thorens td125 mkii circuit board

[Rws62]

Can Anyone help me with the electronic adjustment ? i cannot figure out which pots to adjust for each speed .All AC voltages for each speed are good. but the dc voltage in step 1 , 45 speed is 76mv and should not exceed 5mv. Ialso cannot get the strobe to stop in any speed..Thanks ....Rob

[Rws62]

disreguard the dc voltage problem. the problem i'm having is identifying the adjustment pots. there are 3 rows of 3 pots. I'm guesing that the front row left to right, nearest the the switch is 45spd second row 33.3 and back row 16. I'm also guesing ,the first row back to front nearest the electrolytics is for phase 1 adjustment, middle row for pase 2, and last row for speed adjustment.can anyone confirm or corect me on this....Thanks .....Rob

[bubba45]

Have you tried the service manual in here?

http://www.vinylengine.com/library/thorens/td125.shtml

[Rws62]

yes , i have the service manual. the board layout isn't labeled and I'm not familiar with schematics

[bubba45]

OK. I was looking at one of these earlier and I'll see if I can recall it - turn the whole TT upside down with the switches at the front closest to you. You should have the circuit board in front of you but green side up so all you can see are the tracks in the PCB and the bottoms of the solder points for the components?

It should be laid out in front of you as in the 19th picture in this thread:

viewtopic.php?t=29065

I'll call the edge of the PCB closest to you the bottom and the edge furthest away the top.

If so you cannot see any of the components but if you could you would have the 2 large capacitors to the right and the 3 columns of potentiometers in front of you.

The 3 points you want to use to measure with your multimeter are to the left rear of the board just above the multiple solder points for the op amps.
They are the bottom of the 3 solder points for the 3 wires to the motor and are in a rough triangle shape. If you clean around them a little and get a light at the correct angle you should see that they have slightly raised letters next to them.

The left hand solder point of the 3 is 'BL' (has the blue motor wires soldered to it - I think),
'GE' is the centre one (definitely has the 2 black wires for the motor soldered to it) and as is the apex of the triangle of solder points,
'RT' is the right hand one (and I think has the red motor wire soldered to it).

The Potentiometers are arranged in 3 columns of 3 pots to a column and in each column 16rpm is the top, 33rpm in the middle and 45rpm at the bottom closest to you.

The 3 in the left hand column are for fine tuning pitch control,
the middle column is A1 for Phase One for all 3 speeds (voltage measured across GE & RT)
the right hand column is for A2 for Phase 2 for all 3 speeds (voltage measured across GE & BL)

Or as you put them in rows - top row is 16, middle row is 33 and bottom row is 45 and for each speed

left pot is fine tuning pitch control
middle pot is A1 and for adjusting for Phase 1(voltage measured across GE & RT)
right hand pot is A2 and for adjusting Phase 2.(voltage measured across GE & BL)

When adjusting the pots to get the correct voltages going to the motor in each phase for each speed do it with a very light hand as they are very sensitive.

Everything I have described is with the PCB green side up and hopefully makes sense?

[Rws62]

You made it perfectly clear! Thank you so much . I'll reply after the adjustments. Thanks again... Rob

[Rws62]

Thanks Bubba45. All voltages are dead on and steady. The strobe is perfectly still in all speeds. There is a quick vibration upon start up. Quiets after a second or two. Wonder if I should start it up at 16 spd , then switch to 33. ....Rob

[bubba45]

Hi Rob
I'd stick with starting it on 33rpm it shouldn't you any difficulty. Has this deck been in storage for a while? If so give it a good long solid run for a couple of hours. Once a kind VE member had fixed the circuit board on mine I ran them for about 8 hours. Didn't have it playing but just running away in the background one evening.
Does yours have all the original capacitors or have you replaced any?

[Rws62]

I just changed the 2 electrolytic caps. and yes the guy I got it from said it was in storage for about 15 yrs

[bubba45]

In that case I would leave it running for a couple of evenings even if you're not listening to it seems to help the electronics settle down a bit. Also have you put a new belt on? Sometimes they need to be manually stretched a little when you 1st get them.
They are great turntables aren't they? I absolutely love mine. I think they are fantastic pieces of kit.

[Rws62]

Yes,they are Wonderful turntables. I did put a new belt on. Give it a little stretch? By the way .How much oil should I be adding to the platter bearing?

[LousyTourist]

Yes,they are Wonderful turntables. I did put a new belt on. Give it a little stretch? By the way .How much oil should I be adding to the platter bearing?

I filled mine up to the top of the lower bearing race. You can also just go for it, fill it to whatever level, reinstall and remove the platter again, mop up the spilled oil, and consider it good.

[bubba45]

Basically I use the same method as Lousy Tourist with most TT's with this kind of bearing tbh.
I was advised a few years ago to put oil in the bearing well and insert the spindle, when it's settled take it out and see if any oil has spilt over the side. If not add a few more drops to the bearing well and repeat until, when you take the spindle out there is a small amount of oil spilt over the side. That way you know your bearing well is full.
I think the only table I haven't done this with is a Systemdek IIX and that's because it has a spiral oil pump spindle.
As for the belt see how tight it is around the motor pulley and the inner platter. If it sits nice and snug over the 2 of them it's OK.
If it's tight and feels like it only just fits over the 2 with a bit of an effort, take it off and give it a gently stretch along it's length. Not much, but just enough to loosen it a tad.
I think Joel (who used to work for Thorens) has done a tune up guide on here - it's s sticky at the start of the Thorens forum (?) - and he recommends it. I tried it and the belt seems less likely to ride up the pulley and touch the belt guides on the motor when setting it up.

[Rws62]

Filled the oil,Slight stretch to the belt,Nice smooth start up no noise.installed ortofon 2m blue cartridge and holy cow! Amazing soundstage and detail.and they say it takes about 20 hrs to warm up. It is truely the best Turntable I 've heard. Thanks for helping me through my first turntable tweak. I get back after the cartridge break in. Regards...........Rob