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Cheap oscilloscope for setting up a Technics SP-10
Cheap oscilloscope for setting up a Technics SP-10
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Old 26th June 2011, 05:04 PM   #11
Mooly is offline Mooly  United Kingdom
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Cheap oscilloscope for setting up a Technics SP-10
I see the time is ticking...

20mhz is fine for 99% of the stuff in these forums. Dual trace, yes.
The Hitachi V series were good, I used to use a 50mhz bench one as part of the day job.

Given a choice (not sure what this is) you should look for one with a high final anode voltage to the CRT as that gives a bright sharp trace. Something of the order of 6kv or more.
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Old 26th June 2011, 05:13 PM   #12
Andy5112405 is offline Andy5112405  United Kingdom
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I've always used Tektronics.

A working 465 or 475 can be got for around 100.

My current one is a 468 Storage Scope that I got at Government Surplus for 200.

Keeping them accurately calibrated is a different matter, but that doesn't normally concern the DIYer.
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Old 26th June 2011, 05:33 PM   #13
johnm is offline johnm  United Kingdom
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Thanks Mooly/Andy

Just realised that that Hitachi is collection only - so I'll have to leave that one.

There's a Tektronix 475 currently for 40 which ends in a couple days so I'll keep my fingers crossed for that (he says, probably having scuppered his chances at getting it cheap by mentioning it on a public forum!).

Having gotten the SP-10 back together again, it's all working fine. Strobe is rock steady on 33 & 45rpm, but I noticed on 78rpm the strobe moves VERRYYY very slightly to the left, and then to the right every couple seconds or so. Perhaps this is normal, though I suspect that I probably do need to re-adjust those pots using an oscilloscope to ensure everthing is absolutely spot on (damn... I hate being a perfectionist!). So really I'll be buying the oscilloscope just for that as I cannot afford to get it serviced.

Last edited by johnm; 26th June 2011 at 05:38 PM.
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Old 26th June 2011, 05:36 PM   #14
Andy5112405 is offline Andy5112405  United Kingdom
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TBPO calibration is a bit of a fad. For the DIYer the original calibration is probably OK.

Just ask him if the vertical deflection amplifiers both work OK. They are irreplaceable if damaged.
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Old 26th June 2011, 05:37 PM   #15
Andy5112405 is offline Andy5112405  United Kingdom
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Whoops I should have said Y Attenuators.

The input attenuators are very sensitive. If they have been over-voltaged then they will be goosed.
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Old 26th June 2011, 05:58 PM   #16
Mooly is offline Mooly  United Kingdom
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Cheap oscilloscope for setting up a Technics SP-10
Gould,
Gould OS300 Dual trace 20MHz oscilloscope and probes | eBay UK

Why don't you mark the pot (VR102) and just tweak it slightly left and right. I haven't looked at the circuits for turntable and I might be wrong, but I wouldn't be surprised if it doesn't make much difference until the point where lock is lost
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Old 27th June 2011, 11:23 AM   #17
johnm is offline johnm  United Kingdom
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Thanks for the Ebay link Mooly - I got outbid by a POUND in the last 20 seconds! Arghhhhhh

I'll try for that Tektronix one if it doesn't go sky high.

I would try the pots, but it looks so complicated (judging by the rows upon rows of chips and transistors and the circuit diagrams) I wouldn't want to run the risk of making anything worse. It might actually be spot on as it is, but I have a feeling that slight strobe 'judder' on the 78rpm setting shouldn't be there on this direct drive motor system, and that will translate into flutter when listening... though to be honest I'll probably never play a 78!

You can see how complex a circuit it is here: http://downloads.nakedresource.com/v...ro_service.pdf
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Old 27th June 2011, 11:54 AM   #18
Andy5112405 is offline Andy5112405  United Kingdom
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If you really want a 'scope from E-Bay don't risk bidding for it.

Decide on how much you want to pay as a MAXIMUM price. Don't bid until the last 10 seconds and bid that maximum amount. That takes away the temptation to overbid and will always win against the opportunist bidders who hope to get something for nothing.

If you can risk the last 3 seconds then even better.

Good Luck.
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Old 27th June 2011, 01:50 PM   #19
kevinahcc20 is offline kevinahcc20  United States
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Andy has it right...early bidders on eBay simply dither the price up where the only important bid is the final one. The right strategy is to set your limit price and bid that in the last seconds.
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Old 27th June 2011, 07:25 PM   #20
johnm is offline johnm  United Kingdom
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I usually do wait until the last possible moment to bid, but in this instance I bid with 20 seconds to go as there hadn't been any bid 'action' up till that point. That'll teach me to be so blasse!
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