Troubleshooting CA-800

Discussion in 'Fisher' started by warriorfan, May 8, 2017.

  1. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    Well the bug has bit me and I am now an addict! Been wanting to finally put a system together and turned out my sansui au-717 was needing some repair to fix a dropped channel. Not wanting to trash it out led me here, and with the great help of some members it was decided that wasn't the best piece have as a first repair attempt. The sansui will get some much needed love in the next few months and in the meantime something else was just needed....

    I picked up a nearly free fisher system yesterday! It included a ca-800 amp, st-290t turntable, fm 600 tuner, and a cr 124 tape deck. I wantes to be more careful with the the ca 800. I powered it up hooked up my phone to the aux inputs. Relay clicked and I noticed I only had a reading on the sweep on the right side. Time to play!

    I cleaned it up with deoxit in all the pots and did a quick visual inspection before firing it up. Turn it on after hooking my phone and a klipsch center speaker to the A channel on the ride side. Sound! Then like a dummy, I try the left side. The sweep jumps to full power and before I shut it down I smoked my speaker! Nice. I also noticed a slight puff of magic smoke rise from the vicinity of the power switch. Also blew the fuse on the left channel. Back to trouble shooting...

    I now looked a little harder for burnt areas on the board of the power switch and in the area I saw the smoke.
     
    Last edited: May 8, 2017
  2. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    Pics of what I found.

    20170508_091647.jpg 20170508_091708.jpg 20170508_091724.jpg 20170508_091801.jpg 20170508_091935.jpg
     
    Last edited: May 8, 2017
  3. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    If anyone has the service manual I would appreciate It! The only one I have found requires me to join the site it was on.

    I found some trouble areas and anxious to start tracing them. J04T IS burnt in the middle. C25 has what appears to be burn marks on the solder side and it looks like J02X looks lkeep it may be burnt as well. I would venture to say that someone else has been in this unit and fixed these same areas before?

    How am I doing so far guys? I know I haven'the got to the hard stuff yet, but this is all new to me and I am feeling optimistic. Lol! Thx much. Ryan
     
  4. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

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    Location:
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    These are symptoms of a blown power pack. It railed and blew out at least your speaker. Also D01 looks suspect. And I haven't gotten into the manual yet. This will NOT be an easy fix. You've got problems that cascaded out from the blown pack all the way to the tone control board, possibly the power switch board, and other's. Unless you know someone that does this and has the equipment to diagnose the problem and then fix it, it's not worth the time, effort or $$$ to fix it.

    Hifiengine.com has the manual. Registration is free.

    Lesson learned???? On every NEW piece of gear, use a DBT (current limiter) to test the new gear and save your speakers or at worst minimize damage. You put full rail DC voltage to the speaker and blew it's voice coil. It can be fixed by a shop.

    My very strong suggestion is if you've never worked on an amp before, STOP! Find something lower on the food chain to learn on. These amps are technically challenging, and if you've blown a STK, you WILL NOT find an original (except maybe on a donor unit) as Sanyo has NOT built them in 20+ years. Plus SANYO doesn't exist anymore. Panasonic dissolved them 5 years ago along with FISHER. Suggest you find a WORKING CA-800 and use this one for parts.

    Larry
     
    Last edited: May 8, 2017
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  5. warriorfan

    warriorfan New Member

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    Winamac,Indiana
    Well crap! I can't win for losin.
     
  6. larryderouin

    larryderouin Do I get Food, Med's, or more gear this Month? Subscriber

    Messages:
    20,140
    Location:
    Glen Burnie Md.
    We've all BTDT at one time or another! So don't knock yourself for at least trying. If you like the CA-800's styling, find a CA-880 which has discrete outputs (you can still find TO-3's). It's in the same class but doesn't have the big meters which IMO are an anachronism. All they are is voltage meters with the face set for watts. And they aren't accurate either. But make sure it's working both sides before plunking down your $$$. I would make a suggestion and tell you to become a subscriber so you can check out BARTERTOWN. It's AK's combination swap meet, Garage sale, and it's a subscriber only section. So no outside BS, no fee's, and all the sellers are AK members. You get a better selection of gear here, it's generally in a lot better condition, and it's 1st come 1st served. No bidding wars, etc. You usually get your $25. worth back on your 1st big purchase as the gear is in better condition for working gear, it's been worked on or overhauled, and there are parts galore. You just have to look for them.
     
