The ultimate dual 500 "rising from the ashes" build

Joe in the bulletin pictured the Collector and Emiter are reversed with new B- fused supply added.
This is what I have done.
Please advise Me if this is incorrect.
 

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Joe here is a board that I think Przem did a while back. The 22 ohm resistor is gone in it.
 

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Ok I have opened up one of the factory full comp units. The phase segmatic is wrong. Please see correct lay out This is good for both 400 and 700 using .33 ohm emiter resistors.
 

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So to update all that may care. We have made a few steps forward today. I will never admit to connecting the control board output driver supply B-lines to the positive fuse instead of the negative one. If such a thing did happen it would not be responsible for taking those drivers now in the trash to a quick and painfull death.

So so now we have no DC offset , like .5 mv , and a nice .340 bias I will connect the protection circuit and then put the load resistor to it tonight. If all goes well then I will load test the other channel.
 
Sounds like good progress. In this game, you learn by blowing up shit LOL
 
grapplesaw said:
So to update all that may care. We have made a few steps forward today. I will never admit to connecting the control board output driver supply B-lines to the positive fuse instead of the negative one. If such a thing did happen it would not be responsible for taking those drivers now in the trash to a quick and painfull death.

So so now we have no DC offset , like .5 mv , and a nice .340 bias I will connect the protection circuit and then put the load resistor to it tonight. If all goes well then I will load test the other channel.
Click to expand...


Glen I am proud of your "complete disclosure" attitude.....I have at times been ashamed of what I had to relate to those reading the thread, but felt it was the right thing to do. We are human, we make mistakes, we also learn from them....
 
Got both channels running

only a two drivers and one pre driver installed so far.

Added protection circuit back in and added 51pf caps as per bull item to control board output drivers. Now get a slight wave in the signal pattern on the scope. Does in both channels
did not do earlier. Like 2 or 5 cycles and a few mv variation. Any ideas any one

added video of low output on .1 volt setting

right channel bias short up and I can only get it down to .4880 turned to max down. Photo shows bias before at .360 or so.
Again any ideas.
 

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Ok it is scope
the wave patterns fluctuations stop on 1 volt division setting

still got high bias Near .5 volt not input or output
 
Well no smoke yet.

Got 1.5 volt out put and rock solid wave form. Had on x10 magnification on.


Curious scope show 4 divisions, +2 and -2 divisions, on 1 volt division setting. Probe on X1
That should be 4 volt measurement on scope but voltmeter shows 1.5 Volts.
 
No input or output both channel 1 hour in.
.4 and .1 mv dc offset
bias climbed to
Left at.5 volt and right at .55 after small out put during that time.

idle now for 5 minutes and bias back to normal. I thought if you put the power out this would actually drop bias mv as it gets warmer. Or have I got that wrong

off to bed as I am not thinking straight
 
The regulated voltage is steady with +14.9 and -15.22
In Line voltage 119
rail voltage on back planes left and right 116 volts with 240 volts across caps, interesting difference there.

Idle about 10 minutes and right bias has shot up again from .36mv L and R to about .550mv. I can only rev back to .500mv. And holding there Left has risen to .400mv
 
I can tune left bias from .020mv to about .800 mv with the vary resistor. The right does not go done to below ,495 and goes up to the same .800 range. Some voltage coming from some were else I guess getting in. Oh but where???
 
laatsch55 said:
Got some 5088's??
Click to expand...
Hi Lee

regulated voltage age steady at 15 and 14.6 on low voltage setting 76 volt rail
yes I have those but first I switched with an other ready to go and tested good 3403 and still same. Checked and supply voltage to the veri resistor low and fluctuating. Poked around and did not find anything obvious resistors in that path in spec. Cleaned flux from a few solder connects. No change. Tested two diodes d106 and d 107 with ohm meter on diode test. Fired up and now voltage is up and bias is down.
Will let run for a while to warm up.

15 minutes no change all steady. I will heat a few joints to make sure the solder is correct.


25 minutes gone and bias up to .550 again on right.

Turned both resistor pots to minimum and max - voltages are similar on both sides. Base voltage is similar on left and right both at low and high pot setting.

Both 3403 are 77' F

Base voltage on q105 and q101 are the same.

Collector voltage Q106 .100 mv lower on right in Min bias setting and equal in high bias setting.

Protection circuit?????
 
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