Discussion in 'Exclusively Sansui' started by Fhamre, May 3, 2018.
Sure you are..
Well... I slept at a Holiday Inn last night .LOL
Not sure what to say to that? Sorry?
Re the plug wiring. Note on the unit I have installed the two spades are the same size.
Tomorrow I may change those two regulators and possibly the small signal transistors.
Now I get the reference.
Did a little 5000 movement this am to see if the problem went away. Dam, sure enough I got the glow. Tried it again no glow.
Seriously this is not fun. I will pull the driver boards to see if that makes a difference and then I will look over the power supply boards for solder issues etc.
Maybe I'll fix the buzz along the way.
I inspected both power supply boards. Replaced all transistors on the low voltage PS board. Just because.
So I am still trying to sort out two issues. A short somewhere that occurs as a result of moving the unit. Random occurrence.
And the other issue a low tone buzz through both speakers when relay engages.
I tried pulling the driver boards one at a time to narrow down the buzz source . But buzz with or the other DB installed. No buzz with no driver boards but that should not be surprising.
any chance of recording the unwanted noise ?
Try slightly flexing the various boards. Cracked solder joints on connector jacks or pins or intermittent connectors on the boards. Some fasteners may be utilized to securely ground the boards to the chassis ground and may be loose or oxidated/dirty.
If the buzz is only occurring during power up as it’s going through speaker protection phase, my first guess is the problem would be in the speaker protection section of the circuitry. Have you checked that or are you shotgunning?
Will get back at it tomorrow and will try your suggestions as well as post a clip on YouTube.
Well did a short video of the buzz!
Still probing and moving the unit to try and get it to short and then hopefully fix it.
So far today haven't had it short.
I did have another look at the driver boards.
I know the SM does not show any fusistors in the unit but I didn't like the look of R31,32 150 ohm, and R23 and R26 220ohm. They just had that fusistor look. So they were replaced the 150ohm resistors were pretty close but the 220ohm were way out of spec.
ie.480,660,680 and 890ohm.
The resistor replacement did not make the buzz go but I still feel better. I did fine tune the bias after just to be safe.
first time i heard that from an amp without a synth plugged into it .
am wondering if the noise might stay without a speaker load .. will need a scope to see it really .
i forgot whether it was one or both channels ? and if you tried separating pre from mains ?
Both channels. The 5000 is just an amp. Only switch in the back is for mono or 2 channel.
There is a connection to the buffer amp from the power supply board. Not sure if amp would function with buffer amp with no power supply.
Something is not charging or stabilising in a regulated supply quick enough. If I get time I'll have a look and see if I can make some suggestions .
Would appreciate it.I do have new power supply caps on order.
yes .power supply 99.9 percent . am thinking this is happening until speaker loads makes it stop .. or its simply a coincidence .
i can take a guess for now at c05 c06 power supply not doing their job properly .
do you have a scope ?
I do have a Tek 2235. I am still learning the scope. So some hand holding maybe required.
Note all electrolytic caps replaced and all the transistors on F-2521.
My new power supply caps come tomorrow.
I can't seem to make the unit short out after moving it so hopefully that is behind me.
Still got the buzz.
Any ideas? All the boards have been recapped and many transistors replaced.
Are all voltages on the PS on spot?
I'll report back.
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