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Old 27th Apr 2020, 6:21 pm   #1
Paulus.d
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Default Lockdown project - Sony TC-200

Got my Sony TC-200 out of storage as a lockdown time filler .... its got a missing outputtransformer on one channel , the other is very quiet....

Ill check the caps and voltages to hopefully fix the low output but cant replace the OT....
Can a high impedence output be taken from the circuit at a point before the output transformer so I can hook it up to an external amp and still use it ?
Regards Paul
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Old 29th Apr 2020, 5:25 pm   #2
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Default Re: Lockdown project - Sony TC-200

A real shame the output transformer is missing and a shame that Sony added the high output impedance outputs (Jack and Auxiliary DIN) on the output side of the output transformer.

It should be possible will need some studying.
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Old 29th Apr 2020, 6:23 pm   #3
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Default Re: Lockdown project - Sony TC-200

Yes...I'd noticed that... silly Sony designers, even the VU recording meters come after the output transformers...

I've been playing with this one today using my DVM and noticed a resistance between the 2 100mf caps in the one can ..yes there is a 150ohm resistor there so I disconnected it ..the resistance was still there...
I replaced the cap with a 32mf-32mf ... channel one sprange to life .... however the cap got a bit warm so I stopped.

I recapping is gonna be nessary ...
Regards Paul
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Old 29th Apr 2020, 6:47 pm   #4
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Default Re: Lockdown project - Sony TC-200

It's an efficient design, loudspeaker, line out, record output, negative feedback, level reference, all essentially from one place.

The output valves an odd ball, nearest near sub I can find is a 50C5...HL92.

Lawrence.
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Old 2nd May 2020, 1:40 pm   #5
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Default Re: Lockdown project - Sony TC-200

100uf caps came in ...fitted them only to find it the same.....chanennel plays normally for 30 seconds , then it rapidly goes quiet..
It does sound like a cap breaking down to me but i've no idea where to even startAnyone give me any pointers ... I'd love to get this working
Regards Paul
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Old 2nd May 2020, 2:09 pm   #6
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Default Re: Lockdown project - Sony TC-200

Quote:
Originally Posted by Paulus.d View Post
Yes...I'd noticed that... silly Sony designers, even the VU recording meters come after the output transformers...

I've been playing with this one today using my DVM and noticed a resistance between the 2 100mf caps in the one can ..yes there is a 150ohm resistor there so I disconnected it ..the resistance was still there...
I replaced the cap with a 32mf-32mf ... channel one sprange to life .... however the cap got a bit warm so I stopped.

I recapping is gonna be nessary ...
Regards Paul
The 150 ohm resistor should not be disconnected, from the circuit it is R1 a 150 ohm wire wound 4 watt that connects between the 2 can electrolytic capacitors (in the same can), C1-1 (100uF) and C1-2 (100uF). I believe the function of R1 is a voltage dropper/current limiter and would expect the output of R1 at C1-2 to be a somewhat lower voltage than the other end of R1 at C1-1 (145V verses 125V in Playback mode according to schematic).

This is quite common where the dropper resistor (s) is physically fitted at the joint can terminals.

There also should be a 1k resistor going off from C1-2/R1 to another 100uF C3.
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Old 2nd May 2020, 2:15 pm   #7
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Default Re: Lockdown project - Sony TC-200

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Originally Posted by Paulus.d View Post
100uf caps came in ...fitted them only to find it the same.....chanennel plays normally for 30 seconds , then it rapidly goes quiet..
It does sound like a cap breaking down to me but i've no idea where to even startAnyone give me any pointers ... I'd love to get this working
Regards Paul
Would suggest you monitor the main DC HT voltages to see what is happening to the voltages using a DVM/DMM or analogue volt meter if you have one.
Note - at initial switch on it is not unusual for the HT voltages to start higher than normal and then as valves warm up/stabilise, after around 15 -30 secs the voltages should drop down/stabilise to normal running values.
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Old 2nd May 2020, 2:25 pm   #8
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Default Re: Lockdown project - Sony TC-200

Yep I connected the caps back up and resistors as per the drawing. It takes 30 sec or so to warm up them plays for 30-60secs ..thenfades away to nothing ...
This is on channel one....Channel two is missing the OT...could that be dragging the volts down? How can I disconnect this channel two so that it's not trying towork? pull the valves??
Regards Paul
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Old 2nd May 2020, 2:40 pm   #9
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Default Re: Lockdown project - Sony TC-200

I would not have thought that the missing output transformer is causing the voltage to drop. Try removing the output valve on channel 2 and if necessary also the pre-amp valve.
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Old 2nd May 2020, 2:42 pm   #10
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Default Re: Lockdown project - Sony TC-200

