fisher 500tx
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That's like taking a car in to a mechanic and saying "it makes a funny noise and it won't run". Could be any number of things wrong with it, and will cost you more than you are willing to put out, unless you get more specific as to what it does(or doesn't) and when, what function is on, how the pots, switches are set, what you were listening to at the time, left and right speaker, or just one or the other speaker, or the noise came out of the receiver itself.
also one more thing, put your location in your profile, so we know where in the world you are. It kinda makes it easier to reply and carry on conversations.
One last thing......WELCOME TO AK!
DO NOT PLUG IT IN UNTIL We are ready to perform some diagnosics.
Build yourself a DIM BULB TESTER. You're gonna need it to keep from making a boat anchor of the 500-TX.
CAREFULLY open up the TOP and BOTTOM cases, put the screws in baggies, and mark them. Then take pictures of the top and the bottom of the unit with all the parts showing. I particularly want to see the power supply board. That's the BIG BOARD underneath, between the back and the BLACK RECTANGULAR BOX (POWER Transformer). Take Closeup of any scorched areas. DO NOT REMOVE PARTS or DISCONNECT any Wires UNLESS DIRECTED TO.
POST THE PICS:
Then give a detailed synopsis of what happened. FOR EXAMPLE.....it was running playing FM Stereo, Volume @ 2, Tone controls centered, Loudness off. Tuner was in Manual mode (there are also Preset, and Auto Scan). When I heard a loud Screeching sound from BOTH Speakers for about 3 seconds then all was quiet. I turned it off immediately and unplugged it. I noticed no smoke or unusual odors from the receiver. The heatsink and the transformer were very hot to touch.
I checked the fuses on the power supply but they were good by meter, out of circuit. END EXAMPLE
This tells us that the idle voltage and bias are WAY OFF due to the excessive heat from the heatsink and the transformer is laboring due to excessive load. There are a bunch of things that can cause this, the chief among them is dried out caps. They in this case would need to be replaced on the power supply and the large 1500uf cap next to the amps. Plus replacing the small caps and other parts on the power supply. then once we got the power supply under control, we'd use the Service Manual to set the idle voltage and bias. This will cool down the heatsinks, and the main output transistors.
Then we'd concentrate on making it able to last the next 20-30 years without problems, by replacing all electrolyic caps, and other parts. They are just plain worn out. FISHER Designed these to run HARD at the edge of the envelope for the transistors of the period. New transistors are heavier duty and won't run so hard, while putting out everythig that FISHER designed into the unit.
It ain't gonna be cheap. But where else can you buy a TOTL receiver from a Major US manufacturer and keep it running to spec after 43 years. Follow the directions and you'll end up with a functionally near new unit that will play for decades without problems.
Larry
also one more thing, put your location in your profile, so we know where in the world you are. It kinda makes it easier to reply and carry on conversations.
One last thing......WELCOME TO AK!
DO NOT PLUG IT IN UNTIL We are ready to perform some diagnosics.
Build yourself a DIM BULB TESTER. You're gonna need it to keep from making a boat anchor of the 500-TX.
CAREFULLY open up the TOP and BOTTOM cases, put the screws in baggies, and mark them. Then take pictures of the top and the bottom of the unit with all the parts showing. I particularly want to see the power supply board. That's the BIG BOARD underneath, between the back and the BLACK RECTANGULAR BOX (POWER Transformer). Take Closeup of any scorched areas. DO NOT REMOVE PARTS or DISCONNECT any Wires UNLESS DIRECTED TO.
POST THE PICS:
Then give a detailed synopsis of what happened. FOR EXAMPLE.....it was running playing FM Stereo, Volume @ 2, Tone controls centered, Loudness off. Tuner was in Manual mode (there are also Preset, and Auto Scan). When I heard a loud Screeching sound from BOTH Speakers for about 3 seconds then all was quiet. I turned it off immediately and unplugged it. I noticed no smoke or unusual odors from the receiver. The heatsink and the transformer were very hot to touch.
I checked the fuses on the power supply but they were good by meter, out of circuit. END EXAMPLE
This tells us that the idle voltage and bias are WAY OFF due to the excessive heat from the heatsink and the transformer is laboring due to excessive load. There are a bunch of things that can cause this, the chief among them is dried out caps. They in this case would need to be replaced on the power supply and the large 1500uf cap next to the amps. Plus replacing the small caps and other parts on the power supply. then once we got the power supply under control, we'd use the Service Manual to set the idle voltage and bias. This will cool down the heatsinks, and the main output transistors.
Then we'd concentrate on making it able to last the next 20-30 years without problems, by replacing all electrolyic caps, and other parts. They are just plain worn out. FISHER Designed these to run HARD at the edge of the envelope for the transistors of the period. New transistors are heavier duty and won't run so hard, while putting out everythig that FISHER designed into the unit.
It ain't gonna be cheap. But where else can you buy a TOTL receiver from a Major US manufacturer and keep it running to spec after 43 years. Follow the directions and you'll end up with a functionally near new unit that will play for decades without problems.
Larry
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Also search 500tx on this and the Vintage Solid State Forum. There are quite a few overhauls done on them in the last few years. The 800-T is a 500-TX but with a Multiple Voltage Transformer, and a remote control for export use. It was sold overseas in military Px's. They use the same Service Manual. Download it from the AK Database. Then study the living hell out of it. There will be a spot exam on it Friday.
Larry
Larry
Larry, Thank you so much. for reply about my Fisher 500tx problem. I did as you informed above. I opened up top and bottom cover, but I did not find any scorched areas. I saw that the Fisher amp was very clean and very well managed amp. I thought it would be better to send it to specialist in new york and to repair it thoroughly. Thank you again.
