Fostex R8 dont turns on after voltage problem

Nanecour

Nanecour

New member
Hello everyone!!
I have a Fostex R8 recorder that works at 120v, and by mistake I plugged it in at 220v. It turned on for 5 seconds and turned off on its own. I have looked at the two main fuses (number 36 of the manual) and in principle they are fine. Does anyone know if there is another fuse? What could have been broken?
Thank you all in advance
 
Any number of things could have happened. Fuses aren’t for an over-voltage protection at input, they are to cut power when there is an unusually high demand for current downstream of the power supply. So…fuses don’t help you with what you did and likely wouldn’t be compromised. The first thing I would consider is if you roached the main power transformer. That’s the first thing in the path after the power switch.
 
sweetbeats said:
Any number of things could have happened. Fuses aren’t for an over-voltage protection at input, they are to cut power when there is an unusually high demand for current downstream of the power supply. So…fuses don’t help you with what you did and likely wouldn’t be compromised. The first thing I would consider is if you roached the main power transformer. That’s the first thing in the path after the power switch.
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I´ll check it.
Do you know how I can check it?
What cables should I check?
Do you know if I should isolate the transformer first or can I check it with the cables in place without cutting them?
Thank you very much!!!..
 
You have to input the correct power at the primary input and measure the output of the multiple secondaries using the service manual as a guide.
 
sweetbeats said:
You have to input the correct power at the primary input and measure the output of the multiple secondaries using the service manual as a guide.
Click to expand...

sweetbeats said:
You have to input the correct power at the primary input and measure the output of the multiple secondaries using the service manual as a guide.
Click to expand...
Sorry to bother you again.
I have the service manual but I can't find the voltages in the transformer schematics.
Could you please tell me what they are (the voltages) or if you have the sm what is the page? In the SM that I have, the transformer appears in the diagram on page 57, but i can´t find the voltages.
Thank you very much again.
 
I don’t have that information. I don’t usually see that in a service manual. The voltages need to be sufficient to be above the minimum threshold for the regulator in a regulated DC supply.
 
Before applying power again I'd measure the resistance of the transformer windings and check that they are sensible. Also check for any leakage between windings. I would then check the bridge rectifiers and smoothing capacitors with a suitable meter. Chances are that simple multimeter checks with the power off will show you if there is a fault in the power supply.
 
I agree 100%. It is likely there are multiple faults now that include both the main transformer and the power supply. But you can start with the transformer. Set your multimeter to resistance. There are two wires from the power cord and switch that are likely the same color. Those go to the primary winding. Then there are three wires that connect to the fuse PCB. Two are likely the same color. Those connect to the secondary winding. The third wire is a center-tap. Remove the fuses to isolate the transformer measure resistance between either primary wire and any secondary wire. There should be absolutely zero continuity. Then measure resistance across the two primary wires and note the resistance, and then measure for resistance across the two secondary wires, note the resistance. Lastly measure for resistance across each secondary wire to the center-tap… it’s the values. Post the values and your findings here.
 
jamesperrett said:
Antes de volver a aplicar energía, mediría la resistencia de los devanados del transformador y verificaría que sean sensibles. También verifique si hay fugas entre los devanados. Luego comprobaría los puentes rectificadores y los condensadores de suavizado con un medidor adecuado. Lo más probable es que unas simples comprobaciones con el multímetro con el suministro eléctrico apagado le muestren si hay una falla en el suministro de energía.
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jamesperrett said:
Antes de volver a aplicar energía, mediría la resistencia de los devanados del transformador y verificaría que sean sensibles. También verifique si hay fugas entre los devanados. Luego comprobaría los puentes rectificadores y los condensadores de suavizado con un medidor adecuado. Lo más probable es que unas simples comprobaciones con el multímetro con el suministro eléctrico apagado le muestren si hay una falla en el suministro de energía.
Click to expand...
thank you very much!!!! I´ll do.
 
sweetbeats said:
I agree 100%. It is likely there are multiple faults now that include both the main transformer and the power supply. But you can start with the transformer. Set your multimeter to resistance. There are two wires from the power cord and switch that are likely the same color. Those go to the primary winding. Then there are three wires that connect to the fuse PCB. Two are likely the same color. Those connect to the secondary winding. The third wire is a center-tap. Remove the fuses to isolate the transformer measure resistance between either primary wire and any secondary wire. There should be absolutely zero continuity. Then measure resistance across the two primary wires and note the resistance, and then measure for resistance across the two secondary wires, note the resistance. Lastly measure for resistance across each secondary wire to the center-tap… it’s the values. Post the values and your findings here.
Click to expand...
Thank you very much you too. I will do everything you tell me. I have measured and there is no continuity, so I know it is broken. I'm going to buy a new transformer, and then check everything else. I'll let you know when I get the transformer.
 
There should be no continuity from the primary winding to the secondary winding. Please post specific results of your testing.
 
sweetbeats said:
There should be no continuity from the primary winding to the secondary winding. Please post specific results of your testing.
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Hi!!
Results:
between either primary wire and any secondary wire ----- zero continuity
two primary -------- zero
two secondary ------- 0,06
each secondary wire to the center-tap --- zero

Looking for the new transformer hahaha. isn´t it?
 
I’m going to assume your numbers are in ohms. Details help.

If my assumption is correct, then yes I think so. And don’t assume that’s all. Once you have a proper transformer you need to power it up with the power supply isolated and check the outputs for correct voltage and look for AC ripple ideally with a scope. Then apply load and see if it still is correct. And then after all that there may still be damage downstream.
 
sweetbeats said:
I’m going to assume your numbers are in ohms. Details help.

If my assumption is correct, then yes I think so. And don’t assume that’s all. Once you have a proper transformer you need to power it up with the power supply isolated and check the outputs for correct voltage and look for AC ripple ideally with a scope. Then apply load and see if it still is correct. And then after all that there may still be damage downstream.
Click to expand...
Yes, ohms... sorry.
So i'll do it and I will tell you.. Now I have to look for a transformer ;)
Thank you very much again!!!
 
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