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Fisher 400-T score

rossm

rossm

AK Subscriber
Subscriber
Hi All,
Picked up a very nice Fisher 400-T at an estate sale. Used a variac and dim bulb to slowly bring it back to life. Both channels work. AM/FM works but tuner is stuck. It's a keeper so I need to clean it up and recap. Does anyone know of any restoration threads on this unit ? I downloaded the service manual, but I don't see much info on the web
Thanks
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Thanks for that link!!
I did search and came up with 8 pages, mostly concerning the 400 tube model. Did see a post saying there were different versions of the 400T.
Is there any way to figure out the date of mfg with the serial number?
 
 
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First, try to find a service manual. Most of the Fisher SS units were very similar in design but all had minor variations from that.
 
As for the tuner, you actually can bypass the regular tuner and use the 4 or 5 presets, which are adjustable. Just push on the end of each preset, then tune each one to a different stationby turning the outer portion of each knob (AFC OFF, this is the outer part of the manual button at the bottom), set your stations and then turn on the AFC. This will give you 5 preset's like the preset buttons on most cars from the 50's and 60's (and even some 70's cars) before digital tuning became fashiionable. The presets are FM only so no AM.

The tuning variable cap inside the box is AM only. There is a variable pot on the back of the box for FM. The FM on the 400 was all electronic and the AM section ran thru the variable cap inside the box. You can free it up by setting the unit on it's back and applying a penetrant oil like PB BLASTER or liquid wrench around the shaft at the top outside and then on the inside bottom (while the unit is upright). Use a syringe with a blunt needle to apply a few drops WITHOUT getting it on the fins inside. If you do don't worry about it right now, we'll take care of it before you start it up again. (In Next parag) Let the penetrant soak in overnight. Then try to turn the knob by gently rocking it BACK AND FORTH. There will besoma If it won't budge, add some more penetrant and let it soak. Keep it up daily until it breaks loose but DO NOT FORCE IT. Just rock the knob back andforth until you can get full range of the dial.

Get some CRC QD ELECTRONIC CONTACT CLEANER at Home Depot in the Elect. Dept. This stuff is NON-RESIDUE which is what we want for the fins on the variable cap inside the box. AFTER YOU GET THE KNOB TO WORK FULL RANGE, drip a drop of TURBINE OIL (Zoom is good Ace Hardware has it.)on each end of the box on the outside at the shaft. Let it sit overnight and ocassionally work the dial full range. Next day remove the top of the box, and lay the 400-T on it's side or back. SPRAY the INSIDE of the box along with the UNMESHED FINS until you can see no dust, dirt, junk on the fins (both sides of each one.) They have to be absolutely clean or you won't get good reception or reception that is higher or lower in frequency than the dial indicates. Let it sit in the sun for a couple of hours, then check operation of knob and dial pin full range BEFOR you power it up and check for operation of the tuning knob in MANUAL FM and or AM.

I've got to find a parts unit of this model so I can gut it for the varactor panel for my 500-TX, as 500-TX parts units are getting priced ridiculously high!!!

.
 
I have a 600-T and it uses the same tuning arrangement for the FM. The FM front end is varactor diode tuned, so it has no moving parts. The resistor on the back of the tuning capacitor in your unit is the tuning for the FM. The tuning capacitor is only for AM tuning, but the internal shaft of the tuning capacitor is connected to a gear for tuning and the gear has its limits on strength. When the old lubrication at the pivot points seizes up it needs to be treated with penetrating oil and worked very gently to avoid damaging the gear teeth. There are bearing surfaces at the front and back of the tuning capacitor, both of which can seize up and place undue stress on the gear surfaces if forced. This also sometimes happens even to volume and tone controls shaft rotation. The lubrication dries up and becomes quite stiff. I have had to disassemble controls to clean and lubricate their shafts in some stubborn cases. Penetrating oil such as the PB Blaster can often do a good job of freeing up the shafts and then follow up with some 3 in 1 or similar lubrication for the long term.

In the 600-T there is a zener diode that regulates the FM DC tuning voltage source. If this voltage is off, the rest of the tuning may be shifted or unstable. I think the 400-T is similar in this respect. Watch for overheated resistors associated with the zener and it may possibly need to be replaced.

