The Fisher 440-T FM Receiver
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Here we go again...
The next unit for the bench is a Fisher 440-T receiver I picked up recently. Here's a photo of it, from the eBay ad:
[Image: http://www.philcoradio.com/images/phorum...e00004.jpg]
Yup...pretty grungy. I'm hoping the front panel can be made to look decent, in spite of all of the numbers having been rubbed off around the volume knob, and the words "Volume" and "Tuning" nearly rubbed off. If I can get rid of the panel's overall dirty, grungy look (plus getting the knobs clean), I'll be satisfied.
It came in with a dead left channel, but a working right channel.
A look under the chassis:
[Image: http://www.philcoradio.com/images/phorum...e00003.jpg]
You will notice that the under-chassis layout is very similar to the Fisher 4400. The main difference between the two: The 440-T is all-silicon, whereas the 4400 uses germanium driver and output transistors.
I did some checking with my signal tracer, and found that the signal made it all the way to the 1500 uF coupling electrolytic between the left channel output transistors and the speaker - on the other side of this electrolytic, the signal was lost.
I also noticed that dry electrolyte was coming out of the ventilation holes in both output coupling electrolytics. In fact, several of the electrolytics looked as if they had seen better days.
So, this evening, I began replacing them.
I have only six more to go - plus that AC line bypass cap. But since I am getting close, I tried it out again a little while ago.
Success!   We have audio in both channels now!
The right channel sounds a bit muddy compared to the left channel, but since I still have some more electrolytics to replace in the audio chain, I am hoping that replacing those will take care of that issue.
I'll find out tomorrow...
--
Ron Ramirez
Ferdinand IN
Posts: 15,286
Threads: 531
Joined: Oct 2011
City: Jackson, NJ
Solid state is easier, ain't it.
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
In some ways, yes.
Tonight, the right channel in my Fisher 220-T, which we were using as a sort of home theatre receiver, went kaput (extremely low, almost but not quite silent). So there's another for the repair queue.
I'll just replace it with my 202 Futura for now. I'll move the 4400 to my home office in place of the 202, once the festoon lamps arrive.
--
Ron Ramirez
Ferdinand IN
Posts: 15,286
Threads: 531
Joined: Oct 2011
City: Jackson, NJ
Well, there's a challenge!
That happened a lot in the Soviet amps, but then those were designed marginally. I often found transistors' max voltages on a par with working voltages, their dissipation close to the max allowed, not adequately cooled etc.
I was a repairman for all my friends and acquaintances.....
Posts: 239
Threads: 10
Joined: Dec 2013
City: Columbia, SC
The toner transfer method used to mask etched PCBs works really well for transferring graphics on to anything solid. I'm wondering if you could reconstruct the dials with it.
Basically you mirror your image, print it with a laser printer on magazine paper, iron the graphic onto a surface, wet the paper and peel it off. I've even used it on wood, might be worth a shot if you can recreate the graphic.
That is, of course, if you even care 
(This post was last modified: 03-01-2014, 10:14 PM by skyscraper.)
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Hmmm...
[Video: http://www.youtube.com/watch?v=krD4hdGvGHM]
Might be worth looking into. But, where do you get "magazine" paper?
--
Ron Ramirez
Ferdinand IN
Posts: 239
Threads: 10
Joined: Dec 2013
City: Columbia, SC
I cut it out of a magazine  If the cut is reasonably straight, it won't jam a laser printer. The clay on the surface keeps the toner plastic from fusing with the paper itself, and blocks the original printed ink in. When the iron melts it, the toner image transfers clean. Onto copper anyway, I'm not sure about aluminum or stainless.
I'm sure there are plenty of guides online, it's a very common hack with electronics guys.
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
--
Ron Ramirez
Ferdinand IN
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Not a good day today.
I installed the remaining electrolytics and replaced the AC line bypass cap, only to find that I had lost audio in the right channel.
