Must learn to leave thing's alone. [solved]

steve j · 6750

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Offline steve j

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on: April 02, 2015, 04:14:25 PM
Thought i might clean up a few ordinary looking solder joint's,No problem flowed some fresh solder on joint's but thought while i have the Smash on the bench would do some voltage check's.Make note to myself in the future not to drop the probe from DMM across terminals on the transformer 6.3v.Checked the transformer seems OK but after changing out 5818 diodes just in case, powered Smash back up fried 2 diodes after 30 seconds.Any ideas where to go from here.Hang head in shame!!!!!
With the transformer connected only to the mains 240v.
175v
6.5v
Please try not to Laugh too much......
Steve.
« Last Edit: May 10, 2015, 08:48:52 AM by Caucasian Blackplate »


Offline Paul Birkeland

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Reply #1 on: April 03, 2015, 10:18:37 AM
What was the original problem that lead you to replace the 1N5818 diodes?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline steve j

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Reply #2 on: April 03, 2015, 11:33:25 AM
After dropping the probe across the transformer terminals and had checked transformer voltages i put the Smash back in to my setup only to have a hum coming through the speakers,switched off and checked transformer again seemed fine thought i may have shorted out a diode so changed out the diodes only to have them fail.Have ordered some new in5818 diodes from RS,the diodes i had on hand were purchased off ebay,will try new diodes and go from there.
Regards, Steve.


Offline steve j

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Reply #3 on: April 22, 2015, 02:11:46 PM
Fitted diodes and 10000uf16v cap switched on Smash and a whisper of smoke came up from the transformer Doh!!!
Guess i need to order a new transformer another cap and probably filament regulator board.

Steve.


Offline Paul Birkeland

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Reply #4 on: April 23, 2015, 05:46:04 PM
The transformer is very difficult to destroy, you probably roasted something mounted above the transformer.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline steve j

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Reply #5 on: April 24, 2015, 12:25:33 AM
Checked out transformer and Paul you are correct ,the transformer still livesI will have to check what I have stuffed up.
Steve.


Offline Grainger49

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Reply #6 on: April 24, 2015, 02:25:13 AM
The high current that fried your diodes also molested your power supply caps.  It might be prudent to replace them as well.  Verify that the resistors in the power supply are within 10% of the labeled value.  If they are out of spec, replace them. 

The closer to the transformer the worse the destruction.  One resistor might be bad the next one Ok.


Offline steve j

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Reply #7 on: April 24, 2015, 12:08:08 PM
Thank,s Grainger I was not sure if the power supply caps needed to be replaced but for the small cost i will change caps and resistors.The bit that annoys me is the Smash sounded So good before my brain fade.
Steve.


Offline steve j

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Reply #8 on: May 10, 2015, 12:46:48 AM
Smash is back up and running thank's for the help Grainger and Paul.
Steve.


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