Should I power this thing up?(I HAVE NO VARIAC)

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  • jiroy
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by TechGeek
    Hello?
    Sorry Techgeek , i had some clients . Well , you treat a rectifier just like it is 4 diodes bridged together , the first one goes from ~ sign to the minus sign , the second goes from ~sign to the positive sign , the third goes from the plus sign to the negative sign and the fourth goes from the plus sign to the negative sign ...

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  • rhomanski
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Diodes are a single PN junction. They conduct in one direction only. On semiconductors the arrow always points at negative. Therefore put the negative lead on the band of the diode and it should conduct. It will still show resistance because it's a "semi" conductor. That's why a diode mode is nice. It shows the voltage drop. One way is infinite the other is around a half a volt. A rectifier is merely a diode bridge. It kinda makes a rough DC out of AC. So, figure out which leg is positive and negative and check it. Best done out of circuit. If you can find the paperwork on the rectifier it will show you how it's setup. I would suspect your unit is somewhere from 1976 to 1980 manufacture date. Before then they usually had four simple diodes for a rectifier after that they went to black plastic faces.

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  • ReeceyBurger123
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Check on youtube on how to test a bridge diode easier to do that writing and possibly causing confusion, basically a rectifier has 4 diodes in side of it, normally the pins are labelled on it where the diodes are.

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  • TechGeek
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Hello?

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  • TechGeek
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    how do I check rectifiers?(i'm only quite knowledgeable in computers)
    And check all diodes?
    Last edited by TechGeek; 08-01-2016, 06:20 AM. Reason: reason

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  • jiroy
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by TechGeek
    mine can go all the way up to 2000k. So plug it in and give it a go?
    Put it at 20 Kohms (assuming it is digital and not Analog ) , and do tests on diodes and rectifiers without turning on the Fisher unit ..

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  • TechGeek
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    mine can go all the way up to 2000k. So plug it in and give it a go?

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  • jiroy
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by TechGeek
    uhhh... I don't have a diode checker on my DMM, only resistance, VAC, VDC, and that's about it. Need a photo?
    It's okay , you can always test at 20 k-ohms .

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  • ReeceyBurger123
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Ahh right ok, its a little harder with resistance mode as it wont be able to find a voltage drop just resistance across the part/circuit. Maybe pick a cheap DMM up ? You can get them off ebay for £3 with probes with diode test. Still with resistance as its high as you said, chances of it being shorted is nothing.

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  • TechGeek
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    uhhh... I don't have a diode checker on my DMM, only resistance, VAC, VDC, and that's about it. Need a photo?

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  • ReeceyBurger123
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Use diode mode on your meter.

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  • jiroy
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by TechGeek
    How do I check transistors for shorts and/or rectifiers? The output diodes on the PSU are far from shorted, one reads almost 200K resistance.
    A regular diode would pass the voltage one way and block it the other way , put your DMM on Diode level , and test diodes in the PS . Rectifiers are primarily diodes , like one rectifier is composed from 4 diodes typically , so you measure rectifiers like a 4 diodes measuring ..
    Note that some diodes could give erroneous measures on board if it's relayed with some resistance . In such case , you have to remove one leg of the diode .

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  • TechGeek
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    How do I check transistors for shorts and/or rectifiers? The output diodes on the PSU are far from shorted, one reads almost 200K resistance.

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  • jiroy
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Since no silicons are shorted , fuses are okay , then why not ..Capacitors , if dried , will show different symptoms , but not much more than the fuse can handle .
    Those Fisher were something , Akai are better , and the twos were formidable if equipped with JBL's , the good old days .

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  • kaboom
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by TechGeek
    I have no variac, so no slow controlled powerup
    That's a big myth. A Variac doesn't limit current. How would it? It's nothing but a variable autoformer- a dead short on its output will pull excess current even with the knob way down.


    IOW, even with a Variac, you still use a "dim bulb." Try a 40W lamp in series with the line, and verify all power supply voltages begin to come up. Then a 60W, 75. The amp should be working at this point- check across emitter resistors for excessive voltage= means amp bias "ran away." Fix this before larger lamp or full line voltage.

