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800-C Restoration

Discussion in 'Fisher' started by audmod01, Nov 12, 2018.

  1. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Thanks to Matt, I now have an 800-C to restore. He had one output transformer and I had another one I bought from the internet. I have ordered a set of knob brights and I have one question regarding them - The two knobs at the top on either side of the dial (speaker selector knob and tuning knob) are different. The one at the left has a raised rib on the ridged surface while the tuning knob does not have the raised ridge. The raised ridge on the speaker selector knob points to the lettering on the bezel to indicate the user's choice. Does the speaker selector knob come equipped with a knob bright that has the black dash to also point to the user's choice or is it a blank bright with no black dash? It makes sense that the tuning knob does not have the black dash on it, but the speaker selector knob might not have come with a black dash on it since the knob surface has the raised pointer ridge on it. Anyone?

    Here are a few pictures of the unit:
    800-C Received web 01.jpg 800-C Received web 02.jpg 800-C Received web 03.jpg 800-C Received web 04.jpg 800-C Received web 05.jpg 800-C Received web 06.jpg
    800-C Received web07.jpg
    Matt also sent me a great collection of electrolytic capacitors and multi-turn controls I can use in installing an IBAM mod and other upgrades as part of the deal. I am indebted to Matt for his help! I plan to fully restore the unit and add the EFB circuit and the IC stages between the Line stages and the Output Driver/Phase Inverter stages. The AM Loop Antenna is missing, but I have a donor AM Loop I can use, but will need the mounting bracket for it too.

    In the photo of the underside of the chassis you can see the blue painter's tape on the leads for one output transformer. That is the transformer that I had on hand and I placed the tape over the leads while passing them through the chassis opening for them. This makes the installation go easier. Matt sent some of the mounting hardware for the transformer and I had some on hand. Some of the leads of the transformer I had on hand will have to be extended as the seller clipped them short.

    The left and right ends of the chassis have some corrosion that has leached through the plating, so clean-up there will be needed and some light sanding followed by some primer and Krylon Satin Nickel paint to cover up those areas. The rest of the chassis is in very good condition and will only need cleaning. The S/N is 47223 Q which places it in the later production group. This one will be really nice when finished.

    Joe
     
    Last edited: Nov 12, 2018
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  2. larryderouin

    larryderouin Turn it UP, POP? PLLUUEEEZZZZZEE Subscriber

    Messages:
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    Joe; Both my Executive's and Stand alone 800-c have the Raised pointer and the scribe line on the Selector knobs. The tuning knobs have no raised pointer and a plain cap.
     
  3. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Larry;

    Thanks for that information! That is what I expected. So the speaker selector knob will get a cap with a dash pointer and the tuning knob does not. I am in the process of cleaning the ribs on the plastic of all the knobs. Over the years they all get grease and dust embedded from handling.

    Joe
     
  4. AlTinkster92

    AlTinkster92 AK Subscriber Subscriber

    Messages:
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    NC
    Joe, just a curious question if you don't mind, when you turn the tuning knob down to the 108 end of the dial does the turning effort increase as you get closer to the 108? Dave had to modify mine as it use to get hung up. Wondering is all these 800c's do this is all. Nice receiver! AL
     
  5. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    AL;

    I will have to check. I remember the issue being brought up. It could also be an issue with some 500-C models. One thing that is different between 800-C models and 500-C models is the dial cord arrangement and the shape of the chassis edge (right side viewed from the front). The 800-C has a metal flange that is bent inward about 30 degrees or so. The 500-C doesn"t except on their first released serial number sequence group. That was changed to a straight right angle edge when the 500-C front end changed to using 6CW4 Nuvistor tubes, second serial number sequence group and up.

    Joe
     
  6. fred soop

    fred soop Super Member

    Messages:
    2,025
    If the turning effort increases at one end of the dial, the several turns around the tuning shaft itself are probably getting overlapped and further turning requires pulling one section of string out from under another section. Fixing this requires some trial and error tweaking of those parts nearest the tuning shaft.
     

