Purchased 800C to restore: currently working perfectly

Discussion in 'Fisher' started by Skibrain, Mar 13, 2017.

Tags:
  1. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    Problem stays on V13 when I move the 7 watt 1.2K to pin 1 on v11 from pin 1 V13. Which it shouldn't have changed anything.
    at 115V AC. still have the 1.2K 1 watt resistor in original location on pin 8.
    Some pictures show it moved to Pin1 on v13

    Testing with black probe on chassis ground.
    Red probe on test point. i.e which ever pin mentioned starting at v10, v11, v13, v14.
    All measurements are in volts.

    Pin 1 407, 407, 407, 407
    pin 4 407, 407, 404, 407
    Pin 5 .169v, .08v .15v, .096v
    Pin 6 -24, -24, -24, -24
    Pin 8 408, 408, 405, 408
     
  2. larryderouin

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

    Messages:
    18,509
    Location:
    Glen Burnie Md.
    These are the pinouts of the 7591 with Screen Stability and Kathode resistors added. Pin 1 is used on the socket as a mounting point for the Screen Stability resistor on the SOCKET ONLY! It is NOT CONNECTED in the tube.

    Pin 1 is the INCOMING SCREEN voltage to the screen stability resistor. It ends at PIN 4. Pin 4 and pin 8 are Screen voltage AFTER the 100ohm(not 10 ohm)STABILITY Resistor.
    Pin 2 & 7 are the Filaments or HEATERS.
    Pin 3 is the Anode (plate) Voltage
    Pin 4 is the G2 or Screen Voltage (See Pin 1)
    Pin 5 is the Kathode or G3 Voltage (the 10 ohm resistor goes to ground here)
    Pin 6 is the incoming G1 or GRID VOLTAGE.
    Pin 7 is the Heater (See Pin 2)
    Pin 8 is the other side of the G2 or Screen Voltage (See Pin 4 & Pin 1)

    7591 pinout.jpg
     
  3. larryderouin

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

    Messages:
    18,509
    Location:
    Glen Burnie Md.
    How about a complete tube socket pin voltage of each 7591. Pins 2 thru 8. Heaters are ACV, Everything else is DCV. Just the Pins, nothing else.
     
  4. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    I did discover I had 17.5 VAC to ground on the chassis. I was standing in my socks in the garage and I touched the edge of the case with my little finger edge and got the 60 hz buzz. So I put one probe to the garage floor and the other to the chassis and got 17.5 VAC reading. ( where is my leakage? Bad resistor to ground? Maybe one of the pin 5 to ground resistors? Maybe on V13?

    Here are my measurements on all the pins minus Pin1 which is 424V except on V13 425V.

    V10- V14 left to right

    AC in at 117 VAC

    pin 2 3.35 3.34 3.33 3.32
    pin 3 459 459 458 459
    pin 4 424 424 422 425
    pin 5 .1v 0v 0v 0v
    pin 6 -25.4 on all tubes pin 6
    pin 7 3.25 3.25 3.23 3.23
    Pin 8 424 424 422 425
     
  5. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,146
    Location:
    NYNY
    You have long leads on your pin 5 resistors. Lift one leg of a resistor that is now reading 0v as you've indicated in post #64 and let us know what it reads. Moving forward, all measurements should be done at 117vac under no signal conditions. Volume to its lowest setting, selector switch to AUX. You know you have sound, albeit distorted, so that's a good thing. If you become concerned at any point, you can run a signal to make sure you have sound but return to the no signal condition for any further testing. What we're trying to do is eliminate variables so the discussion isn't about apples and oranges.

    In post #61 you mentioned that you've left the 1.2k resistor in its original position despite a prior exchange as to its preferred location. Let's eliminate that variable now and forever by simply moving it to pin 1. Before attaching it measure it to make sure it is still good. Assuming the 100ohm screen stability resistors are still good, and assuming the connecting wires daisy chaining all the pin 1's together are correct and secure, the Screen Stability modification is complete and correct.

    You replaced the cans. Let's make sure they are connected correctly by posting a tight shot of the bottoms of each can showing all the connections. If possible, make sure the designations of the respective tabs are clearly visible. I don't know if Hayseed marks the bottoms. If not, use an editing tool or otherwise clearly indicate which tab is what and what can is what.

