Lockdown project - Sony TC-200 - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

Paulus.d · 3rd May 2020, 7:51 pm

Right side of R5 is 76v.... left side is 29v

During these measurements it's entered fault condition...the volume fades to nothing .. the voltages haven't changed..
Paul

ms660 · 3rd May 2020, 8:35 pm

Next, in playback with the fault condition present check the voltages on V101 and X101...

V101 anode (pin 6) screen grid (pin 8) control grid with volume control turned up (pin 9) and cathode (pin 3)

X101 collector (junction of R105 & C104) base (junction of R104 & R103) and the emitter (junction of R107 & the +ve of C103)

Also determine whether the pre-amp transistor (X101) circuit is the early type (germanium transistor) or the later type (silicon transistor) as the expected voltages are different.

Can we assume that the Rec/Pback switch contacts are clean and making contact and that the tape path's ok?

When measuring the base and emitter voltages you need to know to at least one place after the decimal point on the meter, eg: if say on a higher range the meter says 7 volts but on a lower range it says 7.12 volts it's the lower range meter reading that's of interest.

Lawrence.

DMcMahon · 3rd May 2020, 8:53 pm

Quote:

Originally Posted by Paulus.d

Also ..even in low volume state...the volume control is still active ...

Would make sense.

DMcMahon · 3rd May 2020, 8:56 pm

Quote:

Originally Posted by Paulus.d

Right side of R5 is 76v.... left side is 29v

During these measurements it's entered fault condition...the volume fades to nothing .. the voltages haven't changed..
Paul

So very close to schematic (Playback) values.

DMcMahon · 3rd May 2020, 9:01 pm

Quote:

Originally Posted by Paulus.d

okay here's what I measured...

Pin 7 ....154v
Pin6 ....stablised at 116v
Pin 5 ..... 0 but hums when touched by the probe
Pin 1 ....7.2v
point 3 ....9.7v
point 4 ...... 77v

Paul

Point 3 is the left side of R5 so why is the reading substantially different from Post 42 reading of R5 left side ?

Paulus.d · 3rd May 2020, 9:12 pm

Okay...
Pin 6.... 19.2v
Pin 8..... 0.82v
Pin 9..... 0... and humming when touched
Pin 3 .....0.26v

Record switches and heads are clean

Don't know how to find transistor type... Channel 2's one is a different number and design , OC140

DMcMahon · 3rd May 2020, 9:14 pm

How is the quiet output being determined, i.e. internal speakers (with Line output set to Speaker), line output from Jack socket to Hi-Fi/High impedance headphones (output set to Line), Line output from auxiliary DIN to Hi-Fi or external speaker (output set to speaker) connected to Jack socket.

Paulus.d · 3rd May 2020, 9:17 pm

Quote:

Originally Posted by DMcMahon

Quote:

Originally Posted by Paulus.d

okay here's what I measured...

Pin 7 ....154v
Pin6 ....stablised at 116v
Pin 5 ..... 0 but hums when touched by the probe
Pin 1 ....7.2v
point 3 ....9.7v
point 4 ...... 77v

Paul

Point 3 is the left side of R5 so why is the reading substantially different from Post 42 reading of R5 left side ?

when I measured Point 3 I must have got confused and measured the wrong side of R105...
Paul

DMcMahon · 3rd May 2020, 9:26 pm

Quote:

Originally Posted by Paulus.d

Okay...
Pin 6.... 19.2v
Pin 8..... 0.82v
Pin 9..... 0... and humming when touched
Pin 3 .....0.26v

Record switches and heads are clean

Don't know how to find transistor type... Channel 2's one is a different number and design , OC140

Screen grid pin 8 is particularly low, try and check out R113/C107.

Paulus.d · 3rd May 2020, 9:40 pm

Screen is at .82 from switch on passed fault condition....reading remains the same...
also update read Pin 9 while varing the volume level ..ranges from 0 to 1.1 during fault condition..

Paulus.d · 3rd May 2020, 9:47 pm

R113 and C107 are linked to Pin 1 of V101. voltage reading starts at 36v then stablises to 18v ... fault condition kicks in ..reading does not change
Paul

DMcMahon · 3rd May 2020, 10:09 pm

Hi Paul,

Are you sure that is V101, my reading of the schematic shows junction of R113 and C107 connected to pin 8 of V101 and you measured 0.82V there before ?

