Fada model 790 resistor question
6/15/2008 11:48:07 PMGeorge T(63164:0)
Happy Fathers Day to all of you dads out there. Hope you all had a great day.
I acquired a Fada 790 series B the other day and noticed that 2 of the resistors are fried big time. I hadn't seen resistors like these before but I'm pretty certain that is what they are. They are wire wrapped and appear not to have much of a coating. The one is hooked up to the tube where one side of the AC is hooked up on pin 6 and the other end is hooked up to lug #1 on the lug bar with the wire that goes to the on/off switch. The other is on pin 5 of the same tube and goes to #2 lug on the bar and is hooked up with the other side of the AC line and a 100K resistor that goes to #3 lug and then to the tuning condenser. The tube is a 25Z6G. I think these are the 660 ohm 2 watt and the 200 ohm 2 watt but I still have a lot to learn about reading schematics and not sure which resistor goes to which pin both are open and I can't get a reading off of them. Any help would be greatly appreciated. Thanks Again, George T.
I acquired a Fada 790 series B the other day and noticed that 2 of the resistors are fried big time. I hadn't seen resistors like these before but I'm pretty certain that is what they are. They are wire wrapped and appear not to have much of a coating. The one is hooked up to the tube where one side of the AC is hooked up on pin 6 and the other end is hooked up to lug #1 on the lug bar with the wire that goes to the on/off switch. The other is on pin 5 of the same tube and goes to #2 lug on the bar and is hooked up with the other side of the AC line and a 100K resistor that goes to #3 lug and then to the tuning condenser. The tube is a 25Z6G. I think these are the 660 ohm 2 watt and the 200 ohm 2 watt but I still have a lot to learn about reading schematics and not sure which resistor goes to which pin both are open and I can't get a reading off of them. Any help would be greatly appreciated. Thanks Again, George T.
6/16/2008 9:19:33 AMEdd(63165:63164)
From your wiring path description:
Looks what you have found yourself are some wirewound RF choke coils of which there are 3 other units used over near the 6BE6 filament supplies and the6AL5 filaments . CHECK and see if that is right … They should measure as quite a low resistance, ( A-B, B-C ) or if the unit took a heavy lightning hit on the ac line in its past history, that possibly might account for 1 of the two now being open, with even one being open, the set wouldn’t work.
The mentioned power resistors are over on the power section yellow highlighting and I really don’t expect any problem….. with both of them being open.
Marked up Schematic reference:
73's de Edd
6/16/2008 8:21:04 PMGeorge T to Edd(63175:63165)
Hi Edd,
Your right, I can see it now. The one that is hooked up to the 5th pin does show .1 ohms the other one is blown. I might be able to solder it back together. If I can't repair it would you happen to know were I could get a replacement or something that would work in its place? They do have another one on Ebay right now might have to get it and make one good one. Thanks A Million For Your Help, George.
Your right, I can see it now. The one that is hooked up to the 5th pin does show .1 ohms the other one is blown. I might be able to solder it back together. If I can't repair it would you happen to know were I could get a replacement or something that would work in its place? They do have another one on Ebay right now might have to get it and make one good one. Thanks A Million For Your Help, George.
6/17/2008 6:54:23 PMEdd to George T...Come in pls(63185:63175)
Ohhhhtay..on the choke coil being open, either by overload or just as likely due to a terminal connectivity issue.
Since I am blind on this end, how about doing an inspection and see if it might actually be a coil wire wrap to lead wire problem.
Also, if it happens to be the outer winding connection….YEAAAAAH… you can merely unwrap a single turn to get a connectable length for scraping and re soldering.
If you need further help to make up one from scratch, need to know the size of core (core inner dia-+-length)that it is wound upon, also check with a magnet to see if the form has a hidden permeable inner core element, also the wire gauge used and the number of turns and if it is more than a 1 layer coil.
In this sets FM choke coil function..... an ~10 UH value of unit is needed, yet with its using adequate wire gauge to acquire an ~ 250 ma current passage capability (over spec’d..at that).
Standing by to see how you come out.
PS.... in the interim…a jumper wire will suffice if you want to evaluate the AM aspect, as those multiple choke coil functions are associated with the FM perspective of operation of the set.
73's de Edd
6/17/2008 7:55:42 PMBruce(63188:63175)
:Hi Edd,
:Your right, I can see it now. The one that is hooked up to the 5th pin does show .1 ohms the other one is blown. I might be able to solder it back together. If I can't repair it would you happen to know were I could get a replacement or something that would work in its place? They do have another one on Ebay right now might have to get it and make one good one. Thanks A Million For Your Help, George.
:Your right, I can see it now. The one that is hooked up to the 5th pin does show .1 ohms the other one is blown. I might be able to solder it back together. If I can't repair it would you happen to know were I could get a replacement or something that would work in its place? They do have another one on Ebay right now might have to get it and make one good one. Thanks A Million For Your Help, George.
As I remember these they are a single layer and easily rewound. As they are in the AC circuit if they are both blown or one blown a piece of wire can replace them both until you can construct new ones. Wind them on almost any carbon resistor of suitable physical size.
Bruce
6/17/2008 9:15:30 PMGeorge T(63198:63188)
Hi, I'm going to pull the blown one out tonight and see what I can do with it. It is a single wound choke and looks pretty simple. Just have to put it under the old magnifing glass and check it out. Thanks Again, George. Will let you know what happens when I get my wife to plug it in.
6/17/2008 10:50:38 PM<<<<< IT LIVES >>>>>(63200:63198)
Well soldered the ends of the coil wires, had the wife plug it in while I took cover and it came to life. It plays really good. I think I'll replace the caps, clean it up and put it in my collection. The choke had shorted out from the strap on a loose electrylic that was hanging under the chassis.
Thank You All So Much, George T.
Thank You All So Much, George T.