Author Topic: [solved] HM204 auto trigger does not work  (Read 5203 times)

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Offline Armadillo

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Re: HM204 auto trigger does not work
« Reply #25 on: February 25, 2018, 10:12:02 am »
Sarah is right. It should be -12V. I figured it should be typo or another of the inconsistent measurement since you can get minus output out of the opamp.
Worth to check it nevertheless.
 

Offline ChrisGTopic starter

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Re: HM204 auto trigger does not work
« Reply #26 on: February 26, 2018, 05:07:42 pm »
Hi Sarah, Armadillo,

Without the CA082E in the socket pin 8 measures 11.8V and pin 4 measure -11.8V. Socketed Pin 8 and 4 drop to 11.31V and -11.34V respectively. Indeed a measurement mistake from me last Saturday. Awaiting new CA082E's to be delivered this week. Let's see what this brings. Appreciate your help
 

Offline ChrisGTopic starter

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Re: HM204 auto trigger does not work
« Reply #27 on: March 01, 2018, 12:59:42 pm »
Hi all, I've received the 3 CA08Es at home. Shall I just put a new one in and check what happens? Or better to change the VR's and measure the surrounding components before doing so?
 

Offline sarahMCML

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Re: HM204 auto trigger does not work
« Reply #28 on: March 02, 2018, 04:01:34 pm »
Hi again,

Unless you've checked the values of the various resistors  around IC320 with at least one end disconnected from the pub, I'd not worry too much about the lower readings. As suggested, clean the pot wipers gently if you can, then insert a new CA082E into IC320 and see what happens!

Regards, Sarah
 

Offline sarahMCML

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Re: HM204 auto trigger does not work
« Reply #29 on: March 08, 2018, 03:33:54 am »
Hello ChrisG,

Just out of interest, did you get any further with the repair of your oscilloscope's trigger circuits?

Regards, Sarah.
 

Offline ChrisGTopic starter

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Re: HM204 auto trigger does not work
« Reply #30 on: March 08, 2018, 06:36:05 pm »
Hi Sarah,

I've not been able to due this yet due to other priorities. I hope to spend time again next week on this. Actually quite keen on getting is sorted out and will order some cheap components around the CA082E just in case they're faulty. Once you get into it, it can be quite annoying to not have such components readily available.
 

Offline ChrisGTopic starter

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Re: HM204 auto trigger does not work
« Reply #31 on: March 12, 2018, 06:59:17 pm »
Hi Sarah, Armadillo,

I've just slapped in the new CA082E... and... it works! Now remeasuring the voltages and need to put the knobs on too. I did not (yet) change the VR's as it seems to work still. :-|
 

Offline Armadillo

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Re: HM204 auto trigger does not work
« Reply #32 on: March 12, 2018, 07:22:38 pm »
Great! Enjoy.... :-+ :clap: :scared: :-+
 

Offline ChrisGTopic starter

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Re: HM204 auto trigger does not work
« Reply #33 on: March 12, 2018, 08:01:44 pm »
Well... I've also ordered the wrong VR's (too large @ 250mW). So I'm pleased it works now. Thank you for all the help and I have now some spares too :-)
 

Offline sarahMCML

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Re: HM204 auto trigger does not work
« Reply #34 on: March 13, 2018, 02:07:41 am »
Hi Chris,

Well done, and I hope that it'll give you good service into the future.

Regards, Sarah.
 

Offline ChrisGTopic starter

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Re: [solved] HM204 auto trigger does not work
« Reply #35 on: March 14, 2018, 09:16:54 am »
Thank you Sarah and Armadillo. It feels great to have achieved this small accomplishment. Mechanically and functionally it seems to function well. I do believe some sort of calibration would be needed still though and that would be quite the difficult task and there is not so much material on that.
 


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