What the heck?  I checked and doublechecked wiring...nope, no wiring errors...no solder bridges.   Output and driver transistors are OK...voltages at the output transistors seem to be OK...and going by the signal tracer, it even seems to have a clean signal all the way through the output coupling capacitor. But the output transistors became quite warm, and it appears two of those little 3 watt resistors connected to one of the output transistors were stressed by something as they just have that "stressed" look (darker than the other, similar resistors).
I should have quit while I was behind. But, oh no, I just had to attempt to clean that front panel using a procedure I had found at AudioKarma.
Something told me not to soak the panel, so I just used some warm water and detergent. I stopped when some of the lettering came off around the far right knob. 
Then I attempted using polish, as suggested...and quit when I polished off the bird that was the Fisher logo.    
Yup, there are some days when you should not attempt any work at all on electronics...
--
Ron Ramirez
Ferdinand IN
Posts: 1,106
Threads: 88
Joined: Jun 2011
City: Tacoma
State, Province, Country: Washington
Maybe you have a problem with the speaker switch?
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
I had already cleaned it with DeoxIT, along with the other switches/controls. However, it is looking like tomorrow will be a snow/sleet day from work, so I might try hooking the speakers to the "remote" terminals instead of the "main" and see what happens. I'll even try switching left and right speakers - while I find it highly unlikely the right speaker failed, I suppose anything is possible...
--
Ron Ramirez
Ferdinand IN
Posts: 15,286
Threads: 531
Joined: Oct 2011
City: Jackson, NJ
Well, if you cleaned-touched things, you probably shorted one of them things. Unless Deoxit decided to conduct where it shouldn't but then it is temporary - it will dry up.
I had this when sprayed switches in Heathkits - some droplets got on the tuning cap and I got sparks. Then it dried up.
Think back of what you touched.
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Brenda - your suggestion was right on. I'm home today due to the ice and snow, so I decided to try connecting the speakers to the "remote" terminals instead of the "main". I put the speaker switch in the "remote" position, held my breath, turned the thing on, and voila - I have loud, clear sound in both channels. Thanks!
So now I have two reasons to find a 440-T junker - a better faceplate and a good speaker switch.
Photos to follow.
--
Ron Ramirez
Ferdinand IN
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
Some pictures.
[Image: http://www.philcoradio.com/images/phorum...e00002.jpg]
Almost all of the electrolytics under the chassis have now been replaced.
But I missed two when I was writing up my "need to order" list:
[Image: http://www.philcoradio.com/images/phorum...0003-1.jpg]
You can sort of see them above, partially hidden under the two 1.2K resistors.
I noticed that, as I observed Saturday evening, that the right channel sound is still not as bright as the left channel sound, although the volume of both seems equal now. I may have to take a look at the tone control board, plus replace those two electrolytics that I missed.
A photo of the 440-T in operation - notice that, without the faceplate, it looks very similar to the 4400 without its faceplate:
[Image: http://www.philcoradio.com/images/phorum...0004-1.jpg]
Now, for your edification, I present the next two pictures as examples of what not to do to the extremely delicate faceplates of these receivers:
[Image: http://www.philcoradio.com/images/phorum...e00005.jpg]
[Image: http://www.philcoradio.com/images/phorum...e00006.jpg]
Don't polish, soak, or otherwise attempt to clean these - you can only make them look worse, not better.
Now, other than some more electronic work to see why the right channel seems "muddy" compared to the left, I need to decide whether I want to try Skyscraper's idea of transferring some artwork, or just finding a junker 440-T with a better faceplate. Since I probably need a speaker switch, a junk 440-T might be a better option. So comes the challenge of finding one...
--
Ron Ramirez
Ferdinand IN
Posts: 1,113
Threads: 14
Joined: Feb 2013
City: Irvington, NY
How does the top of the chassis look? Are there any more electrolytics on the IF and MPX boards?
I have not worked on one of these in years, but I recall there were more PCBs on top. I still have one and may dig it out and see if it still works!
Users browsing this thread: 1 Guest(s)
|
