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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 14th Mar 2021, 8:13 pm   #1
The General
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Default Sun CCT-10 Coil Condenser Tester

Found this coil condenser tester on Ebay, probably paid too much for it but I'd been looking for one for ages.

This seems to be a holy grail of Sun testers, I don't think many were sold & they seem to be rare even in the USA. This one is an export 240V model which has to be even more rare. The serial number indicates that it was built in late 1973.

It tests ignition coil output which is displayed on the scope, it also checks condenser leakage, capacitance & series resistance. Plus an ohmmeter feature. Sun get full marks for a clear easy to read meter & the whole unit seems rugged & well made.

Well the whole kit seems in good condition, most importantly the coil test cable with its voltage divider was included, the DC test lead was missing but it was a simple job to make one up with some figure of 8 cable & croc clips. The two pole connector on the other end is an Amphenol microphone connector which I found on EBay.

Opening it up everything was in good order & fortunately unmolested. I found the operating instructions on the internet but as for a schematic, forget it. So as it was a piece of test gear with which I was completely unfamiliar I decided to reverse engineer it & sketch one out. That kept me occupied for a while as even though the unit's operating principles were very simple, the multi pole switches were not.

Well once I'd figured out how the thing worked it turns out to be very basic; the scope timebase is driven at mains frequency, the coil output driving the Y plates directly via the external voltage divider. Condenser capacity is measured by repeatedly charging it to a fixed voltage & then discharging through the meter, the action being performed by a fast acting relay driven by an oscillator. Series resistance appears to be an ESR measurement, achieved by putting the condenser into an RF oscillator circuit & measuring the resulting grid bias voltage of the 12AU7 oscillator valve.

So, little needed to be done in terms of restoration, the electrolytics in the power supply were tired so I replaced them, I also tested the 12AU7 which was OK. One wire was resoldered onto a switch tag & I found a knob to replace the missing one on the calibration control. Then it was time to test.

I found an old coil to try & it worked very well, the scope astigmatism is pretty poor but having found a photo of a CCT-10 display on the internet it seems that is normal. Adjusting the focus control to get a sharp vertical part of the trace gives the best display. The capacitance range was unreliable though, the fast acting relay wouldn't activate reliably, this turned out to be a leaky Zener diode which wasn't regulating the power supply voltage. Naturally, it didn't have any recognisable markings on it.....

So it was down to the empirical method of using a regulated PSU to find the best working voltage which turned out to be 7V. With a new Zener in place (6.2V plus a series diode of 0.7V) the relay buzzed away happily & the capacitance range is surprisingly accurate despite the simplicity of the circuit.

A new power cable & a good clean completed the job.

So in conclusion, the unit's operating principles are extremely simple, almost crude in fact but having said that, it performs its intended function very well & is accurate enough for its intended purpose. Simplicity implies reliability & ruggedness which is important in its intended operating environment.

It will be used, mainly for checking magnetos on small engines.
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Old 14th Mar 2021, 8:19 pm   #2
The General
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Default Re: Sun CCT-10 Coil Condenser Tester

I've attached my hand drawn schematic here, hopefully it may help someone if anyone has a similar unit. There doesn't appear to be much service info for Sun kit on the internet.

Mark
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Old 21st Mar 2021, 10:40 am   #3
vinrads
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Default Re: Sun CCT-10 Coil Condenser Tester

Nice one Mark.

Love the hand drawn diagram not at all like my hand drawn ones, looks professional. I have a old car diagnostic thingy lurking in the overspill shed somewhere, supposed to be getting it working . I keep it covered up out of sight out of mind, this thing is full of valves. It looks like you are into cars so will be putting it to good use.

Mick.
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Old 21st Mar 2021, 10:55 am   #4
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Default Re: Sun CCT-10 Coil Condenser Tester

Well done Mark.

It's good to read a short but interesting success story about something out of the ordinary rather than yet another lengthy thread about a record player which goes nowhere.

You've done other owners of these testers a service by producing a nice clear circuit diagram too.

Should be a very useful tool now it's working again.
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Old 23rd Mar 2021, 4:52 am   #5
Uncle Bulgaria
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Default Re: Sun CCT-10 Coil Condenser Tester

Beautiful drawing - very clear and well laid out. Congratulations on a successful project, too!
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Old 23rd Mar 2021, 6:42 am   #6
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Default Re: Sun CCT-10 Coil Condenser Tester

Superb work, and a useful end result.

DG7-32? I thought those were a European type. A little surprising that Americans designed them in, but needs must if there isn't much choice.

With asymmetric plate drive the astigmatism is, I suppose, inevitable, and will vary over the screen. CRTs running higher EHT tend to be less affected.

You saved it from being turned into yet another CRT clock

David
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Old 24th Mar 2021, 8:56 pm   #7
The General
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Default Re: Sun CCT-10 Coil Condenser Tester

Gents - thank you for the very kind comments regarding my refurbishment story & for my drawing skills. I tried to keep it short & not too verbose & risk a borefest. I've generally put my more unusual restorations in 'Success Stories'. I have a few other unusual items, if anyone is interested I'll post them here as they are finished.
I'll share my drawing technique as it may help someone.
After I've drawn out a circuit it's naturally extremely rough, I'll then sketch it out in a more logical fashion & get it laid out as clearly as possible with a minimum number of lines crossing. Then I'll redraw it very lightly on squared paper & after checking for mistakes, ink it in with a fibre tip drawing pen & a stencil. Then rub out the pencil lines with an eraser. Then I photocopy & scan the result, the copier doesn't reproduce the squared paper, leaving only the drawing. Can all be done in an evening in front of the TV.
David, you're right about the CRT, it's actually a Philips part. The unit is American made but Sun did have a factory in King's Lynn so they may have already been using the Philips tube there. I had to suppress a shudder when you mentioned turning it into a CRT clock.....
For some reason, Sun used the vertical deflection plates for the horizontal sweep & the horizontal plates for the vertical trace. Not sure why, but the sensitivities for each are different so this may be a factor.
Mick, I too have a car diagnostic thingy which is a bit of a long term project, it's a compact version of one of the Sun big box testers. I'll post it here assuming it turns out ok....
BTW, I see you are from Chesterfield, that's Mrs. General's home town, she used to live on Boythorpe Road & still has family there.
Mark.
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Old 26th May 2021, 9:51 pm   #8
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Default Re: Sun CCT-10 Coil Condenser Tester

Very nice CCT-10 schematic, thanks. I purchased a Sun Model 60 Coil-Condenser Tester on E-Bay a while back. This tester appears similar to the CCT-10 except for the packaging. The Model 60 I purchased is missing the tubes and transformers. I was never able to find a schematic that provides the part numbers for these missing parts. But, thanks to your fine schematic, I can now identify the part no. for the tubes and secondary voltages for the transformers.
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Old 3rd Jun 2021, 11:21 am   #9
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Default Re: Sun CCT-10 Coil Condenser Tester

hi Walter, thanks for your kind comments. I believe Sun also made a CCT-10 in a narrow case which could be fitted into a rack of other modules which together make up one of the 'big box' testers. It sounds like this is what you have. If you need any photos to help with your resto, PM me & I'll try & help.

Mark
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