Probably should have mentioned this at the beginning�� Had thought it could be the belt. Will get a proper Thorens one. Will have to wait till next month though as wife is getting difficult about all the time and money going on something that's not for her benefit! But I do realise that all the stuff I've done so far is valuable in terms of future proofing.
Hah,mine wants me to put price stickers on all of my equipment so that when I kick the bucket she'll know how much to sell it all for!
And whatever you do,don't let her find out how much this stuff sells for.
They have these funny ideas about new kitchens and bathrooms being far more important than our ''junk collection''😱
And whatever you do,don't let her find out how much this stuff sells for.
They have these funny ideas about new kitchens and bathrooms being far more important than our ''junk collection''😱
Got a new belt and decided to replace all the pots with new ones. Reset all the voltages and got the strobe nice and stable. Turned turntable off and came back to it later and 33rpm was running slow but eventually the strobe became static after about 10 minutes. Switched to 45rpm and again the strobe was bouncing back and forth, not by much, but enough to be able to hear it in the music. Now looking at 33 it is running fast and to get it stable again I have to move the red wheel to the right. So are there any other components on the circuit board that can be replaced that could be causing these issues? I have not changed any resistors yet. I have also sprayed the red speed wheel with De-Oxit about 5-6 times. Thanks.
I would try installing a fixed resistor in place of the speed adjust pot just to see if the problem lies there. You've really got me scratching my head now!!
Do you mean the red speed adjustment wheel? (I have already replaced all the pots on the board) I think this may be causing problems as speed is not staying constant with the wheel in the middle even after I have set voltages/ frequency. Also, it seems that 33 is being affected too. My earlier issues with 45 looked more obvious because the inconsistency was being amplified at the greater speed. Also, I have noticed when adjusting speed with the red wheel, sometimes if i move the wheel one way, the strobe goes in the other! Maybe a replacement wheel may help, if I can find one!
Yes,the speed wheel is the one I was referring to. If this is the problem,finding a replacement will not be easy. Just disconnect one lead and tack in a 2K5 resistor to see if there is any difference in stability.I've always thought that wheel is cool looking,but way too open to the elements.
The only other resistors that affect all speeds are R16 & R26. If they are drifting or noisy,this would produce the same symptoms. Also,did you clean the contacts in the bulb socket? I've seen this cause problems too.
The only other resistors that affect all speeds are R16 & R26. If they are drifting or noisy,this would produce the same symptoms. Also,did you clean the contacts in the bulb socket? I've seen this cause problems too.
Thanks for the advice, again! I will try these things. What is the best way to clean the bulb contacts? Would shooting a blast of De-Oxit D5 up there suffice? Thanks.
Also, it seems that when the unit is turned on after being off for the night it keeps speed well but then begins to drift after 10 mins. Does this suggest heat and resistors?
Clean the bulb pins and socket contacts by spraying control cleaner into the socket and then inserting and removing the bulb several times.
Interesting about the drift timeline; this would indeed suggest a thermal issue.
While it usually affects resistors,I have seen transistors go stupid with temperature changes as well.
Two easy options here: You can get a can of component cooler,or just bring a hot soldering iron close to suspect components.
This is without doubt one of the most uncooperative TD-125's I've seen yet!
Interesting about the drift timeline; this would indeed suggest a thermal issue.
While it usually affects resistors,I have seen transistors go stupid with temperature changes as well.
Two easy options here: You can get a can of component cooler,or just bring a hot soldering iron close to suspect components.
This is without doubt one of the most uncooperative TD-125's I've seen yet!
If the transistors do need looking at I notice that BC147 does not seem to be available anymore. What would be a modern reliable replacement for it?
By the "sound" of it (forgive the pun) it might just be the contacts, but I would still take a closer look at the trimpots. Be careful with de-oxit or other chemicals as older trimpots may not be that stable, and the carbon may go off.
On mine, I replaced all pots with cermet (from PIHER) and it works like a charm. It's an EMT 928 though, slightly different electronics I believe, and the speed is 33/45/78, all three stable and working fine.
Documented my renovation here: EMT 928 Renovierung
This is in german though, hope you can still benefit. otherwise just PM me no problem
good luck
alfred
On mine, I replaced all pots with cermet (from PIHER) and it works like a charm. It's an EMT 928 though, slightly different electronics I believe, and the speed is 33/45/78, all three stable and working fine.
Documented my renovation here: EMT 928 Renovierung
This is in german though, hope you can still benefit. otherwise just PM me no problem
good luck
alfred
My apologies, just re-read and saw that you already replaced the pots.
In my case, a lot of care had to go into setting the 500 Ohm pots, along with the little light bulb that sits on the PCB ("La501"), this is the amplitude control of the oscillator and it needs to be just right to work. You may need to check the sinusoidal signal with a scope, is that something you can do?
In my case, a lot of care had to go into setting the 500 Ohm pots, along with the little light bulb that sits on the PCB ("La501"), this is the amplitude control of the oscillator and it needs to be just right to work. You may need to check the sinusoidal signal with a scope, is that something you can do?
No, I do not have a scope only a multimeter. Is the multimeter not sufficient when setting voltages?
Well, the 500 Ohm pots need to be adjusted so that the output of the oscillator is a nice, good-looking sine wave with low distortion. all the rest of the circuit depends on this.... a multimeter may not be enough for that purpose. A first checkpoint could be to measure the amplitude of the oscillator output at different speed settings - it should always be the same voltage, and no variations over time. but it may not be precise enough to detect the problem.
I noticed that if I turn up too much (lamp starts glowing), some oscillations at low frequency (= reaction speed of the lamp) appeared, and it might be the cause of the problem in your case.
If you have a friend with a scope, that would be perfect, alternatively you could use a little USB scope (from 40 euro onwards) or use the input of the soundcard of a notebook (make sure to run on battery, to avoid ground loops when measuring) and use a voltage divider in front of the input. There is lots of freeware that would be usable for this purpose - we are talking 50Hz or so....
I noticed that if I turn up too much (lamp starts glowing), some oscillations at low frequency (= reaction speed of the lamp) appeared, and it might be the cause of the problem in your case.
If you have a friend with a scope, that would be perfect, alternatively you could use a little USB scope (from 40 euro onwards) or use the input of the soundcard of a notebook (make sure to run on battery, to avoid ground loops when measuring) and use a voltage divider in front of the input. There is lots of freeware that would be usable for this purpose - we are talking 50Hz or so....
just checked, there are lots of scopes on the market that connect to the USB port and use the PC as display, plenty of choice even below 60 euro - might be an investment to consider....
Well on my unit the bulb is on all the time and particularly bright on 45rpm, is this correct?
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