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Thread: Solarus --no output

  1. #1
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    Solarus --no output

    ive got a 69 Solarus here . Just installed all the correct tubes , this one is the el34 / 7199 version .
    I have no output ...when probing the el34s , pins 3 and 4...i can barely hear a little noise..with Volume on 10....where normally you can hear a fairly loud pop or noise . Ive double checked the wiring of the 7199 .

    swapped out the 1st 2 pre tubes

    All voltages are perfect everywhere including bias. Ive probed the entire amp with a plastic chopstick , moved every wire , cant see anything burnt or damaged .

    Starting to think it might be the OT ?? Is there anything else to look for on these old Sunns ??

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    Supporting Member The Dude's Avatar
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    Got a schematic?

    Edit: Is it this one?

    http://www.prowessamplifiers.com/sch...arus_EL34.html

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    yes---sorry forgot the scem

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    Check the speaker AND wiring for function.

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    Do you have a scope? If so use that, if not use a DVM set for AC volts and trace signal through the amp.

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    no scope

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    ok---so i ran a test tone into the input about 2k . Checking with AC meter i start at 13vac at the 1st 12ax7 and it ramps up each stage , and i get up to 55 - 60 vac at the outputs of the 7199 , that head to the el34s . Sound about right ?

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    13V input is really hefty, so I suppose 55-60V at the PI out is reasonable. At any rate, you have signal there and no output, so the problem is in the output section. You said, "All voltages are perfect everywhere including bias", so I presume plate and screen voltages are there? Check signal right at the output tube grids just to make sure it's getting there. If so, I'd do some quick resistance checks on the OT.

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    yes---every reading is great--according to that scem . ill check the el34 grids ---thanks

    i think i saw 13v out of the 1st 12ax7

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    Have about 50vac to the el34 grids

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    That's really hot. You might want to back down your generator. You should see about 1/10th that at the V1 plate.

    Edit: Sorry, I was typing during your last post. This is in response to post #9.

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    I'd unhook the yellow and orange taps from the OT secondary and hook a speaker directly to one of them to eliminate a possible jack or jack wiring issue.

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    Quote Originally Posted by The Dude View Post
    I'd unhook the yellow and orange taps from the OT secondary and hook a speaker directly to one of them to eliminate a possible jack or jack wiring issue.
    tried that---nothing

    the 1k/ 2w and 680 ohm/2w are good ---right by the OT in the scem

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    Sadly, this is looking like a bad OT. Check primary and secondary resistances and see if you can spot an obvious failure- i.e. open winding, etc. If it is the OT, it's not going to be cheap since this is an ultra-linear amp. It would probably be cheaper to reconfigure/modify the circuit and use something more standard.

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    Quote Originally Posted by The Dude View Post
    Sadly, this is looking like a bad OT. Check primary and secondary resistances and see if you can spot an obvious failure- i.e. open winding, etc. If it is the OT, it's not going to be cheap since this is an ultra-linear amp. It would probably be cheaper to reconfigure/modify the circuit and use something more standard.
    thanks-- i dont know if i want to go that route . I think the Dynaco replacements are $140 ?

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    $140 is a lot less than I would have guessed.

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    That's not bad. To be honest, it's been a long time since I looked for a replacement OT for a UL amp.

    I'd still make some resistance measurements on your OT. You hate to spend that much money and the problem is elsewhere. I always do every check possible before I shoot an output transformer.

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    Well, once you decide it ha to come out, pull it, and take the end bells off and try to check the connections between winding wire and the insulated lead wires. Might have a failed connection or a broken wire.

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    ^^^^^^ That! Another good reason to do the resistance checks. It might lead you to a simple transformer repair instead of replacement.

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    I just took resistance readings on a Dynaco 40W amp that sits near my computer as a chrome monument. Plate to plate, 185 Ohms. One side to center tap, plate 102.4 Ohms, screen 34.2 Ohms. Other side, plate 88.3 Ohms screen 29.6. One side went crazy with my meter, had to clip a short across the secondary.

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    Quote Originally Posted by loudthud View Post
    I just took resistance readings on a Dynaco 40W amp that sits near my computer as a chrome monument. Plate to plate, 185 Ohms. One side to center tap, plate 102.4 Ohms, screen 34.2 Ohms. Other side, plate 88.3 Ohms screen 29.6. One side went crazy with my meter, had to clip a short across the secondary.
    These readings are very close to what i just measured on mine !

    also 1 side plate to other side plate = 300 ohms
    1 side screen to other side screen = 102 ohms

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    What about the secondary?

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    Quote Originally Posted by The Dude View Post
    What about the secondary?
    If you really gotta know,

    4 wire measurements to the black common wire (no averaging):

    4 Ohm tap, 0.36390
    8 Ohm tap, 0.48331
    16 Ohm tap, 0.71211 (1047 Ohm feedback network in parallel)

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    Quote Originally Posted by The Dude View Post
    What about the secondary?

    OR1 TO BLK 1 OHM

    OR2 (not used ) TO BLK 0.8 OHM

    YELL TO BLK 1.2 OHM

    PRIMARIES TO SECONDARIES `---OPEN

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    Quote Originally Posted by loudthud View Post
    I just took resistance readings on a Dynaco 40W amp that sits near my computer as a chrome monument. Plate to plate, 185 Ohms. One side to center tap, plate 102.4 Ohms, screen 34.2 Ohms. Other side, plate 88.3 Ohms screen 29.6. One side went crazy with my meter, had to clip a short across the secondary.
    is that trans dead then ??

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    is that trans dead then ??
    Not clear yet.The DCR readings are not suspicious, but a shorted turn won't show in DCR readings. I recommend the neon bulb test.

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    Ok---i found it.....................the freakin power tube sockets must be really dirty or corroded , (i cleaned them) or need tensioned . I pulled the el34s out and stuck in a diff pair just to try that--amp fired right up ! The original pair now works too.


    Now onto the rest of the Bolloks.........pretty bad low freq hum going on..its there with Master at 0, and whats weird is it kind of goes away when turrning the Master vol from 3 -6 , then it returns at 7-10 real bad ! All the high voltage electrolytics / filter caps are new


    The trem circuit works ! The reverb = i can hear it trying if i bang on the tank...but no verb out of the speaker. The cables seem to be ok..

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