    Assuming your meter is not malfunctioning, you should now check the voltages at the can tabs, meter at vdc, variac at 117vac, your negative black probe solidly clipped to a good chassis ground.

    List the voltages at each can. Preferably like below. It makes it easier to read and follow:

    C-87
    A
    B
    C
    D

    C-91
    A
    B
    C
    D

    Now, assuming all the connections and components associated with the power tubes are in good working order, list your the readings at each pin again. The voltages from the cans as well as the pin voltages will give us a better picture of what's going on. Mind you, you're going to have to sort through your prior work to pick up where that stray AC is coming from. I'm going to assume it was recently introduced. Otherwise, it was always there and you simply didn't realize it. Be careful.
     
  6. larryderouin

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

    Messages:
    18,509
    Location:
    Glen Burnie Md.
    Hayseed marks the bottoms as per guidelines for capacitor identification. I'm thinking he didn't or hasn't changed the .1uf cap to ground off the line cord with a safety cap. C110 and R147. replace both. 1/4w for the resistor is ok.
     
  7. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    OK, Thanks Fisher, Dave, Larry.
    I did replace the C110 and R147 from MetalBone kit. checked the solder joints all ok unless the cap is bad.
    Here is my plan, based off your recommendations and some findings of my own.
    1. I moved the 1 watt 1.2k resistor to pin 1 on v13.- fixed the weird voltage problems on V13- I have 4 pictures and all have it on 8. Only the picture NotDigital posted and logic, says it should be on pin 1. It is OK now.
    I had to add a piece of wire off another resistor to make it long enough, but I will change these all out with Metal film resistors after-just using metal bone stuff to get it working correctly now. ( Ignore the sloppy work currently. moving, checking, trying to get it right.) All wires and resistors will be lined up nicely when i finalize this.

    1. Trying to find the -15.8 V AC on my chassis. Looking through all my changes from metalbone kit and 3 can Caps.
    2. Pictures attached of the 3 can caps.
    Can cap voltages:

    C87- capacitor closest to the back of the receiver. 40, 40, 40, 20
    Symbols of connector in front of voltage, as I have no idea which is A. B. C...

    a. ^ 322V
    b. [ 380V
    c. U 414V
    d. 220V

    C91- capacitor with the 200 50, 50, 50

    a. ^ 212V
    b. [ 212V
    c. U 224V
    d. 201V

    Tube Voltages again:
    V10-V14 left to right

    Pin 1 - 418V all tubes
    Pin 2 - 332V 333V 332V 331V
    Pin 3 - 454V 453V 454V 453V
    Pin 4 - 417V all tubes
    Pin 5 - .170V .081V .167V .095V
    Pin 6 - -25V all tubes---- this is way low- I should be at -17V correct?
    Pin 7 - 3.23V 3.22V 3.21V 3.21V
    Pin 8 - 417V across all tubes

    Not done yet below:

    1. I'm going to replace the 10 Ohm resistors from Pin 5 to ground- short legs
    2. Install 5 k Potentiaometer to replace R119 to get the voltage up to -17V. I have the 2.7K now.

    .1uf cap to ground off the line cord with a safety cap. C110 and R147. replace both. 1/4w for the resistor is ok.[/QUOTE]

    I may replace these again just to make sure the cap isn't causing the problem. This AC voltage on chassis seems to vary, but it may just be my connection to ground. ( which is the probe on my DVM onto the cement garage floor )
    IMG_2208.JPG IMG_2211.JPG IMG_2214.JPG
     
  8. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    I just went and checked if the 17-38 VAC on the Chassis was present when the power was off. It is still there.
    You tell me, but either that C110 is leaking or I have a wire that is partially exposed on that input?
    I think I have another capacitor. does it have to be exactly the same .01 uF?
    Can I just lift the capacitor from the chassis ground to test?

    Thanks,
    Ken
     
  9. larryderouin

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

    Messages:
    18,509
    Location:
    Glen Burnie Md.
    Lift it out 1st. If the voltage goes off then you found the culprit.

    When you change out the 10ohm resistors, don't forget the 220ohm heater circuit resistors from the filament connection on 2 of the tubes need new grounds now. Run them direct to the chassis grounds now instead of Pin 5. I mentioned them in an earlier post (too tired to find it right now.)
     
