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Author Topic: st head not doing watt it use to  (Read 4689 times)

gpkull

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st head not doing watt it use to
« on: August 22, 2007, 03:31:56 AM »
pops 12/1 w 10k. 1000rpm w/ m.m. supermax pulley. the set up was flawless for a 100 hrs or so. im not shur watts happin. the riod run super wiith or wirhout a load. freq allways hung pritty close meaning we had a gov to do its job. thats a scarry thought. today there was an odd scene.  the gov went hunting (rpms up and down). this had never happened before and it looked like the riod was takin a beatin. bellows of smoke pickin up slackin on theway down. the jamb nut had come loose between the set me and the jam me nuts on the gov linkage to the rack.  the rpms were going up and down. got that figured out got a steady 60.5 hz but now the volts are 104 per leg. this has always been wired 230 and havent modified anything. the reostat on the avr seems to have lost its control. any body got a clue ?

ronmar

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Re: st head not doing watt it use to
« Reply #1 on: August 22, 2007, 03:50:23 AM »
Maybe the surging shook something loose inside the genhead.  Did you go thru and solder all the crimp on terminals on the wire ends?  The crimp on terminals were terrible quality and poorly done on my ST.  I soldered every one of them to keep them from vibrating loose from the wire.  What type AVR do you have on yours, or does it just have a voltage control variable resistor on the field circuit? most ST's don't have an AVR.  Since it is putting out some voltage, that most likley means that the winding circuits are in tact.  Check all the electrical connections around the AVR circuitry.

If I had this type situation on my harmonically excited ST head, I would suspect that one of the 4 rectifyer diodes had failed or come loose and I had lost some of my excitation current which would cause the lower voltage.

Ron 
PS 6/1 - ST-5.

gpkull

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Re: st head not doing watt it use to
« Reply #2 on: August 23, 2007, 12:24:38 AM »
tks the ends were taken care of in the beginning.  this head has an avr with a reo. for volts adj. this used to be very sensitive when setting but now has little effect and the volts are low. i do like the doide gone bad approch and will check for ac coming out of the rectifier. i do not suspect the surging had anything to do with this but murphy follows every thing and body. when the load is taken off the volts do come up but still cant sqeeze much over 240 at 60.5 hz. yes good things come in big packages too and this is one of them just got to iron out a wrinkle or 2 . the avr does read volts from the output taps and also uses a reo. for a preset if you will. yes it does control volts to the feild. i cannot say watts in the avr box as i dont know buy its more than a dimmer switch the label resembles a menu at oreintal resterant for those who dont speak english. will post the cure for shure

gpkull

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Re: st head not doing watt it use to
« Reply #3 on: September 09, 2007, 03:14:41 AM »
finally got the ity bity gook box opened up. the avr that is. the pot has a bd spot as it binds up. not a stop on either end but rough in between. it has " 2K2" on its side. neither pops or i are electronic gaget gooruses but have more than the basic knowledge of semiconductors if such exstits. we figure 2K is 2000 ohms (just a guess) the other 2 aint shure about. see ins how the rough spot is probably wiped the carbon brush off the arm we are shootin for a 6$ fix . will have more output on the output in a week or so as we figure her out. as i said will post the cure for shure

Doug

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Re: st head not doing watt it use to
« Reply #4 on: September 09, 2007, 03:40:01 AM »
No disrepect implied but thats the first post written in Yank that I have a hard time reading lol.

In honour of your previous post I will reply at some future date in high Canadian.....

2 k is 2000 ohms, good luck on the fix
It's a Good Life, If You Don't Weaken

Doug

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Re: st head not doing watt it use to
« Reply #5 on: September 09, 2007, 04:30:28 PM »
Though the extra two was a type - o lol...
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gpkull

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Re: st head not doing watt it use to
« Reply #6 on: September 11, 2007, 04:40:48 AM »
no the 2k2 was not a typo it was as posted the 2kpot didnt fix . there is more going on. sorry doug i would never doubt your knowledge or question it. as before i will post my  findings and as always will let everyone on this site know  watt i know

Doug

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Re: st head not doing watt it use to
« Reply #7 on: September 11, 2007, 06:31:58 AM »
question it.....

Untill you see a scan of my tickets, you never know who you are dealing with.....

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gpkull

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Re: st head not doing watt it use to
« Reply #8 on: September 12, 2007, 05:05:37 AM »
many thanks to all. this simple little fix isnt watt is supossed to be. the 15k head worked flawless. bad spot in the pot thought we had it all figured out. not so. im not going to loose sleep but will post the corection for this  matter