Fisher KM-60

Drummerboy2

Well-Known Member
I recently bought a Fisher KM-60 and sent it to Mike Zucarro for repair and alignment. All I can say is wow! this is a very nice sounding tuner.

After a week of listening I had a failure with the output tube but popped another 12AX7 in and it was up an running and sounding even better and more quiet. I have been enjoying this Fisher tuner every day as I'm working on other's gear but I get that one song that just catches my attention on how deep and wide this soundstage is and this is still in stock form! It's great on live performances!

I have a chance to pickup a Fisher FM 200b so this will be interesting how they compare. Will report back.

BTW, I have read in other forums that once the Fisher KM-60 is aligned properly with good strong tubes all you have to do after that in the future is put new tubes in and never have to align it again since the alignment was done to good tubes? Is there any truth to that?
 
With most tube tuners, I think you can align it once and replace tubes without changing the alignment. Tube tuners and televisions could never have existed if the small interelectrode capacitances in tubes varied enough from tube to tube that you could not hold an alignment.

Full disclosure: I also have a Fisher KM-60 sitting beside me that may need an alignment because it does not sound as good as my Sherwood 2100 II but going by the design, should sound as good or better.

One design feature of the KM-60 that shows up in a few other tuners (but not many) is the bridge neutralization where the capacitors at the bottom of the IF transformer primaries are not returned to ground but to the screen grid. The screen grid also has a capacitor to ground and the series connection of capacitors provides negative feedback into the screen that allows the use of tubes with a wide range of transconductances without affecting the gain all that much. The bridge neutralization helps ensure the IF strip is immune to regeneration.
 
With most tube tuners, I think you can align it once and replace tubes without changing the alignment. Tube tuners and televisions could never have existed if the small interelectrode capacitances in tubes varied enough from tube to tube that you could not hold an alignment.

Full disclosure: I also have a Fisher KM-60 sitting beside me that may need an alignment because it does not sound as good as my Sherwood 2100 II but going by the design, should sound as good or better.

One design feature of the KM-60 that shows up in a few other tuners (but not many) is the bridge neutralization where the capacitors at the bottom of the IF transformer primaries are not returned to ground but to the screen grid. The screen grid also has a capacitor to ground and the series connection of capacitors provides negative feedback into the screen that allows the use of tubes with a wide range of transconductances without affecting the gain all that much. The bridge neutralization helps ensure the IF strip is immune to regeneration.

Amptramp, Thank you for the info. This makes since but since I'm new to tube tuners I wanted to just make sure before I start gathering the new tubes for my Fisher KM-60. Since I had it aligned recently I have only changed the audio output tube since the original died soon after I got it home. It sound ok but nothing really to make me say wow. Once I replaced that 12AX7, it transformed the sound from OK to wow! I then bought a Tung-Sol reissue 12AX7 gold pin, it has about 7 hours on it now but has really made this tuner sound really nice and it still has the rest of its original Fisher tubes and still In stock form.

I should be receiving the new Jensen Copper Foil PIO caps tomorrow. I will install these and see what this nice sounding tuner after that upgrade along with the new Takman resistors sounds like.

One thing about this tuner that it has a very wide and deep soundstage that is just amazing. Live performances are just awesome sounding.
 
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I received the Jensen's today and installed them along with the Takmans. After a few hours, the sound is just awesome and still getting better by the hour/s. Can't stop listening! :)
 
Fisher made some great tuners in the tube era. The KM-60 was essentially the kit-built version of the FM-50B, which I have an example of. The FM-50B may have been at the bottom of their tuner line, but the one I have works great even on most (if not all) of its original tubes and parts. One thing to make sure of: if you ever need to replace the "Stereo Beam" eye tube, make sure to get an EM84A, and not a plain EM84. The 'A' version is more sensitive than the regular EM84, which won't work properly unless the circuit has been modified. Good luck!
-Adam
 
Actually,the KM-60 has a far superior front end than the two-gang-one-tube-wonder that the FM-50 series is saddled with.
 
