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Audio equipment

CV 1200 dual amplifier

Miguel B
hace 5 años
hace 5 años
https://adjuntos.yoreparo.com/imagen_post/0005/01/299bf0b01a3e6ab98e7aada1bafa10bc736b60e3.jpeg" alt="" /> https://adjuntos.yoreparo.com/imagen_post/0005/01/2d0d268ce0916e3275ee9dd57d78ca9e1698885a.jpeg" alt="" /> [img] https://adjuntos.yoreparo.com/imagen_post/0005/01/e25aef0a1adecdddaaaaaaaaaaaaaaaaaaaaaaaa » img] Hello everyone. I hope you can help me with my amplifier. I summarize. I have no idea of electronics, but I think with help I can get my first amplifier repaired because I love the sound. First the relay did not jump on power up. I have changed a capacitor that appreciates burned, it remained the same, then I have changed transistors bs 709, 2 N 6101 and other 4. I turn it on and to my surprise the relay already jumps, but at the same time it burns the fuses of the amplification board. I'm already lost Please, can you give me a cable, hahaha. I have the scheme. Thanks and regards.
jomi
jomi
38.143
hace 5 años

do you have how to measure ohmiaje and voltage?

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Miguel B
hace 5 años

Yes. Although I have only checked continuity and the npn and PNP transistors, I have seen the re form. Thanks for answering so fast.

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jomi
jomi
38.143
hace 5 años
hace 5 años
Read this post to upload photos How to upload photos Looks like you have a short on the amplifier. [b] Without connecting the equipment to the network, measure the resistance (on a lower scale) between points + A and -B of the source with respect to mass. Measure and tell us what you find
Miguel B
hace 5 años

Sorry for my awkwardness, but I don't know how to transfer a scheme to the image of the ampli. I better send you a picture and tell me the points that I have to measure and how. If it seems good to you and it doesn't bother you. By the way, how can you add photo to the message?

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Miguel B
hace 5 años

The points that I have to measure are the ends of the large capacitors that are close to the power supply or is it behind the board, where is the printed circuit ?. Thank you.

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jomi
jomi
38.143
hace 5 años

OK upload a photo where you see the transformer and the bridge diode

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Miguel B
hace 5 años

Sorry jomi, I've been trying to upload photos for a while, how milk photos are uploaded to your comment ?.

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Miguel B
hace 5 años

I don't see anything where it appears to add or attach a photo or anything similar. I keep trying. Thanks again for your patience and answers.

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Miguel B
hace 5 años

Hi, good morning jomi. I have finally been able to upload a photo that is, I believe what you ask. I have more of the opposite part of the plate. Thanks and regards.

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jomi
jomi
38.143
hace 5 años

With the equipment disconnected from the mains. Measure with the ohmmeter between the ends of each of the yellow 4700 uF filters
What values do you have in ohms?

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Miguel B
hace 5 años

Good.
Multimeter, black on with, red on Omega and lower position stays at 1. Change to 2k and the value is rising and rising, slower and slower I stopped at 1,800.

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Miguel B
hace 5 años

All connected. Only the fuses are missing, does that matter?

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Miguel B
hace 5 años

That in both filters the same.

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Miguel B
hace 5 años

I have measured again waiting for more time. In one it remains stable in 1,686 and the other in 1,345. red always on more of the component.

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Miguel B
hace 5 años

If I reverse the polarities when measuring it goes down to minimum values and then starts to rise.
I try to give you all the possible data, since as I told you I have no idea of this, in case it can help you with anything. Thank you.

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jomi
jomi
38.143
hace 5 años

That tells you that the filters load and unload. If there were a short, it would indicate low resistance near zero or zero.
I imagine you tried the lowest ohms scale

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Miguel B
hace 5 años

On the lowest scale (200), mark 1. The measurement I tell you is in 2K.

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jomi
jomi
38.143
hace 5 años

And if you cross the tips of the ohmmeter on that scale that marks?

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Miguel B
hace 5 años

I check it and tell you in the afternoon. Thank you.