  10. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,146
    Location:
    NYNY
    I've attached a copy of my notes when I restored my 1st 800-C. It gives you the correct can cap terminal designations, i.e. symbols and letters.


    I earlier posted a link to a thread discussing the magic voltage "-17." That's the voltage indicated in a perfect laboratory world. Re-read the discussion and you'll see that what you're really after is the correct voltage @ pin 5 of the output tubes. That is not to say that other voltages aren't important --- just that THAT measurement, if on target, will likely mean everything else is within range of what you want/need.

    Splicing in a 10k pot to adjust the bias voltage will give you more swing at pin 6. A 5k pot may do it; I just don't know. Manipulating that pot is a perfect exercise in adjusting the pin 5 voltage.

    For now, make sure your cans are correctly connected and correct the AC issue.
     

    Attached Files:

  11. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    8,317
    Location:
    Ball Ground, GA
    If not already stated, the reason that you are measuring 2.5 vdc across the one 100Ω Screen Stability resistor is because the 1.2K 1 watt resistor is still connected to pin #8 of the output tube socket it connects to. It should be moved to pin #1 which will correct that problem.

    Again, if your output tube quiescent current levels are truly as low as you indicate, then that will cause serious distortion. Make sure that your indications at pin 5 are real, and then act accordingly.

    Dave
     
  12. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    This maybe somewhere in the forums, but I think this is critical to know. AC on Chassis problem.
    I'd like others to test this and see if they have the same situation. ( Measuring from chassis to earth ground.)
    What I found is making sure Hot side of plug is on the switch side and neutral on the grounded or plug side( connection to J18, J19 external AC plugs.- Nuetral)
    The cord on mine is smooth side Neutral and ridge side ( single mold line) hot. ( original brown wire plug )
    If I measure AC chassis to ground with these reversed as I was doing, with my plug orientation marked, I always had 17-35+VAC on the chassis even when switch was off. Reverse the plug and there might be a stray 1 volt. (probably ground reference. ( Garage floor )
    Problem solved and helped distortion problem- Which it started when I marked my plug- Coincidence of when I made other changes.
    Please let me know if this is the case on other 800C's.

    Now to get the voltage at pin 6 to -17V with Potentiometer in r119 position. That will probably fix my distortion as I'm at -25V.

    Looking at all the others pieces first. Need to go to work now.

    Thanks everyone for all the input and references that I will need to validate. ( Larry, NotDigital, Dave..)
     
  13. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    OK, I have to stop for a while or give!
    I put the 5K pot in place of R119 ( 2.7K ) no change in voltage on Pin 6 and V13, V14 start thermal runaway.
    I turn off and return to the 2.7K and same thing. ( As I measure on v13, v14, Pin 6 just keeps increasing voltage... -20, -15, -10, -5, -2...)
    V10 and V11 not so. -24.4V at the 116V on the variac.
    I did change the Pin 5 -10 ohm resistors out but this started before I did this. ( all are at 10.1 ohms metal film resistors )

    Can I take the V13, V14 tubes out to see if I can back track this? Run with just V10, V11?
    Also I think this started when I switched to Aux-tape no volume. I did hit speakers again and they are playing.

    A 5K volume Pot should be ok in r119 correct? or not? It sets OK. I set it to 2.8K to start.
    Going to look at the can Caps again.

    I think I heard of another Fisher in the area and am going to check it out tomorrow. Also a Sansui 1000A, but they seem to have more heat problems and I have enough problems now.

    Next steps
    See any problems here?
    IMG_2218.JPG IMG_2220.JPG IMG_2221.JPG
     
  14. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    Just to verify my C87 Can Cap.

    2.7k ohm 1 watt resistor across [ to ^
    orange wire to resistors far side of receiver
    22k from ^ to no marking on cap
    No Marking on cap purple wire to V19 via resistor
    No Marking on cap 12K ohm to ground tab on cap can.
    U orange wire to pin1 V10
    [ blue wire to v10, v11 bias pot
    [ cap to diode conection
    Picture to help my description.
     

    Attached Files:

  15. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,146
    Location:
    NYNY
    I'm afraid I'm at a loss as to what happened and where you are.