Joe
 
Thanks for all the help !!!!
I have been using 3 in 1 oil every day for the past week with no movement in the tuner. So I will take a look at pb blaster

I see that pb blaster is in a spray can, do you just spray it on as is, or spray it into a jar and use a dropper or syringe
 
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IMG_7428.JPG Ok, have the pb blaster now, waiting on it to work its magic!!!
 
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Syringe the PB BLASTER at the points shown. 5 places. The thru shaft from the dial string (2 places), the front pin at the larger gear into the box(1), and both sides of the back of the fin shaft (2). Make sure when the PB blaster is installed "WITH A SYRINGE" the unit is on it's BACK and the bearing holes are vertically oriented so the pb will wick thru capillary action into the bearing/bushings. RE-READ my POST #6 above.
 
Hi all
Update on this project !
I finally got back on this project today. After All the soaking, the tuner was still locked up. My only hope was to remove the tuner and try heating it up with my solder gun
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It only took about 3 min with the tip of the iron on the end of the brass shaft. The fins slowly rotated at first, after a couple of min rocking back and forth it was loose as a goose.
I cleaned the fins with some electrical cleaner
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My biggest fear was getting the dial string back on, but that went pretty easy.

Now I have a hum in the right Channel, more to come
 
If you have some Zoom Turbine oil, Sewing Machine Oil, or Last Resort 3 in 1 oil in the BLUE CAN (don't use the red can as it has parrafin in it) put a drop or two on the end bushings with the unit on it's ends and let it soak in (rotate the knob occasionally). Wipe off excess. Rotate end to end and use it.
 
Was wondering if anyone had experience with this model. The power supply has 2 large 2000 mfd 55 v caps and they each appear to be 2 caps in each can, but the sm only shows 2 2000 mfd 55v, unable to see the back side, looks like a bear to get off. Do the metal clips pull up off the pins ?

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Thanks
 
They are single 2200uf caps. Just un-solder them from the board and pull them off the adhesive on the board. Lay the new ones down on the board and bend the leads to go into the holes. Clips???? The board is held down by the plastic pins in the corner. Pinch them with needle nose and pull straight up. Replace with 3300uf 63v caps. https://www.mouser.com/productdetai...=sGAEpiMZZMtZ1n0r9vR22YedwoaFxdzah1imGJXIE6I= Put a dab of Shoe Goo on the board and push the new caps into the shoe goo to hold them down.
 
larryderouin said:
They are single 2200uf caps. Just un-solder them from the board and pull them off the adhesive on the board. Lay the new ones down on the board and bend the leads to go into the holes. Clips???? The board is held down by the plastic pins in the corner. Pinch them with needle nose and pull straight up. Replace with 3300uf 63v caps. https://www.mouser.com/productdetail/nichicon/uvy1j332mrd?qs=sGAEpiMZZMtZ1n0r9vR22YedwoaFxdzah1imGJXIE6I= Put a dab of Shoe Goo on the board and push the new caps into the shoe goo to hold them down.
Click to expand...

The 2 caps on the left are single ? But they each have 3 leads ? I don’t understand

Ps not doubting your knowledge, I just want to know more about this.
Thanks
 
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If the lead is on the top, it's just a stabilizer it's not connected electrically. It was used to prevent the cap from breaking loose during transport from the factory to the dealer. Remove it with the cap and just glue in the new one. The new one at 3300uf will be slightly smaller.
 
larryderouin said:
If the lead is on the top, it's just a stabilizer it's not connected electrically. It was used to prevent the cap from breaking loose during transport from the factory to the dealer. Remove it with the cap and just glue in the new one. The new one at 3300uf will be slightly smaller.
Click to expand...
Cool, thanks for that information!!
So the cap leads will just pull out of the little metal holes on the ckt board (when I heat them up) and I don’t have to pull the board to unsolder them ? Otherwise I thought about cutting the leads close to the cap body and soldering the new caps to the old leads
 
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You still have to De-Solder from the back. The Metal holes are stiffeners Fisher had put in the boards. IIRC from working on mine the power supply had wires on 2 or 3 sides, and undoing the corner pins allowed it to lift enough to do the solder work. Try not to disconnect any wires unless you take a lot of pictures from different angles and make a diagram.
 
When removing the capacitors (or any other parts) note that a lot of Fisher PC boards will have the leads flattened mechanically on the foil side of the board so the parts would not fall out before soldering. That flat spot may be able to be pulled through the hole or it may have to be cut off.
 
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