Thank you for that explanation, However, i think i need a bit more help, can my multimeter even do it? I just like to confirm or if i need to buy another one.
Haha, well i barely have time to work on it. maybe an hour per day. I barely use this multimeter so i have little experience with it, got it from a friend.
So please be patience with me 🙏👍.
So please be patience with me 🙏👍.
@wiseoldtech Do you find measuring the A/C on the rails to be a good indicator of the PS caps doing their job?
You are trying to fix an old Technics set without even your own meter...
Be very careful.
PS (and other) caps, buy regular long life 105 degree, from a good brand and reputed seller, and check with the schematic if any differences are there with the actual set.
I am not sure if you got the set new, may have been repaired without your knowledge.
There exist graphic type meters, and digital multi meters with capacitance function, starting at less than 20 Euro at places, maybe you can think of getting one. Will be handy.
Be very careful.
PS (and other) caps, buy regular long life 105 degree, from a good brand and reputed seller, and check with the schematic if any differences are there with the actual set.
I am not sure if you got the set new, may have been repaired without your knowledge.
There exist graphic type meters, and digital multi meters with capacitance function, starting at less than 20 Euro at places, maybe you can think of getting one. Will be handy.
I have amplifiers (Pioneer/technics and other) from the 70s and 80s and the power caps are still within tolerance after all this years.
I think you are taking the wrong approach with your amp, you should 1st look for what is causing the fuse to blow and only then look into service the amp properly.
I know that people want to help but he hasn't found the fault and the talk is already about replacing old (original) components that most likely are still in perfect condition (electrolytic capacitors have a wide tolerance range up to 20%).
I think you are taking the wrong approach with your amp, you should 1st look for what is causing the fuse to blow and only then look into service the amp properly.
I know that people want to help but he hasn't found the fault and the talk is already about replacing old (original) components that most likely are still in perfect condition (electrolytic capacitors have a wide tolerance range up to 20%).
Yes reread what OP already has written. The design imperfection is clearly too light rated diodes of which 1 out of 4 became a short a few times already. Some japanese brands made serial mistakes like these in the eighties/nineties. The cynical repairman then learns that the devices that have most issues are liked most by the average consumer 😉
Those vintage caps may be the salt of the Earth but please explain what a shorted diode causes.
Those vintage caps may be the salt of the Earth but please explain what a shorted diode causes.
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The amp blown a fuse ?
There is a shorted rectifier diode ?
Replaced the diode for similar or uprated ones ( if uprated one replace all 4)
Test amp (use bulb protection)
Does the amp work ?
If answer is yes problem solved.
The answer to your question is a blown fuse.
There is a shorted rectifier diode ?
Replaced the diode for similar or uprated ones ( if uprated one replace all 4)
Test amp (use bulb protection)
Does the amp work ?
If answer is yes problem solved.
The answer to your question is a blown fuse.
What is going to happen to a polarized electolytic capacitor when you place AC across it? Ever installed a cap backwards?
Your point about fixing the problem before launching into replacing a bunch of parts because of age is in my opinion dead on. I would just add replacing the PS caps with replacing all 4 diodes, the readings the OP gave in post 1 do not inspire confidence in the other 3 being good. I would also install slightly larger diodes, probably 5 amp instead of the stock 3 amp. Again, this is all opinion.
As a guy that repairs stuff often I think this is the best advice ever.
He already had blown fuses and shorted diodes a few times. What does that tell?
Is this game of 5 questions ?
Don't take me wrong I'm not against the OP changing whatever he want it is his amplifier after all, but why make a simple problem a complicated one ?
Again the most probable answer is diode is working on the limit, overheating and shorting in the end taking the fuse with it.
PS: the OP doesn't say how many times it happened before only that it did happened
Don't take me wrong I'm not against the OP changing whatever he want it is his amplifier after all, but why make a simple problem a complicated one ?
Again the most probable answer is diode is working on the limit, overheating and shorting in the end taking the fuse with it.
PS: the OP doesn't say how many times it happened before only that it did happened
So it blown ONCE before in the same condition (power outage) that points to inrush current causing the problem (underrated diodes)
According to the P300D datasheet it is 3A Maximum Average Forward Rectified Current
According to the P300D datasheet it is 3A Maximum Average Forward Rectified Current
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I would replace the four rectifier diodes with 5A types (so I hope everybody is happy).
Put a 100W lamp in series and power on.
Power supply elco's will probably be O.K., to be confirmed with measuring + and - rail voltages.
Do not over complicate things, first repair the fault.
If relay does not click, power IC is the main suspect.
Put a 100W lamp in series and power on.
Power supply elco's will probably be O.K., to be confirmed with measuring + and - rail voltages.
Do not over complicate things, first repair the fault.
If relay does not click, power IC is the main suspect.