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Old 17th Jan 2019, 11:52 am   #41
NorfolkDaveUK
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Default Re: Sony TC-458 not changing speed .

Thank you Freya , I have checked those and they do all seem fine but I will be changing them in due course anyway . .
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Old 30th Jan 2019, 2:06 am   #42
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Default Re: Sony TC-458 not changing speed .

OK so I`ve put this back on the bench . I have stripped the motor , all seems well in there , I have probed the FG with the scope and its giving a sine at 3v p-p , so thats correct , this really has me flummoxed . I spent another couple of hours on it tonight and got no where with it . Really would like to get this one done its a nice machine would be a shame to part it out .
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Old 30th Jan 2019, 10:35 am   #43
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Default Re: Sony TC-458 not changing speed .

What speed is it actually running at?

Lawrence.
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Old 30th Jan 2019, 11:49 am   #44
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Default Re: Sony TC-458 not changing speed .

its not running at any speed mate . Its running too fast period .
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Old 30th Jan 2019, 11:55 am   #45
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Default Re: Sony TC-458 not changing speed .

And you're sure it's not a mechanical problem?

Lawrence.
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Old 30th Jan 2019, 11:56 am   #46
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Default Re: Sony TC-458 not changing speed .

When i probe the rest of the IC with thescope with the ground clip on the chassis , i get a sine at every pin , its supposed to give be a triangle etc according to the "supplement" in the manual .
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Old 30th Jan 2019, 11:57 am   #47
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Default Re: Sony TC-458 not changing speed .

Quote:
Originally Posted by ms660 View Post
And you're sure it's not a mechanical problem?
The switch is working fine bud .
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Old 30th Jan 2019, 11:58 am   #48
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Default Re: Sony TC-458 not changing speed .

I`m still getting really low voltage at the transistor C901
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Old 30th Jan 2019, 11:59 am   #49
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Default Re: Sony TC-458 not changing speed .

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Originally Posted by NorfolkDaveUK View Post
When i probe the rest of the IC with thescope with the ground clip on the chassis , i get a sine at every pin , its supposed to give be a triangle etc according to the "supplement" in the manual .
I've pointed out before that Chassis is not servo ground.

Lawrence.
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Old 30th Jan 2019, 12:01 pm   #50
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Default Re: Sony TC-458 not changing speed .

Yeah I understand that bud , but if I do a continuity test between pin 12 and chassis it is the same on this one .
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Old 30th Jan 2019, 12:33 pm   #51
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Default Re: Sony TC-458 not changing speed .

If it's 0 (zero) ohms it sounds like a short somewhere.

Lawrence.
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Old 30th Jan 2019, 3:44 pm   #52
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Default Re: Sony TC-458 not changing speed .

Check C658 (10uF, 16v) for shorts, or just replace it.
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Old 30th Jan 2019, 5:20 pm   #53
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Default Re: Sony TC-458 not changing speed .

S803 or CP801 bypassing the servo?

Lawrence.
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Old 30th Jan 2019, 8:49 pm   #54
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Default Re: Sony TC-458 not changing speed .

OK Lawrence. I think you may be on to something. Looking at the control switch circuit, pins 5, 6 and 7 are short whether the switch is closed or not. That's not right is it? Resistance is 0.07 with the switch open. Probably the 0.1uF caps there are short. I've got a 0.33uF with a 100ohm resistor in it but it's not going to fit in that hole. I'll get creative for now and fit it in on wires and see if that fixes it and if it does I'll get a better cap.

Last edited by NorfolkDaveUK; 30th Jan 2019 at 9:00 pm.
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Old 30th Jan 2019, 9:13 pm   #55
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Default Re: Sony TC-458 not changing speed .

After removing the panel , the panel its self is working correctly , and the caps aren`t short out of circuit ....


Sorry 8tracker , I missed your comment . board has been recapped bud. A caps checked and correct .

Last edited by NorfolkDaveUK; 30th Jan 2019 at 9:18 pm.
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Old 30th Jan 2019, 11:10 pm   #56
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Default Re: Sony TC-458 not changing speed .

Board replaced and 5 6 and 7 no longer short , but no change to the symptoms . i.e. still no speed control .
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Old 30th Jan 2019, 11:25 pm   #57
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Default Re: Sony TC-458 not changing speed .

I`m getting wrong voltages all over the IC . pin 8 should be 15v and its 4.6v , pin 11 should 1.8v and its 6.4v (this is a different board from the beginning of the issue remember. The board is having no effect on speed whatsoever , the 2 trimmer pots have no effect . So effectively I have no speed control at all . Where is the power for this board coming from and what should it be . I`m struggling with all the little power supplies all over the place .
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Old 31st Jan 2019, 10:22 am   #58
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Default Re: Sony TC-458 not changing speed .

The B+ for the servo board comes from the mains transformer via the rectifier (D651)

Remember that servo ground isn't chassis ground.

Lawrence.
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Old 31st Jan 2019, 11:05 am   #59
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Default Re: Sony TC-458 not changing speed .

Thanks Lawrence , that where I thought it was so I`m not going completely bonkers here ..haha . I have 11v at the cathode which is 5v too low .
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Old 31st Jan 2019, 11:41 am   #60
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Default Re: Sony TC-458 not changing speed .

When I originally got this machine , the power selector was put in the wrong place (it came from Germany so should have been on 220v) . The paper thing is not stuck to the machines any more so my thinking is it had fallen off , the owner had no idea where to put it back and just put it back anywhere . When i get them the first thing I do is check they are on the right setting for where I am , it was on 220v , which is not correct for the UK but good enough , and plugged it in . The lights were really bright and the transformer was making that "uh oh" sound so I unplugged it straight away , looked at the manual and after swearing a lot , put the selector where is should have been (pin 6 , red , 240v) . My fear is , that the original owner , just carried on regardless with the attempted repair and has damaged the transformer , although , its working fine everywhere else . I think the grey tap may have bought it , 5v is a lot to drop . If I move it to 220v (pin 5 vio), it goes up to 12v at the cathode which should be enough to carry it , but its not making any difference . Its driving me nuts I know that ...haha
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