David

DMcMahon · 3rd May 2020, 10:20 pm

I can see where I am going wrong, pin 8 is the suppressor grid, the screen grid is pin 1, but pin 1 is not shown on the schematic and it looked like the screen grid was pin 8 on the schematic.

Paulus.d · 3rd May 2020, 10:24 pm

Okay ....
Have noticed that the amp produces hum when Pin 9 is probed..... so the issue is before this point ... the music fades away but the amp at Pin 9 is still amplifing...

A big thank you to you all for helping me with this ...I have no idea how todo this on my own and actually it's very interesting work ...
Regards Paul

ms660 · 4th May 2020, 11:08 am

Pin 8 instead of pin 1 was my error, my apologies, I was going by the schematic without checking the PCB layout.

I would check the transistor voltages next and also find out what's printed on the case of the transistor in terms of ID, either that or ID the value of R107, that should tell us whether the transistor in the preamp is germanium or silicon and therefore which voltages on the schematic to compare with the voltages measured.

It's funny how things stick in the mind, I remember that head type number PP30-4202 from when I used to service them back in the 1970's.

Lawrence.

DMcMahon · 4th May 2020, 12:24 pm

Poor schematic not identifying pin 1 (screen grid) and showing pin 8 correctly next to the Suppressor grid but also right next to the Screen grid, it fooled me.

DMcMahon · 4th May 2020, 12:27 pm

Quote:

Originally Posted by DMcMahon

Quote:

Originally Posted by Paulus.d

Okay...
Pin 6.... 19.2v
Pin 8..... 0.82v
Pin 9..... 0... and humming when touched
Pin 3 .....0.26v

Record switches and heads are clean

Don't know how to find transistor type... Channel 2's one is a different number and design , OC140

Screen grid pin 8 is particularly low, try and check out R113/C107.

The OC140 does not appear to be an original listed transistor, does the soldering look like it may have been disturbed/replaced ?

Is channel 2 the problem channel with now signal ?

DMcMahon · 4th May 2020, 2:42 pm

Quote:

Originally Posted by DMcMahon

Quote:

Originally Posted by DMcMahon

Quote:

Originally Posted by Paulus.d

Okay...
Pin 6.... 19.2v
Pin 8..... 0.82v
Pin 9..... 0... and humming when touched
Pin 3 .....0.26v

Record switches and heads are clean

Don't know how to find transistor type... Channel 2's one is a different number and design , OC140

Screen grid pin 8 is particularly low, try and check out R113/C107.

The OC140 does not appear to be an original listed transistor, does the soldering look like it may have been disturbed/replaced ?

Is channel 2 the problem channel with now signal ?

Typo error in last line above, should have read "Is channel 2 the problem channel with low signal ?"

ms660 · 4th May 2020, 2:49 pm

When I worked for Sony we had reams of manual amendments and revisions for tape recorders and other stuff, here's a better set of schematics showing the valve pinouts and the transistor pre-amp differences:

http://sportsbil.com/sony/TC/TC-200.pdf

Lawrence.

DMcMahon · 4th May 2020, 2:59 pm

Certainly a lot better, no ambiguity now with pins 1/8

Also see it identifies the output Pentode as 30A5 which I had seen on the artwork drawing, but IT was not shown on the schematics I was looking at and parts list called it 30M-P23.

3rd May 2020, 7:51 pm	#41
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Lockdown project - Sony TC-200 Right side of R5 is 76v.... left side is 29v During these measurements it's entered fault condition...the volume fades to nothing .. the voltages haven't changed.. Paul