    In post # 72 your reported that you corrected the stray AC issue by reversing the plug. Assuming that the problem is corrected, you then attempted to address the bias issue by inserting a 5k pot. Assuming no other changes, you then report that you have "thermal runaway" at V-13 & V-14. Everything else remaining the same, I don't see how that could happen, particularly since you set the pot at essentially the same resistance as the resistor you just removed. What is more perplexing is that when you re-insert the 2.7k resistor, you report that your pin 6 reading is now fluctuating unlike before when, with the same components, you had a steady pin 6 reading of -24vdc. Frankly, my suggestion is that you take a short break and do nothing but re-examine everything you have done making sure all your connections are where they should be. Many of us have been where you are, me included for sure! Sometimes a short break will give your thinking a re-charge allowing you to see what was not obvious at first.

    I've attached a picture of a correctly wired C-87. From the picture you can see the semi-circle on the bottom tab and the square on the left tab. That should allow you to orient your can to check the proper connections. If you are confident that the connections are correct, I would re-solder the can to the chassis as it appears you have not done so. Simply twisting the tabs to anchor the can is OK, I guess, but soldering the tab as was originally done is the better practice.

    Hang in there!!! C-87 Bottom.JPG
     
  16. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    Thanks Fisher! I did as you have stated above! So I am taking a break and hoping to score another Fisher Receiver this AM.
    If it's an 800C I'll be in luck. I can then back track.
    Can I run with out the V13, V14 7591 tubes removed, or should I see what is causing that voltage on those to initially go negative ( -18 when it first starts then starts rising about 1 volt per 3 seconds- on Pin 6 so in a short time Pin 6 on V13, V14 is near 0 volts and rising.

    Thanks for the help. An pictures of the wires on Can Cap 87 would be appreciated. That is the only one that I didn't get clear shots of it appears. I want to make sure I have that I didn't get the orange wires reverse or the purple and blue.

    Taking a break and going back through everything and ordering some metal Film resistors, since it appears nobody has them around here anymore locally.
    Thanks Again,
    Ken
     
  17. larryderouin

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

    Messages:
    18,509
    Location:
    Glen Burnie Md.
    Cap designations for Hayseed caps are top to bottom. A,B,C,D Note the Square, triangle, 1/2 circle and no marker. These are correct. FISHER marked the schematics wrong for the units that have the power supplies on the right side of the schematic and then moving LEFT. The CAP SECTION of the multiples CLOSEST to the Transformer is marked "D". It should be "A". In this way it will follow the cap.

    On the HAYSEED Caps the MARKERS onthe BOTTOM of the cap are NOT up against the terminals, but are partially hidden by the chassis now with the cap installed.

    Take off the RED CAP TO 87D. It doesn't belong there. Ground the end of the cap you removed from 87D. Otherwise it's wired correctly.

    STOP! WALK AWAY FROM IT for a few days! You've gotten the "Jumping Bean Syndrome" which is highly prevalent in new audio hobbiest in Southern California, and is working it's way up the coast quickly. IT's like OCD and ADD mixed together, as you concentrate on the current piece of gear but jump all over the chassis chasing problems you caused by not finishing that area(for example you're working on the Phono section, and your ADD flips you to the bias circuit. Then you go chasing stuff back in the phono section when it doesn't work and you have a hell of a time figuring out where you left off.) We've all had it in one form or another but have overcome it for the most part. It's incidient and pops up at the most inoportune times (kind of like a part of the anatomy when we were young.)

    Concentrate on the task at hand, and if there is the slightest inclination for asking a question, STOP, GET ON THE Computer and ASK! DO NOT Work on it until you have an answer that you understand 100%!!! ASK QUESTIONS, ASK QUESTIONS, ASK QUESTIONS! And wait for the answers. Sitting on your hands may sound like a 3rd grade thing to do, it actually teaches you patience. Wait for the answers, while sitting on your hands. Just like your Father and too many Adults probably told you bwhen you were growing up, the only dumb question is the one you DON'T ASK! IT's True! Just look at all the guys sitting in the Unemployment lines because they thought they were too good to ask a stupid sounding question. It may seem like the rehab on the 800c is going slower than molasses in Alaska in the Winter, you'll find that the time goes by faster with you NOT getting ahead of yourself and having to redo the mistakes you made, after not asking the questions that were piling up inside your head. Also if you are not sure of something ASK!!!!! BTDT, got more than a few T-Shirts (although they are faded and thin, with a few holes).