     

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  7. rufleruf

    rufleruf Poor Impulse Control Subscriber

    Messages:
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    I'm happy to see the quick progress - I'm glad you decided to take this on.
    You must have more discretionary time than me. I've been trying to finish the same 500-C for 6 months... I guess having a 6 year old in the house is some excuse.
     
  8. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Matt;

    Yes, since I am retired, I can change priorities from one project to another. My problem is finding the energy to complete each project. I often get into a new project before I complete an existing one. For sure, don't neglect your children. They are your investment in the future and need your care, love, teaching and time.

    I need to take my 500-C out of its storage box and check its end to end tuning as discussed above with Fred. I have a suspicion that the first S/N sequence of 500-Cs has the same issue as the 800-C models with the dial cord overlapping itself as the unit is tuned to the top of the FM band.
    Chassis Right Side web.jpg
    This is an image of my 500-C during restoration. It shows how closely this version of 500-C matches the dial cord arrangement of the 800-C. That design of the 500-C changed as the next S/N sequence was produced with the 6GK5 RF Amp tube and the 6DW4 Nuvistor tubes in the front end. I hope to get the comparison done later today.

    Joe
     
  9. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    In the process of checking for Dial Cord overlapping, I discovered two issues: 1) There is no dial pointer; 2) the unit will only move from the top end of the AM or FM dials to a point about 1/3 down dial and stops. The Dial Cord appears not to be strung correctly and may even be too short. It looks like one more full loop around the pulley on the ganged tuning capacitor may be missing. The tuning stops right where the fixed end of the cord passes through the slot in the outer edge of the capacitor pulley. I have a dial pointer from the 610-ST parts chassis and found that it will fit the space and the edge of the 800-C dial OK, but I only needed to trim the far end of the pointer to clear the top edge of the dial back-up plate upper edge. I am lucky that I had a pointer to use. It may be too long, but for now I am just after functionality.

    I removed the cover of the RF Front End to see how far down the dial the unit would tune. You can see where the ganged capacitor stopped due to the Dial Cord issue in this photograph:
    Tuning Issue web 01.jpg
    next step will be to find the dial cord stringing diagram and see if it was re-strung from the wrong end of the dial or something simple like that. You can see that this chassis does have the small spring positioning dial cord guide along the bottom string to the capacitor pulley.

    In the meantime, from what I can see this unit may not have the dial cord overlap issue. I will not know for sure until I get the Dial Cord re-strung. Is the Dial Pointer supposed to be white? And, how far up the dial face does it reach? Currently I have the pointer cut about 1/4 inch below the top of the dial back-up plate, so it is currently going well above the top edge of the dial glass. My guess is that it probably only has a white painted area that reaches perhaps 1/8" above the to edge of the FM Dial frequency numbers. If it were to go any higher than that it would reach up under the tail feathers of the Fisher Bird on the dial.

    Joe
     
  10. rufleruf

    rufleruf Poor Impulse Control Subscriber

    Messages:
    1,154
    Joe,

    I found a dial pointer on my work bench this weekend - maybe belongs to you? Let me know if you want me to send it.

    Looking at a lot of 500-C's, the 10001 - 19999 series had the same tuning pulley as 800-C as pictured in the previous post. The 30001 on had the familiar black pulley. Not sure about the 20001-29999 range. Anyone have one from this range to check?
     
