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13 hours ago, RogerH said:

Hi John,

it is entirely possible that the Resistor R1 has simply been cooking over the years and finally popped for no other reason than being fed up.

Perhaps it was a little under rated power wise (t save money - just like a TRiumph)

 

Roger

Quite possible, have seen that on old cct's

You could just replace R1 and then stick a meter across it and switch on if there is a large volt drop then there is another fault on the board, too much current being drawn thru the 24V supply.
Can you send me the notes and diagrams. I think you have my email.

mike

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Mike, I'm afraid not, or not that I can find!  PM me please?

Access to that resistor is nigh impossible when the board is fitted to the  machine.    No doubt this is why the 'touch posts' were included in the design.

Edited by JohnD
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I tested the board on the bench this am.    The identified capacitors were probably short circuited (very small resistance, or a fixed resistance on the multimetet).   I learn that these are "tant caps", tantalum capacitors, that are notorious for failing, sometimes catastrophicly, so earning the name "Match heads"!   So I checked a few more, and to my unskilled hand they seemed odd too.     There may be a lot wrong with this board, that the burnt resistor is the only symptom.    I do not admire my ability with a soldering iron - sorry, Roger! - and there may be a lot of soldering to do!      So I've decided to take up the offer of my friend Nigel of the south west MC, who has a small collection of these things, to do his best with it. 

Sorry to let the side down and not DiY, but I fear I would make the board worse, not better, and when it doesn't work at all right now, that's not easy!

Thanks to all here who have advised me! I'll let you know progress.

John

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John

Understandable. Electronics can seem like a black art and always has a mind of its own even when you think you understand it......
If your friend fixes it we need a full breakdown of what had failed!

cheers

mike

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  • 4 months later...

I have a crypton Cruisemate 440 with exactly the same board and fault .It appears to be a common fault and mate is fixing it for me. He thinks a transistor elsewhere has blown out causing the fault .last Week I was giving a talk at a local car club about tune up machines and their club Crypton 336 machine had also blown the same resistor . my main machine is a TICrypton machine ,series 2000 which is different in that it has a small box called a EAM run by an Ancient PC with floppy Drive. I am searching for books, leads etc to run this one but i also have a few circuit diagrams for 1970's Crypton machines, the ones with valves. If anyone is interestedI can copy them down but i need the exact model number as there are a lot of them .And in no particular order. 

Cheers! Ron B.

IMG_0431.jpg

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My contact elsewhere has vey kindly replaced the "tant caps" on my boards, but to no avail!    So if you know of someone whop can fix these near antiques, I'd be most grateful for their details.

I have some geeral instruction manuals that must have come wiht the machine, but no maintenace or repair details.   My Machine is a 335, Model No.335X/FA10360 and Serial No. CTS51967/5.   Apart from the "EAM" (the box on the bottom tray?) yours is near identical to mine.

John

Crypton 1.jpg

Edited by JohnD
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  • 1 month later...

Hi guys - I am a classic car owner (but not a TR) who has a Crypton 335 diagnostic analyser. Like John's, mine also has a screen with no trace.

Following the advice on this forum, I discovered that on board 8, R1 had fried. The tantalum capacitor C33 had turned black and the plastic spacer between TR24 and the PCB showed signs that TR24, too, had got quite hot. Again following advice on this forum, I replaced C10, C33, TR24, IC1, IC2 and of course R1. The good news is that this has stopped R1 frying but the bad news is that there is still no trace on the screen. I guess something else must be amiss.

I only add this post for the sake of completeness and for the sake of those using search engines to try and troubleshoot Crypton 335 faults.

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  • 2 months later...

I worked on these machines when they were new and still do. If they are not used for a number of years then the tantalum beads can go short circuit and may take out other components. These caps can be 4.7 or 10 micro and usually orange in colour. They may or may not burn up but will measure s/c with an ohm meter

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