Fisher made some great tuners in the tube era. The KM-60 was essentially the kit-built version of the FM-50B, which I have an example of. The FM-50B may have been at the bottom of their tuner line, but the one I have works great even on most (if not all) of its original tubes and parts. One thing to make sure of: if you ever need to replace the "Stereo Beam" eye tube, make sure to get an EM84A, and not a plain EM84. The 'A' version is more sensitive than the regular EM84, which won't work properly unless the circuit has been modified. Good luck!
-Adam

I have read that you can you use a EM87 in place of the EM84A and it's a drop in replacement with even more sensitivity than the EM84A. The EM84A is really hard to find, so I may end up going with the EM87 since they seem to be easier to find. Thanks for the info!
 
Actually,the KM-60 has a far superior front end than the two-gang-one-tube-wonder that the FM-50 series is saddled with.

This Fisher KM-60 is a really nice sounding tuner and I have been happy with it so far. It can pull in some distant stations I thought it would have issues with but no issues so far. Compared to the Fisher FM-200b, as of right now the KM-60 is sounding better. I'm also still trying to use the functions as per the user's manual with and without the Microtune to see if everything is functioning properly. So far it seems ok. but a little weird how it grabs the stations. I have turned off the Microtune and it a litte more normal in tuning in stations. I just think for the sound it may need new output tubes, the KM-60 had a similar sound when I first got it home and the new tube in the output did the trick. Sounds way better than with the stock Fisher tube.
 
Of all of the Fisher tuners,my preference is the KM-60.It is a stripped down unit with the entire emphasis on performance;no frills or unnecessary gadgets to impair or get in the way of the signal. An excellent front end,four tube IF and one of the best multiplex decoders ever designed makes this one special.
The only caveat is build quality,which is easily redone if required:)
 
Of all of the Fisher tuners,my preference is the KM-60.It is a stripped down unit with the entire emphasis on performance;no frills or unnecessary gadgets to impair or get in the way of the signal. An excellent front end,four tube IF and one of the best multiplex decoders ever designed makes this one special.
The only caveat is build quality,which is easily redone if required:)

I totally agree! While I was away from my last post I went up on the roof and replaced my Stellar Lab Yagi antenna. It was good but I started to notice some hiss in the back ground of the music on this one station from a City college here in SD. To be honest I alway had an issue getting that station but the Stellar Lab was doing a good job up to recently. I had recently bought a FM 2500HD FM Antenna from Denny's TV Antenna. This is supposed to be very close to the Winegard 6065 FM antenna that is now discontinued in performance. Well, this FM 2500 is awesome! The station I had trouble with is now dead silent in the background and signal strength is way better.

Now my Fisher KM-60 sounds awesome! I don't want to change anything now in it. This is just one amazing sounding tuner!
 
Thanks for the report on the Denny 2500. It's the only one I've seen. I recommended to Denny that he send one to Brian Beezley for evaluation, but I got no response. Is your Steller the 3-element or the 4-element one?
 
Thanks for the report on the Denny 2500. It's the only one I've seen. I recommended to Denny that he send one to Brian Beezley for evaluation, but I got no response. Is your Steller the 3-element or the 4-element one?

My Stellar is the 4-element Yagi.
 
Actually,the KM-60 has a far superior front end than the two-gang-one-tube-wonder that the FM-50 series is saddled with.
According to this forum post, the FM-50B and KM-60 both use a single tube front end, though the FM-50B uses a 6AQ8, and the KM-60 uses a 6DJ8. Also, judging by the schematic, tuning capacitor C37 in the KM-60 only has two sections, though it's a bit hard to read. Granted, there apparently was a factory-built version of the KM-60 offered as the KM-61, so who knows.
I have read that you can you use a EM87 in place of the EM84A and it's a drop in replacement with even more sensitivity than the EM84A. The EM84A is really hard to find, so I may end up going with the EM87 since they seem to be easier to find. Thanks for the info!
I looked up the tube data, and the EM87 does indeed seem to be very similar to that of the EM84A. The only modification you might have to do would be to change the value of R44 (as shown in the schematic/manual I linked to above) from 470k to 100k. While you're in there, you might want to take an out-of-circuit reading on R45, as high-value resistors (in this case, 1.8MΩ) tend to drift in value.
-Adam
 
Mine has the 6DJ8 cascode front end and a 6AQ8 oscillator / mixer with an EM84A/6FG6 tuning eye and appears to be the same as the published schematic.
 