  11. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Matt;

    Don't worry about the dial pointer. I pressed the one from my parts 610-ST unit into service and painted the length of the pointer white. I can always go back and paint part of it black where not appearing OEM. I took the time to clean the dial glass front and back plus scrubbing the other knobs. The face bezel got a cleaning too and looks a bit better. I managed to get the dial restrung correctly second try. I did not have to change the dial cord. I think whoever had attempted to restring it in the past started from the wrong end of the dial plus misunderstanding the pictorial diagram in the manual. I have never found one yet that was entirely clear about how to do it. In any case, it now will tune from end to end and I do not see the cord overlapping itself, so this one was one of the series that had been modified enough that the dial cord is no longer exhibiting that problem.
    After Dial Restring web 02.jpg
    The dial pointer is currently on the dial cord with a slip fit. There is some tension on the brass fingers where the cord passes through the end of the pointer, so once I get the unit operating I can position it for correct frequency indication and then tighten the fingers and add a drop of glue to secure the pointer on the cord.

    So far I have not had the issue of the dial lettering flake off on a Fisher that I have worked with. I used some Windex on the front glass surface (sprayed on a paper towel first). On the back surface I breathe on the glass to deposit a thin film of moisture then wipe with a soft cloth. Several repeats are generally enough to bring the glass back to a clean shine without damaging the lettering at all. The idea is to use moisture very sparingly, certainly not soaking it with liquid and keep rubbing to only enough to clean the glass.

    While I had the top and bottom covers off of the RF Front End, I took the time to lubricate all the tuning capacitor pivot points with some 3-In-1 oil applied with the tip of a small screwdriver. Each pivot point and grounding finger area got a very small drop - just enough to take care of the small surface area involved. At the front bearing which has steel ball bearings, I used somewhat more oil, but not so much that it would run. There is a small drive gear shaft just below the capacitor shaft and that got an oil drop too. I did the same at the bearing of the flywheel shaft from the front tuning knob. When finished the dial will spin a fair distance with a twist of the tuning knob. It may free somewhat more as the oil re-liquefies some of the old dried out oil.

    Joe
     
    Last edited: Nov 13, 2018

     

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  12. bhamham

    bhamham AK Subscriber Subscriber

    Messages:
    2,030
    Location:
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    Looking very nice, Joe!

    About 6 or 7 yrs ago I was cleaning a dial glass on a 400 and the numbers started sliding around. My heart sunk to my stomach.
     
  13. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Yesterday I began adding some lengths of wires to those of the audio output transformers since both of the ones I have came from other units as replacements. The person who owned the unit before Matt acquired it must have cut the transformer leads when removing the OEM transformers. Additionally, the replacements that Matt and I were able to obtain for restoration had had certain wires cut really short when the transformers were removed to sell them. When the time came to wire the replacement transformers into the circuitry, some wires would not reach to the required destinations under the chassis. I hunted through my pack-rat pile of wires until I found wires that at least had the correct body color, although I did not have any wires with blue body and a white stripe. To keep the color codes correct I added a white heat shrunk band close to the plate connection to the blue plate lead that originally had the white stripe. It is important to keep the plate leads connected as originally. I finally completed the addition of extension leads to the transformer enough to permit a normal installation.

    The next task was to connect the wires to their proper destination. This is a real challenge, if you are trying to maintain the original circuitry designed into the unit. When people cut transformer wires out of a receiver there can be no expectation that everyone will do it the same way. This particular chassis had its unique challenges regarding the speaker wiring. It took me spending hours of ohm meter tracing before I finally determined what color of wire had to be connected at multiple places under the chassis. I intended to maintain all of the original functionality that Fisher designed and built into the receiver. In this case it meant making sure the Speaker 1 and Speaker 2 wiring was correctly reconnected and that the wiring for the original Center Channel terminals was functional. Some of the wires that had been cut on this chassis had short pieces of the original wires still connected where they originally were. Some were clipped off right at the terminal where the wire was soldered and left no remaining part of the original wire and its body color for reference.

