Discussion in 'Fisher' started by RS Steve, Jul 6, 2016.
Wiggle the 6gk5 (v9) to start with. Checkit on a tester to makesure it tests ok,
Thanks Larry, she is working now but sounding like it has reverb with the station. I imagine I will need to study Dave's FM thread and see if I can get it fixed.
These were my voltages I pulled so far. I'm pretty sure I got 126mv but didn't write it down and will have to recheck.
Pin # 6 = -17V
Pin # 4 = 394V
Pin # 3 = 446V
Check the pot (R215)at the mpx on top when in stereo. Make sure it's centered or very close to it. If that doesn't work, You can swap V100 with V102 or V101 with V102. V102 is the amplifier tube while V100 and V101 are the 19kc and 38kc tubes. I would suspect V100 or V101 more than V102. If that doesn't work, send the mpx to Dave.
I find that the mpx tubes need to heat up for quite some time before it operates correctly, even with a new set installed. The FM is acting quirky until the unit runs for about 15 minutes, I deoxed all the pins on the tubes a second time just to make sure. Could just need a good bit of run time to get all the components happy again after so many baths. All I know is, I'm pleased there are no sparks or smoke, and very minimal stink.
Check the heater voltages on V1 thru V8(12vac) V9 thru V15 (6Vac) and then V100 thru V102(6vac). Then check B+1(206v) and B+2(160v) on the MPX. 10% variance either way should be ok for the B+. Heater voltages should be no lower than 12.0v or 6.0v. It almost sounds like the heater voltage is too low and it's taking 15 minutes to warm up enough to work correctly. V16 thru V19 are 12vdc.
The plate(Pin3) and screen(Pin4) voltages are a little high, but I'm presuming you are hooked up directly to the wall with a slightly higher voltage than 117vac. Check your heater voltages and adjust the unit to get the heater voltages to 6.3v or 12.6v (depending on what tube you are checking). Once you get the heaters in line, the rest should fall in with no problem.
I thought the tubes seemed to be running pretty warm although not red plating . I will do more checking when I have time. Thanks Larry!
Steve - can you get any strong FM signals to register 4 on the signal strength meter?
That picture was taken when I was tuned to a very strong station, but the antenna I was hooked to could be better. It couldn't go to 4.
I had the receiver hooked to my variac, when I tested the voltage out of it, I got a reading of 119v. So it seems like my voltage to the outputs is running high.
I had my Variac set to 117V today and took a bias reading of .30V across the sampling resistor, pin 3 was 439V, pin 4 was 374V. I will need to get some small grabber test leads to feel comfortable checking the small tube readings, there is way too much stuff in the way for my alligator clips and probe.
The strongest stations today were making the meter just touch the 4 on the scale, the dial is reading about 3 notches off to the high side. The stereo signal is still quirky, but seems better than yesterday. The receiver is sounding very good, it has two original Fisher 7591's and two GE 7591's that all match very strong, this unit has plenty of power.
I need to start studying how to build the individual bias board, and get that mod installed in some of my receivers. I did one for my KX-100 before, but most likely will be a bit different on the receivers.
Finally got back to the stinker 800-C today, I installed a bias trimmer and plugged directly to wall voltage for the first time. I found out the output tubes are not matched to well, they varied from .36 V to .32 V.
The FM worked better without dropping out, so running on the variac at 117 V was not powering the tuner section enough before. I can't get any AM stations though, need to try and find the problem with that. Hopefully it's just a tube causing it.
About the smoke odour: I've got once a small 6AQ5 console pull smelling like an ashtray (and yes, I'm a smoker but always outside of the car/house) and it eventually vanished after a few months, no cleaning. Sure, my nose and taste aren't as sensitive as a non-smoker...
This receiver must of spent its whole life in a multiple heavy smoker home, it still stinks when you put your nose to it, but doesn't put off a stench when using now. I'm surprised it works after so many baths.
This by far has been the most challenging restoration of a Fisher tube receiver yet, hard to believe ole stinky seems to be working on all functions now. FM and AM are still very low on reception gain, and the tuning pointer is off quite a bit, but at least they now bring in stations. Ole stinky is looking pretty good these days, just took a ton of patience and having to put it away a few times and take deep breaths before coming back to it. I thought about parting it out a few times, but glad I didn't. If I charged for my time invested in this ash tray, I'd have to sell it for 3 grand!
Looks like I will need to find someone to align the tuners, not much else I can do to sir nicotine.
Glad to see that you have made this much progress. I've been there too considering the amount of time spent on a receiver versus what it could be sold for. Ours is a labor of love for the product and the period it came from. Look at some of Dave's recent comments about receivers and tuners that will not achieve a level 5 or better on the signal strength meter being an indication of at least one IF stage transformer with bad capacitor(s) internally across winding(s). For Fisher 500-c and 800-C the values of the internal capacitors have been determined so there is hope even there.
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