newb question on resistance reading

tamarind · 1954

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Offline tamarind

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on: May 23, 2014, 10:39:56 PM
Hi

I'm up to the resistance checks on my crack. When the probes on my overly cheap DMM are touched together on 200 setting I get a reading of 1.2 ohms. When I do my tests on the crack for the terminals that should show 0ohms I also get 1.2 ohms.

Am I correct in thinking that this means the reading is ok? i.e actaully 0?


Thanks


Offline Grainger49

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Reply #1 on: May 24, 2014, 12:50:17 AM
You are spot on.  I'm impressed that you thought to touch the leads together to get a reference for the zero readings.

So 1.2 Ohms or even just about anything under 2 Ohms can be called zero.


Offline tamarind

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Reply #2 on: May 24, 2014, 04:46:58 AM
Great thanks! I've plugged the mains in with the tubes in but they are not glowing at all unfortunately. The fuse tests out ok.

I'll take the advice of the manual and have someone look over my wiring to verify.


Offline Paul Birkeland

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Reply #3 on: May 24, 2014, 06:36:51 AM
Quote from: tamarind on May 24, 2014, 04:46:58 AM
Great thanks! I've plugged the mains in with the tubes in but they are not glowing at all unfortunately.
The twisted pair of wire leaving power transformer terminals 4 and 5 makes the tubes glow.

If there's a bad solder joint there, then the tubes won't glow, and none of your voltages will be correct.  Also double check that the octal socket is positioned properly.  (With the key notch facing forward)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline tamarind

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Reply #4 on: May 24, 2014, 06:16:08 PM
Ok so I've worked out why there is a problem. The wire leading from inside the transformer that wraps around terminal 4 has been severed. Probably after making a number of attempts to clean up the join.  :'(

Is this totally fubar now? i dont know how i can get that wiring back.


Offline Doc B.

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Reply #5 on: May 24, 2014, 07:03:18 PM
If it were me I would gently nudge the cut wire as close as possible to the terminal and bridge the two with solder. If too big a gap I might try to lay in a short piece of wire. This is kind of post graduate hacking, takes a little practice and patience. And if that didn't work I would buy a new transformer.

Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline tamarind

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Reply #6 on: May 24, 2014, 07:30:47 PM
Here is the first ugly attempt that actually works. I am now getting glowing from the tubes.

This isnt exactly a pro job at the moment, would it be better to try and redo it or just go ahead with the voltage checks?



Offline tamarind

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Reply #7 on: May 25, 2014, 01:12:05 AM
Ok I went around the board and did some cleaning up, desoldering and soldering and replacing some melted wires and the LEDs started working as well. From then on the Voltage tests all passed.

Thanks for your help. Now to plug the headphones in and try it!


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