3rd May 2020, 8:35 pm	#42
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Lockdown project - Sony TC-200 Next, in playback with the fault condition present check the voltages on V101 and X101... V101 anode (pin 6) screen grid (pin 8) control grid with volume control turned up (pin 9) and cathode (pin 3) X101 collector (junction of R105 & C104) base (junction of R104 & R103) and the emitter (junction of R107 & the +ve of C103) Also determine whether the pre-amp transistor (X101) circuit is the early type (germanium transistor) or the later type (silicon transistor) as the expected voltages are different. Can we assume that the Rec/Pback switch contacts are clean and making contact and that the tape path's ok? When measuring the base and emitter voltages you need to know to at least one place after the decimal point on the meter, eg: if say on a higher range the meter says 7 volts but on a lower range it says 7.12 volts it's the lower range meter reading that's of interest. Lawrence. Last edited by ms660; 3rd May 2020 at 8:47 pm. Reason: additional info

3rd May 2020, 9:12 pm	#46
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Lockdown project - Sony TC-200 Okay... Pin 6.... 19.2v Pin 8..... 0.82v Pin 9..... 0... and humming when touched Pin 3 .....0.26v Record switches and heads are clean Don't know how to find transistor type... Channel 2's one is a different number and design , OC140

3rd May 2020, 9:14 pm	#47
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,604	Re: Lockdown project - Sony TC-200 How is the quiet output being determined, i.e. internal speakers (with Line output set to Speaker), line output from Jack socket to Hi-Fi/High impedance headphones (output set to Line), Line output from auxiliary DIN to Hi-Fi or external speaker (output set to speaker) connected to Jack socket.

3rd May 2020, 9:40 pm	#50
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Lockdown project - Sony TC-200 Screen is at .82 from switch on passed fault condition....reading remains the same... also update read Pin 9 while varing the volume level ..ranges from 0 to 1.1 during fault condition..

3rd May 2020, 9:47 pm	#51
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Lockdown project - Sony TC-200 R113 and C107 are linked to Pin 1 of V101. voltage reading starts at 36v then stablises to 18v ... fault condition kicks in ..reading does not change Paul

3rd May 2020, 10:09 pm	#52
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,604	Re: Lockdown project - Sony TC-200 Hi Paul, Are you sure that is V101, my reading of the schematic shows junction of R113 and C107 connected to pin 8 of V101 and you measured 0.82V there before ? David

3rd May 2020, 10:20 pm	#53
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,604	Re: Lockdown project - Sony TC-200 I can see where I am going wrong, pin 8 is the suppressor grid, the screen grid is pin 1, but pin 1 is not shown on the schematic and it looked like the screen grid was pin 8 on the schematic.

3rd May 2020, 10:24 pm	#54
Paulus.d Hexode Join Date: Mar 2008 Location: Margate, Kent, UK. Posts: 355	Re: Lockdown project - Sony TC-200 Okay .... Have noticed that the amp produces hum when Pin 9 is probed..... so the issue is before this point ... the music fades away but the amp at Pin 9 is still amplifing... A big thank you to you all for helping me with this ...I have no idea how todo this on my own and actually it's very interesting work ... Regards Paul

4th May 2020, 11:08 am	#55
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Lockdown project - Sony TC-200 Pin 8 instead of pin 1 was my error, my apologies, I was going by the schematic without checking the PCB layout. I would check the transistor voltages next and also find out what's printed on the case of the transistor in terms of ID, either that or ID the value of R107, that should tell us whether the transistor in the preamp is germanium or silicon and therefore which voltages on the schematic to compare with the voltages measured. It's funny how things stick in the mind, I remember that head type number PP30-4202 from when I used to service them back in the 1970's. Lawrence.

4th May 2020, 12:24 pm	#56
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,604	Re: Lockdown project - Sony TC-200 Poor schematic not identifying pin 1 (screen grid) and showing pin 8 correctly next to the Suppressor grid but also right next to the Screen grid, it fooled me.

4th May 2020, 2:49 pm	#59
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Lockdown project - Sony TC-200 When I worked for Sony we had reams of manual amendments and revisions for tape recorders and other stuff, here's a better set of schematics showing the valve pinouts and the transistor pre-amp differences: http://sportsbil.com/sony/TC/TC-200.pdf Lawrence.

4th May 2020, 2:59 pm	#60
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,604	Re: Lockdown project - Sony TC-200 Certainly a lot better, no ambiguity now with pins 1/8 Also see it identifies the output Pentode as 30A5 which I had seen on the artwork drawing, but IT was not shown on the schematics I was looking at and parts list called it 30M-P23.