Troubleshooting Resistance

[shcaz]

Newly finished initial build on the Stereomour.  In doing initial resistance checks, everything checks OK, save for one measurement.

Here is situation:
-Resistance check to terminal 11 gives no reading
-This terminal is B side connection to output transformer, A side reads fine (1.4K ohms)
-Checked connections, resoldered
-Desoldered both ends of wire, checked wire continuity - 0 resistance, resoldered, still no luck

Only additional clue is that the OT-2 terminal #5 (terminating connection from terminal 11) is loose in the OT-2 unit.  I suspect the connection is faulty internal to the OT-2 unit.

Any additional suggestions?  My first build BTW.
Steve

[shcaz]

Another step that appears to isolate the the OT-2 as the issue:

-Resistance measured between terminal 10 & terminal 5 on the 'good' OT-2 measures 200 ohms
-It measures infinite on the 'bad' OT-2 transformer

Ideas on next steps?

[2wo]

This may be your first build but it sounds like you know what you're doing.

Till someone in authority can reply. Maybe check around the suspect terminal. Maybe the wire is not solderd well, or broken right there. just be careful, the wire you are looking for may be fine and easily damaged. use good judgment...John       

[JC]

Same here.  I don't know the circuit at all, so I can't be of much help.  But, it sure sounds like you are in the neighborhood.  If one of the transformer terminals was a little loose, it is very possible that the relatively fine magnet wire coming out of the interior of the transformer to the base of that terminal either broke or has come de-soldered enough to be causing your issue.  Since you have already determined that there is a resistance difference between the good side transformer and the bad (ain't stereo grand!), then I would recommend a very close look at the terminals in question on the bad one.  Particularly to see if each has a wire that looks like it is well soldered to the base of the terminal.  The good side transformer may give you a good look at how it is supposed to appear.

After that, it will depend on what you find on your visual inspection.

[Grainger49]

Steve,

It sure sounds like you are on top of it.  If I have this correctly, you have measured the resistance of the primary side of output transformers.  One measures 200 ohms the other is open.

That sounds like a bad transformer.  But without a manual, there are only a few out there, I can't be certain.

Call Bottlehead when you determine you have a bad part.  They will help.

[shcaz]

Thanks all for replies and input.

I'm not sure if I'm testing the primary side or not (I'm doing some research output transformers in general), but am simply comparing resistance readings from the 'good' output transformer to the other.  At this point I'll contact Bottlehead next week - actually gives me freedom to take some time on the base...

BTW, great forum and incredible level of participation and willingness to help.  Much appreciated.  I can't wait to finish the initial build and start experimenting with variations discussed in other threads.

Steve