    Not shown on the schematics is the color code of the leads of the output transformers, so here is the legend:
    Red = B+ for transformer Primary Center Tap
    Blue = Plate lead for V11 (Left) or V14 (Right)
    Blue/White = Plate lead for V10 (Left) or V13 (Right)
    Black = Common speaker lead
    Brown = 4 Ohm speaker lead
    Green = 8 Ohm speaker lead
    Yellow = 16 Ohm speaker lead
    The brown, Green and Yellow leads go to the terminal strips on the rear of the chassis that are marked as "Impedance Select" terminals. The Black wires go to specific terminal strips under the chassis where wires then connect to the Speaker Select switch at the front of the chassis. Since the Left channel Impedance Select terminals are closest to the output tube sockets, I decided to wire those first (the brown, green and Yellow leads of T2). Then the brown, green and yellow leads of T3 connect to the Impedance Select terminals of the Right Impedance Select terminals. When those are finished they cover up the connections to the Impedance Select Left Channel terminals.

    All of this took me most of the morning. Sometimes the way schematics are laid out leads to a certain amount of confusion until one has taken time to trace existing wiring and relate from where and to where each wire goes. Check and double check and even triple check before connecting wires and soldering them in circuit! The speaker wiring is one of the most confusing aspects of these receivers.

    I have not looked at the owner's manual for the 800-C as to what impedance of speaker is to be used at the Center Channel Speaker terminals, but there are 25 ohm 5W wire-wound resistors in circuit with the leads to the terminals at the rear of the chassis. I don't imagine it would make much difference whether 4, 8 or 16 ohm speakers are used there, but probably should be chosen to be the same impedance as that of the Left and Right channel speakers of the system. Both the 25 ohm wire-wound resistors and the 330 ohm 1W resistors for the headphone jack are on the back of the Speaker Selector switch. there is a metal cover that snaps on or off of the chassis to protect the switch and its wiring.
    Output Xfmr Wiring web.jpg
    This picture shows where the Black leads of each channel's output transformer go.

    After getting all the speaker wiring sorted out and connected correctly I decided to stop for the rest of the day. I took a lunch break between connecting the Black leads and then the Brown, Green and Yellow leads for the rest of the transformer secondary for each channel. There is plenty of work remaining and I do not choose to push myself too much from day to day. I find that if I do, I tend to make more mistakes. I have been removing solder splashes and debris as I proceed. Removing old wire from terminal lugs often results in solder splashes and pieces of wire that should not be left behind. They can lead to shorts and much grief later on if not cleaned up as you go. Good lighting and eyesight is important here!

    Joe
     
  14. AlTinkster92

    AlTinkster92 AK Subscriber Subscriber

    Messages:
    3,281
    Location:
    NC
    Glad that dial string works fine Joe, here's a pic of the modification Dave G did on mine, works perfect now. The groove on the brass shaft was "re done" so that there is no binding...
     

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  15. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Al;
    Interesting! I note that the modified flywheel shaft looks just like the shaft on the S/N sequence that my unit includes.

    Joe
     
  16. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Today I finally completed all the audio output transformer installation and figured out the speaker wiring. The way Fisher did the transformer secondary leads was confusing at first. I determined that the yellow 16 ohm leads do not connect to the 16 ohm Impedance Selector terminals at the back of the chassis. Instead they connect very close to the transformers at terminal strips where R27 and R29 plus C21 and C22 are mounted. I discovered remainder pieces of the original yellow wires at those locations. Smaller solid insulated wires go from there to the appropriate 16 ohm Impedance Selector strips at the back of the chassis. Only the brown (4 ohm) and green (8 ohm) wires actually connect to the Impedance Selector strips at the back of the chassis. I covered the blue and blue/white plate leads above.
    Output Xfmr Wiring Complete web.jpg
    I made the secondary black wire leads longer than they have to be as well as the red B+ leads. The long 1.2K ohm orange power resistor connected at the middle of the screen grid bus between the output tube pairs is R128 on the schematic in the power supply. I will be making changes at the output tube sockets to add protection resistors for each screen grid. 10 ohm 1/4 W resistors will be added at each cathode to ground in order to measure cathode current in each output tube accurately. I will add IBAM controls so I can adjust each output tube's current. My first objective is to get the unit operational and make sure that each channel works before proceeding on to any significant modifications.