According to this forum post, the FM-50B and KM-60 both use a single tube front end, though the FM-50B uses a 6AQ8, and the KM-60 uses a 6DJ8. Also, judging by the schematic, tuning capacitor C37 in the KM-60 only has two sections, though it's a bit hard to read. Granted, there apparently was a factory-built version of the KM-60 offered as the KM-61, so who knows.


Good grief,I will suggest that you re-read that post. Are you actually reading the schematics?


Just to clarify for anyone else who may be mislead by these ongoing erroneous statements,here is an actual quote of the first post from your link:

''Both deliver the best bang for the buck in the $100 range for tubed on-board MPX models. The KM-60 in particular is one of the very best sounding tubed tuners at any price, with the later 6DJ8/6AQ8 front end and no automatic beacon circuit in the audio path. More musical than the FM-100B. And easier to get up and keep running than a Scott or Dyna (had 'em both, both are nice). It can be user aligned in mono. The KM-60 is a kit model, so you need to double check the assembly quality per example. All are a little misaligned, and are transformed into swans once aligned. The KM-61 is the factory version, but is rare. The FM-50 is the KM-60, factory-built, but with the earlier 6AQ8-only front end (and no meter)''.


The FM-50 (A&B) utilizes a single 6AQ8 tube in conjunction with a two-gang (C6A-B) tuning capacitor.
The KM-60 utilizes a 6DJ8 tuned RF amplifier feeding into a 6AQ8 oscillator/converter in conjunction with a three-gang (C37-A-B-C) tuning capacitor.

In order to allow others to verify for themselves,here are the two relevant manuals with schematics:

file:///C:/Users/User/Downloads/Fisher-FM-50-Service-Manual.pdf

file:///C:/Users/User/Downloads/Fisher-KM-60-Schematic.pdf
 
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I also forgot to mention that the tuning eye in my KM-60 was dancing around a lot. After I made the antenna switch from the Stellar Lab to the FM 2500HD, the dancing has gone down quite a bit to were you can barely see it now but it is still moving.
 
According to this forum post, the FM-50B and KM-60 both use a single tube front end, though the FM-50B uses a 6AQ8, and the KM-60 uses a 6DJ8. Also, judging by the schematic, tuning capacitor C37 in the KM-60 only has two sections, though it's a bit hard to read. Granted, there apparently was a factory-built version of the KM-60 offered as the KM-61, so who knows.

I looked up the tube data, and the EM87 does indeed seem to be very similar to that of the EM84A. The only modification you might have to do would be to change the value of R44 (as shown in the schematic/manual I linked to above) from 470k to 100k. While you're in there, you might want to take an out-of-circuit reading on R45, as high-value resistors (in this case, 1.8MΩ) tend to drift in value.
-Adam

I have to find that post again but from what I remember it said the EM87 was a drop in replacement with no circuit mods needed. The only difference you would see was that when there was no station present, the EM87 tuning eye would totally open up compared to the EM84A but everything functionally was the same if a tad more sensitive.
 
Good grief,I will suggest that you re-read that post. Are you actually reading the schematics?


