion that just looks like dirt.

    Today one of my auction orders came in. I was expecting an assembly manual for my Fisher FM-60 tuner and instead got the complete assembly manual for the KX-100! Nice! I had a question into the seller because the title said "FM-100 Service Manual", the pictures showed an "FM-60 Service Manual" and they cleared it up by telling me that it was the FM-60. Well it was all wrong and I received it for a KX-100. Well, I'm happy. I needed it anyway. It's got the correct diagram with the simplified "fixed" bias network. I think they had a set and got confused about which was which and what the real model number was. They probably had both a KX-100 and FM-60 Service Manual at some point and got them cross-up.

    BTW, I had picked up a Fisher 500B that had its original tubes (at least most were original). It has some 12AX7's in it that I could test and possibly use for the KX-100 testing later. I'll get a count of how many and take them to my local parts house that has a tester to see if they are any good.
     
  14. rufleruf

    rufleruf AK Subscriber Subscriber

    Messages:
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    Tim,

    Brasso will make the knob brights look pretty good. Others may object but I have used it on faceplates too and it seems to do a pretty good job on stains without attacking the lettering. Per the sticky about cleaning a Fisher, somewhat heavy duty ammonia applied with a stiff toothbrush and some patience will remove some chassis oxidation. I recommend working outside on this. Just buy a cabinet if it's too ugly for you once you have exhausted your cleaning options.

    Nice score on the KX100 manual. I've been casually looking for one for a while with no luck.

    In my experience the Telefunken 12ax7's are almost always good, you might just go for it until you get a tester.

    BTW - what color is the jewel on your faceplate? Mine has a non original red LED and I've been wanting to replace it.
     
  15. Tim D

    Tim D AK Subscriber Subscriber

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    Location:
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    Yeah, I accidentally/fortunately fell into that service manual.

    I thought I had some brasso around here. I'll give it a try and report back. Ammonia huh? Hmm. If the brasso doesn't help I might give it a try.

    The local electronic parts dealer has a tube tester. I'll take them in and get them checked.

    Mine has an emerald green jewel. Sounds like yours wouldn't be original. LED? Yep that's not original tech from the sixties.
     
  16. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    I didn't see anything on Canadian spec's in the Assy manual. And nothing in the Service manual for the X-100-B which looks like it's the factory assembled non-kit version. Apparently the US and CANADIAN spec at the time MAY have been similar enough that modification was not necessary.

    C2 might be kind of hard to stuff as C2B is 40uf 500V and 500v electrolytics are somewhat hard to find. You can either series 2 350v caps(with balancing resistors) underneath, or try to find a 2 section cap, 1st section 200uf 250v, 2nd section 40uf 500v. In the 2nd option (finding a cap) I would try Hayseed Hamfest and just ask them to build all 3. This gives you the correct caps, with correct voltages and he gets the info on the KX-100 & X-100-B to add to his database.

    The tuner (FM-60?) would actually be a KM-60. I've got a 1st gen KM-60 Service Manual and an extra assy manual without the large blow up picture diagrams and schematic. But I have the 3 blow up diagrams and schematic I can get copied. PM sent with DETAILS.
     
  17. Tim D

    Tim D AK Subscriber Subscriber

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    Oops my bad. I think I was thinking FM radio and FM-1/FM-3 Dynaco. Yep, it's a KM-60.
     
  18. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    BTDT! :mad: Quite a few times.:confused: Welcome to the club. :jump:
     
  19. rufleruf

    rufleruf AK Subscriber Subscriber

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    Tim, My local electronics store has a tube tester and it is so crazy worn with loose pins and lack of maintenance that everything I test comes out bad. Just a warning....
     
  20. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    That'll give you some more practice Matt. Ask them if you can restore it. They pay for sockets and other parts. You supply labor!:D:D:D
     

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