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JohnW

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Posts posted by JohnW

  1. 2 minutes ago, babadono said:

    Roger...you tightened it to the chassis. But how is attached to the board itself? If soldered it can crack, if just a mechanical connection it can oxidize. Details...details..that's where the devil hides....

    It's screwed into the board and into the chassis. I loosened and re-tightened. 

    But perhaps the whole issue was shitty resistors? 

  2. 11 minutes ago, captainbeefheart said:

    Looks like the boards have a ground trace where I circled in red where the boards mount to the chassis. Possibly check them as well and make sure they are good.

     

     

    grounds.png

    That's what I loosened and tightened. 

    Thanks again for all your patience and help. 

    (not that we're done here, of course :) )

  3. 21 minutes ago, captainbeefheart said:

    Intermittent issues are enough to drive anyone crazy sometimes. Let's hope the problem is gone for good now but from experience it most likely will come back.

    Undoubtedly. But this little victory makes further battles worthwhile. Thing sounds truly amazing. I think I'll keep it, and do what I can to keep it alive, for now. 

    • Like 1
  4. 3 minutes ago, captainbeefheart said:

     

    R9 only passes current for rectifier boards A and B. Board C shouldn't be of concern right now until you get the amp up and running.

     

    If I was tasked at repairing this unit I would remove rectifier boards A and B and put them on the bench. I would use my variac to input the desired AC voltage to LP55 and LP56 on board A. Note you have to connect board A to board B with a wire between L54 and LP 63. I would then put a resistive load at the output of both boards A and B, maybe 20mA or so should be fine. Then I would power it up while monitoring AC current draw and quickly take voltage readings around Q1 and Q2. This should tell me which board is messed up and possibly which part.

     

    If I didn't have the means to do that I would probably remove boards A and B and yes remove transistors, diodes, and capacitors and test them out of circuit.

    I was afraid you'd say that. :D

    New caps are on the way. I should likely just buy new transistors and diodes as well, since I can test resistors in the board. 

    I almost want to pay someone locally to dig into this, because I'm in way over my head. 
    But I'm stubborn af

     

    • Like 1
  5. On 2/14/2022 at 1:29 PM, captainbeefheart said:

     

    The filter cap (C4) is on the rectifier board and is connected via a trace. It's painfully clear that we still have a major problem so the rectifier board should be removed and fully tested. We just need to find if the fault is on the rectifier board or after it on the load side where LP53 connects.

     

     

     

    On 2/14/2022 at 1:04 PM, babadono said:

    The ones going to the loads not the inputs. So if I am decoding the manual properly/sufficiently I would say the red,orange and possibly the white/orange. Double check me please @captainbeefheart. It is possible that the filter caps are dried out old electrolytics and are not performing as they should. Also there is a member here who fixes Klipsch subwoofer amp boards and he swears that glue sometimes becomes conductive.

    Ok, so you're suggesting I remove the Red, Orange, and White/Orange wires from Rectifier A and then try powering it up again with the R9 resistor in place? 

    Any idea how the board is grounded? 

    Should I learn how to build a Dim Bulb Tester before I do this?

  6. Should I just go through every board and check continuity from every solder point to every solder point? 

    On 2/14/2022 at 7:35 PM, captainbeefheart said:

     

    200k should be good.

     

    As for capacitors when you pull the old ones off measure the lead spacing on the board and also the casing diameter. Caps have gotten smaller and the 2200uF 35v that I linked below has a 7.5mm lead spacing. Case diameter is most likely not going to be an issue since caps have become smaller but using too small lead spacing makes the capacitor sit weird on the board so you should try and get a capacitor with the correct lead spacing. Digikey is nice because you can use the lead spacing as a search criteria along with voltage rating and capacitance and view the results.

     

    https://www.digikey.com/en/products/detail/rubycon/35ZLH2200MEFC16X25/3564493

     

    It looks like the lead spacing on the currently-installed 4700uF 35v filter capacitors is about an inch...can't seem to find a matching pair. Any guidance?

  7. 3 hours ago, billybob said:

    Yes, my mentioned about a relay switch also. It is the click that is typically heard seconds after turning on a unit.

    Guess you are looking to replace suspect cap(s) now. 

    A couple of Youtube on the 430s interesting. Following here...

     

     

    If you have links, that would be great...so far all I can find is sales demos and Rosie O'Kelly...which I haven't found particularly helpful. 

    • Like 1
  8. 47 minutes ago, billybob said:

    Yes, my mentioned about a relay switch also. It is the click that is typically heard seconds after turning on a unit.

    Guess you are looking to replace suspect cap(s) now. 

    A couple of Youtube on the 430s interesting. Following here...

     

     

    Unless I'm mistaken (and I very well could be, I am obviously a novice here), I don't believe it has a relay when you power it up...at least I don't hear one when it starts...is there one in the schematics? I believe I read that there isn't one as well. Because if that's the case...not having one might be the source of our initial overload issues. 

     

    • Like 1
  9. 22 minutes ago, babadono said:

    Yea but were these close to you? Only about a half hour from me. Probably some flipper, expect to see 'em for sale again for double.

    The odds are with you. 

    They were an hour from here. But I just went $2500 in debt for a pair of La Scalas.

    • Like 1
  10. 18 minutes ago, captainbeefheart said:

    You can pretty much rule out diodes and transistors because when they fail they are gone and it would behave like a hard short showing the voltage across R9 continually increasing and not just stop at 5.5v. That is 670mA and almost 7 watts dissipation for R9.

     

    I got my money on a capacitor that is showing high leakage current from the oxide layer not forming properly when powering up. If you are bored waiting for parts start by pulling C4 off the board and short across the leads for 10 seconds. After you do that measure it's resistance and see what happens, my guess it will be a very low resistance at first and then start to form but stop somewhere in the 20k-30k area of resistance. If that's the case you can then try and slowly reform it by current limiting it with a DC bench supply but I would say it's not worth it. BTW that's how you can check all the power supply capacitors when removed from their boards, short the leads for 10 seconds and then measure their resistance. A normal capacitor will read low for a second or so and then quickly jump to infinite resistance once the oxide layer forms on the anode. If you find a capacitor reads below say 1Meg resistance it will pull too much leakage current to use in circuit.

    Was just shopping for new capacitors from Parts Conexxion. It's not like they don't need to be replaced, right? 

    I'll pull the C4 and test it, but it'll probably be later this week. 

    Here's my Parts Connexion shopping cart: will these work? 

    https://www.partsconnexion.com/cgi-bin/sc/order.cgi?storeid=*20b7b4534d0a875b77f1157d6bb78322a865&function=show

  11. I don't think I mentioned some pertinent, important details:

    I bought this from some guy in Arizona for $200 who knew nothing about stereo gear. He sent it to me in an old Epson printer box with "EASTER" magic markered on the side, and the receiver was protected by laundry. 

    That's right, no bubble wrap, no wadded paper, not even a blanket. Just old, XXXL tshirts, shorts, and yes...underwear. Three pair. I am not joking. 

    I didn't check how well laundered they were, but there was a faint scent of detergent when I opened the box, and I'm going to tell myself that it came from the clothes being freshly laundered and that is the last thought I will give it, for obvious reasons.

    The box was taped shut with silver air conditioning insulation tape. 

    The fact that the unit actually works is a miracle. 

     

    • Haha 1
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