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  7. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    Thanks Larry.

    I am bored and home so this gives me something to do more than anything. I'm not out anything if I end up chucking the amp in the garbage and the rest of the stuff can go to evilbay. I do like the style of this amp and it was just going to get used until my sansui is repaired. Would have been a sweet gift to my pops or oldest son. Still messing with it and downloaded the manual.

    I have resoldered the wire on J04T and moved the good fuse from the right channel into the left. Powered on and played music through my phone. I got smoke from R02 and shut it down. Will mess around some more after bit

    I sure hope I don't offend anyone doing what I am doing? I see guys of some automotive forums that get upset when someone tries to learn something new and you can see the lack of patience often gets a little rude sometimes. I am not pretending to know what I am attempting to do and I don'the expect to have anyone waste their time helping me if one doesn'the feel inclined to do so. If me posting here is deemed below the standard I would hope a moderator would let me know and I will gladly step. I am having fun with a hobby that I just newly got into and we'll I am having fun.

    Now off to see how to test this darlington pack. I may just swap them around and verify it is bad that way?

    BTW magic smoke stinks like no other!
     
  8. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    Lol I digress! Man this stuff is hard! I am going to set away and read some basic tutorials on testing basic components first. Testing in circuit with a diode was enough to stop me.
     
  9. Tom B

    Tom B AK Subscriber Subscriber

    Messages:
    1,029
    Location:
    Bay Ridge, Brooklyn New York
    I wouldn't swap around the power packs, as you can now cause cascading problems on the good side. There is a guy on ebay who sells the powerpacks for ~ $12.00 shipping included "STK0080A / DARLINGTON POWER PACK (qzty)". You definitely have a bad Powerpack, and maybe a bad emitter resistor (2X.22ohm) The emitter resistor is the white porcelain rectangular component in front of the power pack. It should read 0.022 ohm from the center to each of the 2 sides. I expect that one side will show open, causing a high DC potential on the output. Thats what blew your speaker, and what caused R02 (big 2w) to start burning when you had headphones on. You could have other issues such bad transistors, diodes or other resistors, but it is possible the issue is just power pack and resistor, or just powerpack. That STK0080A produces 80W RMS and can really crank.
    I would not connect ant speaker, or headphones until you get the problem fixed. I would suggest that you use 2A fuses for the troubleshooting, as well as a dim bulb tester. When power up the unit with a dim bulb tester, connect your voltmeter to the speaker out and make sure the voltage shows as close to "0" volts DC when the relay engages. If it is showing +55v or -55v you still have a problem, but I think the powerpack and emitter resistor (if it is bad) should fix it. When you are convinced that the problem is fixed, (you hear or see the relay engaging, and the DC volts is close to 0v on both outputs, then you can test with headphones/speakers. If it is now working good, you can put the 4a rated fuses back in.
    Good luck
    tom
     
  10. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    Thanks Tom!
     
  11. Tom B

    Tom B AK Subscriber Subscriber

    Messages:
    1,029
    Location:
    Bay Ridge, Brooklyn New York
    Sii as well. Just don't use any STK0080 as well as the STK0080ii. Just don't use the plain STK0080 as they are not the same as the "B" version or "ii" version.
     
  12. Bassblaster

    Bassblaster Super Member

    Messages:
    1,813
    Location:
    Cambridge, Ohio
    There is absolutely ZERO need to do that...
    the CA-800/880 are some of the simplest amplifiers ive seen. not too bad once you get a rough idea of the circuit IMO
    Ummm, no it doesnt. it also uses the STK-0080
    It has the same meters also...


    Oh boy this will be good... i HAVE a CA-800 that im in the process of completely rebuilding, SERVICE MANUAL - https://www.hifiengine.com/manual_library/fisher/ca-800.shtml

    AT FIRST it looks like a blown STK-0080. now dont worry there's no need to try and replace it with a "new" STK-0080 pack when you can replace them with fully discrete packs with all new parts, no need to try and find a donor unit that someone else suggested... - http://audiokarma.org/forums/index....placement-for-sx-780-and-others.721181/page-7

    If you want to see my CA-800 its here - http://audiokarma.org/forums/index.php?threads/fisher-ca-800-rebuild-thread.763531/

    Service manual states the CA-800 uses STK-0080A's. not sure the difference between the B and mark 2 versions.
     