    I probably could have pulled out my 500-C and looked at how the transformer wires were connected in it, but right now it is in the bottom box of a vertical stack of three boxes, each containing a heavy piece of electronic gear. I just did not feel like dealing with lifting all of them and straining my back. My youngest son will be able to do that for me, so I will just wait.

    Joecm
     

     

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  17. rufleruf

    rufleruf Poor Impulse Control Subscriber

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    Looking good Joe. I'm sure there are a lot of folks (myself included) who would have sent you some detailed pictures.
     
  18. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    Matt;

    Sometimes I forget what a great source of information this site is! I do believe that when the task is difficult and involves some frustration, that the information gained in working on a unit tends to stay more indelibly in our brains. Most all of the receivers or amplifiers I have ever worked on still had their audio output transformers in place and working. That makes replacement or repair of one much easier as pictures can be taken before removal and/or sketches made to show the original routing of wires and associated components. I probably could have pulled out my 500-C and looked at its output transformer connections as a guide, but when I thought of it, my son was away from home and not there to pull it out of storage. I have to be very careful how much pressure and strain I put on my back unless I want to pay for it with headaches and low back pain the rest of the day.

    An item of interest to me is always the approximate date of manufacture. I examined the IF transformers in the receiver and here is what I found:
    FM 1st IF interstage Xfmr = 65-22
    AM Detector Xfmr = 64-51
    FM 2nd IF interstage Xfmr = 65-19
    FM 3rd IF Limiter Coil = 65-21
    FM Ratio Detector = 65-16
    I briefly tried to see the date codes on the electrolytic cans and other IF or Mixer Xfmrs, but their date codes were oriented in such a manner that a casual inspection could not determine their information. This gives only an approximate date range for manufacture. I know of no way to get any closer to an actual date a unit may have left the factory. Another interesting item I noticed was that the audio output transformer that I had bought has thru-rivets holding its end bells in place. The one that Matt supplied with this unit has thru-bolts. The power Xfmr in this unit has thru-rivets instead of bolts. The best I could tell in this cursory inspection of component parts, the output IF Xfmr from the FM Mixer in the RF Front End has no date code or part number on it. If it does, it is facing the metal shield over the ganged tuning capacitor. The three visible sides have no ink or stamped lettering in the surface of the aluminum shield. The same thing was an issue when I was trying to see part numbers and date codes on the other AM Front End Xfmrs.

    The end bells and leaves of the power transformer have some scratches with visible rust on them. I need to decide if I want to disconnect all its leads, remove from the chassis, drill out the thru-rivets and sand, prime and repaint the end bells & leaves or find a way to do the task with the transformer in place on the chassis. The latter would be far easier, except that I would still need to remove the can electrolytic capacitors so that the end bell facing the center of the chassis could be accessible for work. Removing the electrolytics and restuffing them with new internal parts would permit easy access to the end bells of the power xfmr. I probably should do that anyway.

    Joe
     
  19. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    The knob brights I ordered arrived in the mail today, so I took time to install them on all the knobs and took this picture:
    Knob Brights Replaced web.jpg
    Joe
     
  20. audmod01

    audmod01 Super Member

    Messages:
    1,278
    Location:
    Tioga, TX
    One of my friends asked me for details about the knob caps that I applied to the knobs. They were purchased through eBay and they do have a black painted dash pointer or indicator on their surface. The spot where the dash is does not have a stamped depression in the surface of the machined brass. I do not think these have a lacquered surface, so I will need to add that using some clear lacquer with an artists brush. I have a small can of that purchased from a hardware store. I did clean the brass trim ring on the back side of the large diameter part of the knobs and will have to add some clear lacquer there to help prevent corrosion after cleaning them. Here is a close-up of one of the knob caps:
    Knob Cap.jpg
    This is not the greatest photo, but as good as my digital camera will do.

    Joe
     

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