    This to be done AFTER EVERYTHING ELSE HAS BEEN FIXED!!!!!
    The BIAS CIRCUIT pot is a 10K trimmer, not a volume pot. Different types and tracking. One is linear and the other isn't linear. Big difference. IF you want to go with a single adjustment, get a 10K Bournes trimmer (I'll give you the link to the part to make sure it's the right one for you)http://www.mouser.com/ProductDetail/Bourns/3386P-1-103LF/?qs=sGAEpiMZZMvygUB3GLcD7rufck0TIBKy52IOA1%2bUkM8=.

    You tie together the middle pin with either of the outer pins. Then connect it to the wires from the bias circuit. Pull ONE (1) TUBE. Put your Meter on OHMS and put one probe on the bias wire on the bias caps side of the pot. Then put the other probe to the bias wire at the tube connection and adjust the POT for the HIGHEST OHM (Resistance reading). Take off the meter and reinstall the tube.

    TURN THE SETTINGS Knob on the DMM to DCV. Put the BLACK PROBE ON A CLEAN SHINY CHASSIS POINT (alligator clip it to the chassis) and your Red probe on PIN 5 of Each OUTPUT TUBE (Mini Grabber here). Turn on the unit and let it warm up 15 minutes while watching the reading on pin 5 Write down the Readings once they stabilize. They will be really low. Average the readings and pick the tube that is closest to the average. Put your red probe back on that tube and adjust the bias to 310mv. Then re-measure the remaining tubes and write down the results in mv. TURN OFF UNIT, and post measurements.

    NOTE: The - voltage on the schematic for -17 was FISHER's ideal for a quad of perfectly matched 7591's. Obviously back then when you went to the drug store and bought 4 output tubes you didn't get a matched quad (plus there was no explanation for either the -17v or matching tubes, so noone knew better. Actually -17v, along with all the other stuff FISHER did to these units, in the all consuming race to better everyone else in Watts, was too much close to ZERO (0) volts in that th tubes were actually being overdriven past their maximum ratings. So a way had to be developed to measure the tubes and get consistent readings. The cathode load voltage readings are easy to read and convert to milliamps (move the decimal 1 place, using a 10ohm resistor). You can then calculate the percentage of max dissipation of the tube with basic 2nd grade math (back in my day it was 3rd or 4th grade math depending on whether you went to Catholic Schools or public schools). The 7591 tube has a maximum dissipation of 19W. You want to ideally set them to between 70% to 80% of maximum dissipation. We'll get into the math in a future post. This will cool down the tubes somewhat, put them into an ideal operating state, and even tho the total wattage of the unit is less by a few watts, the distortion levels are a bit better also.

    The single adjuster is really used for a tightly matched quad as is the stock configuration. For long term adjustments with either slightly mismatched or wildly mismatched tubes you can build a IBAM or IBBM (Individual Bias Adjustment or Individual BIAS/Balance Modules.) The difference is one adjusts just the bias of the tubes to a set point that is the same. The other Balances a pair to 0.0v between them then biases the pair to the set point. They both get the job done but the IBBM board does it better. They are both interactive between tubes so you are constantly adjusting one then the other 3 (or 1) so they all match. But once you get them matched it's all good.

    If your tubes are the original I highly suggest building either board. They will overcome most inconsistent bias readings in the tubes. If you get a set of new EH's or Tung-Sols, I would still suggest either board to get and keep them tightly balanced.