YoungKim
YoungKim
fresh767@ver
New Member
Hi guys,
I have two Fisher 500TX's and want to recap, and whatever else is needed to have them perform going forward. I purchased the original one, Fisher 500TX_#1 in 1970, IIRC, and I have a couple of problems with it, which I'll list below
.
Fisher 500TX_#1 (my first born)
The AM is good. The FM, however, is pretty much nonexistent - nothing at low volumes and only hum at higher volumes. I believe I screwed the pooch a month or two ago when I enjoyed one too many gin & tonics while checking the units after several years of idleness. My wife said she found the unit in question on (all night). I had FM problems afterward.
Fisher 500TX_#2
Working rather well. FM is strong and sounds fantastic (I'm listening to it now). Manual, Tune-O-Matic and Autoscan work well
. AM is somewhat weak but might be the onboard antenna and my location.
I purchased a variac and brought each unit up to 117v slowly to make these assessments. I'm a novice/noobie but an experienced DIYer and looking forward to the adventure. Any help as to what to do and what not to do would be VERY much appreciated! Thanks for any help. The cap listing by Sterling245 should prove invaluable, as well!
FredF
I have two Fisher 500TX's and want to recap, and whatever else is needed to have them perform going forward. I purchased the original one, Fisher 500TX_#1 in 1970, IIRC, and I have a couple of problems with it, which I'll list below
.Fisher 500TX_#1 (my first born)
The AM is good. The FM, however, is pretty much nonexistent - nothing at low volumes and only hum at higher volumes. I believe I screwed the pooch a month or two ago when I enjoyed one too many gin & tonics while checking the units after several years of idleness. My wife said she found the unit in question on (all night). I had FM problems afterward.
Fisher 500TX_#2
Working rather well. FM is strong and sounds fantastic (I'm listening to it now). Manual, Tune-O-Matic and Autoscan work well
. AM is somewhat weak but might be the onboard antenna and my location. I purchased a variac and brought each unit up to 117v slowly to make these assessments. I'm a novice/noobie but an experienced DIYer and looking forward to the adventure. Any help as to what to do and what not to do would be VERY much appreciated! Thanks for any help. The cap listing by Sterling245 should prove invaluable, as well!
FredF
AM. Hang a wire (spkr wire is ok) out a window about 10-15ft. The higher the better. See if AM improves. If you know direction of transmitter orient wire 90* to that direction.
FM 500TX is a 1st gen varactor tuner. Kinda Funky. On the back of the AM Tuner CAN, there is a .033uf 250v capacitor (usually teal in color axial). The one's I've done over the years, this is the most problematic. Replace it as cheap insurance. any good film cap will do. You may need to recap the tuner/muting/mpx board. And the varactor board underneath.
Pittsburgh is full of hills as you know, so FM would be more affected than AM as FM is line of sight and hills, tall bldg's, even construction of your house will affect reception. So getting an antenna up as high as you can is imperative for good reception (roof antenna on a rotator or a j-pole type.)
FM 500TX is a 1st gen varactor tuner. Kinda Funky. On the back of the AM Tuner CAN, there is a .033uf 250v capacitor (usually teal in color axial). The one's I've done over the years, this is the most problematic. Replace it as cheap insurance. any good film cap will do. You may need to recap the tuner/muting/mpx board. And the varactor board underneath.
Pittsburgh is full of hills as you know, so FM would be more affected than AM as FM is line of sight and hills, tall bldg's, even construction of your house will affect reception. So getting an antenna up as high as you can is imperative for good reception (roof antenna on a rotator or a j-pole type.)
fresh767@ver
New Member
Larry,
Thanks for your reply, I appreciate your help. Pittsburgh is full of hills, for sure. Luckily, I live on the crest of a high one. A longer wire brought in a few more stations it seems but some of them (weaker ones?) at lower volumes. It's not something I'm too concerned about at the moment though - I hardly ever listen to AM. I notice the FM is great on my Fisher 500TX_#2, as stated before, in my original post using the Tune-O-Matic and Autoscan.
Q1: From your reply, I'm assuming the varactor tuner is the culprit since it tunes FM differently from the other two. I will change the .033uf 250v capacitor on both units soon and see what happens.
Q2: Another question I have is, before changing out some/all of the electrolytic caps, should I continue to let the units warm for a short while by starting at about 30vac and up to full power (117v) in a couple of steps, until the recap; the transistors & power transformer barely get warm to the touch (not even perceptible) to touch using headphones @ 117v.
Q3: Could the lack of FM on the Fisher 500TX_#1 be attributable to the same cap on the varactor, as well?
Thanks for any suggestions and help.
FredF
Thanks for your reply, I appreciate your help. Pittsburgh is full of hills, for sure. Luckily, I live on the crest of a high one. A longer wire brought in a few more stations it seems but some of them (weaker ones?) at lower volumes. It's not something I'm too concerned about at the moment though - I hardly ever listen to AM. I notice the FM is great on my Fisher 500TX_#2, as stated before, in my original post using the Tune-O-Matic and Autoscan.
Q1: From your reply, I'm assuming the varactor tuner is the culprit since it tunes FM differently from the other two. I will change the .033uf 250v capacitor on both units soon and see what happens.
Q2: Another question I have is, before changing out some/all of the electrolytic caps, should I continue to let the units warm for a short while by starting at about 30vac and up to full power (117v) in a couple of steps, until the recap; the transistors & power transformer barely get warm to the touch (not even perceptible) to touch using headphones @ 117v.
Q3: Could the lack of FM on the Fisher 500TX_#1 be attributable to the same cap on the varactor, as well?
Thanks for any suggestions and help.
FredF