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Oh Blimey I bought a CNC Lathe !!!!

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awemawson:
 :bang: Well I MAY have been chasing Red Herrings  :bang:

I was doing some tests with a load on the 5v rail to see the effect on the power V-Fet that is the main switching element, and sure enough with a load on. the 'On Time' increases (as does the frequency). Then it occurred to me, suppose that unloaded (as I've previously been testing), insufficient current is passing for the + & - 15 volt rails to be established, and the feedback loop is only monitoring the 5v rail? So I put a moderate load on the +15v rail (or rather the feed to the input of the 7815 which is out of circuit), and spun it up still with a load on the 5v rail - wohay - yes - volts! So on a roll I put the 7815 back in circuit, and we are developing 15.1 volts across the +15v rail. Can't do the -15 7915 as the postman hasn't brought them yet.

... this may be positive progress, but I'm keeping my fingers crossed  :wave:

Fred Bloggs:
Andrew

Glad to see that progress is being made  :beer:

Switch mode psu's are, and always will be a pain in the rear  :bang:

In the mid 90's I used to work for for a major British engineering company that produced power control equipment, One of my jobs their was to look after a production line that built approx 50,000 switch mode psu for for their products, I was responsible for the custom and COT's test equipment and supporting the shop floor staff and I spent upto 20 hours a week looking for obscure faults ( the designers where never interested as it was current product, they only interested in the new toys)

Nearly all of the shop floor staff where ladies - hundreds of them!! :bugeye: but that is another story.

Fred

DMIOM:
Fred,
your message just brought back a memory.

Aeons ago (before PCs, in fact I think it was before CP/M and WordStar) I was responsible for a dedicated word processing system made by "Xionics". One of the secretaries had endless trouble with her workstation hanging. We gave her several replacement workstations, she crashed them all; workstations that crashed for her worked OK for the other staff; and if she went to someone else's desk she would crash their workstation. 

We joked that it was due to her 'magnetic personality, but one of my colleagues then discovered it was due to a combination of silk and satin  :zap:

Dave

SemiSkilled:

--- Quote from: DMIOM on May 03, 2013, 07:28:15 AM ---
but one of my colleagues then discovered it was due to a combination of silk and satin  :zap:

Dave

--- End quote ---


Ah yes, research is a wonderful thing   :D


Lee

awemawson:
 :ddb: :ddb: :ddb: RING THE CHURCH BELLS  :ddb: :ddb: :ddb:
 :clap: :clap: :clap: Let everyone have Monday as a Holiday :clap: :clap: :clap:

Postie brought the 7915 today, I rapidly installed it and - plugging the logic card and option card into the intermediate power board (which had the fault) ...whoohay :  we get "A6" which is "OK I'm here, now talk to me"

Pictures:

A/ Logic card loaded on, powered up showing "A6"
B/ Overview of same
C/ Re-assembled on high power chassis and still "A6"

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