KX200 and km60

fisher1

New Member
Hi, This is my first post here. I just bought a fisher kx200 and km60 from a friend for the price he paid at a garage sale....$10.00. I have been involved with tube guitar amps and thought this would make a great project. There is no sound like tube sound. I have read through many threads and have learned alot. I would like to thank Adpopulum for his indepth documented rebuild of the kx200.
The km60 seems to work well...fired it up with a variac and pluged it into my Eico amp. It seemed to pull in stations quite well. It has all the fisher tubes..all original. I will be replacing the rectifier and all electrolytic caps soon. I read about the RS rectifier part# 276-1181. So I will use that.
Now the kx200 is another story. It has black tar that has leaked out of the power transformer and also has an "added on" 100r 25watt resistor inbetween the power transformer and the first sd1 and sd2 diodes? (see picture) All the voltages from the transformer seem to be low due to the resistor.I fired this amp up using a variac and found that the voltage at the first cap is 367v. The schematic reads 405v. Probably due to the resistor. Does anyone know if that was to save the output tubes from the higher voltage and prolong tube life?
One of the output tubes is bad and the other is marginal should I go with JJ's so they fit in the cabinet? Any tips on cleaning the chassis? and faceplate? Also correct me if I am wrong, the C1 cap is not grounded, the one with the paper on it?
Do most of you replace all the can caps? or let them ride if they test good? Are their any other resistors I should change? Or any other parts that need replacement(will replace the diodes,all electorlytics under chassis and clean all pots). Any other suggestions are welcome.
Thanks for your time.
 

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I've found that a mixture of one part ammonia to 6 parts water works well for cleaning the chassis on Fisher tube gear. You can use the mix on faceplates too, don't let them soak for over a minute though.

I've heard that the JJ 7591s aren't a very reliable tube. They do sound good in a 500C, but I run EH in my 800C. The EH tubes have been quite reliable. But the large bottle of the EH tubes prevents the cabinet on the integrated amp from fitting.

I haven't been in my Fisher tube gear for restoration yet, so I'm not sure about your electrical issues with the KX-200. Stick around, we have lots of Fisher experts who can help you out. But, if you need some premium parts for your Fisher, contact Jim McShane. You have some fine gear there. BTW, welcome to AudioKarma!
 
Thanks for your advice Jailtime, and the warm welcome. I will try that cleaning method out!
 
Hi, welcome.
You got a deal there, even if you have to scavenge a transformer off that auction site.

You want old stock 7591s in that because the EHs are too tall for a cabinet. JJ's have spotty quality.

Can caps should go in time, but try to get it running first so you have a known working baseline . . . unless you're well versed in this stuff.

I find that if you don't replace the can caps (the electrolytics), the unit isn't as powerful. It doesn't have to be done yesterday unless they are bulging, heat up a lot, or are shorted.
Edit: Add:
It sounds like someone was trying to take some load off that transformer. See how it works before pursuing restoration. if you can get it operating and get sound out of it, the unit is far easier to troubleshoot.
Don
 
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Thanks for the reply Audiodon. It seems to me that the P.T. is putting out the correct voltage at all of the points on the schematics minus the voltage droped by that 100r resistor. I have checked all the voltages at all the tubes and all seem to be correct.


Those old 7591 tubes are expensive! I don't know if I will go that route.




I will continue to replace the electrolytics and diodes ,find some 7591's and further test. It seems to me that all the basics are there to operate. I just need to replace some parts. Thanks
 
Nothing wrong with running it Nude and using EH 7591's in it. It's such a tight squeeze with the new tubes that it's recommended NOT to either put the top on, or if you HAVE to have the top on, use original 7591's. If the 200's case has the cutout in the back for screen, either remove the screen or get it lifted like a 1000 amp has. there's a pic of one with the raised screen around the forum somewhere. Might be the show us you fisher gear.

Larry.
 
Seems to be the general consesus to use EH 7591 tubes over the JJ's. I have used EH 7868 tubes in one of my guitar amp restorations, and they seemed to work well. They are a very clean sounding tube.



I always can fab a new screen for the amp with the EH tubes.




Thanks, Larry
 
If you use EHs, the leftmost tube won't fit whether a screen's in or not in the cabinet because of the wood cutout. I'm not sayin' don't get 'em, I'm sayin' the cab will be out of rotation for a while . . .
You can get a quad of EHs cheap, get everything humming, and replace with others when the accounts fill up again. Then you'll have backups.

You could limp by with a pair of EHs in the rightmost pair and use the two good 7591s you have, but they won't bias up the same way.
 
That got me wondering about left EH tube fitting. I took a 6l6gc and test fitted it in the left tube socket. It is taller than and EH 7591 but still cleared the wood by about an 1/8". I haven't checked if the EH 7591 is a larger diameter though. Great point Audiodon ! I really would like to keep the chassis in the wood cabinet....which I just refinished.





Do most or all of you Fisher owners keep the 2 prong cord or switch to a 3 prong?
 
Some of the tube dealers like the JJ 7591. I would assume that if you buy them from a dealer who does burn-in and matching, they're probably going to be just fine.
 
Do most or all of you Fisher owners keep the 2 prong cord or switch to a 3 prong?

Just keep the original cord if it's in good condition. The hot lead of the cord is wired to the fuse, orient the plug so that the hot lead is in the narrow slot of your outlet. You'll minimize hum issues this way.
 
Thanks for the tips guys. My cord is in good shape so I will keep it. I have replaced the rectifier in my KM60 with the the RS rectifier. How do you get the voltage back to spec. I have installed a 300r 5watt resistor in series with the high voltage wire going to the first cap,and it brought the voltage back down to spec. Although the 5watt resistor seems to be getting quite warm. Should I use a 10 watt resistor or some 5-10 watt dropping diodes in series?
 
I have just found that 3 12volt 5watt diodes wired in series with the hi voltage wire (from the recto to the first cap) has lowered the voltage from 224v to 197v. The spec is 194v. Glad to see that selenium recto removed , and thoes diodes run much cooler than those 5 and 10watt resistors I started with.



Hope this helps some people.
 
I don't usually drop the voltage. I usually just replace electrolytics and coupling caps and let 'er rip. But, to each their own. Some use bucking transformers, others voltage dropping resistors like you did.
 
It was a good score from a good friend who just bought it for the tubes. My dad had a fisher reciever back in the 60's... don't know the which one or what happened to it. Now I have my own. Thanks.
 
I just purchased a nice Fisher KM-60 FM Tuner last night and want to replace the 2 electrolytic caps right away, but want to make sure I have the values correct.

The smallest under the "T4 "Ratio Deflator" is marked:
-25 70 degrees C
+ EB
W. Germany
+ 8/50
ROE (Roederstein)
This cap has evidence of dry, gray, powdery corrosion of some sort on one end, but no uf value is evident.

##############################

The larger cap in the WX module, is marked:
350 V -
1uf
W. Germany
ROE (Roederstein)

##############################

Any suggestions for replacement brands / values?
 
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