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Miguel B
hace 5 años

What I have checked again have been the transistors, placed on the board, only continuity and there is a BD 709 and a BD 140 that give me continuity, the others well. They are both I believe in the same channel. It may be that they have been damaged when connected to the mains and the fuses have blown or that when they are welded to the board the continuity is not correct. You see, I tell you everything I think can tell you something.

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Miguel B
hace 5 años

Also tell you that the condenser that had burned is the one that appears in the part of the scheme in position c 1400. I took the burn to the electronics store and nothing was visible and through the scheme I checked that it puts 47 n, and I already bought and install the one it has now, a little smaller, but they told me that it didn't matter. From there, the starter relay started to jump. Then when I put the new transistors is when the fuses blow.

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Miguel B
hace 5 años

Proven 4700 MDF capacitors at minimum scale (200), mark 1, inverting the poles, black in + and red in -, also mark 1.

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jomi
jomi
38.143
hace 5 años

Just in case you solder the bridge diode and retest continuity in the 4700 capacitors. In the photo you sent it must be the rectangular black one. on the bottom. Without the bridge diode it measures again between the terminals of the C of 4700 if the short follows, it indicates a short in the output circuit. You must look patiently for the transistor that causes it.

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Miguel B
hace 5 años

Okay. I discard the bridge diode, I measure the 4700 again, if they continue to give the same measurement I re-solder the bridge diode, I connect everything and connect to the network and if it continues to blow fuses, transistor by transistor until I find what is wrong inside this same plate . I understood you well, no? Thanks and regards.

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Miguel B
hace 5 años

Just in case, I will send you a short photo of the board by the printed circuit in case you can see in it something that can indicate the place of the short.

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Miguel B
hace 5 años

And thank you. I appreciate your interest. Let's see if we can revive this ampli.

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jomi
jomi
38.143
hace 5 años

You are on the right track
Go to the corner and buy a kilo of patience.
You will need it.

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Miguel B
hace 5 años

Well, after two technicians told me, one that pffff that was very old, that I was more interested in buying another and the other one that good, that I was not sure that it will look good, because you will tell me. Patience ?, There are in abundance here. Thanks again for yours. I soldered the bridge diode and measured the 4700 again, it remains the same. Now, as you say, check all the other transistors. Greetings from Seville.

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jomi
jomi
38.143
hace 5 años

You do not need to buy all. Solder one by one, noting your number and location. Measure it on a low scale and if it's okay, solder it. If it's bad, make a list on paper and write down the steps you take to avoid mistakes. If you find bad, write it down as bad to look for the new one later

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jomi
jomi
38.143
hace 5 años

I forgot, check the form with a magnifying glass. Suddenly there is a crossing caused by welding.

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Miguel B
hace 5 años

Thank you very much again partner so I will. And at least one of these days I tell you that my AMPLIFIER sounds again.

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Miguel B
hace 5 años

Hello jomi, I have checked all the transistors, there was in each channel 1 defective BC 558, I have replaced them, how they go in pairs I have preferred to put the new ones 4. The fuses continue to blow. I have desoldering the bridge rectifier and checked according to a tutorial and correct. I have tried to connect the 4 connectors on the board one by one. One that is before the bridge, well, another that has 2 pins well, the one on the opposite side of the fountain well, jumps when I connect the one that comes out of the front of the ampli with three red, yellow and black pins.

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Miguel B
hace 5 años

He may be saying something obvious, but here I am. Can you please guide me on how I can continue looking for the fault ?, Diodes ?. Thanks and regards.

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Miguel B
hace 5 años

I have uploaded another photo where the connector that blows the fuses appears disconnected.

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jomi
jomi
38.143
hace 5 años

Is the connector with white and red yellow wires?

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Miguel B
hace 5 años

Exact.

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Miguel B
hace 5 años

No, sorry, is that it appears in the photo without connecting, black, red and yellow. On the board, where it is connected, L appears an inverted T and R.

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Miguel B
hace 5 años

Good Morning. Could they be diodes that were wrong? Thanks and regards.

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