If the unit is of a vintage that has paper capacitors it is possible that one of these could be leaking/passing DC and leading to voltage reduction.
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Old 2nd May 2020, 2:49 pm   #11
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Default Re: Lockdown project - Sony TC-200

Check C110 (C210) at anode of output valve to output transformer and C2 at input to C1-1, these are oil filled paper and potentially could be troublesome.
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Old 2nd May 2020, 3:04 pm   #12
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Default Re: Lockdown project - Sony TC-200

According to myDVM, the voltage at the point of C1 C2 is 194V...then massively decreases to 111v over 30 seconds... C1 -1 C1-2 are new 100uf 400v ones..
Regards Paul
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Old 2nd May 2020, 3:08 pm   #13
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Default Re: Lockdown project - Sony TC-200

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Originally Posted by DMcMahon View Post
Check C110 (C210) at anode of output valve to output transformer and C2 at input to C1-1, these are oil filled paper and potentially could be troublesome.
I swapped them over ....it made no difference... is itunlikely there'd both go down together?
Paul
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Old 2nd May 2020, 6:24 pm   #14
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Default Re: Lockdown project - Sony TC-200

Looked through my junk box ... havent got spares for C2 , C110 - C210 paper caps....
Dont know about testing them as the behavior would suggest the cap is breaking down under load?
Paul
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Old 2nd May 2020, 6:33 pm   #15
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Default Re: Lockdown project - Sony TC-200

If C110 or C210 were leaking or S/C it wouldn't affect the HT to any great extent although it could affect the sound output depending on what the resistance was, I would change C108 and C208 and C2 as a matter of course as well as them.

Lawrence.

Last edited by ms660; 2nd May 2020 at 6:37 pm. Reason: removed and added some text
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Old 2nd May 2020, 6:46 pm   #16
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Default Re: Lockdown project - Sony TC-200

Quote:
Originally Posted by Paulus.d View Post
According to myDVM, the voltage at the point of C1 C2 is 194V...then massively decreases to 111v over 30 seconds... C1 -1 C1-2 are new 100uf 400v ones..
Regards Paul
Yes a large drop, maybe more than I would expect. When you say "point of C1 C2" did you mean "C1-1 C2" or C1-1 C1-2" ?

For "C1-1 C2" the 111V would be around 34V low to schematic, for "C1-1 C1-2" the 111V would be around 14V to schematic, the schematic values of course are only nominal values.

Try removing the valves 1 at a time to see if any have any big effect on the final voltage.
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Old 2nd May 2020, 7:49 pm   #17
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Default Re: Lockdown project - Sony TC-200

Quote:
Originally Posted by Paulus.d View Post
Quote:
Originally Posted by DMcMahon View Post
Check C110 (C210) at anode of output valve to output transformer and C2 at input to C1-1, these are oil filled paper and potentially could be troublesome.
I swapped them over ....it made no difference... is itunlikely there'd both go down together?
Paul
Agree that unlikely that both have failed. If you can measure capacitance would not do any harm to measure them and the ones that Lawrence suggest to make sure they do measure as capacitors, i.e. have not shorted, additionally also can measure their resistance to make sure not shorted.
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Old 2nd May 2020, 7:52 pm   #18
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Default Re: Lockdown project - Sony TC-200

Even though your HT drops a lot and is lower than schematic value I am not sure if that itself is the fault or just a symptom or maybe even normal in this case. Even with lower voltage than schematic value would still expect some sort of half reasonable sound level.
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Old 2nd May 2020, 8:01 pm   #19
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Default Re: Lockdown project - Sony TC-200

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Originally Posted by Paulus.d View Post
Looked through my junk box ... havent got spares for C2 , C110 - C210 paper caps....
Dont know about testing them as the behavior would suggest the cap is breaking down under load?
Paul
If you had an insulation tester/meggar you could test the capacitors at a voltage close to their operational voltage. I personally would just disconnect one end leaving the other end connected to the DC supply and measure the disconnected end of the capacitor for any DC voltage passthrough, would not expect to get much, if any voltage on a good capacitor. This involves working on live voltage so personal safety has to be your main consideration.

Also realise that capacitors may well hold a voltage charge for some considerable time.

Also before attempting to measure capacitors for resistance/capacitance ensure they are fully discharged first.
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Old 2nd May 2020, 8:12 pm   #20
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Default Re: Lockdown project - Sony TC-200

For C108/C208 if you do not have any immediate replacements you could just measure the DC voltage at their connections to the control grid pin 5, should be very small DC voltage present if caps are good. They are not listed as paper but could still be leaky.
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