|
Viewing 1 to (35 Total) Technics SX-FA1 no load. Blue screen. |
Total Posts: 2
Joined: February 3, 2016
|
Hello dear friends, I hope somebody will help.
I am engaged in repair of musical instruments for over 5 years, this is my hobby. I have a Technics SX-FA1 he can't boot. When I press on the keys there is no sound. Programs are not switched. I can not find a chart for FA1 found the scheme of GA1 it is very similar. On this I try turning to you for help.
Voltages is normal. Maybe someone can help?
Best wishes,
Roman
Tags:
Posted on February 4, 2016 at 2:40 PM
|
|
|
United States
Total Posts: 74
Joined: March 19, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
Hello-
Have you looked up the manuals here? Mike is pretty good about posting most and will post any that is needed.
Secondly, if you have a solid blue screen...you're not going to want to hear this, the organ is probably done for. Unfortuanely, unless you can find one cheap for parts, there are no parts made anymore to replace. 
Posted on February 17, 2016 at 10:51 PM
|
United States
Total Posts: 74
Joined: March 19, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
Did you check here:
http://members.technicskeyboards.com/files/pdf-documents/...
There is an owners manual and service manual both
Posted on February 17, 2016 at 10:56 PM
|
United States
Total Posts: 74
Joined: March 19, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
Where it says at the bottom: ALL PDF'S
Type in: FA1
You'll see two pdf's
TECHNICS SX-FA1 REFERENCE GUIDE pdf and
TECHNICS SX-FA1 SERVICE MANUAL pdf
Posted on February 17, 2016 at 10:59 PM
|
United Kingdom
Total Posts: 166
Joined: January 12, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
The fault is usually on the main voice board where the standard Panasonic simple switch power supply lives. You will need to swap out the capacitors associated with the power supply as well as the three transistors including the one on the heat sink. In worse case situations the surface mount comparator chip may have failed. Its a very small dual comparator from the 339 family. This power supply is fed from the 42 volt from the audio amplifier and brings the supply down to the logic levels needed on the board. You will then find the FA1 will work fine with a full display once this has been done.
Dave Tutt
Posted on February 27, 2017 at 10:38 PM
|
United States
Total Posts: 74
Joined: March 19, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
I've sold both keyboard and GA3 awhile back.
Posted on February 27, 2017 at 11:41 PM
|
Total Posts: 2
Joined: February 3, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
The fault is usually on the main voice board where the standard Panasonic simple switch power supply lives. You will need to swap out the capacitors associated with the power supply as well as the three transistors including the one on the heat sink. In worse case situations the surface mount comparator chip may have failed. Its a very small dual comparator from the 339 family. This power supply is fed from the 42 volt from the audio amplifier and brings the supply down to the logic levels needed on the board. You will then find the FA1 will work fine with a full display once this has been done.
Dave Tutt
===============================================
Thanks u dear Dave.
At the moment, my musical instrument is in service, and I'm on vacation. Upon arrival, I will definitely have time for it and try to repair it. Thank you very much for not leaving us without an answer. I will write down the results here.
With best wishes, Roman O.
Posted on March 9, 2017 at 2:24 PM
|
United States
Total Posts: 21
Joined: September 6, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
Hi Dave,
I know this post is almost a year old, but I have an SX-FA1 that is dead. There is 15 and - 15 volts to the main board, but not much more than that. Is it possible for this to have completey failed and this may resolve my issue?
Hi Hope you check these periodically.
Thank you,
Ken
Posted on February 1, 2018 at 12:31 PM
|
United Kingdom
Total Posts: 166
Joined: January 12, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
The display and all the voicing runs at 5 and 3.3volt derived from a 42 volt positive supply from the power amp board via a 6.8 ohm resistor that sits to the bottom left hand corner of the power amp / heat sink board. The important thing is that this resistor protects the voice board so dont just change it without going to the voice board and replacing the simple chopper control circuit key components. You will find a power transistor on a very small heatsink that needs to be changed as well as the three control transistors. You should also change the 1000uf 6v cap for something better say a 1000uf 16 volt high temperature type and also the surface mount comparator chip 393 type. There is also a 47uf 63volt local incoming supply filter cap that should be replaced too. Once done your 3 and 5 volt supplies should return. You should then also get a display and some sounds. If not but you still have the correct volts at the voice board you can check on the output board for +-15 and the main output stage supplies and the dedicated fan supply that must be there and should kick the fans as soon as you turn the organ on.
Let me know how you get on.
Dave
Posted on February 1, 2018 at 1:03 PM
|
United States
Total Posts: 21
Joined: September 6, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
Hi Dave,
Thank you!!!
I am going to replace all the components you nentioned above.
One thing I do notice as you mentioned the fans, they do not turn on when the power is on. Is that something that is controlled by the Main Board one we have power, of should those turn on even with this issue?
