Hi fellow troubleshooters. This is my first post on badcaps. I've recently setup an electronics workbench. i'm also building a studio with old equipment bought faulty at low cost.
I've been into electronics since the mid 80's and particularly in the last few years though only getting hands on with repairs now. My knowledge gaps are significant so I'll be posting here to seek guidance advice and general practical applied learning.
On my bench today is an old ca. 1993-95 Akai hardware sampler. This runs on both a linear and Smps supply. Both are getting on in age and ripple seems fairly high. The smps gives me some 150mv on average but rather alarmingly the supply feeding the sensitive DAC output stage is fed from the unregulated linear supply. This goes to two LDO + - -15v regs that in turn feed the dac through a couple of 78/7905 By this point ripple is down to 34mv but I'd. like to minimise what the main supply feeds and get on top of this rather loud ripple.
The sampler isn't playing well. I see ringing peaks on square and saw waves so there are other issues but i figure start with the supply.
I've attached a shot of the psu board. this is fed by a separate smps which appears ok given its age. These were expensive devices back in the day and Akai specced them quite well.
I've done a quick in circuit cap esr test with a ‘peak' meter and most including the main filter caps look good. The only suspect is the small .47 next to the rectifier which I'll desolder for test later today.
I'll also measure all voltages under load and update the image with these printed in case that helps the process.
So I'd be most grateful for suggestions on what could be amiss here. Is 700mv ripple normal ?
Thanks in advance
I've been into electronics since the mid 80's and particularly in the last few years though only getting hands on with repairs now. My knowledge gaps are significant so I'll be posting here to seek guidance advice and general practical applied learning.
On my bench today is an old ca. 1993-95 Akai hardware sampler. This runs on both a linear and Smps supply. Both are getting on in age and ripple seems fairly high. The smps gives me some 150mv on average but rather alarmingly the supply feeding the sensitive DAC output stage is fed from the unregulated linear supply. This goes to two LDO + - -15v regs that in turn feed the dac through a couple of 78/7905 By this point ripple is down to 34mv but I'd. like to minimise what the main supply feeds and get on top of this rather loud ripple.
The sampler isn't playing well. I see ringing peaks on square and saw waves so there are other issues but i figure start with the supply.
I've attached a shot of the psu board. this is fed by a separate smps which appears ok given its age. These were expensive devices back in the day and Akai specced them quite well.
I've done a quick in circuit cap esr test with a ‘peak' meter and most including the main filter caps look good. The only suspect is the small .47 next to the rectifier which I'll desolder for test later today.
I'll also measure all voltages under load and update the image with these printed in case that helps the process.
So I'd be most grateful for suggestions on what could be amiss here. Is 700mv ripple normal ?
Thanks in advance
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