Just to clarify for anyone else who may be mislead by these ongoing erroneous statements,here is an actual quote of the first post from your link:

''Both deliver the best bang for the buck in the $100 range for tubed on-board MPX models. The KM-60 in particular is one of the very best sounding tubed tuners at any price, with the later 6DJ8/6AQ8 front end and no automatic beacon circuit in the audio path. More musical than the FM-100B. And easier to get up and keep running than a Scott or Dyna (had 'em both, both are nice). It can be user aligned in mono. The KM-60 is a kit model, so you need to double check the assembly quality per example. All are a little misaligned, and are transformed into swans once aligned. The KM-61 is the factory version, but is rare. The FM-50 is the KM-60, factory-built, but with the earlier 6AQ8-only front end (and no meter)''.


The FM-50 (A&B) utilizes a single 6AQ8 tube in conjunction with a two-gang (C6A-B) tuning capacitor.
The KM-60 utilizes a 6DJ8 tuned RF amplifier feeding into a 6AQ8 oscillator/converter in conjunction with a three-gang (C37-A-B-C) tuning capacitor.

In order to allow others to verify for themselves,here are the two relevant manuals with schematics:

file:///C:/Users/User/Downloads/Fisher-FM-50-Service-Manual.pdf

file:///C:/Users/User/Downloads/Fisher-KM-60-Schematic.pdf
Your links point to files on your computer, so I can't view them. I'll admit to not having found an online source for a copy of the schematic for the FM-50B as of yet (lots of stuff for the mono FM-50), but I did look at a partial service manual for the KM-60 (which I posted a link to above), and couldn't find section C of C37. It seems to be a bad scan, as there's a lot of cut-off between pages; indeed, this scan does show the third section. In any case, I wasn't trying to denigrate the KM-60 in any way, just saying that the FM-50B is similar in looks (and, according to RadioMuseum, uses an extra tube vs. the KM-60, though this could be incorrect, and may well be meaningless depending on the circuit/tube arrangement.
I have to find that post again but from what I remember it said the EM87 was a drop in replacement with no circuit mods needed. The only difference you would see was that when there was no station present, the EM87 tuning eye would totally open up compared to the EM84A but everything functionally was the same if a tad more sensitive.
It may very well work without modification. I was just going by the data sheets in the RadioMuseum pages I linked to above for the EM84A and EM87, which shows a difference in that resistor value. My own FM-50B has a nice strong eye tube, and I happen to have found a NOS EM84A (plus an entire FM-50B parts unit), so I have yet to feel the need to try said substitution. I do have an EM87, which is used as a multipath indicator in, of all things, the otherwise fully solid-state McIntosh MR73 tuner. :dunno:
-Adam
 
Your links point to files on your computer, so I can't view them. I'll admit to not having found an online source for a copy of the schematic for the FM-50B as of yet (lots of stuff for the mono FM-50), but I did look at a partial service manual for the KM-60 (which I posted a link to above), and couldn't find section C of C37. It seems to be a bad scan, as there's a lot of cut-off between pages; indeed, this scan does show the third section. In any case, I wasn't trying to denigrate the KM-60 in any way, just saying that the FM-50B is similar in looks (and, according to RadioMuseum, uses an extra tube vs. the KM-60, though this could be incorrect, and may well be meaningless depending on the circuit/tube arrangement.

It may very well work without modification. I was just going by the data sheets in the RadioMuseum pages I linked to above for the EM84A and EM87, which shows a difference in that resistor value. My own FM-50B has a nice strong eye tube, and I happen to have found a NOS EM84A (plus an entire FM-50B parts unit), so I have yet to feel the need to try said substitution. I do have an EM87, which is used as a multipath indicator in, of all things, the otherwise fully solid-state McIntosh MR73 tuner. :dunno:
-Adam

I bought a Telefunken EM87 yesterday. I will post back my results. This tube was a lot easier to find than the EM84A. :)
 
Since I have been enjoying my Fisher KM-60 since it got it aligned and I put some 0.1uF 630Vdc Jensen Copper foil PIO and Takman resistors, I'm thinking to do with this tuner what I was going to do to the Dynaco FM3. I want to put an external power supply with IXYS Hexfred bridge diode package with film capacitors connected to the Fisher via a umbilical cable. This should send this tuner another two or 3 levels up in sound quality!
 
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