Make sure theres no shorts from V+ to GND and V- to GND. your meter might read a quick beep (with rising ohms reading) while doing this, as empty capacitors read short. If all is good, throw the switch
Hey Jaycee! As you said, if I do a continuity reading on the 'donar PSU' -V or +V terminals and th eother lead on the chassis of the Sony amp, I do get a beep for a short period of time, with the resistance display on the multimeter rising fast and then reading zero.
The G reading never beeps and is always zero, so I guess I'm good to go then! Fingers crossed!
Good news - nothing went bang, I am still here, and the VU meters on the Sony both lit up and I could hear the relay clicking home after a few seconds. The bulb flashed briefly and was pretty much off after that.
To employ a Borat-ism... Great success!!!
What's the next stage then - try some music through it into a cheap pair of speakers?
To employ a Borat-ism... Great success!!!
What's the next stage then - try some music through it into a cheap pair of speakers?
Hi John...
It all sounds good so far. I would measure the DC offset across the speaker terminals before connecting anything. It should read below 60mv (0.06volts) at a guess.
Are the output transistors running cool ? Should really check the current (bias) but seems all is OK.
If that's OK then yes, speakers
It all sounds good so far. I would measure the DC offset across the speaker terminals before connecting anything. It should read below 60mv (0.06volts) at a guess.
Are the output transistors running cool ? Should really check the current (bias) but seems all is OK.
If that's OK then yes, speakers
Cool I have an old pair kicking around in the garage so will grab those, and connect my iPod up to the Aux input and see what happens.
There are two adjustment pots on the main board for DC offset so I may well have to adjust those, but will take a measurement as is for the moment.
J
EDIT: DC offset 0.03 on both channels so that looks good. Now for the speakers...
There are two adjustment pots on the main board for DC offset so I may well have to adjust those, but will take a measurement as is for the moment.
J
EDIT: DC offset 0.03 on both channels so that looks good. Now for the speakers...
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Don't adjust anything 'till I have looked at the manual
As long as the offset is OK then just try it carefully. As you turn the volume up the lamp will light. Don't go loud as the rails will collapse... if it seems OK and you want to try it further switch all off and take the bulb out so it gets full power.
As long as the offset is OK then just try it carefully. As you turn the volume up the lamp will light. Don't go loud as the rails will collapse... if it seems OK and you want to try it further switch all off and take the bulb out so it gets full power.
Nope nothing at all and I'm pretty sure the relay is the one on the power amp board, but will check.
There are pre-power phonos at the back of the amp, with a connector between both. I'll remove that and try using the iPod direct into the Sony running as a power amp instead.
I could try the headphone socket too I guess? If that worked then the poweramp would be suspect I imagine...
There are pre-power phonos at the back of the amp, with a connector between both. I'll remove that and try using the iPod direct into the Sony running as a power amp instead.
I could try the headphone socket too I guess? If that worked then the poweramp would be suspect I imagine...
The headphone out might be driven by the power amp.
Is there any offset voltage on the speaker terminals at all? There should be some reading. I'd try going direct into the power amp though as maybe the preamp is whats faulty. Also you can try connecting the pre-out to a soundcard line-in for testing, or even check with a pair of headphones to see if anything's coming out of the pre-outs.
Is there any offset voltage on the speaker terminals at all? There should be some reading. I'd try going direct into the power amp though as maybe the preamp is whats faulty. Also you can try connecting the pre-out to a soundcard line-in for testing, or even check with a pair of headphones to see if anything's coming out of the pre-outs.
OK no luck with headphones either.
BUT the relay click is from the PSU board attached to the IEC inlet (power supply board 'B' 1/2, page 29 of the service manual), NOT the poweramp board as I originally thought.
DC offset on the speakers is 0.03.
The VU meters light up and that's about it.
BUT the relay click is from the PSU board attached to the IEC inlet (power supply board 'B' 1/2, page 29 of the service manual), NOT the poweramp board as I originally thought.
DC offset on the speakers is 0.03.
The VU meters light up and that's about it.
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Be careful if you try that as you don't want full output accidently... headphones are a good idea. You should hear some faint hiss...
Quick check you can do... what's the DC voltage on the case of the output transistors in each channel. All should be zero.
I'll come back with some quick checks in few minutes if you get nowhere.
Quick check you can do... what's the DC voltage on the case of the output transistors in each channel. All should be zero.
I'll come back with some quick checks in few minutes if you get nowhere.
FTFY
Looking good! Make sure your 'function' switchs are set to the right input and that the 'tape copy' and 'monitor' switches are set to 'source.' Play with the speaker selector switch, too, since it may be dirty.
DC reading is approx. -72mV from case of each transistor to chassis (no music playing - it increases if I play music).
Getting absolutely nothing from it not even a hiss.
Following the schematic, I can see power goes from the PSU board (page 30) to the control board. The control board must be working as the meters are on. So I think there's not enough power from the control board to the poweramp perhaps?
I am being yelled at for dinner - back ASAP
EDIT: yep low reading on all four.
I am being yelled at for dinner - back ASAP
EDIT: yep low reading on all four.