    Larry
     
    Last edited: Apr 21, 2017
  18. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    OK so you pegged me to the tee!!
    I'm stopping and taking a day off.
    Oh, forgot to tell you I did buy the Sansui 1000A. Am I crazy? Or hooked?. It has a blown fuse and a leaking cap that I can see. Very clean! been in the attic for 30 years.How much is a good price? Tubes look very good visually. All original
    Missed the AR3's by a few minutes. ( $300 ) For the pair!!!
    I'll get back on tomorrow as it was a long day, just got home. Besides the stop for the Sansui. the other stop was a very old fisher console. ( not my style and too much $350.
    Thanks for all the advice. I'm probably ADD OCD...
    I'll post pictures of the SanSushi- I like the layout of the internals. I has the 2 level control adjustments. ( Bias )
    Ken
     
  19. larryderouin

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

    Messages:
    18,509
    Location:
    Glen Burnie Md.
    Oh BOY! You are a glutton for punishment. And I'm talking from EXPERIENCE here. DO NOT POWER UP THE SANSUI until EVERY, and I DO MEAN EVERY Electrolytic Capacitor and Each and Every SUZUKI or ELNA Film or Paper in OIL(PIO) cap has been replaced. That includes the CAN CAPS! No POWER UP, NOT EVEN ON A VARIAC with a 100W Dim Bulb Tester until you've done this. This is more for your safety than any piece of gear. The Sansui's B+ voltages are 480V or more compared to 430 or so with the 500c/800c. And the Sansui's schematic is infinately harder to read than FISHER's. You've been advised.

    My Sansui 1000A (Single bias pot) I got as my 1st tube receiver back in 2009. It had been in the box the better part of 20 years. All of the 7591's were so weak they barely made a move on the needle on 3 tube testers. The 6AN8's were totally dead, and the 6aq8's were beyond weak! I made the mistake of powering it up (I had been on AK about a week.)on wall voltage. Each and every one of the PIO's lit off like a Chinese new years Dragon! The Voltage doubler caps almost exploded, but just puked all over. I was damned lucky the transformers lived thru it all, as I hadn't checked the fuse (it was a 20A, and bypassed with an aluminium prophylactic! Plan on replacing about $225.00 worth of caps and that includes all 4 of the CAN CAPS from Hayseed Hamfest as NO ONE has exact replacements. You can stuff 2 of them and uprate them at the same time (voltage doubler pair). The other two Hayseed Hamfest.

    There are 2 BIG Ceramic Resistors between the 7591's and the Power Transformer. Make sure each section is reading it's value(there is a single resistor and a dual resistor) and the housing is not cracked. If it's cracked or melted, then you have to replace these. I put up a thread on how to do it, along with the resistors an where I put them (not where they are originally.). We'll get into that later when you start a thread on it in the Sansui Forum.

    Figure on adding some reliability parts. Screen stability resistors (the Sansui needs them more than the FISHER), cathode resistors, etc. No selenium rectifier. Changing the 2 bias pots to 4 bias pots (relatively easy).

    I got mine for $50.00. Including tubes (7591's Tung-Sol's, 6an8's, 6aq8's, 12ax7's, 6ba6,6be6,6au6, 6bl8 12at7) I've put about $450.00 into it in the last 8 years. And it's become my most reliable, and damn near the equal of my 800c's sound quality wise. It runs VERY HOT, so either put small fans pulling out or take off the top and make sure nothing is above it or it will bake. When you have your thread going I'll disclose some tube sub's that work quite nicely in the Sansui and some that don't.

    This one you will HAVE to follow instructions to the "T" and NOT GET AHEAD of yourself or us. Consequences can and will become dangerous if you don't with the Sansui. When it's done right it's a sweet receiver, but if not can be a 8 headed hydra, and you'll get hurt or worse.

    Larry

    Larry
     
  20. Skibrain

    Skibrain Member

    Messages:
    65
    Location:
    Rocklin CA
    Thanks for the advice.
    Of course the estate sale plugged it in. Luckily the 3A 250V 313 slow blow fuse was popped.
    The Sansui will sit a while why I work with all of you on this 800C. I think I'll take today off and Ponder the world of Tubes.
    Also one change the 800C per above recommendation.
    Is this pot OK for replacing the 2.7K resistor to change the pin 6 voltage? 10K, 18 turn .75 watt. Picture below.
    I'm not turning anything on, still sitting on my OCD ADD hands. I might try pulling 1 tube and taking a resistance measurement as per your above suggestions.
    I'll read through your guidance above a few times before I do anything. Then check with everyone prior.
    I really appreciate all the patience with my messing things up. Going back to the schematics to see if I can validate all the Can Cap connections.
    Here are few pictures of the Sansui 1000A also.
     

    Attached Files:

    Last edited: Apr 22, 2017

Share This Page