Thanks again,
Ken
Posted on February 1, 2018 at 2:43 PM
|
United Kingdom
Total Posts: 166
Joined: January 12, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
Fans should kick once when the power goes on and then stop. They are driven from a transistor on the center of the power amp board which in turn takes a feed from a thermistor on the heatsink. It is not actually a good circuit as there is far too much heat in the box for these old machines and it should run more air through the machine or at least have more air grills to allow the heat out. But for most people living in normal homes at no more than 20 degrees C they do okay. Anywhere where the average temperature is higher should consider rather better airflow.
Posted on February 1, 2018 at 3:13 PM
|
United States
Total Posts: 21
Joined: September 6, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
Hi Dave,
While I am waiting for some of the replacement parts, I was trying a few more checks with the Power Supply. The output I have from the transformer is only 35 Volts. Not sure if that is a 110 / 220 volt thing based on where you personally are located.
I am also unsure of where to check on the connectors to make sure that the 35 volts is actually making it to the main board. The schematic I have is a bad copy of an original so, trying to decipher it is somewhat challenging.
Thoughts?
Thank you,
Ken
Posted on February 7, 2018 at 2:30 AM
|
United Kingdom
Total Posts: 166
Joined: January 12, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
35volts AC once rectified produces around 50volts DC which is normal. On load this drops a bit but not that much. Whenever you measure AC at a transformer the DC volts will be around 1.4x that voltage off load. There isn't an easy place to measure the DC except at R34 the 6.8ohm feed to the main voice board or at the inputs to the 15volt regulators near the heatsink on the two 3watt resistors R5 and R6
Connector CN3 pin 3 is the supply to the chopper circuit on the main voice board. DON'T short this to anything else other wise you will be looking for a new voice board. It is far easier to measure it at the resistor if its at both ends it will be getting to the regulator.
Posted on February 7, 2018 at 8:23 AM
|
United States
Total Posts: 21
Joined: September 6, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
Understood. I don't think I am going to see anything just yet. The 6.8 Ohm resistor is bad.
Anxiously awaiting the parts. They were difficult to find!
Thanks,
Ken
Posted on February 7, 2018 at 3:19 PM
|
Total Posts: 1
Joined: February 10, 2018
|
Re: Technics SX-FA1 Completely dead
I have a Technics FA1 that is completely dead except for the power lamp and control panel lamps. I opened it up and found that the 6.8 ohm resistors on the power board were both open so I replaced them. When I powered it on they both overheated and blew out again. I have subsequently replaced the regulator transistors and checked the capacitors to no avail. Any advice? I do have the Technical guide. I have played this instrument for about 8 years and it was working perfectly until it suddenly stopped working.
Posted on February 10, 2018 at 8:21 AM
|
United States
Total Posts: 21
Joined: September 6, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
Hi Dave,
I finally got the parts and installed them in the main board. I am still getting a hot resistor, but also the 1000uf cap is getting hot. Is it possible that one of the diodes D7 or D9? Cant make it out in the plan be bad?
Any insight would be greatly appreciated.
Thanks,
Ken
Posted on February 21, 2018 at 6:39 PM
|
United Kingdom
Total Posts: 166
Joined: January 12, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
If the fast diode is open circuit then there will be nice spikes of voltage across the capacitor and that will do it no end of damage. It also won't do the rest of the circuitry any favours! Check it out of circuit to ensure its good but I would replace it anyway. The voltage across the diode should be no more than 5.1 volts, if it is then the chances are the rest of the board will be damaged.
Posted on February 21, 2018 at 6:51 PM
|
United States
Total Posts: 21
Joined: September 6, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
I should be able to measure that with an Ohm meter, correct. If so, it looks like it is open. I get nothing across it either way.
Do you think the board has been destroyed at this point? I am just wondering if I should be trying to find the illusive Main Board.
Thank you for all your input it is GREATLY appreciated.
Ken
Posted on February 21, 2018 at 7:17 PM
|
United States
Total Posts: 21
Joined: September 6, 2016
|
Re: Technics SX-FA1 no load. Blue screen.
Sorry,
Just went back to the specs on both diodes and they both appear to be fast diodes, do you know which one it might be?
I have attached a snapshot of the schematics.
Posted on February 21, 2018 at 7:22 PM
|
United Kingdom
Total Posts: 166
Joined: January 12, 2015
|
Re: Technics SX-FA1 no load. Blue screen.
They are fast ones yes. You need something like a UR5408 which will work. This is a standard high speed diode which is probably faster than necessary but to find a Panasonic original is pretty difficult.
You can read the diode with a meter but it needs to have a diode test range else it may give odd readings that won't tell you much. Many digital meters don't read diodes well on their resistance range as they use a very low supply which won't work. it has to be enough to bias the diode to conduct so you need to see what your meter can do.
You cannot tell anything about the board until it has power on it. Digital boards are less than easy to diagnose and of course we are not able to do what would have been done in the factory with regard to testing so we have to improvise a little.
Make sure your 1000uf is the right way round as it will also get hot and eventually fail if it is.
There are no spare boards. Spare organs yes but of course they probably have the same fault or worse. 20 or 30 years down the line we have to expect there is going to be a number of these organs that will have to end up in the bin!
Dave
Posted on February 21, 2018 at 8:14 PM
|
