Altec 525 transformer secondary current

[Khron]

Re-tested the resistances after disconnecting the microphone. Upon turning on power

Yeah, no. Those resistances you measure with the power OFF.

https://sound-au.com/articles/multimeters.htm

It helps to know one's tools and how to employ them... Poking around semi-randomly is not exactly the most constructive and/or productive way to go about things.

https://sound-au.com/troubleshooting.htm
https://sound-au.com/articles/troubleshoot2.htm

 

[Pat Maki]

I'll just put Ian's article here in case it helps.....
maybe knowing some values of things like .3mA etc... can help sort stuff.....

Thanks @scott2000

 

[Pat Maki]

Yeah, no. Those resistances you measure with the power OFF.

https://sound-au.com/articles/multimeters.htm

It helps to know one's tools and how to employ them... Poking around semi-randomly is not exactly the most constructive and/or productive way to go about things.

https://sound-au.com/troubleshooting.htm
https://sound-au.com/articles/troubleshoot2.htm

Thanks for pointing me to Mr Elliot's. Very practical guidance in there.

 

[Pat Maki]

Update on this project...since I was getting too high of voltages, put the selenium rectifier back in and that got the unit working properly. After deep diving into how to calculate what value to use for the current limiting resistor that goes after the diodes that replace the selenim rectifier...discovered that I was using a resistor with a much too high value...so high that it was limiting current far too much...after figuring this out, was able to zero in on the correct value for the resistor...which was 15 ohms. Verified this by checking the current value after the selenium rectifier and using that value as a cross-check. Now on to update the other 525 power supply..on that unit, the 250v secondary is way too low, but I found a 250v 50mA transformer at Hammond and once that shows up will add it into the circuit. the other secondary (23v CT) was working fine, so will keep the original transformer and and add the new one...fortunately, after swapping the giant can capacitors (x4), there's plenty of room for the new trafo. Thanks for all the help @Khron and @scott2000 ! Here's a pic of the finished insides...even found some NOS Mallory .25uf 400V caps for a good deal on ebay!

 

[Khron]

put the selenium rectifier back in

YOU NEVER MENTIONED HAVING REMOVED / REPLACED THOSE IN THE FIRST PLACE...

rectifier...discovered that I was using a resistor with a much too high value...so high that it was limiting current far too much

"Thanks" for letting us know what you had actually done...

 

[Pat Maki]

YOU NEVER MENTIONED HAVING REMOVED / REPLACED THOSE IN THE FIRST PLACE...

Does this not qualify as mentioning I did this?

(earlier in this thread) "The DC readings are all too high as well. Like the node between R8/C7 shows 315V, but I'm seeing more like 370VDC. I figured it was because the diodes I used in place of the order rectifiers (RS1 and RS2) weren't high enough using a 10k resistor after RS1 and 300ohm after RS2. I jacked those values up to 77K each and was able to tame the DC voltages, but also not getting any voltage at point 6 of the mic connector (shows 200V in schemo)...."