    Last edited: May 8, 2017
  13. Tom B

    Tom B AK Subscriber Subscriber

    Messages:
    1,029
    Location:
    Bay Ridge, Brooklyn New York
    Yes the manual shows STK0080A's and has the internal schematic showing the same as the STK0080ii, I found the internal schematic of the type ii on line and it shows the same as the "A" version shown in the CA800 service manual. So I make the simple assumptin that the type "A" and type II are the same. The plain STK0080 is a different animal component and lead wise, and could possibly work, but I would suggest using an exact replacement STK0080A, or a replacement STK0080ii because the service manual shows the chip with 10 Active pins and extra transistors, even though the circuit is only using 6 active pins like the STK0080.
     

    Attached Files:

  14. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    The unit I have has stk0080 on the packs.

    Thank you guys for any time you have in helping me! Hope threads like these get used sometime later so this old gear stays runnin.

    Bassblaster...I have been following your thread.
     
  15. Bassblaster

    Bassblaster Super Member

    Messages:
    1,813
    Location:
    Cambridge, Ohio
    First thing i would do is de-solder pins 2 and 9 on the STK packs. those are you positive and negitive supply rails. if it powers on with those packs removed, one of these is the problem. its highly unlikely they fried anything farther back like the tone control. the CA-800 the meters use there own op-amp driving off the pre. so they are not at all accurate. still fun to watch tho.
     
    Last edited: May 8, 2017
  16. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    Thanks bass blaster that will give me something to do if it rains tomorrow. I downloaded the manual too btw.

    How far should I strip this down at this point? This amp looks pretty simple in that aspect, but I don't want to get carried away. I need to order a better soldering iron from parts express but momma has been watching me flip through it with the old I dare your ass look. The garage currently looks like a pawn shop so I best watch it!

    I am more than likely letting the sansui's go to someone here and picking up a fairly comprable tuner and integrated in return. I'm gonna stick around, fix this fisher and hopefully see my sansui live again. Great stuff!
     
  17. Bassblaster

    Bassblaster Super Member

    Messages:
    1,813
    Location:
    Cambridge, Ohio
  18. Bassblaster

    Bassblaster Super Member

    Messages:
    1,813
    Location:
    Cambridge, Ohio
    Off track a bit but I just noticed the plastic housings for the lights look new! Mine are all yellowed and brittle. Yours looks like it may be a low hour unit. Almost like whoever had it blew the power pack then put it in storage for who knows how many years
     
  19. warriorfan

    warriorfan New Member

    Messages:
    40
    Location:
    Winamac,Indiana
    Bassblaster...the whole lot was very clean. It does though smell horrible! I happened to stumble across everything on the app relist it. It was a half hr away and $30. I got to the address given and was met by a angry looking lady and an even angrier looking pit bull. I was asked if I was there to look at the stereo and said yes. She told me to go to the next place up the road and it was there. I get there and it was a horrible looking trailer that was falling in on itself. My buddy said we're gonna die. I said naw as the truck in the drive had firefigher plates on it. Long story short an eldery couple lived there and the neighbor bought the place after they both died weeks apart of of one another. The guy was getti,g rid of stuff before he tore the place down. The floor was rotten in the place and you have to be careful where ya walked. The stereo was partly hooked up and i got tired of messing with it and smelling mold so I just said heck I will take it. It still smells of that place after a good douching of deoxit. I was also offered a old rca system in a 6ft tall cabinet. Had a 8track expander on it and it was also very nice and did work! I passed as the wife would have killed me. I buy a lot of different stuff from cars to canoes and am pretty ecclectic in taste. It never fails there is a interesting story to most of my finds and it amazes my wife sometimes. I'm a bit weird as I believe much happens for a reason in life...whether it's a story, the journey, a conversation, a new friend or a treasure of a piece to enjoy and remember maybe some of the above mentioned. Getting old and my sense of value is wacky?
     
  20. Bassblaster

    Bassblaster Super Member

    Messages:
    1,813
    Location:
    Cambridge, Ohio
    i think $30 for the lot was a steal! i paid $70 for my CA-800 and FM-600.
     

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