Hello,
Hope someone can help me.
I'm new to this forum so hopefully i'm asking the right question. I have Technics SE-A1000 Amplifier wich blows it fuse right away when connected to the AC power line.
Couple things i've already investigated:
1. If i remove the white ribbon cable to the mainboard and put a new fuse in it, the amplifier turns on and i can turn it on and off by pressing the button. (Leads me to mainboard issue)
2. I checked all 4 Rectifier Diodes. First i measured them in circuit, but read some stuff that it might be interffered by other components. Therefore i took them out and measured them one by one.
This is the result:
From top to the bottom.
1. This one seems fine and when measure positive on negative and negative on positive it gives me 0L (I believe this is correct)
2. This one give's me strange readings on both sides. My conclusion is that this one is defective.
3. This one seems fine as well.
4. And this one seems fine too.
However my main problem now is that i cannot find a replacement for these rectifier diodes, they read P300D GI 9512L
Spec sheet
https://www.vishay.com/docs/88691/p300.pdf
I found another one wich is the following
https://www.vishay.com/docs/88516/1n5400.pdf
Does this mean i can safely replace them with a 1N5402 Diode?
Many thanks!
Greetings!.
Mark
Hope someone can help me.
I'm new to this forum so hopefully i'm asking the right question. I have Technics SE-A1000 Amplifier wich blows it fuse right away when connected to the AC power line.
Couple things i've already investigated:
1. If i remove the white ribbon cable to the mainboard and put a new fuse in it, the amplifier turns on and i can turn it on and off by pressing the button. (Leads me to mainboard issue)
2. I checked all 4 Rectifier Diodes. First i measured them in circuit, but read some stuff that it might be interffered by other components. Therefore i took them out and measured them one by one.
This is the result:
From top to the bottom.
1. This one seems fine and when measure positive on negative and negative on positive it gives me 0L (I believe this is correct)
2. This one give's me strange readings on both sides. My conclusion is that this one is defective.
3. This one seems fine as well.
4. And this one seems fine too.
However my main problem now is that i cannot find a replacement for these rectifier diodes, they read P300D GI 9512L
Spec sheet
https://www.vishay.com/docs/88691/p300.pdf
I found another one wich is the following
https://www.vishay.com/docs/88516/1n5400.pdf
Does this mean i can safely replace them with a 1N5402 Diode?
Many thanks!
Greetings!.
Mark
Even if you replace rectified diods with similar or better ones, that may not be the end of the story. Fuses blow because of excessive current. Likely protecting from more damage. I would be very careful when powering it up after diod replacement. I would check output transistors first.
Doubtful too. Especially since it starts normally once the motherboard is disconnected.
it's power integrated circuit on it
it's power integrated circuit on it
I can't understand this
" I have Technics SE-A1000 Amplifier wich blows it fuse right away when connected to the AC power line."
" If i remove the white ribbon cable to the mainboard and put a new fuse in it, the amplifier turns on and i can turn it on and off by pressing the button. (Leads me to mainboard issue)"
" I have Technics SE-A1000 Amplifier wich blows it fuse right away when connected to the AC power line."
" If i remove the white ribbon cable to the mainboard and put a new fuse in it, the amplifier turns on and i can turn it on and off by pressing the button. (Leads me to mainboard issue)"
Alright, I should clarify that in 2014 the amplifier was in for repair after a blown fuse due to a power outage. (the bottom rectifier is a replacement) And this time the fuse blew again after a another power outage.
I was reading on a different forum that one could disconnect the transformer from the mainboard by removing the big white cable. If the transformer would turn on and and being able to power on/off by hitting the power button. The transformer would most likely be fine. So this is what i did and that worked, and so moved on to the mainboard.
I've attached some photo's if anyone can point me where or what exactly i need to measure (I'm not super familiar with the terms for certain components)
Revoxis, you definitely have minimum 1 defective diode but that was caused by something so that is the hard part. Whatever happens, replace ALL 4 diodes and preferably for 5A rated types as 3A is very low for a power amplifier. If the device is very old the filter caps may be shot as well causing way too high currents for the diodes. I would replace the 4 diodes and the filter caps (use higher voltage ratings so that the new caps fit exactly) certainly when they are the old/original ones.
I also don't understand what fiddling with ribbon cables has to do with the issue?! I take you mean switching on just the transformer is OK but when the PCB is connected so with rectifiers, filter caps etc. then the fuses blows? No wonder as 1 of the diodes is kaputt. Try to measure resistance and you'll probably see that is is a dead short. If so then the large filter caps need replacement for sure.
So if I have understood correctly you have investigated and found out the power transformer itself is OK.
I also don't understand what fiddling with ribbon cables has to do with the issue?! I take you mean switching on just the transformer is OK but when the PCB is connected so with rectifiers, filter caps etc. then the fuses blows? No wonder as 1 of the diodes is kaputt. Try to measure resistance and you'll probably see that is is a dead short. If so then the large filter caps need replacement for sure.
