Hello,
I am new user of this forum and obviously I need your help.
I have a problem with an IC of my thorens turntable, a 125 mkII. I am searching for two SFC 2709 E and I can't find them.
Could you please tell me where to buy some ? Or is there an equivalent ? I am not an electronic specialist.
Thank you very much for your help.
I am new user of this forum and obviously I need your help.
I have a problem with an IC of my thorens turntable, a 125 mkII. I am searching for two SFC 2709 E and I can't find them.
Could you please tell me where to buy some ? Or is there an equivalent ? I am not an electronic specialist.
Thank you very much for your help.
Hi Guys,
I've never had to replace one of these - ever. Not unless the table was "struck by technician", or worse.
Here is a picture Leolabs ......
It may be a uA709 or something like that.
So why do you think these need replacement?
-Chris
Edit: They are LM709 in a 14 pin dip. What a guess!
I've never had to replace one of these - ever. Not unless the table was "struck by technician", or worse.
Here is a picture Leolabs ......
It may be a uA709 or something like that.
So why do you think these need replacement?
-Chris
Edit: They are LM709 in a 14 pin dip. What a guess!
Attachments
Hello and thank you for replies.
I have a problem with my 125 mkII. I don't manage to obtain the good voltage on motor power. Then, the motor don't turn but I feel vibrations and I can't turn it by hand.
I have already changed the two big capacitors and four transistors too.
I have changed IC by LM709 and try LM741 too. I have power to motor but it still doesn't work. I have too much power and I can't adjust to good voltage. I have 17V and 12V instead of 8V and 8V for 45rpm for example.
Maybe a wrong IC reference ?
I have no idea of what to do now, so help is welcome. If someone have advice ...
Thanks
I have a problem with my 125 mkII. I don't manage to obtain the good voltage on motor power. Then, the motor don't turn but I feel vibrations and I can't turn it by hand.
I have already changed the two big capacitors and four transistors too.
I have changed IC by LM709 and try LM741 too. I have power to motor but it still doesn't work. I have too much power and I can't adjust to good voltage. I have 17V and 12V instead of 8V and 8V for 45rpm for example.
Maybe a wrong IC reference ?
I have no idea of what to do now, so help is welcome. If someone have advice ...
Thanks
Hi totor,
My bet is that the lamp is open.
Have you checked the wave forms with an oscilloscope? This is a sine wave generator (wein bridge) and nothing more. If you have a square wave, I'd guess the gain control lamp is open. There are two ways to kill the lamp. Run the voltage too high for a long while, or drop the table and the filament breaks.
The two drives are 90° out of phase. At this point, I would re-install the original parts unless they are damaged. The chips are LM709's, but any 709 make will work fine.
I hope the motor is okay after all of this.
-Chris
My bet is that the lamp is open.
Have you checked the wave forms with an oscilloscope? This is a sine wave generator (wein bridge) and nothing more. If you have a square wave, I'd guess the gain control lamp is open. There are two ways to kill the lamp. Run the voltage too high for a long while, or drop the table and the filament breaks.
The two drives are 90° out of phase. At this point, I would re-install the original parts unless they are damaged. The chips are LM709's, but any 709 make will work fine.
I hope the motor is okay after all of this.
-Chris
Hello anatech,
I haven't test sine waves because I have no oscilloscope.
Can I ask you what is the lamp you are talking about ? Is it the bulb that make light when there is too much voltage difference between sine wave ? this bulb is ok and still make light on the board.
I hope I am clear enough, as I said I am not a specialist.
I haven't test sine waves because I have no oscilloscope.
Can I ask you what is the lamp you are talking about ? Is it the bulb that make light when there is too much voltage difference between sine wave ? this bulb is ok and still make light on the board.
I hope I am clear enough, as I said I am not a specialist.
Hi totor,
I hope you are then using an AC voltmeter or a Fluke to measure the amplitudes. DVMs (most) have very poor high frequency response. There is no way to set this table up with cheap meters.
How did you get to this point (why did you start working on the turntable)?
