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Author Topic: walter woods electracoustic amp won't power up.  (Read 10618 times)

EDWARDEFFECT1

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walter woods electracoustic amp won't power up.
« on: October 25, 2010, 07:54:43 PM »
got a electracoustic amp that wont power up.from the power transformer the leads go to a 1k resistor that is enclosed in a gold anodized heat sink( which reads.999k).then it goes into a red square item (c&k u21 rectifier?)that has 2 grounded legs on the bottom and then there are 4 more  legs,but one leg is missing.where can i get this part and does anyone have a schematic so i can figure out where the 4th leg goes.the fuse is good.i haven't got into any voltage checks yet...thanks...ed

J M Fahey

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Re: walter woods electracoustic amp won't power up.
« Reply #1 on: October 26, 2010, 08:50:45 AM »
Try your favorite psychic, he might help. ;D
Seriously,"a square thingie with 6 legs" won't get you very far.
Post a couple pictures and hand draw at least a rough schematic of that area: power cord, switch, fuse, the strange resistor, transformer, up to and including the filter caps.
We are talking 5/6 components here.
Draw what you see, if you don't know what a part is, draw a rectangle and whatever inscriptions it has. Wire colors too.
Good luck.
EDIT: that said, Walter Woods are known for their switching power supplies.
If it has one of them, they are very dangerous and difficult to repair, plus not being drawn with any detail, even if you happen to get a schematic, they just draw a rectangle labelled "switching supply" and that's it.
Remember to post pictures.
« Last Edit: October 26, 2010, 08:55:01 AM by J M Fahey »

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #2 on: October 27, 2010, 02:20:42 AM »
i figured it out its a switch with one of the legs either cut off or burnt off. it goes thru the heat sink and between the fins there is a mini toggle switch. i tryed putting it in the opposite dirrection figuring that might be the problem, but still got the same results.no powering up.got 50v on the b+ and -50 on the b-; also got 12v on the v+ and -12v on the b-. getting 4.7 volts on pin 8 of one of the ic'si will posts pictures in the morning.alot of components have their values sanded off the part,so when you work on this one if you have no schematic and no part identification things could be tough.tryed e-bay and the web for pictures of the switch legs and couldn't find anything.it's a nice setup to work on. it has a cover on the top and bottom of the unit. all amps should be built like this. easy access to the components on both sides of the board.seems like a well made amp...thanks...ed

J M Fahey

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Re: walter woods electracoustic amp won't power up.
« Reply #3 on: October 27, 2010, 10:01:27 AM »
Quote
no powering up.got 50v on the b+ and -50 on the b-; also got 12v on the v+ and -12v on the b-.
You call it "no powering" yet have all the voltages !!!  :o :o
Why did you move that toggle switch? Do you think it had moved by itself?
What if it was a 110/220V selector?
All WW amps I know use switching PSUs, so it might very well be that.(As in PC power supplies)
Are you using a series lamp limiter?
Pictures, please.

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #4 on: October 28, 2010, 06:12:12 PM »
i have a series limiter with a 100 watt light bulb in it.i have all the voltages,but no indicator light and no output.no blown fuse, so i didn't hook it up th the current limiter...the switch is not labeled.this amp reminds me of the klon centaur pedal , where the designer is trying to be sectrative with his circuits by hiding them in epoxy or sanding off the part identification.i have pictures,but  they are to large to send. i have tried previouly a few times and can't get them to this site. any help with uploading would be  great.going to be a tough one to fix.without part identifiacation and no schematic.whatever solder they use on the board has a really high melting temperature.what kind of solder do they use?i have a desoldering vacuume tool and usually it removes the solder in seconds. not on this circuit board...ed
« Last Edit: October 28, 2010, 06:31:55 PM by EDWARDEFFECT1 »

Enzo

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Re: walter woods electracoustic amp won't power up.
« Reply #5 on: October 28, 2010, 08:03:38 PM »
There are many photo sharing web sites, like Photobucket, and you can upload your large photos to one of those and then link to them.

Here is my cat in his halloween costume:
http://i152.photobucket.com/albums/s171/tmenzo/MattRussellandfriend.jpg

J M Fahey

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Re: walter woods electracoustic amp won't power up.
« Reply #6 on: October 29, 2010, 10:21:52 AM »
Hey !! Nice kittie !! He does not look very worried about World events.

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #7 on: October 29, 2010, 06:00:03 PM »
thanks enzo! lets see if it works..more..photos      http://s1093.photobucket.com/albums/i432/edwardeffect1/?action=view&current=Pic212.jpg   thanks....ed
« Last Edit: October 29, 2010, 09:57:30 PM by EDWARDEFFECT1 »

Enzo

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Re: walter woods electracoustic amp won't power up.
« Reply #8 on: October 29, 2010, 08:04:48 PM »
That link works if I cut and paste into my browser.   it would likely work directly as a link if you remove the "@:::" from before the http

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #9 on: October 29, 2010, 09:56:29 PM »
i took the @ out. when you go to the site you can view more pictures.i have pictures of both sides of the board.

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #10 on: October 29, 2010, 10:05:20 PM »
i have voltage going into the chip with a heat sink to the right of the top capacitor to the left of the transformer.i notice it has one of the legs going to the led light circuit trace.got no idea what it is supposed to do as there is no part number on it....here is a picture to go by.....ed    http://s1093.photobucket.com/albums/i432/edwardeffect1/?action=view&current=Pic209.jpg   hope the pictures are ok.if you need anything different let me know? thanks!!
« Last Edit: October 29, 2010, 10:44:13 PM by EDWARDEFFECT1 »

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #11 on: November 05, 2010, 07:30:58 PM »
i have no power to either leg of the top right capacitor in picture #13.it ties in with the 4 leg part with the heat sink to the right of the top right capacitor.i notice also one of the traces of the part is connected to the led which is not working.again no part numbers on the part.i believe its part of the power supply.switching regulator?not sure what is is or what to replace it with. it has 167 volts going to one of its legs.....help!!!! thanks...ed!!

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #12 on: November 05, 2010, 09:23:22 PM »
i'm answering my own question.could this be a rectifier bridge?it has 4 legs. if this is so. i should be able to use a 400v 4amp bridge rectifier as the capacitors are rated at 400 volts...any suggestions of ideas from the pros? thanks...ed!

bry melvin

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Re: walter woods electracoustic amp won't power up.
« Reply #13 on: November 05, 2010, 10:38:19 PM »
It looks like the bridge rectifier in your pic....Shoud have markings  usually~ ~ +- on one side of it. Not sure if 4 amps is enough for this amplifier What is the power consunption of this thing?   

BTW that wouldn't be an LED connected to that recifier at that V...probably is and looks like a neon pilot light.

EDWARDEFFECT1

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Re: walter woods electracoustic amp won't power up.
« Reply #14 on: November 06, 2010, 11:44:52 AM »
thanks for the input! once i get it out of the board;it's  fighting me,i'll see if there are any markings imbossed on the rectifier down near the chip legs. the rest of the chip has been sanded,so that people like you and me have to guess at what it is.seems like the secretive building could work both ways for the builder.someone might find out that they are going to have problems repairing it down the road, so they will buy a simular item that will be easy to maintain if broken.....thanks....ed!!