|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
74.46.241.151
In Reply to: RE: Fisher KX-200 posted by Eli Duttman on June 30, 2015 at 20:17:35
Yes redo the PS and change the bias meter resistor values to change the bias level and make the 7591's last longer as pointed out by Dave @AK. Turns out the Fisher bias mark is at 21 watts which is 115% of the tubes capability. It was worse on the X-202. He calls the two serial tube killers. Nice thread linked below. Thanks as always for chiming in. Do you know Jim McShanes site for non Citation II stuff or do you just inquire there? Thanks in advance.
E
T
Follow Ups:
I know that Jim stocks 'lytics that physically fit in 500C and 800C Fisher receivers. I suspect those parts would be a good fit for the KX-200.
Basically, the "McShane Treatment" is: better B+ diodes, increased capacitance (both filter and decoupling), and inrush current limiting.
You can buck up the bias supply by installing Schottky diodes and making the rail's reservoir cap. a Nichicon KZ (muze).
Current production EH 7591s are intolerant of the liberties Fisher took with the grid to ground resistance limit. Jim's site shows how to fix that with passive parts value changes. I advocate going further and replacing the 12AX7 "driver" tube with a 12DW7. Fisher provides the template for that change in the X-100. ;> ) IMO, ceasing to use the 12DW7 was a "bean counting" thing to buck profits up. :> (( The 'X7 triode makes a VERY poor "concertina" phase splitter.
Eli D.
good tips, but I just tried to change the input select for the first time and its frozen. Overnite lube didn't really help either. Never seen one that didn't loosen up w/lube.
E
T
Keep trying. Maybe a vibrating action on the shaft will help.If it can't be salvaged, just under $5 buys a Lorlin brand replacement from Mouser. :> ) As I previously stated, hard wire 1 set of I/Ps to the phono preamp and the O/P of the phono section, along with all other I/Ps, to the new source selector.
A link is provided below.
Eli D.
Edits: 07/04/15
Taking the knob off and shooting in from the front helped but it is still slow and gummy feeling although I see nothing foreign etc. that might slow it down. At first it was so hard I grabbed the shaft with pliers to turn it fearing I would break the plastic knob it took so much force to turn. Now the knob turns it "OK" but nothing like the other two switches.
Thanks for all your replies
E
T
"Shoot" it some more and keep working it.
Eli D.
Yes,that's the plan. I have a 1927 Crosley radio and I need to relube the tuning knob gear every 6 months. My neighbor that works on guns has a great lube concoction I use. Cheers!
E
T
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: