Hello all,
I have replaced all the capacitors and bad resistors, as well as transistors and diodes.
I rewired the boards and put in new 11000 UF 100 volt caps, as well as gold plated rca jacks and speaker wire terminals.
I went to set bias before hooking up speakers and only read .90 ma on my positive fuse in between capacitor and board. I have never done this much work on an amp at one time. I've mainly just done re-caps..
Can any one please help? I really want to get this guy fired up.
I have replaced all the capacitors and bad resistors, as well as transistors and diodes.
I rewired the boards and put in new 11000 UF 100 volt caps, as well as gold plated rca jacks and speaker wire terminals.
I went to set bias before hooking up speakers and only read .90 ma on my positive fuse in between capacitor and board. I have never done this much work on an amp at one time. I've mainly just done re-caps..
Can any one please help? I really want to get this guy fired up.
You are measuring at the dual fuse blocks mounted on each side with the fuse removed.. Correct? The fuse must be physically removed and the meter probes securely attached to the fuse clips.
Yeah, I removed the fuse.. to no avail.
I hooked up some goodwill bookshelf speakers and I get no sound..
Typical of both channels.
I hooked up some goodwill bookshelf speakers and I get no sound..
Typical of both channels.
Any wiring damaged? Seems odd that the channel you tested is barely drawing any current, also seems odd that both channels aren't working. Can't remember if it's 60 or 65v for B+ and B- but set your meter to measure voltage, connect the black probe to ground (the wire connecting the big filter caps together and measure the + and - screw posts. What are you getting?
Ok, I went through all the wiring on the bridge rectifier which is also new.
I'm getting 124 volts D.C. Across my big filter caps. That's twice what I should be getting.
Could the transformer be bad?
I'm getting 124 volts D.C. Across my big filter caps. That's twice what I should be getting.
Could the transformer be bad?
Mains voltage selector or tappings set incorrectly ? (I haven't a circuit available).
If you have 120 volts across 100v rated caps then something basic is amiss. Don't discount the meter either... check it.
If you have 120 volts across 100v rated caps then something basic is amiss. Don't discount the meter either... check it.
The bias is indeed measured across the positive rail fuse socket (the ones on the bottom of the chassis). You should get a range on 240mA to 300mA. So if you are not seeing that, you somehow may have clamped the MOSFET gates to zero. Thus no current is flowing through these. Try to measure the voltage at the gates. Be careful. But you should have 1.2V between the two gate pairs. It is easy to measure this with a meter across the solder lugs where the 470 ohm gate resistors are connected (3 lug solder strip attached too heat sink).
Ok, I'm getting 62 volts from my the copper buss bar(formerly a wire) and my positive screw post..
Still only reading.9 ma on the b+ fuse. I checked my Klein MM at a wall outlet and read 122 volts. I have a fluke clamp style meter and it reads the same..
Still only reading.9 ma on the b+ fuse. I checked my Klein MM at a wall outlet and read 122 volts. I have a fluke clamp style meter and it reads the same..
BTW: if you measure 124V - you likely have measured across minus and plus of the power supply. Normally that is measured with reference to 0V in the center - or chassis ground. Then you get +60 volts and -60 volts.
OK - now we are getting somewhere. 62V is fine. Now: what do you measure gate resistor to gate resistor? (Across the solder lugs with the 470 ohm gate stoppers)
My brother passed away about a year ago, I inherited this amp and a set of Bose 901's with an eq.. I rebuilt and refinished the 901's including the eq, new capacitors and op-amps and they sound good(not as good as my Polk audio monitor 10bs) but this equipment has sentimental value so I can't express enough gratitude for the help that you guys are giving me.
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