Hello.
Pioneer SA 708.
Problem no -46v on diod bridge .
+46v ok.
Transformer ok on 2 red wires 30v AC.
All 4 diodes 501......504 are ok.
Dessoldered and tested.
No bad soldering or damaged parts.
Need help.
Regards
Pioneer SA 708.
Problem no -46v on diod bridge .
+46v ok.
Transformer ok on 2 red wires 30v AC.
All 4 diodes 501......504 are ok.
Dessoldered and tested.
No bad soldering or damaged parts.
Need help.
Regards
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Is the transformer secondary centre-tap securely grounded - powered down what resistance do you get across the secondary windings?
Something is puzzling me.
Why does the positive rail, starting at the two big caps ends up being negative in the power amp section and vice versa?
Hugo
Why does the positive rail, starting at the two big caps ends up being negative in the power amp section and vice versa?
Hugo
R501 & R502 are ok,10kohm
the transformer secondary centre-tap securely grounded,no problems.
White red 1.....33ohm
White red 2....32 ohm
Red 1 red 2......30 ohm
the transformer secondary centre-tap securely grounded,no problems.
White red 1.....33ohm
White red 2....32 ohm
Red 1 red 2......30 ohm
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I think the voltages are just fine but there is a little misunderstanding in the way they are measured.
You need to put the black negative wire of your meter in-between the resistors and keep it there.
That is the ground connection, the thick black line in the picture,
With the red wire you will measure +46.5VDC on top of R501 and moving it to the bottom of R502
you will measure -46.5VDC.
Hugo
You need to put the black negative wire of your meter in-between the resistors and keep it there.
That is the ground connection, the thick black line in the picture,
With the red wire you will measure +46.5VDC on top of R501 and moving it to the bottom of R502
you will measure -46.5VDC.
Hugo
Measure across red 1 and red 2 should be 33ohm + 32ohm = 65ohm.
Is red 1 to white = 30VAC and red 2 to white also = 30VAC?
Is red1 to red2 = 60VAC?
Excuse me it's wrong measure.
White .....red1.......1 ohm
White.....red1.......1 ohm
Red1....red2..........1.2 ohm
White .....red1.......1 ohm
White.....red1.......1 ohm
Red1....red2..........1.2 ohm
Lynyrd, these measurements unambiguously confirm that the voltages are correct.
Have you measured as the drawing shows?
Top of R501 will read +46.5VDC
Bottom of R502 will read -46.5VDC.
Hugo
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If transformer voltage is good
and diodes are good.
Could be capacitor issue.
Not always a " bad" capacitor
If solder connections look good
and traces look good.
Can be a broken lead inside cap
or non visible broken lead under cap.
lifted traces not easily visible or cracked traces
not easily visible
Can also look for missed corrosion
caused from gluing components
to board.
and diodes are good.
Could be capacitor issue.
Not always a " bad" capacitor
If solder connections look good
and traces look good.
Can be a broken lead inside cap
or non visible broken lead under cap.
lifted traces not easily visible or cracked traces
not easily visible
Can also look for missed corrosion
caused from gluing components
to board.
You measured 93VDC in post #8. This is twice 46.5V. This means the total voltage is present.
Bad solder joints or broken leads could be the problem, as WhiteDragon said.
But then, it would be intermittent.
Can you take a picture with both resistors clearly visible?
Hugo
Bad solder joints or broken leads could be the problem, as WhiteDragon said.
But then, it would be intermittent.
Can you take a picture with both resistors clearly visible?
Hugo