    DC offset should be below 250mV at the point amp comes up on reduced voltage. Some had more offset at reduced voltage- long tailed pair isn't quite symmetrical at this point. If offset minimal, a larger lamp/higher voltage should make DC offset decrease.

    If there are offset and bias pots, clean them! A bad bias pot can take the output/driver transistors out, as well as other components. A set of four Motorola/Onsemi 2119x is about $20.

    Originally posted by dmill89
    It looks like when the RS-1056 was made ~1977, Fisher was owned by Sanyo, like you said it isn't "bad" but isn't anything particularly "special" either.
    True, but there were certainly worse. I won't even mention "Soundesign."
    Last edited by kaboom; 07-31-2016, 11:30 PM.

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  • budm
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    This Fisher is made by Sanyo when they bought out Fisher name, so basically a Sanyo with Fisher name on it.
    You can use 60 Watt lamp for now, or use two 60W in PARALLEL to give 120 W.

    Last edited by budm; 07-31-2016, 11:09 PM.

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  • dmill89
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by rhomanski
    Sorry to tell you this. Fisher was sold by the original owner. Anything that says "Studio Standard" was made after the sale and is not considered to be valuable at all. I have a system I bought in 1984. It just isn't as good as one of the big three, Pioneer, Sansui, or Marantz. It's worth saving. It just won't ever be as valuable as one of the other three. People are discovering what real music can sound like and ditching their digital equipment. That's why you see prices rising on all the old stuff. In the 80's and 90's you couldn't give it away. Now, it's in high demand.
    It looks like when the RS-1056 was made ~1977, Fisher was owned by Sanyo, like you said it isn't "bad" but isn't anything particularly "special" either.

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  • rhomanski
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Sorry to tell you this. Fisher was sold by the original owner. Anything that says "Studio Standard" was made after the sale and is not considered to be valuable at all. I have a system I bought in 1984. It just isn't as good as one of the big three, Pioneer, Sansui, or Marantz. It's worth saving. It just won't ever be as valuable as one of the other three. People are discovering what real music can sound like and ditching their digital equipment. That's why you see prices rising on all the old stuff. In the 80's and 90's you couldn't give it away. Now, it's in high demand.

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  • dmill89
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by TechGeek
    I did a quick Google search and found nothing but mainly eBay ads. Looking on eBay for it turns up about nothing, so maybe either everyone's keeping theirs or these sets are becoming all but common.
    I didn't find any active listings for that particular model (though I did see some similar ones), but a search of completed listings (these go back 90 days) found 3 one for $51, one for $135 and one for $175, the two more expensive ones were tested and cleaned (though it doesn't appear any internal work was done on these, one that has been recapped/re-lamped may be worth more, but maybe not hard to say) and from established sellers (while the $51 one was from a 0 feed back seller with a limited description).

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  • dmill89
    replied
    Re: Should I power this thing up?(I HAVE NO VARIAC)

    Originally posted by goontron
    The Marantz 2325 is going for $1,175.00, i don't get why. These fuckers are deaf! They can't pick up a 1 watt FM transmitter next to the bloody antenna! Yet a yamaha CR640 has no problem picking it up from across the room! Marantz garbage!
    While I generally don't have any complaints with Marantz (but also realize other makes have receivers that are as good or better), the prices have gotten absolutely ridiculous. I have a model 2015 receiver I bought about 10 years ago for around $35 in excellent condition (only needed one bulb replaced), today those are going for around $100-250 for a little 15 WPC receiver with 4 inputs (2 tape, phono, Aux). When I bought the 2015, 2270/2275s were going for $200-300 fully working and in excellent cosmetic condition and $400-500 fully refurbished with new caps and lamps and calibrated, which I thought was pretty reasonable (not "cheap", but ok for a receiver with those capabilities and build quality), today you are looking at double that or more (and a lot more if you want a wood case), there are just too many good alternatives out there for far more reasonable prices to justify that.
    Last edited by dmill89; 07-31-2016, 09:47 PM.

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