So if I have understood correctly you have investigated and found out the power transformer itself is OK.
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Jean-Paul, I'll add that the amp is from the mid-1990's, and the filter caps are special design for this amp.
They may be good, but obviously the diodes need changing.
And the outputs checked using a dim bulb safety test.
I only believe the caps to be OK when the faulty diode is open and not a short circuit. Of course if it would be my amplifier I would replace such old stuff even though it would still be OK, clean the whole device thoroughly, resolder all solder joints, reseat all connectors etc. The normal stuff.
Yes, this is correct the Transformer is working fine. as soon as the Main PCB is connected the fuse blows. So i will have to order new diodes first. I can only find the 3A ones and not 5A ones.
Vishay General diode 1N5402-E3/54 DO-201AD 200 V 3 A
I think this one is correct. By Filter Caps do you mean the large ones?
Those 3A rated diodes might be part of the reason one of them is defective even though it took quite long. 3A types might be original, they are too light rated for a 2 x 70W amplifier. Just an example, I never tried these:
https://www.reichelt.de/gleichricht...MIk9r_0PKw-QIVluR3Ch0VcAKKEAQYAyABEgIl5PD_BwE
Those output relays are also underrated. This device probably is one of those highly appraised devices techs saw/see often 😀
https://datasheetspdf.com/pdf/900181/TE/OSA-SH-224DM3/1
You forgot to reply to a relevant question/remark. Is the defective diode an open circuit or a short circuit? It helps tremendously if the asker replies/reacts to people that try to help out. Otherwise it is one way traffic solely in the interest of the asker. YOUR answer will be more precise and adequate as well.
https://www.reichelt.de/gleichricht...MIk9r_0PKw-QIVluR3Ch0VcAKKEAQYAyABEgIl5PD_BwE
Those output relays are also underrated. This device probably is one of those highly appraised devices techs saw/see often 😀
https://datasheetspdf.com/pdf/900181/TE/OSA-SH-224DM3/1
You forgot to reply to a relevant question/remark. Is the defective diode an open circuit or a short circuit? It helps tremendously if the asker replies/reacts to people that try to help out. Otherwise it is one way traffic solely in the interest of the asker. YOUR answer will be more precise and adequate as well.
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Check with a dim bulb in series when you start it again.
Put a diode bridge rated at about 2 x the continuous power, if you cannot find single diodes (TV parts, see).
In old sets which have bee lying idle, damaged caps can be an issue, so again change them with slightly higher rated types.
The fault may simply have been caused by too much inrush current at start up.
1N4007 diodes in 2K ohm / diode check range show about 0.500 on the DMM, by that measure you have not one but three bad diodes, please check with the relevant spec for that particular type.
Put a diode bridge rated at about 2 x the continuous power, if you cannot find single diodes (TV parts, see).
In old sets which have bee lying idle, damaged caps can be an issue, so again change them with slightly higher rated types.
The fault may simply have been caused by too much inrush current at start up.
1N4007 diodes in 2K ohm / diode check range show about 0.500 on the DMM, by that measure you have not one but three bad diodes, please check with the relevant spec for that particular type.
I'm sorry for the strange reply timings. This is because my replies are moderated since I'm new on the forums 😁
Regarding the diode it's in my first post.
I will post back results here after the weekend.
Cheers!
Thank you, I'll buy some and will check the filter caps as well. I appreciate all the help 👍
Regarding the diode it's in my first post.
I really hope it's just that those power ic's are hard to get it seems.
I will post back results here after the weekend.
Cheers!
Yeah, not used to pictures with background and extra items. That distracts my eyes just like wrong terminology and camouflage expressions as not everybody is a native speaker.
Anyway, when the diodes already blew a few times one better chooses something more sturdy. It would be wise to check if the amplifier has more primary windings and if the right one is chosen. With old stuff here something the 220V tap is chosen while we have over 230V for over 25 years now. Often if is then best to choose the 240V tap if it has one. For some reason this is almost standard with lab equipment.
That caps have had a party with a shorted diode more than once so they're also potentially unreliable. To avoid having to open classic stuff several times replacing all electrolytic caps for something good is not a luxury. A general overhaul to keep it going for another 25 years seems appropriate unless one likes to do a partial repair now and then and start a thread on diyaudio.com.
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I would replace the rectifier diodes with 1N5408 type, check the two big elco's with an Ohm meter
in both directions and reassemble the amplifier.
Put a 100W lamp in series and start it up, no speakers connected.
If after a few seconds a relay clicks, chances are that you are O.K.
If not, carefully measure the relevant pins of the power IC.
You need axservice manual.
in both directions and reassemble the amplifier.
Put a 100W lamp in series and start it up, no speakers connected.
If after a few seconds a relay clicks, chances are that you are O.K.
If not, carefully measure the relevant pins of the power IC.
You need axservice manual.