At this point I would center all the pots and run through the adjustment procedure again. Make sure you are using a meter that is flat to 1 KHz, not one that says it's bandwidth goes to 1 KHz (-3dB). Your lamp should never glow. The voltage is far too high in that case.
-Chris
I hope you are then using an AC voltmeter or a Fluke to measure the amplitudes. DVMs (most) have very poor high frequency response. There is no way to set this table up with cheap meters.
Either your controls are badly misadjusted or the lamp is the wrong one.
That lamp should never be lit. At the most, a dull red glow, very faint. But, yes, the lamp appears to be okay. It's a very low current bulb.
How did you get to this point (why did you start working on the turntable)?
At this point I would center all the pots and run through the adjustment procedure again. Make sure you are using a meter that is flat to 1 KHz, not one that says it's bandwidth goes to 1 KHz (-3dB). Your lamp should never glow. The voltage is far too high in that case.
-Chris
Yes I am using a little Voltmeter with AC position.
I have put LM709 14 pin on the board and I obtain :
- between ge and bt : 12 V
- between ge and rt : 9,4 V
I can't adjust voltage between ge and bt, turning the pot is useless.
I can adjust between ge and rt, but the max voltage I can obtain is 9,4 V.
Then I think the problem is I can't adjust the first one but I don't know where it can come from ... any idea ?
I have started this way because the motor has never turned. I just have bought this turntable and I hope to make it work. I already have a TD166 but this 125 seems really better ... not for the moment ;-)
I replaced pretty much everything in mine. When I bought the TT the board was broken in half, some of the components were replaced with wrong values and the solder job was something ugly. I was going to use it for parts but decided to restore it... I already have a couple DIY units. Anyway, LM709 work (as they should). Check out Steve Clarke's Analogue Dept., if you haven't already. The link will take you directly to a page of interest, but click and scroll around, there is a whole Thorens Dept. including a section about TD125/126.
Hi Bartek,
Yup.
Hi totor,
You can not use that meter. It will read low, maybe a lot low. Therefore you need to have a friend or someone with a real AC voltmeter to set this up for you. At least an oscilloscope can be used to approximate the levels. At this point, I'd stick all the original parts back in unless they are defective. This is an important step.
I use a TD-125 MKII. I think it's an excellent table. It is my best one. I sold two others without any regrets after I got mine. I had to rebuild it ("struck by technician"). I have rebuilt a few others over the years as well. I happen to like the Ortofon brand of cartridges on this table.
So, put the old parts back in. STOP and get some help before you cause some damage. There is no way you will be successful with your meter.
Consider this as well. That table is worth a lot. Worth having an expert work on it. Just make sure the bearing and platter shaft are good, also the motor.
-Chris
Yup.
Hi totor,
You can not use that meter. It will read low, maybe a lot low. Therefore you need to have a friend or someone with a real AC voltmeter to set this up for you. At least an oscilloscope can be used to approximate the levels. At this point, I'd stick all the original parts back in unless they are defective. This is an important step.
I use a TD-125 MKII. I think it's an excellent table. It is my best one. I sold two others without any regrets after I got mine. I had to rebuild it ("struck by technician"). I have rebuilt a few others over the years as well. I happen to like the Ortofon brand of cartridges on this table.
So, put the old parts back in. STOP and get some help before you cause some damage. There is no way you will be successful with your meter.
Consider this as well. That table is worth a lot. Worth having an expert work on it. Just make sure the bearing and platter shaft are good, also the motor.
-Chris
Hi totor,
I think you wil be fine if your technician is any good. My advice was based on the fact that you couldn't win with your meter and no 'scope. Let us know how things worked out. It might be helpful for you to explain to the tech that you are trying to learn, and if he can tell you what was wrong.
You are going to love that turntable I think. Look after it and keep it with you a long time.
-Chris
I think you wil be fine if your technician is any good. My advice was based on the fact that you couldn't win with your meter and no 'scope. Let us know how things worked out. It might be helpful for you to explain to the tech that you are trying to learn, and if he can tell you what was wrong.
You are going to love that turntable I think. Look after it and keep it with you a long time.
-Chris
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