AU717 power supply problem

Audiomania

Audiomania

Active Member
Hi everyone picked up a 717 from a local goodwill that was completely dead no protection lite flash nothing would not power up.Reconditioned the power supply board replaced the fuse resistors on the driver boards and now it powers up but on pins 24 and 26 I am getting a voltage reading of -0.801 the other pins seem to be fine.
pins 23 and 25 -36,50
pins 19 and 17 +38.51
pins 20 ans 18 +39.39
not to familiar with dia of this circuit any help would be appreciated.Thanks
 
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I would start with checking the voltage on the collector of TR08. Should be around -51.

If not, check D10 and D12.

If yes, check R22 and R24.

If all that looks good, start checking all the parts in that area as well as looking for cracked or lifted traces on the board.

What all was done to the power supply? If transistors were replaced verify pin outs. If caps replaced verify polarity.

Rob
 
Thank you, will check those points board was recapped all glue cleaned zd #01 and 02 replaced all resistors that were touched by glue, this amp did not power on at all so it is started from scratch not knowing what the problem was before
 
Well got that fixed voltage seems high on all pins though.
pins 23-25 -42.8
pins 19-17 +45.5
pins 18-20 +45.3
pins 24-26 -40.6

Using 220uf 50v caps in C-23-26 not sure if those are right voltages for this amp.Thanks
Have not reconditioned the tone-phono amp or driver boards yet except changing the fuse resistors on the drivers this amp was dead would not even power on.
 
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Audiomania said:
pins 23-25 -42.8
pins 19-17 +45.5
pins 18-20 +45.3
pins 24-26 -40.6
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Are these currently connected to the intended circuit? or Unloaded? Might have some DC offset issues in the pre-amp circuit with these current supply voltages.
 
Is the voltage selector in the right position? Not sure where you are located.

Rob
 
Yes first thing I checked cover is still off also, located in far north Wisconsin.Can not adjust the driver boards need to be refurbished that is the next task but at least it is up and running will keep you up on the progress.Thanks again for the help.
 
It is clear that the regulated PSU's are not functioning at all, there are a number of electrolytic capacitors that are/were originally rated at 35V on boards you have not yet touched, which will be seeing as much as 45V when they should be seeing no more than +/-33V if the regulators are working correctly.
Audiomania said:
Have not reconditioned the tone-phono amp or driver boards yet
Click to expand...
You say you 'cleaned ZD01 & ZD02' - (I assume this refers to the zener diodes on the F-2663 board), are you sure you re-installed them correctly? - you should see around 13 volts across each zener diode - please check this.

You should not consider this amplifier 'working' or useable until the power supply voltages are correct.
 
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Diodes were replaced and they are installed correctly all the caps replaced and glue has been cleaned on that board and this is not ready to go still have a lot to do was a non working unit would not power on still can not adjust the DC offset due to the condition of the driver boards. I am going at it a board at a time will keep posted on progress.
 
Ok - great - everyone looking forward to a successful outcome here, as it seems to have been quite a basket case. :thumbsup:
 
Little update finished the driver boards and the voltage has dropped slightly after adjustments still are on the high side at pins 23 and 25 about 38v and pins 19 and 17 40v and about the same at the pins at the other side of the PS board I followed lees stereo rebuild guide to the letter still have to do the phono amp and tone control boards.Any help would be great.Also checked all connections and grounds.
 
Feel like a fool found that I had installed the wrong voltage ZD in the PS board now it is at 32v across the terminals and able to adjust properly thanks everyone for your help.And Happy Thanksgiving everyone.
 
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